Corneal And Intraocular Pressure Changes Associated To The Cyrcadian Rhythms: A Narrative Review

To synthesize the current body of research regarding the diurnal variations in intraocular pressure (IOP) and corneal biomechanical and morphological parameters, highlighting their significance in various eye conditions.

Department of Optics, Pharmacology and Anatomy, University of Alicante, Spain.

A comprehensive review of studies on the diurnal variations of IOP and corneal parameters was conducted. The findings from various tonometers were assessed, including the Goldmann applanation tonometry (GAT) and non-contact tonometers. Data on the variations in central corneal thickness (CCT), corneal curvature, and corneal biomechanics across different population groups was extracted and analyzed.

692 references were found and finally 26 were selected after a review. In healthy subjects and those with Fuchs dystrophy, IOP and CCT demonstrate marked diurnal declines. GAT remains the gold standard for tonometry, with the highest reliability. However, its measurements are influenced by CCT. Keratoconus and pseudoexfoliation patients showed significant diurnal variations in IOP. The biomechanical parameters measured by the Ocular Response Analyzer system, especially corneal hysteresis (CH) and the corneal resistance factor (CRF), largely remain stable throughout the day for most eye conditions, with some exceptions. Notably, the corneal morphology diurnal variation, particularly curvature, yielded mixed conclusions across studies.

Circadian rhythms significantly influence various corneal parameters, most notably IOP and CCT. In contrast, some variability in the results in terms of corneal morphological and biomechanical changes with the circadian rhythms has been reported. Further studies should emphasize standardized approaches larger sample sizes, and delve deeper into less-explored areas, such as the effects of orthokeratology lenses on diurnal biomechanical shifts.