How Can I Tell If My Eyesight Is Bad?

Determining whether a person's eyesight is bad can be ascertained through several methods. The Snellen eye chart is often used for visual acuity testing. There is also a common chart for testing degrees of astigmatism. Blurriness, tired eyes or even strained eyes may also indicate a problem, but in general, eye floaters do no indicate poor eyesight.

Using the Snellen eye chart

• The Snellen eye chart can be found in most optometrist's or general practitioner's offices.

  Sharpness of vision is usually tested with the Snellen eye chart. This chart consists of various letters printed on a white background. To determine the smallest line of letters a person can read, the chart has to be set up 20 feet away from the standing person. The person will cover one eye and read the smallest letters they can make out. Another person standing closer to the chart can check for accuracy. Reading the line designated 20/20 correctly is considered normal visual sharpness; anything with a ratio less than one, such as 20/40, is not considered normal and the person may need to wear corrective lenses.

Astigmatism

• Astigmatism is caused by an irregularly shaped eye and may cause blurriness.

  Astigmatism is the condition where one or both eyes may have an irregular shape and trouble focusing an image. This can lead to blurriness. Some people also call this condition stigmatism, incorrectly leaving off the "a." A good way to test for this is using an astigmatism chart. Usually the chart is a set of parallel lines arranged in a circle. At the end of each set of parallel lines is a number. View the chart with one eye closed and then the other, focusing on the center of the chart. The parallel lines should appear equally sharp and distinct; if any appear blurred some degree of astigmatism may be present.

Nearsightedness and Farsightedness

• Both nearsightedness and farsightedness are easily fixed with corrective lenses.

  Sometimes people will suspect a vision problem if their eyes start to hurt or seem to get tired frequently. Whenever these conditions occur it may indicate the eyes are working too hard to focus or are unable to focus at certain distances. If someone can only see up-close objects with good clarity, this person may have myopia, or nearsightedness. Sometimes people with myopia may experience headaches or feel fatigued when performing an activity that involves distance vision.

  In contrast, people who can see well off in the distance but have blurred vision up close are said to have hyperopia, or farsightedness. Usually these people experience strain or headaches when performing work at a closer distance, such as staring at a computer monitor all day.

Eye floaters

• Some people see irregular black spots that seem to float in their vision when they look at bright objects. These eye floaters do not indicate bad eyesight, but rather just normal wear and tear of the eye. Floaters occur when the gel-like vitreous humor that fills the eye breaks off into small pieces. These pieces sometimes float in front of the retina where the eye is focusing, and reflects the floaters' shadows back out into the visual field.

  The number of floaters varies from person to person. In general they are considered to be nothing more than a mild annoyance.