How to Diagnose Astigmatism

Astigmatism is an irregular curvature of the cornea that causes a refractive error in a person's vision. Everyone has this condition to some extent, but only 10 percent of the population has visually significant astigmatism (usually defined as more than one diopter).

Instructions

• 1

  Observe the presenting symptoms of astigmatism. These consist of blurred vision over all distances, eyestrain, fatigue and headaches. Astigmatism frequently occurs with refractive errors such as hyperopic and myopia.

• 2

  Conduct comprehensive eye exams. These tests measure the ability of the eyes to focus and the amount of correction your eyes may require. Astigmatism is a non-spherical refractive error that is more difficult to diagnose because it has both magnitude and orientation whereas a spherical error has only magnitude.

• 3

  Measure the basic visual acuity using a standard eye chart. Visual acuity is expressed as a fraction. A person with 20/40 vision would have to be 20 feet from a chart that a person with standard vision could read at 40 feet.

• 4

  Perform a keratometry. A keratometer determines the cornea's curvature by reflecting a circle of light from the cornea and measuring the reflection. A corneal topography provides a more accurate description of the cornea's shape.

• 5

  Determine the refraction. A phoropter is a series of lenses, and a retinoscope is a handheld lighted instrument that the ophthalmologist combines to evaluate the eye's focusing ability. The patient's responses refine the refractive value.