Walsh & Hoyt: Pupillary Size, Shape, and Function: Examination

Simple inspection of the anterior segment at the slit-lamp biomicroscope is helpful in determining whether or not there is a pupillary abnormality. For example, examination of the cornea may reveal an abrasion or injury that could affect the pupillary size, whereas examination of the anterior chamber may reveal inflammation that explains a small pupil in the setting of ciliary spasm. It may also be important to perform gonioscopy to assess the anterior chamber angle in a patient with a dilated pupil, particularly when there is a history of pain or redness in the eye. Assessment of the iris should include not only inspection of the integrity of the sphincter muscle but also transillumination to determine if there is evidence of iris damage from previous ocular trauma. To retroilluminate the iris, the slit-lamp beam is directed obliquely through the pupil. A normal iris will not show defects, but an abnormality such as atrophy will show reflected light back to the observer. In addition, by placing a wide beam at an angle to the iris and turning the light off and on, the light reflex can be assessed for segmental defects, such as those that occur in eyes with tonic pupils or aberrant regeneration of the oculomotor nerve. One can even draw a diagram showing clock hours of denervation; the diagram can then be used to follow the patients status. Transillumination of the iris and ciliary body under infrared lighting conditions has been shown to be helpful to find other defects.