Does religious fasting affect intraocular pressure or retinal parameters?
Reviewed by Claire Howard

Nearly one billion Muslims fast every year during the month of Ramadan. Due to the difference between the lunar and solar calendars, religious fasting time can range from 11 to 17 hours per day. This prolonged abstinence from food and water provides an opportunity to investigate different aspects of fasting on the human body. This study aimed to assess the effect of religious fasting on intraocular pressure (IOP) as well as retinal parameters and retinal thickness during Ramadan using optical coherence tomography angiography (OCTA). All participants ate a pre-dawn meal and drink, and then fasted for at least 15 hours. The study assessed a total of 61 eyes from 31 healthy volunteers with a mean age of 32.87 ±8.07. A significant decrease was found in the median IOP after fasting at 10.00 mmHg in comparison with the pre-fasting value of 12.00 mmHg (p < .0001). Retinal peri-papillary capillary (RPC) whole image, RPC inside disk, and RPC mean values showed significant decreases after fasting (p= .011, .012, and .032 respectively). RPC whole vessel density (VD), RPC inside VD, and RPC VD mean values also showed significant decreases after fasting period (p= .025, <.0001, and .003, respectively). Results show that religious fasting during the warm season could decrease IOP. It could also reduce the blood flow of the retina, specifically the macula, and the retinal peri-papillary VD. These short-term fluctuations in IOP have the potential to be harmful in patients with glaucoma. Consideration is also needed as to whether fasting should be monitored in patients with underlying ischaemic diseases and diabetic and hypertensive retinopathies.

Evaluation of the effect of religious fasting on retinal vessel density and retinal thickness using optical coherence tomography angiography.
Shokoohi-Rad S, Shoeibi N, Ghasemi Nour M, Bakhtiari E.
NEURO-OPHTHALMOLOGY
2022;46(3):147-53.