Refraction Test
The refraction test is one that you're probably fairly familiar with, but perhaps not under that name. The optometrist or opthamologist will have you look through the photoroptor (or refractor), seen left, at an eye chart 20 feet away. The photoroptor contains lenses of many varying strengths and by moving these lenses into your view one eye at a time, the eye doctor can determine the prescription you need for corrective lenses.
By gauging the effect of these lenses on your vision, the eye doctor can determine whether you have a refractive error, and what that error is. These errors include but are not limited to: astigmatism (hindrance to your ability to focus vision), myopia (near-sightedness), and hyperopia (far-sightedness). |