Eye examination. Image 8 of 15. Man having his eyes examined with a refractor. This instrument is used during eye examinations for clinical measurement and correction of refractive errors of the eye. A series of lenses are dialled into place (centre) as the patient reads a wall chart. The patient's ability to read the chart guides the ophthalmologist in choosing lenses to correct the patient's sight. An eye examination not only identifies sight deterioration, it can also reveal underlying health problems such as high blood pressure or diabetes. A healthy individual should have an eye test every two years. See M450/267- 281 for an eye examination.