Determining your optical prescription

Most likely, the eye care professional will begin the actual examination by determining if you need vision correction -- and if so, the lens prescription that you need. To do this, he or she may use a retinoscope to shine a light through your pupil from about arm's length. (The dark spot in the center of the colored part of the eye, the pupil is actually a hole. It's black because the eye is dark inside). The light is reflected from the back of the eye. By moving the light from side to side and up and down and noting the direction and movement of the reflection, the practitioner begins to determine the 'prescription' or optical lens power that you need to obtain clearest vision. This prescription is further refined when you are asked to look through several lenses and identify which ones provide the clearest vision. By this stage the practitioner will have identified whether you are "nearsighted", "farsighted",having trouble focusing on things close up due to the normal aging process"(presybyopia)", "astigmatic", or have a combination of two or more of these conditions.

Evaluating your eyes' teamwork

Perhaps you aren't farsighted, nearsighted or astigmatic. But if your eyes aren't working well together, impaired vision can be the result. To detect eyes that are not synchronized, the eye practitioner will conduct tests for conditions that result when eyes do not work in tandem. Among those conditions are:Strabismus "also known as lazy eye", the inability of one eye to coordinate with the other eye usually because of an imbalance in the muscles of the eyeball. The result is that both eyes do not point simultaneously at the object being viewed; and Heterophorias, in which the eyes have a small misalignment for which the visual system normally compensates. If the heterophoria is too much for the visual system to correct comfortably, you could experience headaches or fatigue, and the 'phoria' could break down into a strabismus when you are tired or ill.