Glucosamine supplementation was linked to significant, reversible increases in intraocular pressure (IOP) according a small, retrospective study published May 23 in JAMA Ophthalmology. However, the investigators, led by Ryan K. Murphy, DO, from the University of New England College of Osteopathic Medicine, Biddeford, Maine could not exclude the potential for permanent damage.
The investigators retrospectively studied six men and 11 women, with a mean age of 76 years, who had a history of glucosamine supplementation and ocular hypertension (IOP > 21 mm Hg) or diagnosed open-angle glaucoma, a willingness to discontinue glucosamine, three or more IOP measurements within two years, and no associated changes in glaucoma medications or eye surgery. Group A (n = 11) had one to three baseline IOP measurements before starting glucosamine, and group B (n = 6) had no baseline IOP measurements.
IOP increased in group A after starting glucosamine supplementation (P = .001). After glucosamine discontinuation, IOP decreased in group A (P = .002), group B (P = .008), and groups A and B combined (19.5 ± 0.4 to 16.7 ± 3.0 mm Hg in the right eye and 20.3 ± 2.9 to 17.3 ± 2.4 mm Hg in the left eye; P < .001). For any categories or comparisons, the left and right eyes in each patient did not differ significantly.
"Many questions are raised by glucosamine supplementation–associated IOP changes," the study authors write. "This study shows a reversible effect of those changes, which is reassuring. However, the possibility that permanent damage can result from prolonged use of glucosamine supplementation is not eliminated."
Study limitations noted by the investigators include its retrospective design and the very small sample with limited generalizability because it consisted of patients who were at least glaucoma suspects. The study did not account for glucosamine dosage, duration, brand, or compliance.
Coauthor Mona Doss, MA, also from the University of New England College of Osteopathic Medicine, suggests larger, randomized clinical trials are needed to assess dose-dependent increase in IOP with glucosamine supplementation in different patient groups.