Effects of fasting on peripapillary capillary density, peripapillary nerve fiber layer, intraocularpressure and central corneal thickness

Purpose: To investigate the effects of fasting on intraocular pressure (IOP), central corneal thickness (CCT),radial peripapillary capillary (RPC) density and retinal nerve fiber layer (RNFL) thickness during Islamic fastingmonth of Ramadan.Methods: 27 healthy fasting volunteers were enrolled. All subjects underwent full ophthalmic examination andoptical coherence tomography angiography (OCTA) of both eyes. All measurements were recorded first in themorning (8:00-10:00 am) and then in the evening (4:00-6:00 p.m.). First visit was performed during the 2nd and3rd week of Ramadan and then two months later in a nonfasting routine day.Results: Mean age of participants was 40.07±9.29 years. A significant decrease was found for evening IOP(11.17±2.29 mmHg) in comparison to morning IOP (12.00±2.28) (p=0.00) only on fasting days. A decrease wasobserved for CCT both on fasting (6 μm) and nonfasting days (3 μm) (p=0.00 and p=0.02 respectively) in theevening. There was a significant increase in whole and peripapillary RPC density (%) on fasting days (48.79±3.08morning, 49.72±2.85 evening for whole and 50.57±4.06 morning, 51.64±3.71 evening for peripapillary) (p=0.00).Average RNFL thickness was decreased from morning to evening both on fasting days (0.80 μm) and nonfastingdays (1.25 μm) (p=0.00). Optic nerve head (ONH) vertical cup/disc (C/D) ratio was greater on fasting days(0.30±0.25 morning, 0.31±0.24 evening) in comparison to nonfasting days (0.27±0.25 morning, 0.28±0.25evening) (p=0.02).Conclusion: Fasting decreases the IOP and CCT in healthy subjects. OCTA revealed significant difference inRPC vessel density, RNFL thickness and ONH vertical C/D ratio during fasting hours in comparison to nonfastingdays.