Chromatic Pupillometry for Screening and Monitoring of Retinitis Pigmentosa

Abstract

Purpose : Early diagnosis of Inherited Retinal Diseases, such as Retinitis Pigmentosa (RP) is challenging in pediatric patients, because their diagnosis mainly relies on relatively invasive tests. We conducted a pilot study to evaluate the usefulness of chromatic pupillometry in RP.

Methods : We recruited 20 RP cases and 20 healthy subjects based on the following inclusion criteria: age between 8 and 16 years; willingness to participate in this pilot study; a refraction error in absolute value < 5 dioptres; absence of any diseases or drugs that could influence the pupillary response; no corneal or lens opacity; no pupillary alteration. Controls should have no known ocular diseases. The study, approved by the Local Ethical Committee of the involved institutions, adhered to the Declaration of Helsinki. All the subjects underwent the pupillometric protocol described in Fig. 1. Regression models, estimated by Generalized Estimating Equations, corrected for repeated measurements and inter-eye correlations, were fitted to explore differences between cases and controls.

Results : The 20 RP patients, evaluated at a mean age of 12.4 ± 2.62 years, showed a best corrected visual acuity of 0.38±0.44 logMAR. Compared to controls, cases showed a significantly (p-value < 0.05) reduced maximum constriction in response to all the stimuli except #6, as reported in Fig. 2. Moreover, the values of maximum diameter before stimuli #1 and #2 were significantly higher in RP patients and the values of minimum diameter in response to stimuli #1, #2, #3 and #4 were significantly higher in RP patients. We observed that pupillary responses were detectable in all the RP cases, also in those with electroretinogram (ERG) below noise level. Moreover, the maximum constriction in response to stimulus #4 was significantly lower in RP cases with light-adapted ERG responses below noise level compared to those with markedly reduced ERG response.

Conclusions : Pupillary responses to chromatic stimuli were significantly different between pediatric RP patients and age-matched healthy controls. Moreover, pupillary responses were detectable also in patients with ERG responses below noise level, even if reduced compared to patients with marked reduced response. Therefore, chromatic pupillometry could be useful to support diagnosis of RP in pediatric patients and to monitor the related retinal degeneration in clinical trials.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.