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Editors Selection IGR 13-2

Pathophysiology: Factors affecting IOP

Comment by Arthur Sit on:

51987 Effect of Lateral Decubitus Position on Intraocular Pressure in Glaucoma Patients with Asymmetric Visual Field Loss, Kim KN; Jeoung JW; Park KH et al., Ophthalmology, 2013; 120: 731-735

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Intraocular pressure (IOP) has long been known to vary with body position. In particular, the supine position results in an elevation of IOP compared with the sitting position in both normal subjects and glaucoma patients.¹ Furthermore, recent research has suggested that other body and head positions may result in IOP elevations even greater than in the supine position.^2,3 While the contribution of IOP fluctuations in glaucoma pathogenesis remains unclear, one potential role may be in helping to explain asymmetrical disease in glaucoma patients, which can occur despite similar ocular characteristics and identical systemic risk factors. In this manuscript, Kim et al. Investigated the effect of supine and lateral decubitus positions on IOP in a group of glaucoma patients with asymmetric visual field loss. They reported that, while IOP was similar between the two eyes in the sitting position, in the recumbent positions the two eyes experienced different IOP elevations.

While IOP was similar between the two eyes in the sitting position, in the recumbent positions the two eyes experienced different IOP elevations

In the supine position, IOP was significantly higher in the eye with the more advanced visual field loss. In the lateral decubitus position, the IOP was higher than in the supine position, and the IOP of the dependent (lower) eye was higher than the nondependent eye. Interestingly, the IOP difference between the two eyes was greater when the eye with more advanced visual field loss was in the dependent position than in the non-dependent position. These results suggest that eyes with more advanced glaucoma have a different IOP response to changes in body position than eyes with milder disease. However, the significance of these findings to clinical management is not clear at this time. It is possible that a greater IOP rise in the supine and lateral decubitus positions is what pre-disposes to more advanced disease. Alternately, eyes with more advanced glaucoma may compensate for body position changes at a slower rate than eyes with milder glaucoma, and the higher IOP may be a transient effect that lasts longer than the ten minutes allowed for equilibration in the study. Also, the authors did not examine the effect of glaucoma therapy on IOP rise in these treated patients. It is also possible that these IOP changes are incidental findings, and other factors, such as pressure on the dependent eye by the pillow in the lateral decubitus position, are the true causes for asymmetric disease. Finally, the interaction of these IOP changes with other potential risk factors that likely change with body position, such as cerebrospinal fluid pressure and ocular perfusion, remain to be elucidated.

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