The temporal dynamics of miniscleral contact lenses: Central corneal clearance and centration

To examine the time course of the reduction in central corneal clearance and horizontal and vertical lens translation (decentration) during miniscleral contact lens wear and the theoretical influence upon the optics of the post-lens tear layer.

Repeated high-resolution OCT images were captured over an 8h period of miniscleral contact lens wear (using a rotationally symmetric 16.5mm diameter lens) in 15 young, healthy participants with normal corneae. Central corneal clearance and lens decentration were derived from OCT images using semi-automated image processing techniques.

Central corneal clearance decreased exponentially over time, reducing by 76±8μm over 8h. Fifty percent of this reduction occurred within 45min of lens wear and seventy-five percent within 2h, with thinning of the post-lens tear layer plateauing 4h after lens insertion. Lens translation exhibited a similar pattern of change (0.18±0.04mm temporal and 0.20±0.09mm inferior decentration) stabilising 1.5-2h after insertion. The change in the lens fit over time resulted in a small reduction in the power of the post-lens tear layer (-0.12±0.01 D) and induced a prismatic effect of 0.01±0.16 Δ base out and 0.50±0.19 Δ base down relative to the pupil centre.

For the miniscleral contact lens studied, horizontal and vertical lens decentration followed an exponential decay over 8h that plateaued approximately 2h after lens insertion, while central post-lens tear layer thinning plateaued after 4h of lens wear.