Glossary of Terms
- 20/20 vision
This is generally considered to be the average visual acuity. 20/20 means that you can see clearly at 20 feet what the average person can at 20 feet. 20/40 means you can see clearly at 20 feet what people with 20/20 vision can see at 40 feet. But 20/20 is the best vision possible. There are people with 20/15 or even 20/10. In most areas of the United States, a driver’s license requires uncorrected vision of no worse than 20/40. - Aberrometer
An instrument that projects light and then captures the reflected light waves off the eye in order to measure aberrations and refractive errors. - Ablate, ablation
The surgical removal of tissue, frequently with a laser. - Accommodation
The ability of the natural lens of your eye to change shape in order to focus on objects at various distances. - Accommodative lens
This is an artificial lens surgically inserted into the eye in order to remedy vision problems associated with the natural lens. - Astigmatism
A very common type of refractive error. The cause is an irregularity in lens of the eye or the curvature of the cornea. These conditions make fine details hard to see at some distances. - Best Corrected Visual Acuity (BCVA)
This means the best vision correction that can be achieved with contacts or glasses.As an example, if your uncorrected vision is 20/175 but you can see 20/20, this means you have a BCVA of 20/20. - Best Uncorrected Visual Acuity (BUCVA)
Refers to the best vision that can be achieved without correction. So, if your uncorrected vision is 20/200 without glasses or contacts, your BUCVA is then 20/200. - Bowman’s membrane
The layer of corneal tissue between the stroma and the epithelium. - Cataract
This condition is the clouding of the lens in the eye, which blocks light reaching the retina and results in vision that is impaired. Frequently caused by normal aging, when protein clumps form and cloud portions of the eye’s lens. As you age, cataracts usually worsen and if uncorrected will require the damaged lens to be replaced with an artificial lens. - Cornea
The front part of your eye is where your cornea is found. The surface of the cornea, which is curved and clear, is the location at which light enters. It’s often referred to as the ‘window of the eye’ and also provides some external protection for the eye. Many types of vision correction surgery reshape the cornea to correct nearsightedness, farsightedness, and astigmatism. - Corneal flap
At the start of LASIK surgery, a very thin slice of tissue is made on the cornea’s surface. This flap of tissue is then folded back so that the LASIK surgery can reshape the inner layers of the cornea to correct refractive errors. - Corneal topography
The process by which light is projected onto the eye’s surface. The reflected light is measured and used to create a map of the curvature of the cornea and record any irregularities. This map is then used for things such as contact lens fitting, evaluations related to refractive surgery, measuring astigmatism and to assist with the management of corneal disease.. - Dilated
The literal meaning is ‘made wider or larger’, but in regards to the eye it refers to the process by which drops are used to open or dilate the pupil during an eye examination. - Diopters
Refers to measurement of refractive errors in vision. The measurement of nearsightedness is shown in the numbers of ‘negative diopters’, such as -1, -2, -3 and so on. Farsightedness is stated in values of positive diopters (+1, +2, etc). Most vision errors are in the range of -6 to +6 diopters. - Dry eye
Refers to corneal dryness as a result of low tear production. - Endothelium
The inner layer of cells in the cornea. - Epithelial ingrowth
A condition where cellular tissue from outside of the cornea grow underneath the corneal flap. This is one of the possible – although uncommon – complications of LASIK surgery. - Excimer laser
This is one type of laser equipment, the purpose of which is to reshape the cornea and remove tissue from the cornea. An excimer laser is a ‘cold’ laser which emits ultraviolet light. - Farsightedness (hyperopia)
A very common vision problem in which close-up vision is blurry. It’s caused by too little curvature of the cornea, or in some cases not enough distance between the front of the eye and the retina at the back of the eye. In both cases, light entering the eye incorrectly focuses on the retina, which causes the blurred up close vision. - Femtosecond Laser
A very precise laser used in ‘bladeless’ LASIK to cut the corneal flap. - Glare
May be a side effect of LASIK surgery or can be caused by cataracts and other eye conditions. Glare causes additional luster to appear around lights and causes interference especially with night vision. If caused by LASIK, glare will frequently go away after a period of time. - Halos
Halos can make rings to appear around lights at night. The causes are the same as with glare and, like glare, halos will often decrease over time if caused by LASIK. - Higher order aberrations
These are more complex eye irregularities and can cause several vision problems, such as: glare, haros, poor night vision, starburst or even double vision. They can be mild and not cause noticeable problems and most people have at least some degree of higher order aberrations. Modern wavefront technology can now measure these aberrations and they can be corrected by options such as corrective lenses and various types of laser surgery procedures. procedures. - Intraocular pressure
When tension between the eye itself and the fluid within the eye causes pressure in the eye. - Intraocular lens (IOL)
These are lenses that are implanted in the eye either in front of the natural lens or to replace the natural lens. They are designed to improve focus, as well as correct vision problems. - Iris
Is the colored part of the eye. By opening and closing the pupil, the iris is able to regulate the amount of light entering. - Keratoconus
A degenerative eye disorder that causes thinning of the cornea. The result is the cornea changes from a normal gradual curve to a shape that is more conical. This can cause multiple vision problems, including distortion, multiple images, light sensitivity and streaking. It starts in adolescence and reaches peak severity in the patient’s 20’s or 30’s. - Keratomileusis
The use of a lathe and blade to reshape the cornea. This technique was used prior to the development of LASIK. - Keratometer
A keratometer is a device that measures the cornea’s curvature. These measurements are used by eye doctors for contact lens fittings and to assist with eye surgery. - Keratotomy
An incision of the cornea. - Laser vision correction
Eye surgery that uses a laser to reshape the cornea and correct vision errors. Types of laser surgery include: PRK, LASIK, LASEK, and Epi-Lasik. - LASIK (laser in-situ keratomileusis) surgery
A form of laser eye surgery that improves vision by reshaping the cornea. One type of laser is used to create a thin flap of corneal tissue, which is then folded back and a different type of laser is used to reshape the cornea. The flap is then placed in its original position for healing. - Lens
Is a transparent disk located behind the pupil. Light is focused on the eye’s retina by passing through the lens.The lens frequently can become cloudy with age, which is called a cataract. - Low vision
Refers to sight that can’t be corrected with glasses, contacts or eye surgery. This is usually a result of some sort of eye disease such as macular degeneration or glaucoma. - Lower Order Aberrations
Deviations from normal vision are known as aberrations. Blurred images are an example, as are nearsightedness, farsightedness, astigmatism and presbyopia. These are most of the vision imperfections. They are normally identified using a variety of vision tests - Macula
The macula is that part of the eye that resides close to the middle of the retina. Its purpose is to allow objects to be seen in detail. - Microkeratome
A very precise surgical instrument used during LASIK eye surgery to create the corneal flap. - Monofocal (or “standard”) intraocular lens
An artificial lens that is implanted in front of the natural lens or to replace the natural lens. Its purpose is to provide clear vision for a fixed focal point, which is usually distance vision. - Multifocal intraocular lens
An artificial lens implanted in front of the natural lens, or to replace the natural lens, in order to correct near, medium and distance vision in the same lens. - Mixed astigmatism
Astigmatism (which is an abnormal curvature of the cornea) that causes vision problems at both near and far distances. - Myopia
Is also know as nearsightedness. This is when either too much corneal curvature or the eye’s length is too long, which causes light rays to focus incorrectly in front of the retina instead of right on it. The result is distance vision that is blurred. Myopia is the easiest – and most successful – condition that can be treated with LASIK or contacts or glasses. - Ophthalmologist
A medical professional who is either a Doctor of medicine (M.D.) or doctor of osteopathy (D.O.). Both are qualified to treat all eye disorders, including eye surgery. - Optometrist
An eye care professional who is trained to give basic eye care services, such as basic eye health evaluations and vision exams, but who is not a medical doctor - Presbyopia
This is a common vision problem which develops over time naturally. Basically, the eye loses its ability to focus up close or on fine details. It can be treated with reading glasses, contact lenses, or eye surgery. - Presbyopia Lens Replacement Surgery
One of the types of eye surgery that can treat Presbyopia. It’s a procedure that replaces the eye’s natural lens with an artificial lens, which is called an intraocular lens. Cataracts, nearsightedness, farsightedness and astigmatism are all conditions that can be corrected by lens replacement. - Pupil
Is the round, black area at the center of the iris. The pupil controls the amount of light entering the eye by opening and closing itself. - Refraction
A refraction test is used during an eye exam in order to determine the amount of correction needed by eyeglass lenses. The most common way to test is to place a variety of lenses in front of the patient’s eyes and asking which ones make the eye chart clearer. - Refractive error
Refractive error refers to the abnormalities in the cornea, lens, or eye shape, all of which can interfere with focus. - Refractive surgery
Any eye surgery that corrects a patient’s refractive error. Both lens replacement and LASIK are common types of eye surgeries. - Retina
The transmitter at the back of the eye that sends images via the optic nerves to the brain. - LASIK enhancement
An additional LASIK treatment, used when the results of the first LASIK treatment are not as successful as anticipated. - Sclera
This is the part of the eye that is white. Along with the cornea, it givesexternal to the eye. - Small Incision Lenticule Extraction (SMILE)
This is a newer, minimally invasive laser eye surgery procedure, for patients with nearsightedness (with or without astigmatism). A very precise ‘femtosecond laser’ is used to slice a thin disk of tissue from withing the cornea, which leaves most of the surface of the eye undisturbed. The tissue disk is removed through a small opening on the eye’s surface. This improves vision by reshaping the cornea. - Snellen chart
The standard eye chart used to test vision. It contains letters, numbers or symbols in rows of decreasing size. - Stroma
The middle layer of the cornea. It consists of collagen and cells, which together make up the majority of the cornea. - Starbursts
Rays of lights that appear to be coming off a light source, such as the headlight beams of a car. They frequently become denser and longer at night. These can be a side effect of LASIK eye surgery, in which case they often decrease or disappear over time, but can also be caused by cataracts and other eye conditions. - Visual acuity
Refers to how sharp your vision is, which us usually measured by a Snellen Chart. Normal visual acuity is considered to be 20/20. Some people have even better vision such as 20/15 or even 2010. - Vitreous fluid
The clear fluid that fills the eyball between the retina and the lens. - Wavefront
A device that transmits a ray of light into the eye. This light is reflected back from the retina, out through the pupil, where the wavefront device captures and arranges it into a unique pattern that records the specific refractive errors for that patient. These irregularities are displayed as a three dimensional map, which is called a wavefront map.