Melanopsin-mediated pupillary light reflex and sleep quality in patients with normal tension glaucoma

The intrinsically photosensitive retinal ganglion cells (ipRGCs) and sleep quality are impaired in patients with primary open-angle glaucoma (POAG). In this study, we investigated whether ipRGCs and sleep quality were also impaired in patients with normal tension glaucoma (NTG).

We performed pupillometry and sleep quality assessment in 15 patients with NTG and 17 healthy age-matched controls. Pupillometry protocol consisted of monocular stimulation with high illuminance (100 lux) red (633 nm, 300 cd/m² or 15.23 log quanta/cm² /s) and blue light (463 nm, 332 cd/m² or 15.27 log quanta/cm² /s) and binocular pupil measurements. Prior to light stimulation, patients were dark-adapted for 5 min. The late postillumination pupillary response (PIPR_{L ate} ) to blue light was used as marker of ipRGC activity. Sleep quality was assessed by Pittsburgh Sleep Quality Index (PSQI) questionnaire.

The PIPR_{L ate} to blue light was significantly reduced in patients with NTG compared to healthy subjects (p < 0.001), indicating impairment of the melanopsin-mediated pupillary pathway. There was no significant difference in the response elicited by red light (p = 0.6). Baseline pupil diameter and pupillary constriction amplitude to both red and blue light were reduced in patients with NTG (p < 0.05). The global score in PSQI was not significantly different between healthy controls and patients with NTG, indicating normal sleep quality (p = 0.6). Furthermore, we found no correlation between sleep parameters and pupillary light reflex parameters.

Patients with NTG exhibited reduced ipRGC activity compared to healthy subjects, while no differences were observed in sleep quality.