Central retina plays a decisive role in the suppression of pupillary escape

Abstract

Purpose To explore the pupil redilation during persistent light exposure (pupillary escape phenomenon) at the macula and periphery with monochromatic light stimuli. Methods Forty healthy subjects aged 18–64 years (24 females) were examined by chromatic pupil campimetry (CPC) using red and blue 4-s stimuli of 10° radius at the center and 20°-peripheral locations one per quadrant. One glaucoma patient and one achromatopsia patient served as disease models. For statistical analyses, linear mixed-effects models were performed followed by post hoc t-tests. Results A distinct pupillary escape could be demonstrated peripherally (blue 0.099%*s, red 0.153%*s); at the central healthy retina, there was no relevant escape, neither for blue nor red stimulation. Comparing central versus peripheral stimulation revealed highly significant differences in the escape (difference blue 0.100 ± 0.013, red 0.144 ± 0.013, < 0.0001, respectively). In the periphery, the escape was significantly more pronounced for red compared with blue stimulation (difference 0.054 ± 0.013; p = 0.0001). Enhanced pupillary escape outside of the 95% confidence interval of the linear mixed-effects model of the healthy population could be exemplarily shown in a patient with glaucomatous ganglion cell damage. In the achromatopsia example, no relevant escape was found for blue stimulation, but for red stimulation in the periphery in a comparable range to healthy controls. Conclusion The results emphasize that an intact inner retinal network of nerve fibers arising from the central macular region is necessary for maintaining pupillary constriction during a bright 4-s light stimulus and preventing increase of pupillary escape. Increasing receptive field sizes towards the periphery on the level of retinal ganglion cells and less input from central 1:1 connections could be one of the driving mechanisms for pupillary escape.

Influencing Factors on Pupillary Light Responses as a Biomarker for Local Retinal Function in a Large Normative Cohort

“… 1 Specific stimulation protocols have been implemented to separately stimulate cones and rods and to measure certain parameters of the PLR as biomarkers to characterize local retinal function. 2 – 5 …”

“…1 Specific stimulation protocols have been implemented to separately stimulate cones and rods and to measure certain parameters of the PLR as biomarkers to characterize local retinal function. [2][3][4][5] Photoreceptor dysfunction in patients with retinitis pigmentosa (RP) can be objectified by evaluating the reduced PLR in multifocal pupil campimetry (white stim-uli on a flat screen) 6 and chromatic pupillometry (red/blue stimuli). 7,8 Previous studies have shown the value of PLR to full-field chromatic stimulation to quantify the residual photoreceptor function in patients with CNGA3-linked achromatopsia 9 or advanced RP with non-recordable electroretinogram.…”