The biomechanics of intraocular pressure (IOP) remain evasive, but researchers are piecing together a variety of factors that may help doctors control it better. For instance, a new study shows patients who have undergone bariatric surgery experienced a decrease in IOP, even if they had elevated IOP preoperatively. It also pointed to a connection between obesity and higher IOP.

The article, published in Acta Ophthalmologica, looked at 27 obese patients—BMI>40kg/m2, or >35kgm2 with an obesity-related comorbidity—who were scheduled to undergo the weight-controlling procedure, as well as 15 age-matched non-obese patients as a control group. Obesity-related comorbidities included increased blood glucose level (five cases), hyperlipidemia (one case), systemic hypertension (two cases) and, in one case, a fractured vertebra. All the subjects were female.

Before bariatric surgery, the mean Goldmann-measured IOP of the study group was 16.6mm Hg (±3mm Hg). At the six-month follow up for patients who underwent the procedure, that number dropped significantly, to 15.2mm Hg (±2.7mm Hg). No change was observed in the control group over the same timespan.

The researchers indicated that weight loss and a decrease in IOP may be associated, but could not point to any specific mechanism. However, they have some hypotheses that involve the weight loss’s management of contributing comorbidities, such as sleep apnea, hypertension and diabetes. “Bariatric surgery may change gastric signaling, cause early resolution of diabetes,” the team wrote in their paper. They also considered the impact of the procedure on blood viscosity, orbital fat mass and central corneal thickness, all of which could potentially lower IOP.

Viljanen A, Hannukainen J, Soinio M, et al. The effect of bariatric surgery on intraocular pressure. Acta Ophthalmol. 2018:96:849–52.