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Nicole M Putnam, Stephanie Pilcher, David Bowin, Wendy Watkins Harrison; Evaluation of corneal nerve density with contact lens wear. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5720.
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A previous study conducted by our group indicated that hyperopes have a greater corneal nerve density than high myopes. However, the data presented with a lot of scatter, particularly among subjects with low myopia. Since most of the patients in that study were contact lens wearers, we hypothesized that differences in their contact lens wear may be responsible for the scatter. Here we add to that study with additional data on contact lens wear and corneal sensation.
Twenty new healthy subjects between the ages of 21-36 were recruited for the study. They had spherical equivalents between plano and -4.75D, and 18 of the 20 were regular contact lens wearers. Most had little astigmatism but 4 subjects had cylinder between -0.75 and -2.50D. Subjects were questioned about the history of their contact lens wear followed by an autorefraction, a-scan, and corneal sensitivity measurements (Cochet-Bonnet Aesthesiometer). Two corneal nerve scans were obtained for each eye over the central cornea with a Nidek CS4 confocal microscope (460x345 mm field). A single image from each scan with the most nerves was selected for analysis. Nerves were evaluated for density calculations using the ImageJ plugin NeuronJ. One eye was selected for analysis from each subject based on a combination of image quality and refractive error. Data was evaluated through single and multivariate regression.
The data showed a similar spread in corneal nerve density over refractive error and axial length, which was not significantly sloped and presented with a lot of scatter (average 11178 and range 4947-21105 microns/mm2). Subjects ranged from non-contact lens wearers to 20 years of contact lens wear. The lens wearers ranged from 1-7 days/week and 2-16 hours/day (cumulative hours ranged from 2-112 hours/week). There was no significant relationship between corneal nerve density and corneal sensitivity or any parameters of contact lens wear (years, hours/day, days/week, cumulative hours/week). Controlling for contact lens wear in years, hours/day, or cumulative hours a week did not change or improve the relationship between density and refractive error or axial length.
Our data suggests contact lens wear differences are not responsible for the large spread in corneal nerve density measurements for subjects with low myopia. More studies with expanded prescription ranges and numbers of subjects are needed to fully understand this relationship.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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