Increase in central corneal thickness in dry and normal eyes with application of artificial tears: a new diagnostic and follow‐up criterion for dry eye*

Abstract

To investigate the effect of artificial tear application on central corneal thickness (CCT) in dry and normal eyes. Forty eyes of 40 patients with symptomatic dry eyes and 20 eyes of 20 controls were included in the study. A combination artificial tear therapy was given to both groups for 1 week. The CCT was measured with ultrasonic pachymetry before and after the therapy. In addition, at the beginning of the study, 11 dry eye patients and eight control patients were evaluated separately as a subgroup: they received artificial tears every 10 min for an hour to determine whether this might constitute a diagnostic criterion. Results were analysed with a Wilcoxon test, accepting p < 0.01 as significant. The mean CCT in the dry eye group before and after 1-week therapy was 531.5 +/- 16.5 and 559.6 +/- 26.1 microm, respectively (p < 0.0001); thus yielding an average CCT increase of 28.1 +/- 9.4 microm (=5.30%: 1.65% minimum; 7.03% maximum) from baseline. The mean CCT in the control group before and after 1-week therapy was 549.2 +/- 37.8 and 552.3 +/- 39.8 microm, respectively (p = 0.001); thus, yielding an average CCT increase of 3.1 +/- 1.9 microm (=0.56%: 0.00% minimum; 1.18% maximum) from baseline. When the subgroup was evaluated separately, the average increase from baseline in 11 dry eye patients was 10.4 +/- 4.0 microm (=1.89%: 0.60% minimum; 4.26% maximum) after 1 h of artificial tear application, while it was 2.9 +/- 2.0 microm (=0.51%: 0.00% minimum; 0.58% maximum) in eight control patients (p < 0.0001). The CCT in dry eyes increases rapidly and significantly compared to normal eyes after application of artificial tears. It is suggested that this increase could be used as a criterion in the diagnosis and follow up of dry eyes, and that this increase in thickness should be considered in intra-ocular pressure measurements as well as in refractive surgical procedures.