Optical simulations of the impact of vault increase in scleral contact lenses in healthy eyes.

Purpose: To investigate by using computational simulations the optical impact of the change in the vault of two geometries of scleral contact lenses (SCLs).

Methods: Ray-tracing simulations were performed using specialized software in three eye models with different levels of primary SA (6 mm pupil). Two different geometries of SCL were used in such simulations characterized by the conic constants of the anterior surface of the lens (K1, -0.1 and -0.3). Likewise, the fitting of the SCL was simulated for different vaults (50-250 µm). The impact on the quality of the images through the eye models was assessed by analyzing the modulation transfer function (MTF) at different spatial frequencies (10 Lp/mm, 30 Lp/mm, and 50 Lp/mm). This impact was not only simulated for a distant object, but also for intermediate and near objects (vergence demands from 0.00 to 3.00 D). All these optical simulations were performed assuming a centered SCL, but also assuming a downward vertical decentration of 0.5 mm.

Results: The thinnest vault (50 µm) provided the best ocular optical quality in all three eye models for low vergence demands. For medium and high vergence demands, Lens 1 (K1 = -0.3, K2 = -0.4) resulted in a considerable improvement in optical quality in Eye 2 (C = -0.078 µm), while for eyes 1 (C = 0.408 µm) and 3 (C = -0.195 µm), this improvement only tended to happen for medium vergence demands. Overall, all the aberrations increased after lens fitting. Lens decentration did not cause significant variations in the results obtained with the well-centered lenses.

Conclusions: Changes in the vault of a SCL have an impact on the optical quality achieved for different vergence demands independently on the level of SA of the eye in which it is fitted. The clinical relevance of such impact should be investigated further.