Date of Award

January 2013

Document Type

Thesis

Degree Name

Medical Doctor (MD)

Department

Medicine

First Advisor

Nils Loewen

Subject Area(s)

Ophthalmology

Abstract

Relationship of Structural and Functional Asymmetry to Sleep Position in Open Angle Glaucoma

Eberechi Nwogu1, Sonya Thomas2, Daniel Blizzard3, Cecily Hamill4, Vahid Mohsenin5, John Emerson6, and Nils Loewen7

1Yale University School of Medicine, New Haven, CT

2Department of Internal Medicine, Moses H Cone Memorial Hospital, Greensboro, NC

3Department of Orthopedic Surgery, Duke University School of Medicine, Durham, NC

4Department of Ophthalmology, Harvard School of Medicine, Cambridge, MA

5Department of Pulmonology, Critical Care and Sleep Medicine, Yale University School of Medicine, New Haven, CT

6Department of Statistics, Yale University, New Haven, CT

7Department of Ophthalmology, UPMC Eye Center, Eye and Ear Institute, Ophthalmology and Visual Science Research Center, University of Pittsburgh School of Medicine, Pittsburgh, PA

The purpose of this investigation was to collect explorative data on the relationship between lateral sleep position, asymmetric visual field index (VFI), and retinal nerve fiber layer (RNFL) thickness in primary open angle glaucoma (POAG). A POAG subgroup, low pressure glaucoma (LPG) patients have more frequent asymmetric visual field loss and a predominance of left sided loss when compared with high pressure glaucoma (HPG) patients, but no asymmetric risk factors have been identified to this date. We hypothesized that time spent in preferred face-down sleep position correlates with asymmetry of visual field status in POAG.

228 POAG subjects (50 low pressure glaucoma (LPG) and 178 high pressure glaucoma (HPG)) completed a survey that characterized their sleep position as predominantly side, prone, supine or unknown. Twenty-nine POAG patients with known visual field asymmetry underwent 2-3 nights of continuous sleep position monitoring. Sleep position data from the survey and the sleep monitor were correlated with visual field index. RNFL thickness was obtained from the most recent OCT Cirrus exam for all patients and was also correlated with sleep position. Relationship between corneal properties and VFI was explored and the effect of postural change on intraocular pressure (IOP) was investigated. Data was analyzed with the Wilcoxon signed-rank test, Pearson correlation, linear regression and paired t-test.

In the survey, right sided sleepers had a larger absolute VFI difference (right VFI - left VFI) than left sided sleepers, p=0.006. The same was seen in subgroup analysis of HPG (p=0.054) and LPG patients (p = 0.049), respectively. Among POAG patients, right sided sleepers had a lower right RNFL thickness than left sided sleepers (p=0.005).

In the continuous sleep monitoring study, predominant sleep position, expressed as the difference between the percentage of time spent in the right and left position (RL) had a negative association with the relative VFI difference (b= -0.422, p=0.002). Time spent in the prone position was also found to have a negative association with the relative VFI difference (b = -0.79, p = 0.006).

We explored habitual IOP as a risk factor and found that IOP increased with change from sitting to the supine position and this increase was higher in the dependent eye than in the nondependent eye in the lateral decubitus positions but did not reach statistical significance.

In conclusion, this explorative data indicated that lateral sleep position was associated with asymmetric visual field and RNFL thickness in both a sleep position survey and continuous sleep monitoring study. This study will allow to design and power future studies to further investigate a hypothesized relationship between the preferred sleep position and asymmetric damage in POAG.

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