The authors Kim and associates have found that among subjects who prefer the lateral decubitus position during sleep, the eye in the dependent lateral decubitus position had worse field loss in 66% ( P = 0.001) of patients with normal-tension glaucoma and in 71.9% ( P = 0.013) of patients with high-tension glaucoma. In previous articles they have indicated that asymmetric visual field loss in patients with glaucoma is due to intraocular pressure elevation asymmetry when in the lateral decubitus position.

In response to this, I have certain comments to make. It is well established that factors including a rise in intraocular pressure, a decrease in ocular perfusion pressure and a decrease in ocular blood flow influence the manifestation of glaucoma.

In a study by Khayi and associates no significant change in choroidal blood flow or vascular resistance was found during posture change in patients with obstructive sleep apnea (also a risk factor) if they did not have cardiovascular comorbidities.

Kida and associates have found that significant diurnal-to-nocturnal decreases in blood flow occurred in the optic nerve head and macula in the older subjects but not in the younger subjects. In another study by Han and associates, intraocular pressure was shown to decrease with increasing age.

Both age and cardiovascular disease influence ocular dynamics and are risk factors for the manifestation of glaucoma. But in the present article the authors have not commented on using age-matched controls and ruling out cardiovascular comorbidities that could have acted as confounding factors and could possibly have caused visual field loss that was attributable solely to the lateral decubitus position in the subjects studied by Kim and associates.

I recommend the use of age-matched controls and the ruling out of other risk factors for glaucoma in study subjects so as to understand clearly the role of the lateral decubitus position in the manifestation of glaucoma.