A randomized, fellow eye, comparison of keratometry, aberrometry, tear film, axial length and the anterior chamber depth after eye rubbing in non-keratoconic eyes

BACKGROUND: To investigate the effect of eye rubbing on keratometry (K), aberrometry, tear film break-up-time (TFBUT) and anterior chamber depth (ACD). METHODS: Volunteers without any corneal pathology or dry eyes were randomised to rubbing in one eye and the fellow-eye was control. Eye rubbing was performed for 2 min. Primary outcomes studied were anterior and posterior K changes. Secondary outcomes were changes in TFBUT, axial length (AL) & ACD, K changes in various zones, asphericity and aberrometry. Pre and post rubbing K, aberrometry, ACD and TFBUT were assessed in a predetermined sequence. The relationship of the above parameters to axial length (AL) was also assessed. Astigmatism was analysed using vector analysis. RESULTS: Pre versus post rubbing, anterior flatter K further flattened (42.51 ± 1.52 D vs. 42.36 ± 1.53 D, p = 0.003) and the changes to J0 vector in central cornea (−0.16 ± 0.26 D vs. -0.27 ± 0.33 D, p = 0.038) suggested change to against-the-rule (ATR) astigmatism. There was significant change in Z(2) (+2) polynomial following rubbing. We found a positive correlation between axial length and change in posterior K (r = 0.335, p = 0.020). The TFBUT reduced following eye rubbing (15.3 s vs. 13.9 s, p = 0.0001). There was a positive correlation between AL and increase in ACD post rubbing (r = 0.300, p = 0.038). There was a positive correlation between ACD and change in mean posterior K (r = 0.305, p = 0.035). CONCLUSIONS: In healthy eyes, following eye rubbing, there is a significant change in TFBUT and central anterior K changes towards ATR astigmatism. Longer eyes had more changes in posterior K and ACD. Whereas, eyes with deeper ACD showed more steepness of posterior K. TRIAL REGISTRATION: ClinicalTrials.gov ID: NCT02131740. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s40662-017-0084-8) contains supplementary material, which is available to authorized users.