ABC of eyes. Refractive errors.

Divergent rays of light Indistinct vision is most commonly caused by errors of refraction. Doctors do not often have to deal with this problem because patients are usually prescribed glasses by an optometrist. It is extremely important, however, to ask the question: "Is this patient's poor vision caused by a refractive error?" The use ofa simple "pinhole" made in a piece ofcard will help to determine whether there is a refractive error. In the absence ofdisease the vision will improve when the pinhole is used unless the error is extremely large.