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M. Teson-Yvdelo, M. J. Gonzalez-Garcia, A. Morejon, S. Sancho, D. Velasco, I. Fernandez, M. Calonge; Influence of Visual Acuity, Refractive Error and Ocular Dominance in Corneal Sensitivity. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1046.
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The Belmonte's gas esthesiometer permits the evaluation of corneal and conjunctival sensitivity in a more complete way than other available esthesiometers. It is known that some individual factors such as age, iris color or contact lens wear can influence sensitivity thresholds. This study intends to determine the putative influence of best corrected visual acuity (BCVA), refractive error and ocular sensorial dominance (OSD) in mechanical, chemical and thermal (hot and cold) sensitivity thresholds (TM, TCh, TTH, and TTC, respectively) of the cornea.
BCVA, refractive error and OSD were measured in 80 eyes of 20 healthy males and 20 females with a mean age of 44.1 (SEM 2.4; range, 20-72) years. TM, TCh, TTH and TTC were measured with the Belmonte's esthesiometer in the central cornea in two different days (interval,1-6). Thresholds were determined using the method of levels. TM was determined first. The starting eye and the sequence of threshold measurements were determined randomly for each subject. A chi-squared analysis was performed to evaluate the association between qualitative variables. The Fisher exact test was used with sparse contingency tables. To study the differences in continuous variables, nonparametric techniques were used: Mann-Whitney U test for independent samples and the Wilcoxon signed-rank test for paired comparisons.
TM was found to be significantly lower in those eyes with better BCVA (mean ± SEM; TM in the eyes with best BCVA: 49.2±5.7; TM in the eyes with worst BCVA 62.3±6.1). When the refractive error was analyzed, a significantly lower TM was found in myopic eyes for the left eye (TM in myopic eyes 32.9±8.3; TM non- myopic eyes 59.4±6.8), and for the right eye (TM myopic eyes 43.3±11.3; TM non-myopic eyes 72.6±8.2) . No differences in corneal sensitivity were found with the OSD.
Visual acuity and refractive error (myopia) seem to influence mechanical corneal sensitivity. The reason why myopic eyes and eyes with better visual acuity tend to have lower mechanical threshold corneal sensitivity remains speculative and deserves further investigation.
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