Comparison of the influence of corneo-scleral and scleral lenses on ocular surface and tear film metrics in a presbyopic population.

Purpose: To assess and compare the effect of the corneo-scleral lenses (C-ScL) and scleral lenses (ScL) on tear film parameters and central corneal thickness (CCT) in healthy presbyopic subjects.
Methods: Thirty subjects wore two contact lenses (CLs), randomly assigned, of neutral power, but of different diameters, 12.7mm (C-ScL) and 18mm (ScL) and being equal in the others parameters: material (HS100) and centre thickness (0.29mm). At baseline, 20min after insertion and at 8h, the tear meniscus area (TMA) and CCT was measured (with optical coherence tomography) as well as tear osmolarity.
Results: TMA revealed statistical differences for both lenses at 20min (p<0.001), and also at 8h (p=0.003), being greater for the C-ScL. CCT showed statistical differences for both lenses at 20min (p=0.002), and also at 8h (p=0.001), being lower for the C-ScL. Osmolarity did not reveal statistical differences at 20min (p=0.29), while it was statistically different at 8h (p=0.03), being lower for the C-ScL.
Conclusions: C-ScL lead to a lesser reduction in the TMA and a lower induced hypoxic stress than the ScL. Osmolarity levels remained within normal values across the day with no clinical difference between lenses. Both designs can represent a good optical platform for correcting presbyopia as well as protecting the ocular surface by vaulting the cornea.
(Copyright © 2017 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.)