Effects of fasting on peripapillary capillary density, peripapillary nerve fiber layer, intraocular pressure 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 fasting month of Ramadan.

Methods: Twenty-seven healthy fasting volunteers were enrolled. All subjects underwent full ophthalmic examination and optical coherence tomography angiography (OCTA) of both eyes. All measurements were recorded first in the morning (8:00-10:00 a.m.) and then in the evening (4:00-6:00 p.m.). The first visit was performed during the second and third 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 with morning IOP (12.00 ± 2.28) (p = 0.00) only on fasting days. A decrease was observed for CCT both on fasting (6 μm) and nonfasting days (3 μm) (p = 0.00 and p = 0.02, respectively) in the evening. There was a significant increase in whole and peripapillary RPC density (%) on fasting days (48.79 ± 3.08 morning, 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 nonfasting days (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 with nonfasting days (0.27 ± 0.25 morning, 0.28 ± 0.25 evening) (p = 0.02).

Conclusion: Fasting decreases the IOP and CCT in healthy subjects. OCTA revealed significant difference in RPC vessel density, RNFL thickness and ONH vertical C/D ratio during fasting hours in comparison with nonfasting days.