Post-lens tear turbidity and visual quality after scleral lens wear

The aim was to evaluate the turbidity and thickness of the post-lens tear layer and its effect on visual quality in patients with keratoconus after the beginning of lens wear and before lens removal at the end of eight hours.

Twenty-six patients with keratoconus (aged 36.95 ± 8.95 years) participated voluntarily in the study. The sample was divided into two groups: patients with intrastromal corneal ring (ICRS group) and patients without ICRS (KC group). Distance visual acuity (VA), contrast sensitivity, pachymetry, post-lens tear layer height and post-lens tear layer turbidity (percentage area occupied and number of particles per mm² ) were evaluated with optical coherence tomography before and after wearing a scleral lens.

A significant increase of turbidity was found in all groups assessed (p < 0.05). The number of particles per square millimetre was eight times higher after scleral lens wear than at the beginning of wearing the lens for all groups. VA decreases in all groups after scleral lens wear (p < 0.001). All patients showed a statistical diminishing of contrast sensitivity after scleral lens wear (p < 0.05). A significant correlation was found for both turbidity parameters with distance VA but no correlation between turbidity and post-lens tear layer thickness at the beginning was found (p > 0.05). A strong correlation in all groups between the post-lens tear layer at the beginning and differences of tear layer thickness between two measures was also found (p < 0.05).

The VA decrease during the scleral lens wearing, filled with preserved saline solution, was due to the increasing post-lens tear layer turbidity.