A refractive error is diagnosed through a comprehensive eye examination consisting of refraction and visual acuity test. Your family history and other medical conditions will also be taken into consideration during the diagnosing process. Given below are the testing methods in detail for your reference.

Visual acuity test – The test will assess how well you can see at a standard distance. An eye chart positioned 20 feet away will be presented for you to read the letters with increasingly smaller sizes. The reading may take place in both eyes and covering one eye as well. To check your close-up vision, a few lines from a preprinted card will be given. If you are able to see and read all the letters, you are considered to have 20/20 vision.

Corneal Topography – This test usually takes place if your eye doctor notices an unusualness about your cornea. You will be asked to keep your chin and head into a specialized optical instrument and to look at the illuminated displayed pattern displayed on the screen. A digital camera located in the center will capture the reflection, and the information will provide a 3D image of your eye. The completion of the test will provide you with the refractive error for you to have, and the prescription can be used to get the corrective lenses for your glasses or contacts.