Effect of religious fasting on tear osmolarity and ocular surface

To evaluate the effects of religious fasting on tear secretion, tear osmolarity, corneal topography, and ocular aberrations.

This prospective controlled study comprised 29 eyes of 29 healthy men. Before ophthalmologic examination, all subjects underwent corneal topography by a placido disc corneal topography and aberrometry device (OPD Scan II). Tear osmolarity was measured using OcuSense TearLab osmometer. Ocular surface disease index (OSDI) scores, tear break-up time (BUT), Schirmer I test, and lissamine green staining were evaluated. The measurements taken before and during Ramadan at the same hours between 4.00 and 5.00 PM were compared using paired sample t test, and a P value less than 0.05 was accepted as statistically significant.

The mean age of the study group was 27.8 ± 5.9 years (range, 20-47 years). The mean tear osmolarity values were measured as 285.6 ± 8.2 mOsm/L and 293.3 ± 16.0 mOsm/L, whereas the mean Schirmer I values were 14.8 ± 6.0 mm and 10.6 ± 5.3 mm in nonfasting and fasting periods, respectively. Tear osmolarity, OSDI, and Oxford grading scores significantly increased (P=0.02, P=0.002, P=0.003, respectively), whereas Schirmer I values and intraocular pressure decreased (both, P<0.001) during the fasting period compared with the nonfasting period. There were no significant differences in tear BUT, keratometry values, and corneal aberration measurements between nonfasting and fasting periods (P>0.05, for all).

Fasting significantly decreases tear production and increases tear osmolarity; however, it does not deteriorate corneal topographic parameters and ocular aberrations in healthy subjects.