Effect of central and peripheral cone- and rod-specific stimulation on the pupillary light reflex

Abstract

Purpose To assess the effect of central and peripheral stimulation on the pupillary light reflex. The aim was to detect possible differences between cone- and rod-driven reactions. Methods Relative maximal pupil constriction amplitude (relMCA) and latency to constriction onset (latency) to cone- and rod-specific stimuli of 30 healthy participants (24 ± 5 years (standard deviation)) were measured using chromatic pupil campimetry. Cone- and rod-specific stimuli had different intensities and wavelengths according to the Standards in Pupillography. Five filled circles with radii of 3°, 5°, 10°, 20° and 40° and four rings with a constant outer radius of 40° and inner radii of 3°, 5°, 10° and 20° were used as stimuli. Results For cone-and rod-specific stimuli, relMCA increased with the stimulus area for both, circles and rings. However, increasing the area of a cone-specific ring by minimizing its inner radius with constant outer radius increased relMCA significantly stronger than the same did for a rod-specific ring. For cones and rods, a circle stimulus with a radius of 40° created a lower relMCA than the summation of the relMCAs to the corresponding ring and circle stimuli which combined create a 40° circle-stimulus. Latency was longer for rods than for cones. It decreased with increasing stimulus area for circle stimuli while it stayed nearly constant with increasing ring stimulus area for cone- and rod-specific stimuli. Conclusion The effect of central stimulation on relMCA is more dominant for cone-specific stimuli than for rod-specific stimuli while latency dynamics are similar for both conditions.

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

“…In a different stimulation paradigm with increasing stimulus sizes of circle and ring stimuli of lower duration and intensity, an important role of the central retina on relMCA was accordingly shown in a previous study of our group. However, a particular relevance of peripheral retinal stimulation on pupillary latencies was hypothesized [24]. This probably was an effect of stimulus shape and size, as shorter latencies were obtained in the present study for central versus peripheral stimulation when stimulus size and intensity were equally matched.…”

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][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.…”