Chromatic multifocal pupillometer for objective perimetry

Abstract

Purpose: We present infrared chromatic multifocal pupillometry for objective perimetry and determination of retinal cell function in healthy subjects and patients with macular and retinal degeneration.

Methods: A computerized infrared video pupillometer was used to record pupillary responses to short- and long-wavelength stimuli (peak 485 nm and 620 nm, respectively) presented by 76 LEDs, 1.8mm spot size, at increasing light intensities of 10-500 cd/m2 and duration of 1 sec at different points of the 30 degree visual field. Latency, amplitude, constriction velocity and re-dilation velocity of pupillary responses were measured in 19 retinal and macular dystrophy patients and 40 aged-matched controls.

Results: Comparison between control and retinal dystrophy patients demonstrated statistically significant differences (p<0.05) in amplitude and constriction velocity in vast majority (69) of locations in response to short-wavelength stimuli and mostly in peripheral targets in response to long-wavelength stimuli. Macular dystrophy patients demonstrated significantly lower pupillary responses to long wavelength stimuli in majority of the visual field and nearly normal pupillary responses to short wavelength stimuli in majority (58) of visual field locations. High consistency was observed in pupillary responses recorded in serial testing (P<0.001, R=0.74 for long-wavelength and P<0.001, R=0.683 for short-wavelength, n=870).

Conclusions: This study demonstrates the feasibility of using pupillometer-based chromatic perimetry for objective assessment of visual field defects. The device requires minimal patient cooperation and demonstrates defects in rods or cones preferentially according to the light stimuli.