“20/20 vision” is commonly accepted as the standard of normal distance vision for a human being. It means you can see an 8.7mm letter 20 feet away.

By the way, visual acuity at a distance isn’t the only measure of how good your vision is. You could have 20/20 distance vision but still have difficulty seeing at night because of poor contrast sensitivity. Or you could have near vision problems because you’re over 40 and experiencing presbyopia.

The medical term for nearsightedness. Myopia occurs when an eye is too long for the cornea’s curvature. As a result, light rays entering the eye do not come to a sharp focus on the retina at the back of the eye. Instead, they focus further forward, producing a blurred image.

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The medical term for Farsightedness. Hyperopia occurs when an eye is too short for the cornea’s curvature. As a result, light rays entering the eye focus behind the retina instead of precisely on the retina, and a blurred image is produced. A person with hyperopia cannot see distant objects clearly.

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Astigmatism is the result of having a cornea that is irregular in shape. The cornea is normally round. An astigmatic cornea is oblong or “football” shaped, resulting in a condition that generally causes eyestrain, headaches and blurry vision. Astigmatism is often associated with nearsightedness and farsightedness.

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Presbyopia is a condition in which the focusing ability of a person’s eyes has decreased to the point where vision at his reading distance becomes blurred and difficult.

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A Cataract is a clouding or opacity of the natural internal lens of the eye, which causes a visual impairment. The natural lens is located behind the iris, or “colored part” of the eye. The opacity may be a small dot or may involve the entire lens. The opacity in the lens causes the light entering the eye to be scattered, causing images to appear hazy or blurred.

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Glaucoma is an eye disease in which pressure increases in the eye due to clogged or blocked passages. Fluid that normally drains through these passages begins to build up, and the increased pressure can damage the optic nerve. Open-angle glaucoma tends to develop without warning–often painlessly and with no symptoms. Because of this, it can cause damage and blindness more quickly when untreated. Risk factors for developing glaucoma include people over the age of 40; those who have a family history of glaucoma; those who are very nearsighted; diabetics; and African-Americans.

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The most common symptom of macular degeneration is blurred central vision; noticeably worse when reading. In addition, horizontal lines may appear wavy and/or distorted. The most common method of detecting macular changes is the Amsler Grid test. During an eye examination, you are asked to look at the grid’s center dot and asked if you notice any wavy, distorted, missing, or broken lines on the grid. Any one of these irregularities may indicate changes within the macular region of the eye. Your ophthalmologist or optometrist will be able to confirm any suspicions of macular degeneration during a dilated retinal examination.

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There is no known cure for dry eye. However, some dry eye symptoms are caused by medications, eye infections or wearing contact lenses. In these cases, simply eliminating the cause of dry eye will stop the problem. In many cases, however, dry eyes are a lifelong problem. You can relieve the symptoms, but not cure the original cause. Most eye care specialists recommend artificial tear products (ocular lubricants) for their patients with dry eyes. Follow your eye care specialist’s recommendations in order to effectively relieve dry eye symptoms and avoid further damage to your eyes.

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Diabetic Retinopathy is condition where a diabetic persons blood sugar gets too high. When this occurs, the high blood sugar level starts a series of events which end in damaged blood vessel walls. Blood vessels in the eye are small and delicate. As such, the blood vessels in the eye are easily damaged. The damaged vessels can then leak fluid or bleed, causing the retina to swell and form deposits known as exudates.

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Hypertension, or high blood pressure, is a disease that can have serious effects on many parts of the body, including the eyes. Hypertension causes damage to the tiny and fragile blood vessels that feed the retina.

What can be done? To reduce the risk of hypertensive eye disease, regular examinations by a physician are needed to monitor the condition. Hypertension must be controlled as much as possible and the key to control is to follow the advice of your physician.