Date of Award

January 2012

Document Type

Thesis

Degree Name

Medical Doctor (MD)

Department

Medicine

First Advisor

Nils Loewen

Subject Area(s)

Ophthalmology

Abstract

Purpose: Primary open angle glaucoma patients with intraocular pressures (IOP) in the lower range (LPG, below 21 mm Hg) more commonly have visual field damage that is asymmetrically distributed between right and left eye when compared to patients with higher IOP (HPG, above 21 mm Hg). In the absence of other correlated asymmetric glaucoma risk factors during office hours, this study investigates whether sleep position is correlated with asymmetric visual field status.

Methods: 58 patients with LPG and 91 patients with HPG were recruited during visits to the Yale Eye Center of the Department of Ophthalmology and Visual Science at Yale University, School of Medicine. The visual field index (VFI) was calculated from the most recent reliable visual field exam. Participants completed a sleep position survey which classified their dominant position as right, left, supine, prone or unknown. A subset of 15 LPG patients with asymmetric visual field status underwent continuous sleep position monitoring for at 2 nights. All analyses were performed using non-parametric statistical tests.

Results: In the sleep position survey, LPG patients were more often asymmetric (difference of 5% between right and left VFI) than HPG patients (p=0.049). More right sided sleepers had an asymmetric visual field loss than non-right sided sleepers (p = 0.01). Right sided sleepers had a significantly worse left VFI (p=0.028) when compared to non-right sided sleepers. In the continuous sleep monitor data, 8 subjects chose right as their dominant position, 3 chose left, 2 chose prone and 2 were undecided. The dominant sleep position chosen in the survey made up about half (44.6%) of the recorded sleep time. Similar to the survey group, amount of time spent on the right side was correlated with a larger degree of VFI asymmetry (p=0.008). No analogous differences were found for left sided sleepers.

Conclusions: Patients who slept on their right side had greater interocular visual field asymmetry using two independent methodologies. Correlation of asymmetric sleep behavior and asymmetric visual field status with otherwise symmetric findings during the day suggests that unidentified mechanisms occur at night that may cause asymmetric glaucoma progression.

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