The first prototype of chromatic pupillometer for objective perimetry in retinal degeneration patients

We recently demonstrated the feasibility of quantifying pupil responses (PR) to multifocal chromatic light stimuli for objectively assessing visual field (VF). Here we assessed a second-generation chromatic multifocal pupillometer device with 76 LEDs of 18 degree visual field and a smaller spot size (2mm diameter), aimed of achieving better perimetric resolution. A computerized infrared pupillometer was used to record PR to short- and long-wavelength stimuli (peak 485 nm and 640 nm, respectively) presented by 76 LEDs, 1.8mm spot size, at light intensities of 10-1000 cd/m2 at different points of the 18 degree VF. PR amplitude was measured in 11 retinitis pigmentosa (RP) patients and 20 normal agedmatched controls. RP patients demonstrated statistically significant reduced pupil contraction amplitude in majority of perimetric locations under testing conditions that emphasized rod contribution (short-wavelength stimuli at 200 cd/m2) in peripheral locations (p<0.05). By contrast, the amplitude of pupillary responses under testing conditions that emphasized cone cell contribution (long-wavelength stimuli at 1000 cd/m2) were not significantly different between the groups in majority of perimetric locations, particularly in central locations. Minimal pupil contraction was recorded in areas that were non-detected by chromatic Goldmann. This study demonstrates the feasibility of using pupillometerbased chromatic perimetry for objectively assessing VF defects and retinal function in patients with retinal degeneration. This method may be used to distinguish between the damaged cells underlying the VF defect.