The change in focusing of the eye as an object is moved closer. Accomodation is required to see objects clearly up close and is slowly lost beginning at the age of 40. This is why reading glasses are required as a person ages.

Commonly known as a "lazy eye," it results from one eye having much better vision than the other. The eye that sees well does all of the focusing while the eye that does not see well does very little. This results in one eye having good vision and the other having bad vision. Patching therapy is commonly used in an effort to strenghthen the weaker eye.

A chamber filled with aqueous fluid that lies between the cornea and the iris.

The fluid that fills the anterior chamber of the eye. The balance of production and drainage of this fluid is responsible for maintaining the intraocular pressure of the eye. An imbalance is seen in several eye diseases, but can contribute commonly to glaucoma.

The perception of flashing lights which are usually arc shaped secondary to migraine headaches or ocular migraines. In a classic migraine headache, this generally precedes the headache and is often seen in one eye. In an ocular migraine, the aura occurs but no headache is experienced. It typically lasts for about 30 to 45 minutes.

A type of spectacle lens that allows for both distance and near prescriptions to be in a single pair of glasses. The two are separated by a line with distance being on the top and reading being on the lower part of the lens. There is no intermediate/computer distance correction in this type of lens.

Dandruff-like flaking of the eyelids which causes itching, redness, and inflammation of the eyelids. Treated with lid scrubs, warm compresses, and steroid ointments if severe.

A clouding of the lens of the eye which blocks light from focusing on the retina. It typically occurs in the elderly, but can also be seen in younger individuals. Blurred vision, halos and glare from lights at night, and difficulty reading in dim lighting are common symptoms experienced. They can range from being asymptomatic to completely blocking vision which then need to be surgically treated.

Beginning as a sty which is not successfully treated, an infected meibomian gland of the eyelid becomes clogged with material and forms a hard lump. Surgical excision is required by an ophthalmologist.

Hereditary and congenital, individuals have problems seeing either red/green or blue/yellow with both eyes. It can also be acquired by trauma or eye diseases in which case only one eye is affected.

A transparent mucous membrane which overlies the sclera and lines the inside of the eyelids. It helps to lubricate the eye and protect from infection.

A corrective lens which, when inserted onto the cornea, can serve the same purpose as glasses and allow for the improvement of vision. Commonly, soft contact lenses are fit which come in daily, biweekly, or monthly disposables. As well, spherical, toric (for astigmatism), and multifocal (correct distance, intermediate, and near) are available.

The transparent surface of the eye which has power to refract light and allow it to focus on the retina. It accounts for approximately 40 diopters (two-thirds) of the eye's total optical power. It is five tissue layers thick and is the focus of refractive procedures such as LASIK or PRK.

Inflammatory and infectious in nature, an ulcer disrupts the cornea and can proliferate into the entire eye. An optometrist should examine the eye since strong antibiotic treatment is required immediately in order to prevent permanent vision loss.

Bleeding in the back of the eye from uncontrolled diabetes which can cause severe vision loss. Laser treatment as well as diabetic control and blood sugar lowering are treatments. An optometrist or an ophthalmologist should be seen in intervals varying from every three months to yearly, depending on severity.

A condition which causes burning, tearing, redness, grittiness, and even blurry vision. Treatment is with artificial tear drops to remoisturize the cornea. In addition, flax oil, fish oil and omega 3 supplements can aid in tear production and help remoisturize the eye.

An eye that is able to focus an image directly on the retina without the aid of glasses or contact lenses.

A wrinkling of the top layer of the retina which distorts vision. It is typically caused by changes in the vitreous and surgically treated by an ophthalmologist if severe by removal of the membrane.

A fold of skin which functions in protecting and lubricating the eye.

Spots seen of various shapes and sizes due to degeneration of the vitreous which are visible more on a bright background. They need to be examined by an optometrist if there is a sudden increase noted since they may be an indication of something more severe going on. Floaters are not currently treated since the brain adapts to seeing them and will eventually not notice them as much. Also, there are many more risks to the surgical treatment than benefits.

Located in the center of the macula, it is responsible for sharp central vision.

Glasses are composed of a frame and lenses which correct the refractive error of the eye allowing light to properly focus on the retina in order to improve vision.

Also known as farsightedness, hyperopia causes decreased vision at near. If severe, it can also affect distance vision.

A pressure inside the eye caused by the balance of aqueous production and drainage. If increased, it can damage the optic nerve causing glaucoma. Intraocular pressure should be monitored during a routine exam by an optometrist.

The coloured part of the eye which controls the size of the pupil and thereby controls how much light reaches the retina.

A progressive thinning of the cornea causing a change in shape which results in visual distortion, usually beginning in the teenage years. Surgical treatment as well as contact lens therapy is available. A recently new treatment has also emerged whereby collagen cross-linking is used in order to strenghthen the cornea. Keratoconus is a genetic disease so all family members of someone with the diagnosis should be screened and monitored routinely.

A gland that sits on the outer portion of the upper lid which is responsible for tear production. Tear production decreases with age therefore causing dry eye symptoms to become more problematic.

Farsightedness in which the patient usually has good vision even though they require glasses. This is due to the ability to accommodate and compensate for the prescription through eyestrain. However, when there are high amounts of prescription, patients will notice mild blur and will experience frontal headaches. Eyeglasses are extremely important in this situation to relieve the eyestrain and aid in focusing. If left untreated, the condition worsens causing severe headaches and trouble focusing for extended periods of time.

Located between the iris and the vitreous, the lens allows light to focus on the retina and also aids in accommodation. It is this loss of accommodation that causes the need for reading glasses after the age of 40. This is also the same lens that eventually develops into a cataract as the eye ages. It accounts for approximately 20 diopters (one-third) of the eye's total optical power.

A lens can also refer to an eyeglass lens or a contact lens.

A disease of the macula which causes loss of central vision in the elderly. It is hereditary and treatment, as well as preventative treatment, includes vitamins and injection therapy. An optometrist should monitor the condition yearly and a referral to an ophthalmologist should be made if injections are required. All family members of an individual with macular degeneration should be screened for the disease and routinely monitored due to its genetic nature.

Glands which line the upper and lower eyelids. They provide an oily secretion onto the eye which prevents tears from evaporating. Meibomian glands can sometimes get clogged and cause an infection commonly known as a sty. Treatment for this condition is available from an optometrist.

A freckle which can occur in all levels of the eye. It should be monitored yearly by an optometrist for changes in shape, size, color and elevation. If these changes are noted, further testing is required.

A type of spectacle lens which puts an intermediate computer prescription on the top and a reading prescription on the bottom without any dividing lines.

Cranial nerve II which transmits visual images from the retina to the brain.

A person who manages and treats ocular related problems, as well as provides prescriptions for glasses or contact lenses.

High nearsighted prescriptions can become a disease in which the retina gets extremely stretched and thin. Careful monitoring and routine annual exams by an optometrist are necessary as there is a higher risk of retinal detachment. Patients should be aware of an increase in floaters, flashes of light, or a sudden loss of vision.

Yellow-white deposits on the conjunctiva which develop secondary to UV exposure. It is stabilized by the use of sunglasses. A pinguecula can become a pterygium and so should be monitored by an optometrist.

A type of eyeglass lens which redirects light in order to correct double vision.

A type of spectacle lens which corrects distance, intermediate, and near vision with a single pair of glasses without having any dividing lines.

This refers to a droopy eyelid which is either congenital or acquired by trauma or disease. New onset requires careful evaluation by an optometrist. Surgical treatment by an ophthalmologist to lift the eyelid can be necessary.

An error where too much or too little optical power is present in the eye. This prevents light from focusing on the retina but can be corrected with glasses, contact lenses, or surgery.

Separation of the retina from other layers of the eye which causes severe vision loss and sometimes blindness. Often symptoms of flashing lights and floating spots are experienced before and during a detachment. Emergency surgery is required. An optometrist or ophthalmologist should be consulted immedately.

An eye disease which leads to night blindness and also causes loss of peripheral vision. It is genetically inherited and tends to manifest in the second decade of life. No treatment is currently available.

Types of photoreceptors which are concentrated in the periphery of the retina. They function best in dim illumination and allow for night vision.

A misalignment of the eyes causing loss of binocular vision. Vision therapy can sometimes correct the problem. However, surgical intervention by an ophthalmologist is required in the majority of cases.

Bleeding between the conjunctiva and sclera caused by heavy lifting, vomiting, or other activities which change the blood perfusion to the eye. No treatment is required unless the condition is recurrent.

Spectacle lenses which automatically darken when exposed to UV light and then clear when inside.

A type of spectacle lens which corrects distance, intermediate, and near vision in a single pair of glasses but has dividing lines between each zone.

A normal part of the aging process causing a large floater to be seen in the shape of a "C". Other complications can result such as a bleed or tear in the retina and therefore should be evaluated by an optometrist immediately. No treatment is necessary unless other complications occur.

Fibrous strands which allow the lens of the eye to be flexible and accommodate.