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Drs. Kay & Leo Edelsberg are ODs with Optical World offices located in Aventura, Miami, and Jensen Beach, Florida. Optical World locations have provided outstanding eye care for South Florida eye patients for more than fifteen years. Optical World specializes in eye exams, eyeglasses, prescription sunglasses, designer prescription eyewear, prescription sunglasses, and contact lenses.
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Glossary of Eye Terms
Glossary of Terms
20/20 – An expression for normal eyesight. The numbers refer to feet (except in countries that use the metric system, where it’s expressed as 6/6, six meters being approximately equal to 20 feet). The first number refers to the distance between the eye chart and the eye being tested. The second number is a comparison of a normal eye and the tested eye. When the second number is 20, that indicates the tested eye can read the small letters on the chart from 20 feet away, as a normal eye can. When the second number is higher than 20, it indicates impaired vision, more impaired as the number is higher. For example, if a person’s vision is assessed at 20/100, it means that this person must be only 20 feet from the chart for it to look as clear as it does to a normal eye 100 feet away.
AAO – American Academy of Ophthalmology, an professional membership organization for ophthalmologists. Also the American Academy of Optometry, a professional membership organization for optometrists (also called American Optometric Association). ABES – American Board of Eye Surgeons, a professional membership organization for ophthalmologists. It’s affiliated with the ACES, the American College of Eye Surgeons. Ablation – Removal, especially surgically by cutting or abrading. Ablation zone – The area of the cornea to be corrected in laser eye surgery. American Board of Ophthalmology, a medical specialty board which offers education and examinations for ophthalmologists. Upon completing this 1 ½ year program, the ophthalmologist is Board Certified. Abrade – To roughen by rubbing or scraping, thus removing small pieces of surface tissue. Accommodation – The eye’s ability to switch focus from near objects to far objects. It’s done by tiny muscles attached to the eye’s lens, which pull on the lens to change its convexity. As we age, those muscles become weaker and the lens becomes stiffer, a condition known as presbyopia, where reading glasses become necessary to see close-up objects. Acuity – (a-KEW-uh-tee) Clarity or sharpness of vision, commonly expressed as 20/20 vision in relation to the Snellen acuity chart. This is the eye chart seen at every eye doctor’s office, with the big E at the top. Age-Related Macular Degeneration (ARMD) – Deterioration, as people age, of the macula lutea (also called the yellow spot), which is a small area on the retina which gives maximum vision. If left untreated, it results in blindness. AK – Astigmatic Keratotomy, an ophthalmological procedure for correcting astigmatism. Alcon – A manufacturer of medical equipment. Algorithm – A mathematical formula such as is used when preparing for a LASIK, PRK, LASEK or Epi-LASIK surgery, to set the laser’s ablation area on that particular individual’s eyes. ALK – Automated Lamellar Keratectomy, a procedure to correct opacities on the corneal surface. Allegretto – A manufacturer of medical equipment. Allergan – A company that makes ophthalmic equipment and drugs. Amblyopia – (am-blee-OH-pee-uh) A condition where one eye is less used than the other, usually in childhood, without there being any obvious structural reason for it. It causes the less-used eye to deteriorate, becoming worse than 20/20 until, if no treatment is done, it will become useless. Also called “lazy eye”. American Academy of Ophthalmology – See AAO. American Academy of Optometry – See AAO. American Board of Eye Surgeons – See ABES. American Board of Ophthalmology – See ABO. American College of Eye Surgeons – See ACES. American College of Surgeons – A professional membership organization for surgeons. Its members are known as Fellows and often put FACS after their name for Fellow of American College of Surgeons. American Optometric Association – A professional membership organization for optometrists. See AAO. American Society of Cataract and Refractive Surgery – See ASCRS. Ametropia – A generic name for eye conditions characterized by impaired refraction, e.g. myopia, hyperopia and astigmatism. Amsler Grid – A test used to detect defects or distortions in the central visual field. It consists of a square subdivided into many hundreds of small squares by horizontal and vertical lines, with a small dot in the center. Aniseikonia – (a-neece-eye-KON-ee-a) An impaired type of binocular vision where the left and right retinal images are of different sizes. It can occur naturally, and is sometimes induced by refractive surgery. Anterior – An anatomical term meaning the front part of a structure as opposed to the posterior, the back part. Anterior Basement Membrane Dystrophy – The most common corneal dystrophy. An eye condition where the membrane that lies beneath the epithelial cells (surface cells) of the cornea is uneven and traps cells below it which should normally rise above it. It impairs vision, is usually hereditary, and fluctuates in severity over the person's lifetime. It's also called Map-Dot-Fingerprint Dystrophy (a name based on how it looks microscopically), and Epithelial Basement Membrane Dystrophy. Anterior Chamber – The small space behind the cornea and in front of the iris, filled with the Aqueous Humor. Anterior Ocular Segment – A name for the parts of the eye that are in front of the lens, namely, the cornea, anterior chamber, iris and ciliary body. Antimetropia – A condition where one eye is nearsighted and the other one farsighted. Antioxidants – Nutrients that neutralize or destroy free radicals. AOA – See AAO. Aphakia – (ah-FAY-kee-uh) The condition of having no crystalline lens in the eye, as happens when it's been removed because of cataracts. Aphakic Spectacles – Very thick and heavy glasses that in past years were the standard remedy after a cataract operation. They gave distorted peripheral vision. Modern ophthalmologists can instead implant an intraocular lens (IOL). Aqueous Humor – (AY-kwee-us) The clear fluid that nourishes the lens and the cornea, flowing between them, secreted by the ciliary processes. ASCRS – American Society of Cataract and Refractive Surgery, a professional membership organization for ophthalmologists who perform cataract and refractive surgeries. Astigmatic Keratotomy – An eye surgery like Radial Keratotomy, where tiny incisions are made in the edges of the cornea to give it a rounder shape. Astigmatism – (uh-STIG-muh-tiz-um) An eye condition where the cornea is oval-shaped rather than round. This oval shape has two curves: the steeper one and the flatter one. Each curve refracts light at a different angle, sending it to focus on the retina in two different places, and creating distorted vision. It can be mild, with just blurriness, or more severe, with ghosting and severe blurring. In a glasses prescription, the second number expresses the degree of astigmatism you have, and the next number is the number of degrees in the angle of refraction. For example, a prescription of -4.00 – 2.00x34o states that you have 2 diopters of astigmatism at an angle of 34 degrees. Automated Lamellar Keratoplasty (ALK) – A refractive eye surgery that treats myopia. The surgeon uses a microkeratome to cut a very thin shaving or flap from the corneal surface. Then a tiny piece even thinner is removed from the underlying tissue, to flatten the cornea a little, and the flap is replaced. It heals up without any need of stitches.
B scan – An ultrasonic procedure that checks for abnormalities in the eye, and locates foreign bodies within it. Basement Membrane – A microscopically thin layer of tissue below the epithelial cells (surface cells) of the cornea, connecting those cells to the stroma, which is the middle layer of cells in the cornea. Bausch Lomb – A company that makes ophthalmic equipment and products. Best Corrected Visual Acuity – A measurement of your best vision, as corrected by your glasses or contact lenses. Bifocals – The type of glasses we usually call “reading glasses”, where most of the lens corrects your distance vision, and a small area at the lower edge of the lens corrects your close-up vision. They’re used by people withresbyopia. There are alsotrifocals. Binocular – An adjective meaning with both eyes, e.g., binocular vision. Binocular Vision – The use of both our eyes to see, such that the images from each eye blend to form a single image with dept perception. Black Box Laser – A laser (usually imported to the U.S.) used by some eye surgeons that has been altered so it can do LASIK and other laser eye surgeries, but this alteration is not approved by the FDA. The safety consequences of using a black box laser have not been studied and are completely unknown. Blepharitis – (blef-uh-RI-tus) Chronic inflammation of the eyelids. It can be caused by an allergic reaction to some product, excess oil excreted by eyelid glands, bacterial infection, or poor facial hygiene. Blindness – See Legal Blindness. Blind Spot – (a) The place on the retina where the optic nerve enters the eye. No visual cells are on the retina here, so no vision is possible at this place. In this sense, it’s a normal thing. (b) Also refers to any gap in a person’s visual field that corresponds to any area on the retina where visual cells are missing and in this sense, it’s associated with eye disease. Board Certified – This is the phrase used for approval by the American Board of Ophthalmology (ABO), a non-profit and independent organization that was founded in 1916 to certify ophthalmologists. Broadbeam – The term used for applying the excimer laser to the entire treatment area at one time. It’s the typical way laser treatment is done for myopia, hyperopia and astigmatism. See also Flying Spot and Variable Spot. Buttonhole Flap – A LASIK problem where the microkeratome cuts through the top surface of the cornea while creating the corneal flap, while lifting it, or while folding it back. It can be caused by loss of the suction which holds the microkeratome against the cornea, or inadequate suction, or by poor matching of microkeratome to patient. If possible, the flap is replaced, and no further surgery is attempted for several months, after it has healed. Sometimes it can cause scarring which impairs vision, but usually there are no permanent ill effects.
Cataract – An opaque or cloudy area that forms in the eye’s lens, impeding vision. They tend to occur with aging, but can also be caused by trauma. Cataracts are treated by the lens being removed and an artificial lens implanted. See intraocular lens. Central Ablation Zone – The ablation zone is the area of the eye treated by the laser in LASIK surgery. Around it is the transition zone, where the treated area gradually merges with the original corneal surface that lies outside the ablation zone. Central Island – An area of the laser-treated part of the cornea which is erroneously not treated, so that its level remains microscopically higher than the surrounding treated surface. The term islanddescribes its appearance. It causes diplopia (double vision). Ciliary Body – Part of the eye which is in front of the lens, and behind the iris and cornea. It consists of (a) the ciliary muscle which controls the shape of the lens, making it flatter for far distant objects and more convex for closer things; and (b) the ciliary processes, tiny projects which secrete aqueous humor. CK – Acronym for Conductive Keratoplasty. CLE – Acronym for Clear Lens Exchange. Clear Lens Exchange – See Refractive Lens Exchange. Co-management – Collaboration between two or more doctors in caring for a patient. For refractive surgery, usually an optometrist co-manages with an ophthalmologist. The optometrist provides the pre-operative testing and post-operative care, while the ophthalmologist does the surgery itself. Coma – A higher order aberration which makes points of light look like comets with blurry tail-like smudges. It can be diagnosed and treated with wavefront-guided LASIK procedures. Complex Wavefront Retreatment – An off-label use of the excimer laser to do corrective secondary surgery after the original wavefront-guided surgery has left the patient with higher-order aberrations. Concave Lens – The type of lens used to correct nearsightedness (myopia). Concavity is the hollow type of curve that recedes in the center and raises up at the edges, opposite to convex. Conductive Keratoplasty – A type of refractive surgery which uses radio waves through a tiny probe to create planned shrinkage of the cornea, such that hyperopia or astigmatism are reduced, or eliminated. Conjunctivitis – (kun-junk-tih-VI-tis) Inflammation of the conjunctiva, which is a thin mucus membrane covering the inside surfaces of the eyelids and the white outer surface of the eye. It looks reddened and itches. It’s a contagious conditions and can be treated with eyedrops. Contact Lens – A way of correcting myopia and hyperopia, or other refractive error of the eyesight, which consists of curved plastic lenses placed in front of the iris. They’re designed so that they retain good contact with the eye’s surface and remain in place. Contact Lens Assisted Pharmacologically Induced Kerato Steepening – A way to undo overcorrection in laser eye surgery (LASIK, PRK and RK). A tightly-fitting contact lens is placed on the eye and anti-inflammatory eyedrops are used. The goal is to make the cornea more steep, after it’s been made too flat. Contact Lens Disinfectant – A solution for removing bacteria and micro-organisms from contact lenses. Contact Lens, Daily Wear – Contact lenses designed to be worn only during the daytime. Contact Lens, Disposable – Contact lenses designed to be worn once and then thrown out, as opposed to the kind that’s removed, cleaned, and reinserted. Depending on the eye doctor’s prescription, disposable contact lenses can be worn for one day, or for up to a week. Contact Lens, Extended Wear – Contact lenses designed to be worn continuously for up to a week, not being removed for sleep. Contact Lens, Therapeutic – Special contact lenses designed to help heal the eye and protect it while it heals. They’re often used along with eyedrops specially-prescribed to promote healing. Contact Lens, Toric – Contact lenses designed to correct astigmatism, with two curvatures at different angles, one for astigmatism, and the other for hyperopia or myopia. They have the ability to remain in place despite blinking and eye movements, so that they give you clear vision. Convex Lens – Lenses with the opposite curvature to concave lenses. They bulge outwards like a ball and are used to correct hyperopia and presbyopia. Cornea – (KOR-nee-uh) The front clear part of the eye in front of the pupil and iris. It acts as a lens, refracting light rays as they enter the eye. The eye’s crystalline lens refracts them further to focus them on the retina at the back of the eye. The cornea also allows light to pass out through it, making the iris visible, the eye’s color. Corneal Abrasion – A scrape or scratch on the cornea, the front surface of the eye. Corneal Ectasia – A complication of LASIK similar to the inherited condition of keratoconus. It can happen when the eye was over-treated by a LASIK procedure, so that not enough thickness is left in the cornea to contain the eye's internal pressure. That pressure pushes against the cornea and causes it to bulge outward. Vision then becomes progressively worse. Corneal Flap – A small circular piece of the cornea’s surface layer (epithelium) which is cut, all but one section like a hinge, and folded back before the laser treats the stroma. After treatment, it’s folded back into position and heals by itself in a few days. Very occasionally there are complications with this flap. For example, it may have been sized wrongly, or cut too deeply, it might be completely cut instead of retaining a hinge, or it might heal in the wrong position, with a slight wrinkle or with swelling. Many of these complications can be dealt with successfully. Corneal Haze – An after-effect of Excimer laser surgery, where the cornea develops opaque white cells which cloud the vision to some extent. It can cause glare from bright lights and a vague fogginess of vision. It usually clears up after 6 or 8 months. If it persists, there’s an enhancement procedure which can reduce it. As vision correction techniques improve there’s less incidence of corneal haze. Corneal Refractive Therapy – A reshaping of the eye with contact lenses, also called Orthokeratology. These lenses are rigid and worn while you sleep, so they gently persuade the eye to change its shape by the time you wake in the morning. The effect lasts only a day or two, so you need to wear these lenses every night. It was approved by the FDA in June, 2002 and is a non-surgical way of temporarily creating the effect created permanently by LASIK surgery. Corneal Topographical Map – A map of the cornea that shows its surface profile. Corneal Topographer – A specialized camera-computer system which photographs and prints out a map of the surface details of a cornea. This is done before any LASIK procedure. Corneal Transplant – Surgery to replace the cornea, the clear front area of the eye. Corneal tissue comes from a donor and since the cornea has a small blood supply, there is little risk of rejection, and the new cornea can function very well for years. A corneal transplant can be done to treat Keratoconus, uch’s Dystrophy, or damage from a severe infection or injury. It’s a painless outpatient procedure. CRSQA – Pronounced “Surs-kah”. See Council for Refractive Surgery Quality Assurance. CrystaLens – A type of intraocular lens which changes focus between close and distant objects. More information. Crystalline lens – The eye’s natural lens, which is behind the iris and in a healthy eye is completely clear. Light passes through it and is refracted by the lens to focus on the retina. Tiny muscles attached to the lens change its convexity according to where the eye is focused. As we age, it can start to become cloudy (cataracts), impairing our vision. Custom Cornea – The trade name for a wavefront-guided LASIK that uses the LADARVision excimer laser, made by Alcon. CustomVue – The trade name for a wavefront-guided LASIK that uses the VISX S4 Excimer laser.
Decentration – A complication of eye surgery. When centration is perfect, the corneal ablation, or the position of the intraocular lens being implanted, is in the center of the eye, lined up with the pupil. Then vision is perfectly centered through the ablated area and pupil, so that we see clearly and fully, like looking through the center of your glasses. When decentration happens, the ablation has been done off-center, or the lens’ position is shifted, so that vision is partially corrected and partially as it was originally. Degenerative Myopia – Nearsightedness thought to be hereditary, which may start at birth, or in later childhood. It’s a more severe form of myopia and can lead to blindness. It’s associated with to cataract formation and with retinal changes and can lead to retinal detachment. Depth Perception – Our ability to judge the relative distances of multiple objects. Each eye receives a slightly different image. The dominant eye looks directly at it and the non-dominant eye looks from a slight angle. The brain compares these two images and arrives at an estimate of their relative distance. See also Strabismus. Diabetes Type 1 – Insulin-dependent diabetes, also known as juvenile diabetes because it’s often diagnosed in young people. The pancreas, which normally would produce insulin, is unable to do so, so insulin must be injected so the patient can convert sugars and starch into energy. A person with Diabetes, Type 1 or 2, is susceptible to vision problems because the tiny blood vessels in the eyes weaken and start to leak, damaging the retina. See Diabetic Retinopathy. Diabetes Type 2 – The more common of the two types of Diabetes, where the pancreas can produce insulin, but not enough. Insulin may or may not have to be injected for the person to convert sugars into energy. Sometimes Type 2 can be well-managed by sticking to the right diet and exercise routines. Diabetic Retinopathy – (ret-in-AHP-uh-thee) Damage done to the small blood vessels that feed the retina. In the early stage it’s known as background diabetic retinopathy. The small arteries in the retina weaken and leak, which often causes swelling and impaired vision. The later stage is called proliferative diabetic retinopathy. Since the arteries are not functioning well to bring oxygen to the eye’s cells, retinal cells become ischemic (lacking in oxygen). The eye develops new blood vessels (a response known as neovascularization) but these are weak and also start leaking, so the problem becomes worse. Eventually, as the body continues to grow extra blood vessels, which continue to leak, scars can form, and the retina can detach from its membrane at the back of the eye, causing blindness. Lamellar Keratitis (DLK) – Also known as Sands of Sahara. A rare complication of LASIK surgery, appearing between 2 and 5 days after surgery, where inflammation develops between the corneal flap and the corneal tissue beneath it. The cause isn’t certain. It causes blurriness of vision when it’s severe enough. Various measures are usually taken to prevent it, such as use of sterile tape to keep the eyelashes away from the treatment area, rinsing the cornea before making the flap, and rinsing again before replacing the flap. After surgery, medicated eyedrops are typically used to prevent inflammation. DLK needs to be detected promptly so that it won’t impair vision. Usually it responds well to use of corticosteroid eyedrops and sometimes the surgeon will lift the flap again to rinse beneath it. Dilation – Enlargement of the eye’s pupil. The pupil changes size constantly, allowing more or less light into the eye according to how bright the surroundings are. For some eye procedures it’s dilated with special eye drops. Diopter – (di-AHP-tur) The unit of measurement for a lens. Positive diopter numbers indicate the lens is convex (curving outwards) and negative numbers indicate it’s concave. A one-diopter lens will bend straight light rays to focus them one meter away from itself. A two-diopter lens will bend them to focus only a half-meter from itself. A lens with any minus number doesn’t focus the light rays, but scatters them. Diplopia – The term for double vision. Binocular diplopia can occur when both eyes are open, and monocular diplopia when only one is open. Dominant Eye – The eye that looks directly at an object. The non-dominant eye looks at it from a slight angle, and this combination creates depth perception. Double vision – Seeing objects in duplicate, with the second image being lighter and less distinct. Also known as ghosting. Dry eye Syndrome – Insufficient moisture in the eye, which gives a feeling of grittiness, burning, stinging, or uncomfortable dryness, and extra sensitivity to light. It can be a symptom or complication of another condition, or caused by certain medications. It is also a common temporary result of a LASIK procedure. It can be treated with moisturizing eyedrops, eyedrops which stimulate more tear production, or punctal plugs which block the drainage into the nasal passages and sinuses. DSAEK – DSAEK (Descemet's Stripping Automated Endothelial Keratoplasty) is a new procedure devised in 2007 for improving a corneal transplant. Descemet's Membrane (named after French physician Jean Descemet (1732-1810), is the basement layer, the innermost of the cornea's five layers. DSAEK transplants only this very thin layer rather than the entire cornea. The replacement layer from a donor stays in place without the need for any sutures. Recovery from DSAEK is one to three months, as compared to the one to two years' recovery required by a full corneal transplant. Dystrophy – Weakening or wasting of body tissue, such as happens in Epithelial Dystrophies and Stromal Dystrophies, where abnormalities appear in different corneal membranes, causing loss of function and often impairing vision.
Endothelial Dystrophy – See Fuch’s Dystrophy. Endothelium – A lining of flat cells inside the cornea, facing on to the anterior chamber. Epikeratome – A surgical tool similar to a microkeratome, used to make the corneal flap in an Epi-LASIK procedure. It has a blunt separator where the microkeratome, used in LASIK procedures, has a very thin and sharp blade. It’s another way of making the corneal flap and does not involve the use of alcohol, as LASEK procedures do. Each way of making the corneal flap has its advantages and disadvantages and consultation with an experienced eye surgeon will determine which would be best for you. Epi-LASIK – A variation on the basic LASIK treatment, where instead of using a microkeratome to cut the corneal flap before applying the laser, an epikeratome is used. This instrument gently separates the epithelial cells. Epi-LASIK is done for people whose corneas are too flat for traditional LASIK. Epithelial Dystrophies – A group of inherited dystrophies where the surface layer of the cornea atrophies and vision is impaired. See Anterior Basement Membrane Dystrophy, Reis-Buckler’s Dystrophy, and Meesmann’s Dystrophy. (Click here to read more about Epithelial Dystrophies...) Epithelium – A layer of cells which protects the tissue below. In the eye, it’s the outside layer of cells on the cornea. Esotropia – Inward turning of the eyes; crossed eyes. Usually one eye looks straight ahead and the other turns inward. There are several types: Congenital (evident at birth and may continue into Infantile Esotropia); Infantile (usually detected at about 2 months of age and may be accompanied by strabismus and poor gross motor development; Accommodative (usually detected at about two years of age and is related to difficulty with focusing the eyes); and Partially Accommodative (a mix of Basic Esotropia, i.e., non-accommodative, and accommodative esotropia). There is also Pseudoesotropia, which looks like esotropia but is a temporary condition where a young child’s eyes haven’t yet grown the white part next to the nose. The bridge of the nose appears wide and the eyes appear to be both turned inward. This resolves itself as the child’s face develops. Misalignment of the eyes in childhood should be corrected as soon as possible, so that binocular vision (the brain’s ability to use both eyes together) can develop and amblyopia can be avoided. Surgery may be needed; or glasses, an eye patch, or other types of treatment. Excimer laser – (EKS-ih-mur) An ultraviolet laser used in eye surgery and other surgeries. Its name comes from the terms excited and dimer, where excited refers to a molecule which has been stimulated, and is in an excited state, and dimer is the term for a molecule with two identical components. This all refers to the way the excimer laser is created. It’s made from argon and fluoride and gives off pulses of light with a wavelength of 193 nm. Excimer lasers are “cool” lasers, meaning that they’re relatively cool, because all lasers give off some heat. These are very finely-tuned or subtle lasers. Each pulse removes only 1/4000 of a millimeter of corneal tissue, and to get a better idea of how small that is, think of the width of a human hair: it would take 200 pulses of the excimer laser to cut that hair in half. It cuts tissue by breaking bonds within collagen molecules. Its wavelength is such that the ultraviolet light is instantly absorbed by the water within the corneal tissue. The cornea has a high water content, and this absorption of the laser light by the corneal surface prevents it from penetrating any further into the eye. This makes it a good tool for precise sculpting of the corneal surface. Excimer lasers have been used since 1987 for vision correction and were approved by the FDA in 1995 for correcting nearsightedness. Since then, they’ve been also approved for treating farsightedness and astigmatism.
FACS – Fellow of the American College of Surgeons. Farsightedness – The popular term for hyperopia. FDA – U.S. Food and Drug Administration. Floaters – Tiny specks or strands that float in the field of vision. They move when the eyes move so they can’t be directly focused upon. Those shapes are the shadows cast on the retina by small clumps of cells in the vitreous humor. Often they’re more visible against a blank background like the sky or a wall. They become more common with age, as the vitreous starts to thicken and clump together. Mostly floaters are harmless, but if flashes of light accompany them, it could indicate a potential retinal detachment. Flying Spot – A method of applying the excimer laser light used in refractive surgery. A flying spot laser is used, which has a 1mm – 2mm diameter light beam. The computer that controls the laser is programmed to send pulses to changing spots on the cornea, with no spots overlapping. Part of the ophthalmic laser system is an eye tracker, which responds to all eye movement during surgery. So even if the eye moves while it’s being treated, the entire targeted area will be treated, because the treatment plan has determined where the laser should shine, in the series of flying spots that will cover it entirely, and the whole system moves to correspond with any eye movements during surgery. Flying spot lasers can be used in both traditional LASIK procedures and those using wavefront technology. Focusing power of the eye – The combined action of the cornea and the lens to refract light on to the retina. As light enters the eye, it’s refracted (bent) by the cornea, because of the cornea’s curvature. As the light continues further into the eye, passing through the pupil to reach the lens, it’s refracted more, to a variable degree according to how far away from the eye the object is which is reflecting this light. If it’s down the road a ways, like a distant traffic light, it needs to be refracted less in order to land in focus on the retina. If it’s close up, like the clock on the dashboard, it needs to be refracted more. Many people have corneas which refract light either too much (causing it to focus in front of the retina and thus creating nearsightedness), or too little (causing it to focus behind the retina, causing farsightedness). Refractive surgery can correct this by reshaping the corneal surface to make it more or less steeply curved. Food and Drug Administration – The U.S. federal agency in charge of evaluating and approving medical devices (and other things). It’s not responsible for new medical procedures, just for how the new devices are used. For example, it has approved of excimer lasers for treating nearsightedness. Fovea – The central area of the macula, which is the most sensitive area of the retina. The fovea is less than one percent of the retina, but uses over 50% of the visual cortex in the brain (that part of the brain which receives visual information). The fovea is highly sensitive to details of vision but not to dim light, which is why we can see dim objects, such as distant stars, better by not looking at them directly. Fuch’s Dystrophy – A progressive, inherited eye disease (dystrophy) in which the cornea loses cells from the endothelium which normally remove fluids and impurities from the eye. Without those cells, the eye retains too much fluid and begins to swell. By changing the cornea’s curvature, this makes vision blurry, especially first thing in the morning, since while the eyes are closed in sleep, no moisture can evaporate from them. It causes other symptoms, e.g. blisters, light sensitivity, pain, and decreased depth perception. There is no cure, but there are some ways to minimize symptoms. A corneal transplant eventually becomes necessary. Also called Endothelial Dystrophy. (Click here to read more about Fuch's Dystrophy...)
Ghosting – A name for double vision. The eye sees objects in duplicate, with the second image fainter than the main one. Glaucoma – (glaw-KOH-muh) An eye disease where pressure builds up inside the eye. If it isn’t diagnosed and treated, it can damage the optic nerve, reducing the field of vision gradually, until blindness results. It’s treated with special eye drops which lower the pressure. There are several types of glaucoma, the most frequent one being Open-Angle Glaucoma, which has no obvious symptoms at first. About 15% of glaucoma cases are Closed-Angle Glaucoma, and there are noticeable symptoms, such as nausea, eye pain, blurred vision, and headaches. There’s also Normal-Tension Glaucoma, where the intraocular pressure doesn’t build up, and no cause has yet been established for this yet, although there are theories. Congenital Glaucoma begins at or near the time of birth. Secondary Glaucoma is a result of some other illness. Each form of Glaucoma has its own causes and symptoms. Granular Dystrophy – A hereditary eye condition where pale gray granules appear in the stromal layer of the cornea, like little crumbs. It’s usually detected by the time a person is about 20. By age 40 or so, vision will be increasingly impaired as those granules, or lesions, expand, increase in number, coalesce, and penetrate more deeply into the stroma. It can be treated in earlier stages with an excimer laser, or in other ways that remove the granules, and later on by a corneal transplant.
Halos – A visual condition where a light source appears with a blurry circle of light around it, rather than having visible edges. It can be a complication of refractive surgery, and can also occur naturally. It makes night vision difficult. Haze – Clouding of the cornea. It can be caused by inflammation, too much moisture, scar tissue, or some kind of foreign substance as from a medication. Higher Order Aberration – The lower order aberrations are familiar names to most of us: myopia, hyperopia, and astigmatism, and they’re refractive errors. The higher order aberrations are irregularities of the eye that are not refractive. Sixty-four have been detected and measured so far, using wavefront technology. They’re not treatable with traditional LASIK procedures, glasses or contact lenses, but can be diagnosed and treated by wavefront-guided LASIK. Any given eye usually has more than one, which interact, producing symptoms. That means the aberrations can’t necessarily be established based on symptoms. They come into play at night, or in low lighting conditions. Some examples are: Spherical Aberration (irregularity in the eyeball’s shape), which creates halos around points of light Coma, which makes points of light look like comets with blurry tail-like smudges Loss of contrast Double vision Hyperopia – (hi-pur-OH-pee-uh) Farsightedness. It’s one of the lower order aberrations (along with myopia and astigmatism), and is correctible by glasses, contact lenses, and LASIK procedures. The higher order aberrations are more subtle and are non-refractive errors of the eye.
ICL (Implantable Contact Lens) - The name used for the STAAR Myopic Visian ICL™, created by the STAAR Surgical Company and approved by the FDA in 2005 for treating myopia. It’s a refractive lens for use in a phakic eye (i.e., an eye that has its natural crystalline lens intact) and is implanted in the posterior chamber of the eye. Intacs – The trade name for new-moon-shaped plastic implants. They’re an alternative to LASIK surgery, to correct myopia. They’re inserted beneath the side edges of the cornea to flatten its surface by raising the periphery (whereas LASIK flattens the surface by removing tiny pieces from the cornea’s center). However, unlike LASIK, they’re not a permanent change to the cornea, as their prescription can be changed or they can be removed altogether. They’re especially used for people with keratoconus, to correct myopia. IntraLase – A type of laser used to create the corneal flap in an IntraLASIK procedure. In a traditional LASIK surgery, the flap is created by a hand-held device called a microkeratome, with an oscillating blade. In IntraLASIK, it’s created by the IntraLase™ FS laser, a cool light which passes through the corneal surface to the exact location beneath the surface which your LASIK surgeon has programmed into the computer. This ensures that the flap is not cut too deeply or unevenly. For the treatment itself, the excimer laser is used as in traditional LASIK procedures. IntraLASIK – A variation on a LASIK procedure. See IntraLase. Intraocular – Inside the eye. Intraocular lens – An artificial lens which is implanted in the eye to replace the natural crystalline lens. Intraocular lenses are used to treat cataracts and presbyopia. Traditionally they were monofocal, so that you needed glasses for either close-up vision or distance vision. Newer ones are multifocal, with different areas designed for different distances, or can accommodate in a way similar to how the natural lens accommodates for distance. Intraocular pressure – The pressure inside the eye. Besides containing its structures like the lens, the eye contains fluids and when the pressure builds up too high, it can gradually impair vision, a condition known as glaucoma. IOL – See Intraocular lens. Iris – The colored part of the eye which encircles the pupil. Iris Registration – When we go from a sitting position to lying down, as for a LASIK treatment, our eyes move slightly. So if our eyes were measured and diagnosed for treatment while we were sitting up, how can the laser adjust for the slight change in their positions after we lie down? Iris Registration does this, and it keeps the laser targeted correctly throughout the treatment, even if our eyes move during treatment. It's a hardware addition to the VISX STAR laser system for CustomVue LASIK and was approved by the FDA.
Keratectomy – The surgical removal of part of the cornea. Keratitus – Inflammation of the cornea caused by bacteria or a virus. Can leave scarring and cause loss of vision. Keratoconus – (kehr-uh-toh-KOH-nus) A thinning of the central cornea. Instead of being smooth and round, it develops a bulge in the center which deflects light entering the eye, severely impairing vision. It is an inherited disease and may require corneal transplant surgery. Keratometry – (kehr-uh-TAH-mih-tree) Measurement of the cornea’s curvature. It’s done with a keratometer. Keratoplasty – See corneal transplant. Keratomileusis – (KE-ruh-toe-my-LOO-suhs) A name for the way a LASIK procedure is done. Before the excimer laser made LASIK possible, this procedure was done by totally removing the small corneal flap, rather than just partially, and then freezing it, reshaping it, and replacing it on the cornea. Keratotomy – (keh-ruh-TAH-tuh-mee) Surgical incision of the cornea. This is done for a radial keratotomy (RK) procedure, treating nearsightedness by flattening the cornea slightly. Several tiny incisions are made around the periphery of the cornea, extending further inwards to the center in more severe cases of nearsightedness.
Lacrimal gland – The small structure in each eye which produces tears. It’s above the outer corner of the eye, and lacrimal ducts run from the inner corner to the nose. See also punctum and nasolacrimal duct obstruction. LASEK – See Laser Assisted Epithelium Keratomileusis. Laser – Although this is used as a word now, it was originally the acronym for Light Amplification by the Stimulated Emission of Radiation. There are many lasers, all man-made for specific purposes. Laser light has a single wavelength (i.e., color), rather than all colors like everyday white lights. Its waves are directional rather than scattered, and each wave is in step with the next one, which vastly increases the power of a laser light. Laser Assisted In-Situ Keratomileusis – The full name for LASIK. Laser Assisted Epithelium Keratomileusis – The acronym for LASEK, a variation on LASIK used when the cornea is too flat or too thin for standard LASIK. Instead of using a microkeratome, it uses an instrument known as a trephine, with a finer blade, to make the corneal flap, and then the eye is soaked for a half-minute or so with an alcohol solution. This softens the epithelium so that it can be folded back more safely. Laser Thermal Keratoplasty (LTK) – (KER-uh-tuh-PLAS-tee) LTK is a refractive surgery treatment for mild farsightedness. A Holmium laser is used to gently and precisely heat a circular area around the edge of the cornea, so that this edge shrinks a little. The result is a steepening of the cornea, which in farsightedness is too flat. It’s also used to treat presbyopia. LASIK – (LAY-sik) A refractive surgical procedure for correcting myopia, hyperopia and astigmatism. An excimer laser is used to recontour the cornea, making it steeper to correct hyperopia, flatter to correct myopia, and more evenly curved to correct astigmatism. The laser works on the stroma, the corneal layer below the surface cells (epithelium), and access to the stroma is gained by creating a tiny flap on the corneal surface and folding it back. After treatment it’s replaced and heals by itself. Lattice Dystrophy – A hereditary corneal condition where abnormal protein fibers appear on the stroma. In an eye exam, they look like a latticework of curves and lines. They progressively become more opaque and larger, creating cloudiness in the cornea which obstructs vision. They can gather beneath the corneal epithelium, causing it to erode and exposing nerves, which creates severe pain. That pain can be alleviated with eye drops and ointments which reduce the friction when you blink, though in some cases an eye patch is necessary that prevents blinking until the erosions heal. By about the age of 40, there’ll be scarring beneath the corneal epithelium which impairs vision by clouding up the cornea. Early lattice dystrophy can be treated with an excimer laser, and in some cases a corneal transplant is done. Legal Blindness – A definition of blindness which enables a person to apply for government disability benefits. It can be either a visual acuity of 20/200 (or worse), with corrective lenses, in the better eye, or tunnel vision in the better eye of 20 degrees in diameter. This level of blindness is severe, but does not necessarily prevent a person from functioning at all. Lens – The crystalline lens, inside the eye, which refracts (bends) light rays as they pass through the eye to the retina. It’s fully transparent and is convex on both sides (curves outwards). It’s located between the iris, the colored part of the eye, and the vitreous humor, the fluid which fills the main part of the eye’s interior. It’s the second part of the eye to refract light rays, the first being the cornea, which does about 65% of the refraction necessary for clear vision. The lens can change its shape to accommodate light rays coming from near or far distances, and these changes in shape are controlled by tiny muscles attached to each end of the lens. Lower Order Aberrations – The name for myopia, hyperopia, and astigmatism. These are the conditions measured to determine a prescription for glasses or contact lenses, and that can be corrected with refractive eye surgery such as LASIK. The higher order aberrations are more numerous and still be researched and some examples are: halos, glare, and double vision. Low Vision – Visual impairment ; usually less than 20/200 which obstructs daily activities but cannot be corrected with glasses or contact lenses. (See 20/20) LTK – See Laser Thermal Keratoplasty
Macula – An extra-sensitive area roughly in the center of the retina, which enables us to see fine detail and do activities such as reading. The center of the macula is the fovea, which has no nerve cells or blood vessels to interfere with vision, and this makes it the most sensitive area of the macula. It’s also the part of the eye which enables us to distinguish colors. Macular Degeneration – A deterioration of specialized cells in the macula of the retina which normally detect light and color to give us sharp central vision. With Macular Degeneration they deteriorate as we age, causing severe vision loss and even blindness after about age 65. There are two kinds: • Wet (neovascular) – where new little blood vessels grow under the retina, leaking blood and fluid and causing further vision loss • Dry (non-neovascular) – where new blood vessels do not grow, so that this is a less severe form of the disease; however, it sometimes progresses into the Wet form Macular Degeneration is not fully understood, but it appears to be related to advancing age, smoking, heredity, high blood pressure, obesity, inactivity, and some drugs. Also called Age-Related Macular Degeneration (ARMD). Macular Dystrophy – A hereditary type of macular degeneration. In a normal eye, the macula, the central part of the retina, has specialized cells that detect light and color. Macular Dystrophy is a deterioration of these cells so that we see less and less clearly. It is the most severe of the three main Stromal Dystrophies, but the least common. Macular Edema – Pooling of fluid in and around the macular area of the retina, which causes swelling and impairs vision. It causes blurriness, waviness of straight lines, light sensitivity, and a pink tint to the vision. It usually happens as a result of disease or injury and sometimes after eye surgery. Most people recover from it in a matter of months. Manifest Refraction – The eye examination which determines a person’s degree of refractive error. The patient looks through a phoropter, an instrument with an array of lenses, at the eye chart set first at 20 feet away (for distance vision), then at 16 inches away (for near vision). The optometrist or ophthalmologist changes lenses and asks which ones give the clearest image. Meesmann’s Dystrophy – A rare hereditary eye condition where tiny cysts appear on the corneal surface which can rupture. Visual acuity is only minimally affected, but the eyes feel irritated, as if something is in them. It progresses slowly and a corneal transplant may be done in some cases. Mesopic Pupil Size – The size of the eye’s pupil (black circular area inside the iris) in medium lighting conditions, such as a typically lit room, or daylight. Micron – A measurement of length equal to one-millionth of a meter. Microkeratome – (My-krow-KEH-ruh-tome) A surgical instrument used to create a corneal flap during LASIK and some other refractive surgeries. There are two types: mechanical and laser. The mechanical microkeratome uses an extremely sharp and precise metal blade. The femtosecond laser microkeratome uses the laser beam to create microscopically tiny bubbles at a specific depth in the cornea. When thousands of such bubbles are placed next to each other, it creates an incision. A femtosecond is one millionth of a nanosecond, which is one billionth of a second. Monocular – An adjective for vision out of one eye. Also the name of a type of telescope. Monovision – The correction of one eye for far distance and the other for near distance. This is a treatment for presbyopia. Myopia – (mi_OH-pee-uh) Nearsightedness or shortsightedness. When the cornea is too steep, or when the eye is too long, from front to back, light rays focus in front of the retina, instead of on it. This creates blurriness in distance vision but clarity in close vision because the focusing mechanism is too strong, refracting the light too much. Glasses or contact lenses correct it by supplying a concave lens, which reduces the amount of refraction. Refractive surgery such as LASIK corrects it by flattening the cornea, thus changing the strength of refraction so that the light rays land on the retina.
Nasolacrimal duct obstruction – (NAY-zo-LAK-ruh-muhl) The nasolacrimal ducts are the tear ducts which carry tears out of the eyes to the nose. They can become clogged, usually in a child, so that the tears build up within the eyes and overflow. If not treated it can lead to infection. See also punctum, punctal plugs, and lacrimal gland. Nearsightedness – Another name for myopia. NearVision CK – A trade name for Conductive Keratoplasty (CK), which is a treatment for hyperopia.
Ocular Herpes – Herpes simplex, type I. This is the same virus which causes cold sores and it can infect the eyes also. It occurs on the cornea, usually only on one eye, and is also known as Herpes Keratitis. It can affect only the surface, or deeper layers, and can heal well, or can cause scarring, loss of vision and even blindness. Occasionally it develops inside the eye and is then known as Herpes Retinitis or Herpes Uveitis. Symptoms are blurred vision, pain, redness, and light sensitivity. Ocular Migraine – A rare type of migraine headache which occurs around the eye area and brings nausea, vomiting, and double vision. There may or may not be a headache. It usually affects one eye at a time. Vision can become greyed out or wavy and even temporarily lost on that side. The exact cause is not known. Also called Retinal Migraine. Off Label Use – Use of a technology for a procedure which is legal but not specifically approved by the FDA. For example, LASIK was performed using an excimer laser when the FDA had approved use of that laser for PRK but not yet for LASIK. A medical doctor is legally able to use a certain instrument or technology for any given procedure, whether or not the FDA has specifically approved that use. Manufacturers of excimer lasers have sought FDA approval of their laser for LASIK, but that is for marketing reasons and is unrelated to the legality of using it that way. Ophthalmic – Relating to the eye. Ophthalmologist – (ahf-thal-MAH-loh-jist) A medical doctor who specializes in diagnosing and treating eye conditions and diseases. Specialized training is required beyond medical school. Medical specialties are either medical or surgical, and ophthalmology is a surgical specialty, although not all ophthalmologists actually perform surgical procedures. Ophthalmoscope – (ahf-THAL-muh-skohp) A hand-held instrument with a light, used to examine the eye. It was first devised in 1915 by William Noah Allyn and Frederick Welch, who also founded the company Welch Allyn, which today manufactures many medical diagnostic and therapeutic devices. Optical Zone – That area of the eye where light passes through from the pupil to the retina. Light passes through the cornea, then the aqueous humor behind it, then the crystalline lens and the vitreous humor behind the lens, to the retina. Optical Ablation Zone – That part of the optical zone corrected by a laser treatment. Optic Disc – The circular area where the optic nerve meets the retinal nerve fibers, and where blood vessels enter the eye. It’s also known as the “blind spot” because this intersection with the optic nerve and presence of blood vessels interferes with the retina’s function as a camera film. Optician – (ahp-TISH-un) A technician who fits eyeglasses, sometimes grinds them from raw materials, places them in the frames, and verifies their final accuracy. Opticians can fit contact lenses in some states. Each state determines optician qualifications and most require a license for which the person must pass an examination conducted by the American Board of Opticianry (ABO). Some states also have their own exam the person must pass. Optic Nerve – A bundle of nerve fibers about one quarter of an inch wide, which runs between the retina and the brain, and connects with the retina’s nerve fibers. It carries visual information to the brain. Optometrist – (ahp-TAHM-uh-trist) A doctor of optometry (OD), which is not a medical degree. An optometrist diagnoses vision problems and eye diseases, and prescribes glasses, contact lenses, and drugs to treat disorders. They provide post-surgical care, but do not perform surgery. The education is at least three years and most optometrists have a B.A. or more. This is followed by four years at an optometry school, with an examination at the end. Some optometrists have further education and obtain M.A.s or Ph.D.s and can specialize in a variety of areas such as contact lenses, pediatric optometry, geriatric optometry and ocular disease. Overcorrection – A possible complication of refractive surgery, where the vision problem is over-treated, making, for instance, a nearsighted eye farsighted. Usually the overcorrection adjusts itself within months of the surgery. Sometimes overcorrection enhancement surgery can be done to correct the problem. See also undercorrection and regression.
Pachymetry – (puh-KIM-uh-tree) Testing of the cornea’s thickness, done to determine whether the cornea is strong enough for a LASIK procedure. It’s also done for some disorders where the cornea becomes thickened by excess water. The instrument used is a pachymeter. Penetrating Keratoplasty (PK) – A corneal transplant. A full-thickness, circular piece of the cornea is removed and replaced by a similar piece from a donor. It can restore vision to an eye which had previously been blind. Perioperative – Pertaining to the period of time between being admitted to hospital for surgery to being discharged afterwards. A perioperative nurse is one who cares for the patient throughout that time. Peripheral Vision – Also called “side vision”. Vision to each side of where the eyes are focused. Direct vision uses the fovea, the center part of the macula, which gives the most detailed vision. Peripheral vision uses the areas of the retina surrounding the macula which give less detail but better night vision. Without peripheral vision, a person would have only tunnel vision, and would be legally blind. Phacoemulsification – (fay-koh-ee-mul-sih-fih-KAY-shun) A surgical procedure which breaks up a lens containing a cataract, to make it easier to remove. It uses an incision of about 3 mm, through which the tip of an instrument delivers ultrasonic vibration. The resulting tiny pieces of lens material are removed by suction through that same instrument. A foldable artificial lens can be inserted through that same incision and the incision heals by itself. Phakic – An adjective describing an eye which has its natural crystalline lens intact. Phakic Intraocular Lens (P-IOL) – A removable artificial lens which is placed in front of the natural lens, to increase its focusing ability. Phoropter – A vision-testing instrument with many lenses, through which a person looks at the eye chart. As the lenses are switched, the person is asked which one gives the clearest images of the letters on the chart. On this basis, a prescription is determined for glasses or contact lenses. The eye chart is set first at 20 feet away, then at 16 inches away, to test both far and near vision. Phototherapeutic Keratectomy (PTK) – Use of an excimer laser to treat surface corneal irregularities, making the corneal surface smoother, and thus improving vision. This can be done along with a LASIK or other refractive surgery. Sometimes use of this technique can avoid a corneal transplant. Photoablation – The tissue removal done by an excimer laser in refractive surgery. This type of laser a has cool ultraviolet wavelength which is extremely strong. It breaks down the molecular bonds of the corneal tissue targeted, and also evaporates the remaining corneal fragments from the eye’s surface. The term “photoablation” means “light removal”. Photorefractive Keratectomy (PRK) – A refractive surgery like LASIK, where an excimer laser is used to reshape the cornea and correct myopia, hyperopia and astigmatism. It’s used for those who have corneas too thin to tolerate a LASIK procedure. Instead of the microkeratome being used to create the corneal flap, the laser is used, which can do it even more precisely and subtly than the microkeratome. Pink Eye – See Conjunctivitis. Posterior Chamber – The area behind the iris and in front of the vitreous. It’s filled with aqueous humor. Presbyopia – (prez-bee-OH-pee-uh) An impairment of vision which is age-related. Over time, the tiny muscles controlling the convexity of the crystalline lens become weaker. At the same time, the lens becomes stiffer. The result of these changes is that the lens can’t accommodate so well to changes in distance, and vision becomes blurry for near objects. This necessitates reading glasses. When a person who is mildly myopic develops presbyopia, the two conditions tend to cancel each other out. Presbyopia can’t be treated by refractive surgeries like LASIK, but can be treated by implanting an intraocular lens. Presbyopic Lens Exchange (PRELEX) – A term for a refractive lens exchange, where an intraocular lens is implanted to replace the eye’s natural crystalline lens. It’s a treatment for presbyopia. PRK – See Photorefractive Keratectomy. PTK – See Phototherapeutic Keratectomy. Punctal Plugs – Very small plugs of collagen, silicone or plastic that are inserted into any of the punctum (tear drains) as a treatment for dry eyes. One type is absorbable, lasting anywhere from a few days to several months, and if this makes the eyes better lubricated, non-absorbable plugs can be inserted as a long-term treatment. Placement is painless, taking less than a minute. Punctum – A tear drain in the eye. There are two in the upper lid and two in the lower lid. Tears are made by the lacrimal gland in the area above and outside the eye, and spread over the eye with each blink. If the eye is making insufficient tears, becoming dry and itchy, punctal plugs can be inserted, to keep tears within the eye. See also nasolacrimal duct obstruction. Pupil – The circular black opening in the center of the iris. It allows light to enter the eye. In dim lighting conditions, it opens wider and is controlled by tiny iris muscles. Testing the pupil dilation is often part of a neurological evaluation.
Radial – Pertaining to the radius of a circle, which is any line drawn from the center to the circumference. Radial Keratotomy (RK) – (keh-ruh-TAH-tuh-mee) A surgical treatment for myopia. A myopic eye has a cornea which is too steep, refracting light rays too much, so they land in front of the retina, instead of on it, for clear vision. To make the cornea slightly flatter, tiny incisions are placed around the pupil, angled from the pupil out to the edge of the cornea. The number of incisions and their exact location depends on the degree of myopia. Reading glasses – Framed lenses that increase visual acuity for close distances. They become necessary when presbyopia develops after about age 40. See also Bifocals and Trifocals. Refraction – The bending of light rays. To have clear vision, the eye must focus light rays on the retina, which means bending them as they enter the eye. Two structures in the eye perform refraction: the cornea and the crystalline lens. Refractive Error – Too much or too little bending of the light rays entering the eye, so that they focus not on the retina, which would give clear vision, but either in front of it (myopia) or behind it (hyperopia). When the cornea is slightly oval-shaped, rather than perfectly round, it has two curvatures, a steeper one and a flatter one. This also causes refractive error (astigmatism), bending the light rays in two different ways, so that they’re skewed and unable to focus. Refractive error is measured in diopters. Refractive Lens Exchange (RLE) – Also known as Clear Lens Exchange (CLE). A surgery which removes the crystalline lens from the eye and replaces it with an intraocular lens (IOL). This is essentially the same surgery that is performed for cataracts, where the cloudy lens is replaced with a clear one, except that it’s done to correct the refractive error of myopia or hyperopia, rather than to remove cataracts. Refractive Surgery – A surgery that permanently changes the focusing ability of the eye, done to improve or eliminate refractive errors. It could be either lens surgery such as RLE or P-IOL, or corneal surgery such as LASIK, PRK, Intacs or CK. The lens and the cornea are the two focusing structures in the eye. Regression – Return of the cornea after PRK or LASIK to its original refractive error. Post-surgical healing happens on both the surface (epithelium) where the flap was created and in the stroma (next level down, treated by the laser), and these two layers heal at slightly different rates. The planned treatment is designed to slightly overcorrect the refractive error so that after healing, the eye will have no refractive error. But some patients heal more quickly and vigorously than was expected, so that the cornea restores itself back to its original shape, and this is known as regression. See also undercorrection. Reis-Buckler’s Dystrophy – An inherited condition where a spontaneous erosion of the cornea impairs vision and causes increased light sensitivity and eye irritation. It involves the surface layer of the cornea (epithelium) and part of the stroma. It can appear anywhere from ages eight to twenty, and becomes more severe after about age forty. Also called Buckler’s Dystrophy and Buckler’s Syndrome. Retina – (RET-ih-nuh) The inside back surface of the eye, which is light-sensitive, and receives the visual information traveling in on the light waves which enter the eye. It converts the images into nerve impulses which are carried by the optic nerve to the visual center of the brain. Retinal Detachment – The retina has a layer of nerve tissue, and another layer which contains the blood supply. When these two layers separate, vision is lost at the separated area. It can be restored if the detachment is diagnosed early enough. Retinal Vein Occlusion – Blockage of a vein that carries blood from the retina. It can happen in a branch vein (branch retinal vein occlusion), or in the main vein that leaves the eye near the optic nerve (central retinal vein occlusion). Backed-up blood causes an increase of pressure within the vein and capillaries, leading to blood and fluid leakage on the retina. In some cases it can block the entire blood supply to areas of the retina, causing the cells to die and leading to retinal detachment. Retinitis Pigmentosa (RP) – Hereditary degeneration of the retina. It usually leads to legal blindness by progressively reducing peripheral vision. There are three main forms: • dominant, where about half of the family members develop the disease. • X-linked, for which the females are carriers and males develop the disease in alternating generations. • recessive, where there is no family history of the disease, but it occurs on occasion. Rigid Gas-Permeable (RGP) Contact Lenses – Also known as Gas-Permeable (GP) or oxygen-permeable contact lenses. Contact lenses which allows air to pass through them. They are hard, but more flexible than the older-style “hard” contact lenses which were used before 1971. They contain silicone, which is flexible and since it allows oxygen to pass through it, these lenses are more comfortable and healthier for the eye, which needs lots of oxygen. RK – See Radial Keratotomy RLE – See Refractive Lens Exchange
Sands of Sahara – See Diffuse Lamellar Keratitis Sclera – (SKLEH-ruh) The white outer layer of the eye, which is tough and protective. It joins smoothly with the cornea and continues in the back of the eye, connecting with the sheath that covers the optic nerve. Scotopic Pupil Size – The size of the pupil in dim lighting conditions, as in moonlight. Secondary Implant – In some cataract surgeries, the crystalline lens is not replaced. It can be replaced later with an intraocular lens, in a secondary implant procedure. Sjogren’s Syndrome – A chronic autoimmune disease where white blood cells attack glands which produce moisture, as in the eyes and mouth. About 90% of sufferers are female, and although it can occur at any age, it usually begins in the late 40s. About half the time it occurs along with certain other autoimmune diseases, such as Lupus and Rheumatoid Arthritis. It is systemic and can affect the digestive tract, blood vessels, liver, kidneys, and other organs. Symptoms include fatigue and joint pain, as well as dryness in the affected areas. Slit Lamp – A microscope with a strong light and a variety of magnification settings. It can be sized down to a slit for examining an eye and gives detailed views of the structures and fluids in the eye. Snellen Chart – The standard eye chart with one large letter at the top and lines of progressively smaller letters. It is used to measure central vision. Starbursts – A visual condition where light sources appear blurred with spikes projecting from the center. It can be a complication of refractive surgery and can also occur naturally. Strabismus – (struh-BIZ-mus) Also known as crossed eyes and turned eye. A vision condition where the eyes cannot be aligned. One eye turns out, up, or down while the other looks ahead, or both eyes may turn. It can be constant or intermittent. Strabismus impairs vision, as it reduces depth perception. Stroma – The central layer of cells in the cornea, thicker than the other layers. A LASIK or similar procedure targets this layer in correcting the shape of the cornea to improve vision. Stromal Dystrophies – A group of hereditary dystrophies affecting the stroma, the middle layer of the cornea (where LASIK surgery is done). There are three main ones: Macular Dystrophy, Granular Dystrophy, and Lattice Dystrophy. (Click here to read more about Stromal Dystrophies...)
Tear Duct – A tiny passage in the eye which carries tears. The lacrimal gland creates tears, the tear ducts carry them to the eye where blinking distributes them over the surface, and they drain out into the nose through the puncta, of which there are two in the upper lids and two in the lower lids. Topography – (tuh-PAHG-ruh-fee) The contours of a surface; as in corneal topography, which can be recorded by a corneal topographer. Toric Contact Lenses – Contact lenses designed to correct both myopia or hyperopia and astigmatism. They contain two curvatures at different angles and are effective for astigmatism only if they don’t rotate on the eye. Therefore they have a mechanism which keeps them stable. They can be soft or hard. Transition Zone – In a laser procedure, the area between the optical ablation zone and the untreated area of the cornea. The laser removes tissue more deeply in the center of the ablation zone, and gradually tapers off through the transition zone, to the original corneal tissue outside the ablation zone. Trephine – (truh-FEEN) A surgical tool with serrated edges, used to cut circular pieces. It’s used in a LASEK procedure instead of a microkeratome to cut the corneal flap. Trifocals – (TRI-foh-kul) Corrective eyeglasses with three powers of correction: far distance, near distance, and intermediate distance. Typical reading glasses are bifocals which use most of their surface to correct for far distance, and have a small area at the bottom edge which corrects for near distance (reading). Trifocals also have a middle area which corrects for intermediate distance. Bifocals and trifocals are usually prescribed for people with presbyopia. Tunnel Vision – Loss of peripheral vision, so that the eyes see only what is directly ahead. It can be caused by glaucoma or RP and may have other causes.
Undercorrection – A complication of refractive surgery where the outcome is less than was expected. It can occur when the eye heals up more quickly and strongly than usual, so that it undoes some of the corrective work done in the surgery. See also overcorrection and regression.
Variable Spot – A method of applying the excimer laser energy during refractive surgery. The computer that controls the laser is programmed to have it focus on spots of varying sizes across the ablation area, rather than equal-sized flying spots, or in a broadbeam fashion. Vision Therapy – A way of treating vision disorders usually prescribed and planned by an optometrist to improve weak visual skills. It is thought that there are twenty visual skills, such as accommodation, peripheral vision, spatial relations, visual memory and visualization. When one or more of these skills is weak or non-existent, many activities can be impaired, like sports, computer work, and reading. Vision therapy was practiced in Europe in the mid-1800s and began in the U.S. in 1928 by an optometrist. Other names for vision therapy are: eye exercises, visual training, and orthoptics. Visual Acuity – Clear vision with sharp details. Also called central vision. Visual Field – The complete area that’s visible when the eyes are looking straight ahead. VISX – A company that manufactures ophthalmic equipment. Their website. Vitreous Detachment – (VIT-ree-us) Separation of vitreous humor from the retina. If the gel pulls on the retinal surface, it can sometimes cause it to tear, which could lead to retinal detachment. Vitreous detachment occurs more often in older people and those with certain diseases such as diabetes. Vitreous Fluid – The jelly-like fluid that fills the main part of the eye, between the lens and the retina. It’s clear so as to give light rays an unobstructed path to the retina, and to keep that clarity, it contains phagocytes, cells which ingest and destroy foreign matter. Vitreous Humor – The transparent gel that fills the space inside the eye behind the lens and in front of the retina.
Wavelength – The distance between the top of one wave and the top of the next. Used of light waves. Specific wavelengths equate to specific colors. The excimer laser used in LASIK procedures is 193 nm in wavelength, which is an ultraviolet light (beyond the violet area, and therefore invisible to our eyes). Wavefront – Technology used to detect and measure higher order visual aberrations. These are the ocular aberrations other than the lower order aberrations of myopia, hyperopia, and astigmatism, which can be detected by a traditional eye examination. Some examples are glare, halos, and starbursts. The wavefront system shines its specific laser into the eye briefly, and that light is reflected back from the retina, through the pupil, and on to a wavefront sensor. This is done multiple times. What began as a straight laser beam is now a distorted one, after it has passed through the irregularities of that particular eye. The wavefront system records and measures those distortions and creates a 3-D map of the eye. From this map, a treatment is developed to correct the irregularities and improve vision. Wavefront Supported Corneal Ablation – The trade name for the Carl Zeiss Meditec WASCA aberrometer and the MEL 70 or MEL 80 excimer laser system when it’s used for wavefront guided excimer laser ablation for Lasik, Epi-Lasik, LASEK, PRK, and IntraLasik. WaveLight – An ophthalmic equipment company.
YAG Laser – YAG is an acronym for neodymium Yttrium-Aluminum-Garnet, which is the material used to create this laser. It’s a short pulsed and high-energy infrared light with a wavelength of 1064 nm. It’s used after cataract surgery to vaporize tissue. The crystalline lens is inside a capsular bag, which holds it in place. Cataract surgery fragments and removes the clouded lens but not the bag. Afterwards, many patients develop clouding in that bag tissue. The YAG laser vaporizes it in a post-operative out-patient procedure.
Zyoptix – Brand name for wavefront guided custom ablation on the Bausch & Lomb Technolas excimer laser.
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