A unilateral cataract produces a relative afferent pupillary defect in the contralateral eye.
The relative afferent pupillary defect (RAPD) was measured with neutral density filters in ten patients, each of whom had a dense cataract in one eye only. In each instance, the cataract reduced visual acuity to counting fingers or worse, whereas visual acuity in the other eye was 20/25 or better. All patients with mature or nuclear cataracts had a measureable RAPD in the other eye (mean, 0.44 log unit). In each instance, after extraction of the cataract, the RAPD disappeared. Thus, a dense cataract causes an RAPD in the contralateral eye by increasing the pupillomotor effectiveness of the stimulus light and that this is the reason why even a brunescent cataract does not cause an RAPD in the same eye. In addition, two clinical cases are reported. One case records the development of a cataract in an eye with a preexisting RAPD resulting from optic neuritis; as the cataract became more opaque, the afferent defect became smaller and finally was reversed. The other case shows that a traumatic cataract can produce an RAPD in the contralateral eye. Thus, when an afferent pupillary defect is seen in an eye with a cataract, a visual pathway defect in that eye should definitely be suspected.
Lam
B L
BL
Department of Ophthalmology, University of Iowa College of Medicine, Iowa City 52242.
Thompson
H S
HS
D000328:Adult; D000344:Afferent Pathways / Q000503:physiopathology; D000368:Aged; D000369:Aged, 80 and over; D002386:Cataract / Q000150:complications* / Q000209:etiology; D002387:Cataract Extraction; D005131:Eye Injuries / Q000150:complications; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000150:complications; D009902:Optic Neuritis / Q000150:complications; D011681:Pupil Disorders / Q000209:etiology* / Q000503:physiopathology; D015349:Vision, Monocular; D014792:Visual Acuity