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Published on: August 9, 2016
Regional Variations in Postlens Tear Layer Thickness During Scleral Lens Wear
Stephen J Vincent1, David Alonso-Caneiro, Michael J Collins
1Contact Lens and Visual Optics Laboratory, School of Optometry and Vision Science, Queensland University of Technology, Brisbane, Australia.
Objectives:
To quantify regional variations in the postlens tear layer (PLTL) thickness during scleral lens wear.
Methods:
Fifteen healthy adults (22±3 years) with normal corneae were fitted with a 16.5-mm-diameter rotationally symmetric scleral lens in one eye. The PLTL thickness was measured across the central 5 mm at 0, 15, 30, 45, 60, 90, 120, 240, and 480 min after lens insertion using a 12 radial line scan optical coherence tomography imaging protocol. Regional analyses were conducted by dividing the PLTL into 8 equal 45° segments.
Results:
A tilted optic zone was observed immediately after lens insertion with the greatest PLTL asymmetry between nasal and temporal regions (156±22 μm more clearance temporally) and superior nasal and inferotemporal regions (124±12 μm more clearance inferotemporally). The magnitude of lens settling observed in each region was associated with the initial PLTL (r=0.59-0.77, P≤0.02). The superior nasal PLTL furthest from the pupil center stabilized after 90 min compared with other regions which stabilized after 4 hr. On average, after 8 hr of lens wear, the PLTL decreased by 29% and PLTL asymmetries between opposing regions decreased by 30%.
Conclusions:
The PLTL was thickest temporally and thinnest nasally in healthy eyes fitted with rotationally symmetric scleral lenses, most likely because of regional differences in underlying scleral elevation, eyelid forces, and lens centration. Postlens tear layer asymmetries diminished with lens wear, and stabilization occurred more rapidly in regions with less corneal clearance immediately after lens insertion.
