Eye to Eye

Eye Health Definitions & Conditions

Confused by eye conditions and terms? Learn about eye health. Use our small glossary to familiarize yourself with eyecare terms and diseases.


What those fancy words really mean... A glossary of terms.

Accommodation—The ability of the eye to focus clearly on any object.

Acuity—See "Visual Acuity".

Amaurotic EyeA blind eye.

Amblyopia—Lowered visual acuity in one eye. Also called a "lazy eye". An amblyopic eye cannot see 20/20, even with correction, and there is no medical reason for the decreased acuity.

AniridiaAbsence of an iris.

Anisocoria—When one pupil appears to be bigger than the other. Approximately twenty percent of the population is born with anisocoria.

Aqueous Humor—The fluid located in the front of the eye. This fluid is made by the ciliary body and keeps the front of the eye round and healthy. Aqueous humor maintains its own pressure and can change throughout the day. This pressure is what we measure to assess risk for glaucoma.

AsthenopiaAlso called eyestrain. A feeling of fatigue, discomfort, or pain around the eyes after using the eyes for a long period of time.

AstigmatismAn eye with astigmatism does not have a perfectly round cornea. The cornea is the clear dome in front of the colored iris. It is instead, shaped like a football. Because of the shape of the eye, light comes into the eye at different angles, which can make seeing objects at both distance and near difficult.

BlepharitisAn inflammatory condition affecting the eyelid margins around the eyelashes. As debris builds up around the eyelashes, the oil glands of the eyelids get clogged and inflamed. Since your tear film is made of oil and tears, this lack of oil leads to a deficient tear film. This is one cause of dry eye syndrome.

Cataract—The yellowing and hazing of the crystalline lens of the eye.

Ciliary bodyA structure inside the eye that creates the fluid in the front of the eyeball (aqueous humor). The ciliary body also has a ciliary muscle that helps our eyes focus from far to near by pulling on the lens and changing its shape.

ConjunctivitisAn inflammation of the tissue called the conjunctiva. The conjunctiva is the clear tissue located over the sclera, the white part of the eye.

CorneaThe clear portion of the eye that is the first surface light passes through on the way to the retina. The cornea is located over the top of the iris.

Crystalline LensThe part of the eye behind the iris that aids in focusing by changing shape with the help of the ciliary body. With age, this lens hardens and will no longer change shape (presbyopia), and eventually will start to yellow and haze forming a cataract.

DiopterThe unit of measurement we use to determine your prescription. It is designated in quarter intervals.

DiplopiaDouble vision.

EctropionWhen the lower eyelid turns outward. This condition causes tears of the eye to overflow and run down the cheek.

EmmetropiaThe normal refractive state of the eye, no prescription at all. This eye is not farsighted, nearsighted, or have astigmatism.

EntropionWhen the lower eyelid turns inward. This condition causes the lower eyelashes to rub against the cornea.

EyestrainSee asthenopia.

GlaucomaAn eye disease characterized by the atrophy of the optic nerve most often caused by the elevation of the fluid pressure inside the eye (intraocular pressure). This results in peripheral vision loss.

HordeolumAlso called a stye. This is an infection of an eyelash follicle.

HyperopiaFarsighted. The ability to see at a distance easier than up close.

Intraocular pressureThe ciliary body inside the eye makes a fluid called aqueous humor. This fluid keeps the front of the eye round and healthy. The intraocular fluid pressure inside the eye, caused by the creation and drainage of this fluid, is what is monitored to determine your risk for glaucoma.

KeratoconusA corneal degeneration, usually beginning during teenage years, and progresses slowly throughout life. The front lower portion of the cornea starts to thin and push forward creating a cone shape.

MyopiaNearsighted. The eye cannot see objects far away, only up close.

NystagmusA repetitive, rhythmic, involuntary movement of the eyes.

OphthalmologistAn ophthalmologist is a medical doctor who specializes in eye health. He or she has completed a four-year undergraduate program and a four-year medical school program, completing a medical doctor (MD) or doctor of osteopathy (DO) degree. After medical school, a three-year residency in ophthalmology is required to become an ophthalmologist. Most often, ophthalmologists provide care in severe cases of eye disease and invasive surgical procedures.

OptometristAn optometrist completes a four-year undergraduate program, and then a four-year professional program at an optometry school, resulting in a Doctor of Optometry (OD) degree. An optometrist is a health care provider who examines, diagnoses, and treats disorders and diseases within the visual system, the eye, and related systemic conditions. This may be done with glasses or contact lenses, medications, or non-invasive surgical techniques (like removing a foreign body from the surface of the eye).

Optician—An optician is a technical practitioner who designs, fits, and dispenses corrective lenses and frames for the correction of a person's vision.

PingueculaA benign, elevated, yellowish-white mass of tissue located on the white part of the eye near the iris. This is much like a callous on the eye. It is not dangerous, and does not normally need treatment.

PresbyopiaThis usually occurs around the age of 40. The crystalline lens inside the eye hardens and will not change shape to focus up close anymore. Usually a person can wear magnification, like bifocals, to help with this sometimes sudden and frustrating loss of focusing ability.

PterygiumA fold of tissue that extends from the white part of the eye onto the cornea. This is usually seen in individuals who spend a lot of time outside in sunny, windy, and dusty places without proper sunwear. This growth is benign, but can grow into the pupil area and compromise vision. It should be removed with surgery.

Sclera—The white part of the eye.

StereopsisThe ability to see depth; depth perception.

UveitisAn inflammation of the iris and/or ciliary body.

Visual acuity—A term used to express the clarity or sharpness of vision measured at a distance of 20 feet. If you have 20/20 vision, you can see clearly at 20 feet what should normally be seen at that distance. If you have 20/100 vision, it means that you must be as close as 20 feet to see what a person with ideal vision can see at 100 feet.


Eye Conditions & Diseases


Cataracts are a normal change in the crystalline lens of the eye. Over 85% of the population over the age of 60 will develop cataracts. As the lens ages, it yellows and hazes causing blurred vision and a decreased ability to see color and contrast. Cataracts also cause glare, especially during night driving. Cataracts generally progress slowly and do not harm the eye, only decrease your vision. Once a cataract has grown enough to negatively affect your vision, surgical removal is the only way to improve your acuity.

Computer Vision Syndrome

Our visual system was not designed to stare at a computer all day. Our eyes can become very strained if we do not take the proper precautions to rest our focusing abilities. We recommend the 20/20/20 rule. Every 20 minutes, refocus your eyes at least 20 feet away from your computer for about 20 seconds. This can reduce the tired, strained feeling you have at the end of the day. If this does not help, you may want to visit your optometrist and discuss a prescription for computer glasses to aid in relaxing your eyes.


Diabetes can cause dramatic changes within your eye. The fluctuation of blood sugar levels within the body can lead to weakness and damage of blood vessels in your eyes. This damage causes leakage of fluid and blood that can injure the tissues surrounding the blood vessels, which can lead to blindness if left unmonitored and untreated. It is of utmost importance to monitor and maintain a healthy blood sugar level and receive at least a yearly dilated eye exam.

Flashes & Floaters

The vitreous is the gel inside the eye that keeps the eye round and whole. This gel has the consistency of Jell-O. As we age, it will liquefy, change shape, and pieces of the vitreous may be liberated. These pieces floating around inside the gel are called floaters. They can range anywhere from small spots or "gnats", to long lines, or large "spider webs".

The vitreous is attached to the retina of the eye. Occasionally, the vitreous will separate, pulling part of the retina along with it. When this occurs, you may experience a bright flash of light that can be followed by a new floater, or a shower of new floaters. You may also observe a “curtain” of darkness in part of your vision. If this happens, you should be dilated immediately to be sure there is not a hole or tear in the retina. Holes and tears can be treated with laser surgery by a retinal ophthalmologist.


This is a progressive disease of the eye that can lead to blindness if not treated. Glaucoma initially affects your peripheral vision, but will slowly work inward and affect your central vision if it becomes severe. Glaucoma most often damages silently, with no pain or side effects. Basically it's a higher than normal fluid pressure inside of the eye that eventually damages the optic nerve and causes loss of peripheral vision. Fortunately, treatment options do exist to reduce the progression of this disease, so a regular eye exam is very important. There are many prescription eye drops used to decrease the eye pressure and help reduce damage. Recent studies have now shown that many individuals can benefit from these eye drops as a preventative measure if they are found to have dangerously elevated pressures.

Macular Degeneration

The macula is the central area of the retina that controls central vision and color vision. Usually one of the first signs of damage to the macula is distortion to the vision. Patients usually see distortion in straight edges, like door frames that now look wrong.

There are two types of macular degeneration:

Dry macular degeneration is more common and causes slow, progressive changes to vision. The visual loss is usually mild to moderate, but there is no cure for it. Treatment usually consists of adding a multivitamin with anti-oxidants, specifically lutein and zeazanthin. Smoking does increase your risk and will increase the progression of the disease by 30%! Smokers are strongly encouraged to quit and begin a multivitamin that does not contain beta-carotene. It has been shown that taking beta-carotene while smoking increases the risk of lung cancer.

Wet macular degeneration occurs in 10—15% of people with macular degeneration and is a more severe form than dry macular degeneration. Decreased oxygen to the macular area of the eye causes new blood vessels to form. As these new vessels are weak, they tend to leak, causing damage to the macular cells. This is what leads to the "black spot" in the middle of your vision. Laser and medication injection treatments are available for people with wet macular degeneration; however the visual outcomes are highly variable.

Ocular Migraine

This is a disconcerting loss of vision that can occur at any time. Usually an ocular migraine starts in one eye, and will begin as a light or spot that moves into the other eye. Sometimes patients report that they cannot see at all out of either eye, they just see light. Other patients report seeing shapes and shadows in their vision. This alarming phenomenon usually lasts less than 30 minutes, then vision returns to normal and seems unchanged. There is rarely a headache associated with this visual aura. We do not completely understand why these neurological migraines exist, but they seem to be related to stress and/or hormonal changes. If you have any flashes of light or changes in vision it is important to get your eyes checked immediately to rule out a dangerous cause, like a retinal detachment. If the retina is intact and your vision is back to normal, you are most likely experiencing an ocular migraine.

Retinal Detachment

A retinal detachment occurs when the retina tears away from the underlying blood vessel supply of your eye (the choroid). This can happen due to trauma, genetics, or spontaneously with no apparent cause. One risk factor that makes some people more prone to a detachment is myopia. When a person is very nearsighted, their eye is essentially longer than a farsighted eye, causing the retina to stretch and thin. These patients, or patients whom are genetically prone to retinal detachment, should have at least a yearly dilated eye examination. The main signs and symptoms of a retinal detachment are flashes of light and the appearance of a "curtain or veil" coming down and blocking your vision. It usually occurs in one eye only and there will be no pain associated with it. If you experience any of these symptoms, you should see your primary eye care provider immediately.