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Effect of Scleral Lens Oxygen Permeability on Corneal Physiology
Sandeep K Dhallu1, Sonia Trave Huarte, Paramdeep S Bilkhu
1Ophthalmic Research Group, Aston University, Birmingham, United Kingdom.
Significance:
This randomized, masked, crossover clinical study identifies that ≥125 Dk materials should be used for scleral lens daily wear if disruption to corneal oxygen is to be minimized.
Purpose:
Modern scleral lens use has increased and has proven to be successful where other types and materials have previously failed. Although the required oxygen permeability has been modeled, this has not been established clinically.
Methods:
Fifteen masked participants aged 20.7 ± 2.3 years (10 female) 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 compared with 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 8 hours of wear. In addition, comfort scores were obtained using a visual analog scale.
Results:
Scleral lenses with oxygen permeability of 65 Dk resulted in greater corneal thickness (1.37 ± 1.25%) after 8 hours of wear versus ≥100 Dk materials (0.58 ± 0.99%; F = 17.215, P < .001) because of stromal thickening; edema with ≥100 Dk materials was associated with fluid reservoir depth (r = 0.231, P = .05). Fluid reservoir depth decreased similarly with all oxygen-permeable lenses from 325.6 ± 99.1 μm to 174.2 ± 100.8 μm after 8 hours of wear (F = 0.961, P = .44). Oxygen consumption reduced with ≤125 Dk lenses (χ = 604.196, P < .001). Soft and scleral lens wear had no effect on corneal curvature, corneal biomechanics, or ocular hyperemia (P > .05). Soft lenses were more comfortable than all the scleral lenses (P < .05), and the 180+ Dk lenses had the best comfort among the sclerals (P < .05).
Conclusions:
A ≥125 Dk is advised for safe scleral lens daily wear. Scleral lens wear leads to an increase in corneal thickness, regardless of lens-material oxygen permeability because of the fluid reservoir depth.
