Eye examination is the accurate measurement of eyesight (vision). This examination is done by an optician and aims to determine whether a person needs a pair of glasses or contact lenses, and if so in which strength.
Seeing less clearly is the main reason for performing an eye examination. The result of this test specifies the required glasses strength. On the basis of the measurement results, glasses or contact lenses can be made.
The eye examination is carried out with the aid of a refractor, an optical instrument that measures the eye lens strength. This can be a manual refractor (phoropter) or an automatic refractor (autorefractor).
The phoropter is a kind of adjustable pair of glasses. With one eye at a time, the patient must read what he or she sees through the instrument, while the optician puts different slides in front of the eyes until the best result is achieved. The patient himself must partly evaluate the result (subjective eye test).
The autorefractor automatically measures the lens strength. The patient himself has no influence on the result (objective eye test).
In practice, it’s usually preferred to do the subjective eye test, since this provides better results.
During the examination, several measurements are made. If the patient wears a pair of glasses, the optician evaluates these and determines the overall glasses strength.
The optician then measures the intraocular pressure. He uses a device that blows a few ‘puffs’ of dry air into each eye. Next, the optician determines the visual acuity. The patient is asked to read letters in different formats, that he or she will see through the refractor. If less than 100% visual acuity is achieved, the measurement is repeated by the optician, by holding a slide with a small opening in the middle in front of the eye. The examination will take up to 10 minutes.