Association of asymmetrical normal tension glaucoma, obstructive sleep apnoea and side sleeping

To describe asymmetrical normal tension glaucoma (NTG) with obstructive sleep apnoea (OSA; apnoea-hypopnoea-index ≥5) in habitual side-sleepers, and to compare optic nerve head (ONH) blood flow velocity across sleeping positions using laser speckle flowgraphy (LSFG; Softcare, Japan).

Cross-sectional study.

Participants underwent ocular assessments and reported sleeping positions via questionnaires. Intraocular pressure (IOP) and LSFG-derived mean blur rates for vascular (MV), tissue (MT), and entire area (MA) were measured after 5 min in supine and lateral decubitus (LD) positions.

We enrolled forty NTG-OSA patients (21 unilateral; 19 bilateral but asymmetrical) and 29 controls (70% male; mean age 62.9 ± 8.7 years). Interocular characteristics were comparable except that worse eyes had thinner central corneas and reduced MV, MT, and MA in LD positions. In worse eyes, MT was less in the lower LD position (9.00 ± 2.07 au) than in the upper LD (9.27 ± 1.97 au; P = 0.037) and supine (9.61 ± 1.95 au; P = 0.011) positions. Among participants who slept with the worse eye lower, MV, MT, and MA were less in the worse eyes in both lower and upper LD positions versus the fellow eye (all P < 0.05), but not in supine. Among those who slept with the worse eye upper, MV and MT were less in the worse eyes only in the lower LD position (both P < 0.05), with no differences in other positions.

We report an association of asymmetrical NTG-OSA who habitually sleep laterally. Interocular differences, particularly reduced ONH blood flow velocity in the lower LD position, may provide insights into glaucoma pathogenesis.