An Objective Method for Measuring Relative Afferent Pupillary Defect in Glaucomatous Optic Neuropathy—Stimulus Optimization

Abstract

Purpose: To develop a new technique for measuring relative afferent pupillary defect (RAPD) and to find the best stimulus parameters for detecting glaucomatous optic neuropathy. Methods: With a newly constructed pupillometer based on digital video recording, pupillary light reflexes were analyzed during alternating light stimulation. Pupil area was measured in each video frame using computer digital image analysis. The examinations were performed using different sets of stimulus-pause combinations. Subjects with unilateral or asymmetrical glaucoma were studied and compared to normals. Results: Alternating light stimulation of 0.5-s followed by 1-s pause was shown to be the best stimulus pattern for RAPD detection. Conclusion: Infrared pupillometry could distinguish eyes with glaucoma from normal eyes with good sensitivity and specificity.

KEYWORDS:

• Pupillary reflex
• relative afferent pupillary defect
• pupillometry
• open-angle glaucoma
• glaucomatous optic neuropathy