The Effect of Fasting on Anterior Segment Parameters: A Systematic Review.

Abstract

Purpose: To ascertain the effect of Ramadan fasting on the anterior segment. Fasting can affect anterior segment parameters because of altered hydration and metabolism.

Methods: We searched online databases such as PubMed, Cochrane Library, Web of Science, Scopus, Embase, and Google Scholar for relevant records by suitable keywords. Overall, 21 eligible articles were included for the final assessment. Outcomes included types of fasting, tear film, corneal biomechanics, anterior chamber parameters, refraction, and visual acuity.

Results: All 21 articles were conducted after Ramadan fasting. The outcomes revealed that tear breakup time (TBUT) diminished and basal tear secretion (BTS) decreased. Predawn fluid intake temporarily improved tear production. A study revealed that ocular surface disease index (OSDI) scores degraded. Increases in tear osmolarity and inflammatory markers were reported. Transient corneal steepening and reduced corneal hysteresis suggested dehydration effects, while advanced imaging revealed posterior curvature changes. Furthermore, inconsistent results included diminished or augmented anterior chamber depth. No significant changes were reported in refraction or visual acuity.

Conclusions: The results indicated that fasting could alter various ocular structures and functions in the eye. Fasting could change the ocular surface condition, especially during the hotter seasons and longer fasting periods, along with lower parameters such as TBUT, BTS, and result in higher ocular discomfort, as measured by indices such as the OSDI scores. In addition, although the refraction and visual acuity seem to be stable along the fasting period, fasting could alter keratometric values and intraocular lens calculation, leading to suboptimal refractive results after surgeries.