Modern scleral lens use has increased and proven successful, although the required oxygen permeability has yet to be clinically established.1 Delving into this further, a new study in Optometry and Vision Science advises a material benchmark of at least 125Dk for daily scleral lens wear to minimize the disruption to corneal oxygen.

The team of UK researchers enrolled 15 masked participants (10 females) who were about 21 years old and were bilaterally fitted with five different scleral lenses (65, 100, 125, 163, and 180+ Dk) of the same shape profile and one soft silicone hydrogel lens in addition to no lens wear on separate occasions in a randomized order. A masked researcher measured corneal thickness and fluid reservoir depth, corneal curvature, objective bulbar and limbal redness, corneal biomechanics and ocular surface oxygen consumption before and after eight hours of wear. The study also recorded comfort scores using a visual analog scale.

The researchers observed greater corneal thickness (1.37 ± 1.25%) in scleral lenses with oxygen permeability of 65Dk after eight hours of wear compared with those wearing lenses with a materials of 100Dk or more (0.58 ± 0.99%). Additionally, the study found an association between edema in patients wearing a lens with 100Dk or greater material and fluid reservoir depth. Additionally, fluid reservoir depth decreased similarly with all oxygen-permeable lenses from 325.6 ± 99.1μm to 174.2 ± 100.8μm after eight hours of wear. Oxygen consumption fell with lenses that were 125Dk or less.

Also of note: Soft and scleral lens wear had no effect on corneal curvature, corneal biomechanics or ocular hyperemia.

Looking at comfort, soft lenses were more comfortable than all the scleral lenses, and the 180+ Dk lenses had the best comfort among the sclerals.

 “Scleral lens wear leads to an increase in corneal thickness, regardless of lens-material oxygen permeability because of the fluid reservoir depth,” the researchers wrote in their paper.

Dhallu S, Huarte ST, Bilkhu P, et al. Effect of scleral lens oxygen permeability on corneal physiology. Optometry and Vision Science. September 11, 2020. [Epub ahead of print].