Impact of soft contact lens edge design and midperipheral lens shape on the epithelium and its indentation with lens mobility.
OBJECTIVE
To evaluate the influence of soft contact lens midperipheral shape profile and edge design on the apparent epithelial thickness and indentation of the ocular surface with lens movement.


METHODS
Four soft contact lens designs comprising of two different plano midperipheral shape profiles and two edge designs (chiseled and knife edge) of silicone-hydrogel material were examined in 26 subjects aged 24.7 ± 4.6 years, each worn bilaterally in randomized order. Lens movement was imaged enface on insertion, at 2 and 4 hours with a high-speed, high-resolution camera simultaneous to the cross-section of the edge of the contact lens interaction with the ocular surface captured using optical coherence tomography (OCT) nasally, temporally, and inferiorly. Optical imaging distortions were individually corrected for by imaging the apparent distortion of a glass slide surface by the removed lens.


RESULTS
Apparent epithelial thickness varied with edge position (P < 0.001). When distortion was corrected for, epithelial indentation decreased with time after insertion (P = 0.010), changed after a blink (P < 0.001), and varied with position on the lens edge (P < 0.001), with the latter being affected by midperipheral lens shape profile and edge design. Horizontal and vertical lens movement did not change with time postinsertion. Vertical motion was affected by midperipheral lens shape profile (P < 0.001) and edge design (P < 0.001). Lens movement was associated with physiologic epithelium thickness for lens midperipheral shape profile and edge designs.


CONCLUSIONS
Dynamic OCT coupled with high-resolution video demonstrated that soft contact lens movement and image-corrected ocular surface indentation were influenced by both lens edge design and midperipheral lens shape profiles.
Ophthalmic Research Group, Life and Health Sciences, Aston University, Birmingham, United Kingdom.
James S
JS
Wolffsohn
Thomas
T
Drew
Sandeep
S
Dhallu
Amy
A
Sheppard
Greg J
GJ
Hofmann
Mark
M
Prince
D000328:Adult; D003263:Contact Lenses, Hydrophilic; D018592:Cross-Over Studies; D019573:Epithelium, Corneal / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D008297:Male; D011474:Prosthesis Design; D041623:Tomography, Optical Coherence; D055815:Young Adult
contact lenses; edge design; epithelial indentation; epithelial thickness