Importance of unilateral occlusion in examination of the pupillary light reflex in an aged patient with large-angle exophoria-tropia

Abstract

We report on a 60-year-old man, who was referred with a suspected absence of light reflex in his left eye. Exophoria-tropia with a large angle of deviation was found during the alternating prism cover test. The range of eye movement was normal. On macroscopic examination, both pupils appeared to be miotic and the light reflex was prompt, but incomplete. When one eye was occluded, the patient's miosis disappeared and the light reflex became prompt and complete, i.e., normal. Since he subconsciously performed convergence to achieve a phoric position and gradually noted asthenopia, he underwent strabismus surgery for his exophoria-tropia. After surgery, his pupils were normal even in the binocular state. Therefore, doctors should pay attention to the pupillary findings in elderly patients with comparatively large-angle exophoria-tropia, because their pupils falsely appear to be miotic (phoria-miosis) with a reduced or absent light reflex in the orthophoric position.