Effect of topical corneal anaesthesia on ocular response analyzer parameters: pilot study

Abstract

The effect of topical corneal anaesthesia on corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated intraocular pressure (IOPg), and corneal compensated IOP (IOPcc) was measured by ocular response analyzer (ORA). Observational, cross-sectional study. We examined both eyes of 23 healthy volunteers. Patients with external eye disease, previous refractive surgery, contact lenses or topical medication were excluded. ORA parameters were first measured in both eyes. Oxybuprocaïne 0.4% eye drop was instilled in the right eyes (RE) and physiologic saline in the left eyes (LE) as a control to rule out the lubrication effect. After 2 min, the ORA measurements were performed again. Goldmann applanation tonometry (GAT) was finally done. Data are expressed as mean +/- standard deviation (SD). The medians of the four CH, CRF, IOPg, and IOPcc values measured before and after instillation were compared by using Wilcoxon signed ranks tests for RE and LE. The mean age was 39.5 +/- 11.6 years. The mean GAT was 13.1 +/- 2.5 mmHg for RE and 12.8 +/- 2.5 mmHg for LE. In the RE, the respective values for the two sequences were IOPcc = 15.6 +/- 2.6 mmHg and 15 +/- 2.8 mmHg (P = 0.036); IOPg = 15.3 +/- 3.3 mmHg and 15.4 +/- 3.5 mmHg (P = 0.806); CH = 11 +/- 1.3 mmHg and 11.1 +/- 1.4 mmHg (P = 0.563); CRF = 11.1 +/- 1.8 mmHg and 10.9 +/- 1.9 mmHg (P = 0.053). In the LE, the respective values for the two sequences were IOPcc = 15.4 +/- 2.6 mmHg and 15.6 +/- 2.8 mmHg (P = 0.903); IOPg = 15.5 +/- 3.5 mmHg and 15.4 +/- 3.4 mmHg (P = 0.208); CH = 10.8 +/- 1.4 mmHg and 10.7 +/- 1.7 mmHg (P = 0.494); CRF = 10.7 +/- 1.8 mmHg and 10.7 +/- 2.2 mmHg (P = 0.626). Two minutes after instillation, topical corneal anaesthetic slightly decreases IOPcc and also-but not statistically significantly-CRF. We did not find any statistical significant difference in CH or IOPg before and after topical corneal anaesthesia. Further investigation with more patients should be advised.