Eyecare Glossary


An irregularity in the optics of your eye. Nearsightedness and astigmatism are just two of the most important. Everyone has at least a small amount of aberration, but in a healthy eye, they may not affect your vision. In keratoconus or other eye conditions, they can blur vision significantly.


Occurs when your eye changes focus from a distant to a near object. In our 40’s, it declines and results in presbyopia


Generally measured at 20 feet (20/20). 20/15 means that you can see at 20 feet what an average person can see at 15 feet, and is better than average. 20/40 means that you can see at 20 feet what an average person can see at 40 feet and is worse than average.

Advanced Surface Ablation (ASA)

A marketing term for PRK. It is the same procedure.


Occurs when your best-corrected visual acuity is decreased in an otherwise healthy eye. It occurs when the vision is not clear as a child and the signals to the brain are not refined to 20/20. It can be due to a number of factors, but extreme or uneven farsightedness and high astigmatism are the most common causes. Glasses, contacts, and LASIK cannot improve the vision to 20/20.


An opening, hole, or gap. A space through which light passes in an optical or photographic instrument.

Artificial Tears

An over the counter product that can be used as frequently as needed for the temporary relief of dry eyes.


An irregular shape of the front surface (cornea) of the eye that creates distortion in vision. Imagine a half of a tennis ball that is squeezed slightly on the edges to make it less than a perfect sphere.

Best-Corrected Vision

Refers to the smallest letters you can see on the vision chart with the best possible glasses, contact lenses, or vision correction outcome. 20/20 vision is just a reference point. Most young healthy people will be able to see letters on a vision chart that are better than 20/20 with corrective lenses. If you have some sort of pathology, be it cataracts, amblyopia, macular degeneration, or any of a thousand other reasons, you may not be able to achieve 20/20 vision even with glasses. At SharpeVision, 96% of our patients can see 20/20 or better without glasses after their vision correction. About 2% of our patients have a preoperative best-corrected vision that is less than 20/20 (that is, they have never seen as clearly as others, even when they had their glasses on). About 2% of our patients will need a touch more laser to see perfectly, which is called an enhancement


A glasses lens where one part is focused for near vision and one part for distant vision. With contacts, there are rings on the lenses that allow near and distant vision, but they slightly blur your vision and create more glare when looking at light at night.


The uncontrolled squeezing of the muscles around the eyes, which can be disabling due to the inability to open your eyes. Botulinum toxin produced by the bacterium clostridium botulinum is used to relieve blepharospasm, migraines, and other neurological conditions. It prevents the release of the neurotransmitter acetylcholine from nerve endings at the neuromuscular junction and prevents muscle contraction.


A cataract occurs when the usually clear lens of the eye becomes cloudy, which impairs vision. Everyone will get them if they live long enough, and although it usually occurs in our 60’s and 70’s, it can happen at any age.


Like a pimple, it’s a red lump in your eyelid that is a result of a blocked oil gland (Meibomian gland). It can be tender and unsightly. They are treated with warm compresses and massage to try to open up the gland. An eye surgeon can remove them in an office procedure.


Something you were born with and present at birth.


The clear membrane that covers the sclera. When it is inflamed, it’s called conjunctivitis


An inflammation of the conjunctiva that can be from many causes.


The clear dome of tissue that covers your eye. It is reshaped in LASIK and PRK to change the curvature of your eye and allow you to see clearly without glasses.

Corneal Ectasia

A weakening of the cornea causing it to stretch and change shape. It can prevent clear vision or even lead to the need for a corneal transplant. Keratoconus is a type of ectasia.

Corneal Epithelium

The layer of skin cells that covers the clear tissue of the cornea. It is removed in PRK surgery and grows back quickly. It’s the fastest healing tissue in the body and migrates across the surface at about 50μm per hour to repair a defect.

Custom LASIK

Another name for Wavefront Guided LASIK and Topography Guided LASIK.

Depth Perception

The ability to judge the distance of objects from the observer. It involves size, shadows, and other visual cues, and can be fooled or very inaccurate. It does not require two eyes to determine, and therefore depth perception can be maintained with monovision.


The process of putting drops in your eyes that enlarge your pupils so that our doctors can see into the back of your eyes.


The unit of measure of the light focusing power of a lens. It is the inverse of the focal length (in meters). For example: if your contacts are -4, then your vision is blurry for objects that are 1/4 meters (10 inches) away. That means you can see clearly unless an object is more than ten inches away from your eye. This is the average that we see at SharpeVision.


Seeing double. It can be from one or both eyes, and can be the result of a muscle imbalance, uncorrected astigmatism, or other causes. It does not always arise in people with strabismus, as they may suppress one of the images, and not be aware or bothered by double vision.

Dry Eye

A condition where you don’t produce enough tears to lubricate and nourish the eye. Dry eye is very common and risk increases as you age. Contact lens use and refractive surgery can be a factor in developing the condition. It is treated with over-the-counter artificial tears or prescription eye drops.


The brand name of the most potent topical steroid available. It’s used to control inflammation after eye surgery and is only available by prescription.


Additional laser treatment to an eye when the desired refractive result was not achieved. An enhancement is needed after about 2% of all treatments. It’s less likely in younger people with lower prescriptions, but can be needed by anyone and at any time after their first vision correction treatment. Enhancements needed during the first year following you procedure are free of charge. For lifelong coverage, we offer LASIK4LIFE, exclusive to SharpeVision. See Pricing.

Epithelial Ingrowth

A LASIK complication in which epithelial cells grow under the LASIK flap. It is rare during the initial procedure, but occurs in a small percentage of people after an enhancement procedure. It can sometimes affect vision and require the flap to be lifted and the cells removed.

Excimer Laser

The laser we use to reshape your eye. It uses a specific wavelength (193nm) of invisible light energy to precisely remove tissue to just the right amount to allow you to see clearly without glasses or contacts.


The Food and Drug Administration is a branch of the federal government that protects the public through oversight of drugs and medical devices (among other things).

Femtosecond Laser

A femtosecond is one quadrillionth of a second and refers to the amount of time of each pulse of the laser. This laser is the unbelievably precise tool we use to create the LASIK flap.


These occur when small amounts of collagen in the vitreous clump together and cast a moving shadow on the retina. They can be bothersome to disabling but can be removed by a vitrectomy or reduced by a laser treatment.


The “fear of missing out” on something awesome because you lost a contact or forgot your glasses.

Galilei G4

One of the advanced topographic devices we use that measures the curvature, thickness, and size of your cornea. The results help our doctors determine your candidacy for vision correction and the plan for your treatment.


A disease of the optic nerve in which there is progressive loss of nerve fibers that cause a pattern of peripheral vision loss. It is most commonly associated with elevated eye pressure and is managed with eye-drops or surgery.


The term used to describe the glow around lights at night. They are always present immediately after LASIK, but dissipate over 6-8 weeks. They are very similar to what you’d see with a good pair of contact lenses.

Heterochromia Iridis

When your two irises are of different color. There are a few reasons for this, but it’s usually benign.


Also called farsightedness. Hyperopia occurs when your cornea is not curved enough for the length of your eye. It can make near objects blurrier than distant objects, hence you can “see far.”

ICL (Implantable Contact Lens)

A soft biocompatible lens that is placed inside your eye to allow you to see clearly without glasses or contacts. It is an excellent way to correct vision and can be used when LASIK or PRK is not an option. It does not remove any tissue, is reversible, and provides excellent quality of vision. It was FDA approved in 2005 and can now also treat astigmatism.

Infrared Tracking

This technology allows the laser to remain completely focused on the center of the eye, even when the patient moves. You don’t have to worry about keeping your eye perfectly still. The tracker follows the heat given off by your iris. Cool, huh?

IOL (Intraocular Lens)

The artificial lens that replaces your cloudy lens (cataract) and allows you to see clearly at a distance with a single vision lens. A multi-focal IOL is needed to see both distant and near objects clearly.


This is the colored part of your eye. It is actually a muscle that controls the amount of light allowed into your eye through the pupil.


An inflammation of the iris. It can be due to a systemic inflammation such as sarcoidosis, arthritis, or other autoimmune condition. Iritis is generally treated successfully with steroids.

Kamra Corneal Inlay

An extremely thin circular device with a 1.6mm opening that is placed in a pocket in the middle of the cornea. It uses small aperture optics to improve near vision for patients with presbyopia.


A weakening of the cornea that occurs in about 1 in 2000 people. We screen for it during your eye exam.

Lacrimal Glands

The glands in your eye that produce your tears.


Laser Epithelial Keratomileusis. This refers to repositioning the removed epithelium on the surface of the eye after PRK. The technique has been found to not aid in the healing process and has been largely abandoned.

Laser Vision Correction

Refers to either LASIK, PRK, or SMILE

LASIK (Laser Assisted In Situ Keratomileusis)

A mouthful that means reshaping the cornea with a laser. The long definition: a surgical operation to reshape the cornea for correction of myopia, farsightedness, or astigmatism in which the surface layer of the cornea is separated to create a hinged flap providing access to the inner cornea where varying amounts of tissue are removed by an excimer laser.

Lubricating Ophthalmic Ointment

An over-the-counter (OTC) product that contains mineral oil and petrolatum, the same ingredients as Vaseline. It is used at night to relieve more severe dry eyes. A helpful trick is to run the tube under hot tap water for about 20 seconds to make it more liquid. Use only a tiny amount, as any more than that will get on your eyelids and pillow.


The most sensitive part of the central retina. It’s responsible for your best visual acuity and color vision.

Macular Degeneration

The most common cause of legal blindness in the United States. It occurs from damage to the eye’s macula that results in the loss of central vision. The exact cause is unknown, but it appears to be related to a genetic predisposition, smoking, and several other risk factors. Central vision may be blurred or distorted before severe vision loss occurs.

MFIOL (Multi-Focal Intraocular Lens)

An artificial lens that allows you to see both distant and near objects without glasses. They do require a more than normal amount of light to see well up close, and most people will initially see rings around lights. These dissipate over 6 to 12 weeks. They are a great option for someone who never wants glasses.


For people over 45 who are finding they are in need of reading glasses. We use a laser to correct one eye to focus on near objects and the other eye to focus on distant objects. This may seem strange at first, but it works quite well! It can be easily reversed if you don’t get used to it, but we don’t end up needing to reverse it very often. It’s been done with contact lens wearers for decades, and we like to have you test it out first with contacts before the procedure.


Also called nearsightedness. It occurs when your eye is more curved than it needs to be for its length and makes distant objects blurry. You see near objects clearer.


See Myopia

Ocular Migraine

An ocular migraine refers to the visual aura created in the brain that is generally, but not always, followed by a headache. The aura can produce flashing lights, peripheral colors, or blind spots. The aura lasts anywhere from ten to sixty minutes on average, but can last longer.


One of the advanced devices at SharpeVision that measures the Optical Path Deviation of your eye. In simple terms, it measures your prescription for glasses as well as any other aberration due to corneal or lens irregularities. It then transfers that data to the laser.

Ophthalmologist (pronounced: Off-thal-mall-oh-jist)

A medical doctor (MD or DO) who trains for 12 years after high school to perform surgery on the eye. An ophthalmologist completes 4 years of college, 4 years of medical school to get an MD, and then 4 or more years at university learning eye surgery and pathology. They can spend an additional two years to sub-specialize in corneal, retinal, neurologic, oculoplastic, glaucomatous, orbital, or pediatric diseases of the eye.

Optic Nerve

The nerve that carries all the input from your eye to your brain.


A person who is trained and licensed to fit and dispense glasses.


A doctor of optometry (OD) who completes 4 years of college and 4 years of optometry training.


The examination of the eye for defects and faults of refraction and prescribing of correctional lenses or eye exercises.

OTC (over-the-counter)

Anything that can be purchased without a prescription from a health care provider.


This refers to the statistics for any given procedure/surgeon to achieve the desired result. At SharpeVision, we follow all our outcomes data and achieve 20/20 or better uncorrected vision in over 96% of our patients undergoing LASIK or PRK.


The removal of corneal tissue by the laser that occurs without heating it due to a specific wavelength of excimer laser energy.


A degeneration that appears as a small pinkish elevation on the conjunctiva. It is harmless, but aesthetically bothersome. They are generally not removed because the scar can be worse than the pinguecula.


A type of conjunctivitis that is often caused by a virus. It is highly contagious and can last from 7 to 10 days. It is generally treated with supportive care and hygiene to prevent its spread. Antibiotic drops are often prescribed, but have no effect because they don’t kill a virus.

Prednisolone Acetate

A prescription-only topical steroid that is used to control inflammation in the eye, whether it’s from surgery or any other cause.


A condition that happens to everyone at around 45 years old and is a result of the loss of flexibility in the lens of your eye. The lens is what allows the focusing power to change from distance to near vision, and when it starts to become rigid, you lose the ability to focus on objects up close. Unfortunately, no one will naturally have clear distant and near vision in both eyes forever, but we can demonstrate monovision as an option to allow you to see both distance and near without glasses.

Prescription Glasses

The lenses of prescription glasses have three parts: sphere (amount nearsighted or farsighted), astigmatism amount, and direction. Bifocals can be added on top.

PRK (Photorefractive Keratectomy)

Approved in the US in October of 1995, it is as effective as LASIK and is preferred for those with thinner corneas or higher prescriptions. The two procedures are so alike that when someone says they had LASIK, they could have really had PRK. The laser resurfacing of the cornea to improve your vision is exactly the same as LASIK. The difference between the two procedures is that with PRK, a small amount of the corneal epithelium is lasered away to reach the cornea instead of creating a flap in the epithelium that is pulled back and then replaced. Contact lenses have to be worn for about a week after PRK to allow the epithelium to grow back.


A healing response due to injury of the cornea. It appears as the conjunctival tissue migrates out onto the cornea and can cause astigmatism or even block one’s vision. It can be removed, but sometimes returns.


(Pronounced TOE-sis) A drooping of the eyelid that can be congenital, paralytic, mechanical (from a tumor or other mass effect), or drug induced.

Punctal Plugs

Small temporary or non-dissolving plugs that are placed into the small duct at the inside corners of your eyes to prevent tears from escaping down the sinuses. They can effectively treat dry eyes.


The circular opening in your iris where light enters. It’s the black part of the eye.


The measure of your prescription for glasses, contacts, or vision correction surgery.


A prescription eye-drop for dry eye that works by decreasing inflammation in the lacrimal gland which allows for greater tear production. Its only competition in this class is Xiidra


The light sensitive neural tissue that lines the back of your eye. Think of it like the film in a camera.

RGP Lenses (Rigid Gas Permeable Contact Lenses)

These lenses can alter the shape of your eyes and must be removed for at least three weeks prior to your laser treatment, so we can measure the natural shape of your eyes.


The white part of your eye.

SMILE (Small Incision Lenticular Extraction)

This procedure uses a femtosecond laser to create a small lens in the middle layers of the cornea. The small lens (lenticule) is then removed through an incision at the edge of the cornea. It was approved for myopia with astigmatism in September of 2018.

Soft Contact Lens

This is the most common type of contact lens. They can be spherical (don’t correct astigmatism) or toric (correct astigmatism) and should be removed from your eyes at least three days prior to treatment (wear your back-up glasses instead). This minimizes the amount of bacteria in your eyes and allows accurate measurements of your prescription.


A term referring to the way your brain perceives depth and 3-dimensionality due to slightly different images coming from each eye. It’s different from “depth perception” in that depth perception can be achieved with one eye on the basis of visual cues (i.e. size, shadows, and relative positioning of objects).


A misalignment of the eyes due to an imbalance of the muscles and a lack of binocular vision. It can be congenital, the result of an illness, or the paralysis of the muscles of the eye. It can sometimes be corrected with glasses, eye-muscle surgery, or injected botulinum toxin.

Topography Guided LASIK

Also known as Custom LASIK. They are the same procedure.


The FDA approved device that increases tear production by stimulating the nerves in the nasal cavity.


What you will think to yourself (and sometimes say out-loud) in the laser room after your procedure when you sit up and see the room clearly without aid from glasses or contacts. It’s like magic.

Visual Acuity

Sharpness of vision, measured by the ability to discern letters or numbers at a given distance according to a fixed standard. Optometrists use the distant of 20 feet as the standard: 20/20 means you can see from 20 feet away objects that should be clear from that distance. 20/50 means you must be as close as 20 feet to see what a standard person can see 50 feet away.


A procedure to remove all the vitreous (gel) that fills the back of our eyes. It is very effective at clearing floaters, but has a higher surgical risk and almost always causes a cataract to form.


The clear gel like material that fills the space in our eyes that is behind the lens but in front of the retina.

Wavefront Guided LASIK

Also known as Custom LASIK or Topography Guided LASIK. This technique treats your specific amount of nearsightedness and astigmatism as well as any irregularities that are found in the optics of your eye. Most people who see well with glasses will benefit 1 to 4% from this technology by possibly having better quality of vision in dim light. Visual acuity is not generally improved.


The distance between successive crests of a wave, especially the points in a sound wave or electromagnetic wave.


A prescription eye-drop for dry eye that works by decreasing a specific inflammation in the lacrimal gland which allows for more tears to lubricate the eye. Its nearest competitor is Restasis.


“You only live once”- So why wear contacts?


The trade name for LASIK when the Ziemer® Femto LDV Crystal Line and Z4 lasers are used. They have a pulse rate that is 20 times faster and with less energy than other femtosecond lasers, which allows for faster recovery of vision and shorter procedure time. We use Ziemer femtosecond lasers in all of our offices.

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