Scleral Contact Lens Vault Affects Optical Quality for Different Vergences

Scleral contact lens vault may affect optical quality for different vergence demands, according to a series of computed simulations published in Contact Lens and Anterior Eye. These changes operate independently of any primary spherical aberration present in the eye, according to the report. 

Researchers performed ray tracing simulations using specialized software with 2 geometries of scleral contact lenses in 3 simulated eyes of varying refractive error (spherical equivalent [SE], 0.26, −0.26, and −4.08 for eyes 1, 2, and 3, respectively). The team performed fittings with scleral contact lens vaults ranging from 50 to 250 µm and evaluated image quality using modulator transfer function at 3 different spatial frequencies (10 Lp/mm, 30 Lp/mm, and 50 Lp/mm). The investigation considered these visual effects for a variety of viewing distances (33.3 cm to optical infinity) and vergences (0-3 D). 

Overall, the thinnest scleral contact lens vault provided the best optical quality for all 3 simulated eye models at low vergence demands. However, a more prolate vault improved optical quality for medium and high vergences in eye model 2 and for medium vergence demands in eyes 1 and 3. Overall, thicker vaults provided better optical quality for higher vergences, according to the report. 

“This shift in the behavior suggests that there is a vergence demand threshold that must be observed carefully as the practitioner should promote thinner or thicker vaults depending on whether low vergence or high vergence are aimed to be corrected,” the study authors explain. 

Aberrations increased following lens fitting — defocus increased with decreasing scleral contact lens vault values at low vergence (near 0.00 D) and decreased with increasing vault values at higher vergences. Decentration did not affect modulator transfer function in any of the eye models in any simulated vault or vergence conditions. 

Study limitations include the use of simulated exercises and failure to consider the effect of changing accommodation. 

Disclosure: This research was supported by Laboratorios Lenticon S.A. Please see the original reference for a full list of disclosures.