Analysis of Corneal Surface Temperature Changes Following Fingertip, Knuckle, and Fingernail Eye Rubbing

PurposeTo characterize corneal surface temperature changes induced by different eye-rubbing techniques in healthy individuals and to investigate the factors influencing temperature change. SettingEskisehir Osmangazi University DesignCross-sectional experimental study MethodsThis study included 93 healthy volunteers aged 19-29 years with no ocular pathology. Participants performed three eye-rubbing techniques-fingertip, knuckle, and fingernail rubbing-while corneal temperatures were recorded with a high-resolution thermal camera (FLIR A8200sc, Teledyne FLIR Systems Inc., Boston MA, USA). Subjects rubbed their eyes for 20 seconds with their dominant hand. Linear mixed-effects models were used to compare corneal temperature before and after eye rubbing and to examine the effect of covariates. ResultsAll eye rubbing techniques significantly increased corneal temperature (fingertip: 1.02 +/-0.58 degrees Celsius, knuckle: 1.03 +/-0.54 degrees Celsius, fingernail: 1.12 +/-0.52 degrees Celsius; all p<0.001), with no significant differences between techniques (p>0.05). Age showed a negative correlation with corneal temperature increase across all rubbing methods (all unadjusted p<0.05), remaining significant only for the fingertip technique after FDR correction (p<0.001). IHA correlated positively with temperature increase for fingertip and knuckle rubbing after FDR adjustment (p= 0.003 and <0.001, respectively). The subgroup analysis indicated that approximately 0.6 degrees Celsius of every 1 degrees Celsius rise in corneal temperature could be attributed to eye closure alone, while the remainder was likely due to mechanical effects of eye rubbing. ConclusionFingertip, knuckle, and fingernail rubbing each produced a transient but significant rise of approximately 1 degree Celsius in corneal temperature. Greater temperature elevation was associated with younger age and higher corneal asymmetry.