Purpose To characterize corneal surface temperature changes induced by different eye-rubbing techniques in healthy individuals and to investigate the factors influencing temperature change.

Setting Eskisehir Osmangazi University

Design Cross-sectional experimental study

Methods This 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.

Results All 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.

Conclusion Fingertip, 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.

The authors have declared no competing interest.

This study was supported by Scientific and Technological Research Council of Turkiye (TUBITAK) under the Grant Number 1919B012325181 (2209-A).

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The study was approved by the Ethical Board of Non-Interventional Clinical Research of Eskişehir Osmangazi University (Decision no: 18; date: 25.07.2023).

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Yes

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Conflicts of Interest: The authors have no conflicts of interest to disclose.

Funding: This study was supported by Scientific and Technological Research Council of Türkiye (TÜBITAK) under the Grant Number 1919B012325181 (2209-A).

Declaration of generative AI and AI-assisted technologies in the writing process: During the preparation of this work the authors used ChatGPT 5 in order to improve language and readability in some sections of the manuscript. After using this tool/service, the authors reviewed and edited the content as needed and take full responsibility for the content of the publication.

This work has been presented at the Royal College of Ophthalmologists Annual Congress in Belfast, UK, 20-23 May 2024, as a poster presentation.

The dataset created and analysed during the current study is available from the corresponding author on reasonable request.