Variation of Bruch's membrane opening in response to intraocular pressure change during scleral lens wear, in a population with keratoconus.

Purpose: The present study aimed to determine the potential impact of scleral lenses on intraocular pressure (IOP) by analysing the Bruch's membrane opening-minimum rim width (BMO-MRW) while the lenses are worn, in a population with keratoconus.

Methods: Participants were required to have keratoconus and be successfully fitted with scleral lenses for at least 3 months. A new pair of optimised scleral lenses was provided before the study. During the first session, corneal biomechanics was assessed using an air tonometer, coupling Scheimpflug technology. Then, a scan of the optic nerve was carried out using optical coherence tomography (OCT) at 2 h intervals for 6 h. Particular attention was paid to identifying the BMO-MRW, which represents the smallest distance between the BMO and the internal limiting membrane. These tests were repeated, respecting the time at which the initial measurements were taken, while the scleral lens was worn. Results from only one eye were analysed.

Results: A statistically significant change of 10.5 ± 3.6 μm (95% CI [241.3-473.1]; p = 0.02) in BMO-MRW was observed after 6 h of scleral lens wear, compared to measurements without lenses (4.8 ± 3.4 μm; 95% CI [285.1-439.7]; p = 0.18). The fluctuation was greater in participants with keratoconus than found in a previous study of regular corneas.

Conclusion: BMO-MRW became significantly thinner after 6 h of scleral lens wear compared with measurements without lenses. These variations may be associated with a rise in IOP during lens wear. Close monitoring for optic head changes should be carried out for patients at risk. These results should be compared with future longer-term studies including a larger cohort of patients.