Study of the pupil light reflex in patients with Obstructive Sleep Apnea

Abstract

Purpose: To investigate the impact of obstructive sleep apnea (OSA) on the vision of patients through the contribution of the inner and outer retinae (melanopsin ganglion cells, cone and rod photoreceptors, respectively) to the pupillary light reflex (PLR).

Methods: 56 eyes from 18 patients with OSA aging from 36-64 years (mean age of 51.26 ± 7.84 years, 9 females) and 13 healthy control participants aging from 39-74 years (mean age of 54.15 ± 9.59 years, 11 females) were studied. All were submitted to a complete ophthalmological exam. OSA severity was quantified by the number of apneas and hypopneas per hour during polysomnography using the Apneas/hypopneas index (AHI) from moderate (15≤AHI<30, 17 eyes) to severe (AHI≥30, 15 eyes). PLR was measured with an eye tracker (View Point, Arrington); stimuli were presented in a Ganzfeld (Q450, Roland). Pupil responses were measured monocularly, to 1s blue (470 nm) and red (630 nm) flashes with -3, -2, -1, 0, 1, 2, and 2.4 log cd/m² luminances. The normalized peak amplitude (PA) of the PLR and the amplitude of the sustained response (SR) at 6-8 s (median value) after the light offset were measured. Mann-Whitney U test was used for comparison among groups.

Results: The PA for blue stimuli was smaller for patients with severe OSA compared to controls from -2 to 1 log cd/m² (p<0.025). The red PA was significantly (p<0.05) reduced in moderate and severe OSA patients, respectively at 1 and 2 log cd/m²; and at -1, 1 and 2.4 log cd/m². Relative to controls, the SR for blue stimuli was smaller at -2 and 0 log cd/m² in severe OSA (p<0.05).

Conclusions: To our knowledge, this is the first report using PLR to investigate inner and outer retinal function in patients with OSA. Patients with severe OSA had reduced rod and cone contributions to the PLR. They also showed reduced melanopsin-driven responses (but not statistically significant) compared to controls. In moderate OSA only the cone response was reduced. Our data allow to conclude that there is an association between number of apneas in OSA patients and reduced contributions of the outer retinae to PLR.