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Purpose: To determine the recovery of structural and functional corneal sensory nerves within the LASIK flap in order to provide insight to more proximal corneal reinnervation and symptoms post-LASIK. Methods: Twenty participants underwent femtosecond LASIK with a superior flap hinge. Ocular Comfort Index in Chinese (OCI-C), Cochet-Bonnet esthesiometry, and in vivo confocal microscopy were conducted before surgery and 1 week, 1-, 3-, and 6-months post-LASIK to measure symptoms, corneal sensitivity, nerve fiber density, width, and the number of interconnections within the flap (central and mid-temporal regions), and next to the superior flap hinge. Linear mixed models were used to compare differences between corneal regions at each time point post-LASIK and changes over time post-LASIK. Spearman's correlation tests were used to examine the associations between variables post-LASIK. Results: The least reduction in sensitivity (P < 0.03) and in nerve fiber density (P < 0.02) was found near the flap hinge compared to other regions, but no regional differences were found in nerve fiber width and interconnections. Nerve fiber density and the number of interconnections at all regions within the flap recovered over time (P < 0.02). The recovery of corneal sensitivity and nerve fiber width was only seen at the central and temporal regions (P < 0.04). No association was found between sensitivity and nerve parameters, but a higher OCI-C score was associated with a lower nerve fiber density near the hinge (r = − 0.43, P = 0.003) over time post-LASIK. Conclusion: Corneal sensitivity and density are preserved in the hinge, but this preservation of the corneal nerve damage does not affect the nerve morphology. [ABSTRACT FROM AUTHOR]

Aims: To determine the repeatability of ocular surface sensitivity to mechanical stimulation using air stimuli and the effect of contact lens (CL) wear on sensitivity. Methods: Repeatabiliiy 14 subiects (24-39 years) participated. Mechanical sensitivity to warmed (34°C) and ambient (20°C) air was measured for the central cornea (CC), inferior cornea (IC), and inferior con junctiva (ICON). Measurements were taken on 12 days; six morning and six afternoon measurements. Differences between sites, time of day, and stimulus temperature were evaluated. CL wear 10 subjects (22-30 years) participated. Measurements were taken at the same time of day, either following no wear, wear of a CL of oxygen permeability [DkJ of 28 × 10-9 [cm/s][ml O2/ml mm Hg] or wear of a CL of Dk 140 × 10-9 [cm/sj[mi O2/ml mm Hg]. Differences between sites and wear conditions were evaluated. Results: Repeatability: Sensitivity varied between sites (p< 10-90.01), time of day (p<0.05), and stimulus temperatures (p<0.01). There were no significant differences between days. Mean thresholds For eye temperature stimuli were; CC 64.4 (SD 28.6) mI/mm; IC 84.6(40.0) ml/min; 1CON 120.6(40.4) mi/mm and for ambient temperature stimuli were CC 53.9 (16.0) mi/mm, IC 59.0 (20.0) mI/mm; ICON 72.6 (43.7) mI/mm. CL wear Sensitivity varied between sites and wear conditions (p<0.05). Conjunctival sensitivity was increased after wear of highly oxygen permeable CLs but unaffected by wear of low oxygen permeable CLs. Conclusions: The prototype gas aesthesiometer is able to repeatably measure ocular surface sensitivity and measurements are consistent with previously reported techniques. [ABSTRACT FROM AUTHOR]