Here is an overview of some of the more common vision conditions (see Eye Disease for information on glaucoma, diabetic eye disease and cataracts):

Nearsightedness (myopia): a vision condition in which you can usually see close or near objects clearly, but cannot see distant ones as clearly. Due to the shape of the cornea and eyeball length, incoming light focuses in front of the retina.

Farsightedness (hyperopia): a vision condition in which distant objects are usually seen clearly, but close ones appear blurred. Due to the corneal shape and length of the eyeball, incoming light focuses at a point behind the retina.

Astigmatism: a vision condition in which, due to irregular eye curvature, light entering the eye is unable to be brought to a single focus on the retina, resulting in vision being blurred at all distances.

Presbyopia: a vision condition that occurs when the eye's internal lens gradually loses its ability to bring close objects into clear focus. It usually becomes noticeable when people reach the early-to-mid-forties and is a natural part of aging.

Nearsightedness, farsightedness, astigmatism and presbyopia are all treated with eye glasses or contact lenses. In recent years, laser vision correction or other refractive surgery techniques have proved very successful in reshaping the cornea, the clear front surface of the eye, to correct nearsightedness, low to moderate farsightedness, and low to moderate astigmatism.

Conjunctivitis: inflammation of the conjunctiva, the thin, transparent layer covering the surface of the inner eyelid and a portion of the front of the eye. The condition affects people of all ages and appears in many forms.

The three main types are infectious (pink eye), allergic and chemical.

Antibiotics and antivirals are prescribed to treat the infectious forms. The ideal treatment for the allergic and chemical forms is to remove the cause of the inflammation and then treat with prescription or nonprescription eye drops to help relieve the discomfort. Cold compresses may also be advised.

Spots and Floaters: spots (often called floaters) are small, semi-transparent or cloudy specks or particles within the eye's internal gelatin (called the 'vitreous') that become noticeable when they move within the line of sight. They may also appear with flashes of light. (Spots and floaters look like translucent specks of various shapes and sizes.) Most spots are normal and seem to progress with age. However, in some cases, spots can be a sign of eye disease; especially if one notices a dramatic increase of them, or if they are accompanied by persistent flashes of light.

Dry Eye: occurs when your eyes do not produce enough tears or produce tears that do not have the proper chemical composition. Dry eye symptoms can result from the normal aging process, exposure to environmental conditions, problems with normal blinking or from medications such as antihistamines, oral contraceptives or antidepressants. Dry eye can also be symptomatic of general health problems (e.g. diabetes, rheumatoid arthritis, lupus) or can result from chemical or thermal burns to the eye.

The most frequent treatment is the use of artificial tears or tear substitutes. For more severe dry eye, ointment can be used, especially at bedtime. If dry eye is untreated, it can lead to increased discomfort, corneal scarring and even loss of vision.

Please see Children's Vision for descriptions of common conditions including amblyopia (lazy eye) and strabismus (crossed-eyes).