How Does Obesity Affect Retinochoroidal Vasculature?

Subclinical changes in retinochoroidal vasculature occur in obese individuals, according to a study published in PLoS ONE. However, surgical intervention, such as bariatric surgery, may have a favorable outcome on the choroidal thickness in these patients’ eyes.

Commonly caused by excessive food intake, lack of physical exercise, and genetic susceptibility, obesity can increase levels of some vasoconstrictor molecules such as endothelin-1 and angiotensin-II. The condition has also been associated with multiple ocular diseases including glaucoma, diabetic retinopathy, cataract development, and age-related macular degeneration.

Measuring the choroidal vascularity index (CVI) and arteriole-to-venule ratio (AVR) can aid in assessing retinochoroidal vasculature alteration caused by obesity. Few studies have determined such changes in detail while “the effect of correction of obesity by bariatric surgery or non-surgical measures on retinochoroidal vasculature has not been evaluated.”

This prospective observational study included 60 adult patients with exogenous obesity between ages 18 and 70. All participants had a waist circumference of at least 80 cm and were willing to reduce their weight via medical or surgical measures. Any individual exhibiting retinal pathologies that affected retinal or choroidal thickness were excluded from the study.

Baseline evaluations consisted of a general physical exam, including measurements of mean arterial pressure, best-corrected visual acuity via the Snellen chart, intraocular pressure, and mean ocular perfusion pressure. Patients’ past comorbidities and treatment histories were also recorded.

During the study window, 30 patients underwent bariatric surgery (group A) and 30 underwent conservative weight management (group B), including diet therapy and exercise. After 3 months, researchers followed up with all patients and conducted ocular examinations, fundus photography, swept-source optical coherence tomography, and optical coherence tomography angiography. Thirty age- and gender-matched eyes of normal participants were included for comparison.

Of the 60 participants, 47 were male, and the average age was approximately 47 years. Researchers found that, compared with healthy controls:

• Baseline choroidal thickness was lower in the 60 participants with obesity
• Subjects with obesity had higher mean (SD) CVI: 0.66 (0.02) vs 0.63 (0.04) (P < .01)
• Obese subjects exhibited smaller mean foveal avascular zone areas: 0.26 (0.07) vs 0.45(0.32) (P < .01)
• Obese individuals had a higher mean retinal capillary density index (CDI): superficial plexus, 0.7 (0.04) vs 0.68 (0.06) (P = .04); deep plexus, 0.38 (0.02) vs 0.35 (0.06) (P = .01)
• Obese subjects had lower mean AVR: 0.68 (0.05) vs 0.70 (0.03) (P < .01)

After 3 months, mean choroidal thickness significantly increased in group A (329.27 [79] μm; P < .01), but group B exhibited no changes compared with baseline. “No significant change was noted in CVI or CDI at 3 months in either group compared to baseline,” the researchers note, although AVR significantly increased in group B (P = .03).

“Increased adipose tissue in obesity has been associated with widening of venules, implicating microvascular dysfunction in the etiology of obesity,” the authors wrote. In addition, obese individuals have decreased nitric oxide (NO) levels, which can result in impaired vessel dilatation. The investigators hypothesize lower levels of NO and increased levels of vasoconstrictor in obese individuals may be responsible for decreased blood flow in the choroid.

The study results demonstrated both retinal and choroidal microvasculature appear to be adversely affected by obesity. Relatively small sample sizes and short follow-up periods serve as limitations to the study.

Reference

Agarwal A, Saini A, Mahajan S, et al. effect of weight loss on the retinochoroidal structural alterations among patients with exogenous obesity. PLoS One. Published online July 9, 2020. doi:10.1371/journal.pone.0235926