Positive association between melanopsin expressing ganglion cell and retina nerve fiber layer thinning in glaucoma.

Abstract

 

Purpose

 

To assess the integrity of melanopsin expressing ganglion cells (ipRGCs) through the pupillary light reflex in patients with glaucoma compared to controls.

 

Methods

 

76 eyes of 38 patients with primary open angle glaucoma and 36 eyes of 18 controls were included. Among patients, 24 eyes had advanced, 12 eyes had moderate and 40 eyes had initial glaucoma, according to Hodapp-Anderson-Parrish classification. Patients were tested in the dark with light only from the Ganzfeld (Super Color Ganzfeld Q450 - Roland Consult), which generated the light stimuli for the test. Pupil diameter was measured with a View Point System eye tracker (Arrington Research Inc.) consisting of two infrared cameras fit to an eyeglass frame. For pupillary response, stimuli were generated by blue and red monochromatic LEDs. To optimize and stimulate the photosensitive ganglion cells expressing melanopsin, flashes of 470 nm were used and a 1 second duration at 250 cd/m2 with alternating flashes of 630 nm, also of 1 second duration to stimulate retinal photoreceptors only. Functional evaluation was performed using the Humphrey Field Analyzer II, 24-2, SAP and FDT Matrix. Structural analysis was done by Cirrus OCT. Complete eye examination on both eyes for all patients and controls were also performed. We analyzed the correlation between the peak and sustained response to melanopsin and the structural and functional alterations in glaucoma patients.

 

Results

 

The mean sustained response in the 250 cd/m2 for blue for both groups was 0.427 ± 0.104 and for the peak response to melanopsin for blue for both groups was 0.519 ± 0.060. For the OCT Cirrus the average thickness for both groups was 82.81 ± 17.332 microns. For the Mean Deviation (MD) SAP and FDT the averages were -5.080 ± 7.21 and -3.534 ± 6.508, respectively. There is an association between the mean (RNFL) thickness in OCT and the pupillary response variable for the sustained response for blue and no association for SAP and FDT. (p= 0.024, p= 0.978 and p= 0.429, respectively) (GEE by SPSS 17). There is a strong association between the severity of glaucoma disease (Hodapp-Anderson-Parrish classification) and sustained response for blue flash (p= 0.006) Graph 1.

 

Conclusions

 

There is a correlation between the mean RNFL thickness and the pupillary response. The thickness reduction can lead to a worsening of the sustained response at 250 cd/m2 in blue flash.

 

 

Keywords: 668 pupillary reflex • 667 pupil • 496 detection