The effect of oxybuprocaine on corneal thickness as measured with optical coherence tomography

Abstract

Background: No previous study in South Africa has used optical coherence tomography (OCT) in assessing corneal thickness changes following the instillation of an anaesthetic.

Aim: The purpose of this study was to investigate the short-term effects of oxybuprocaine 0.4% on corneal thickness.

Setting: The study was conducted at a university eye clinic in Westville, KwaZulu-Natal.

Methods: A total of 34 (N = 34) participants, of both genders, aged 18–25 years participated in the study. Data collection commenced once ethical clearance was obtained. Baseline measurements of central corneal thickness (CCT) (within 0 mm – 2 mm of the corneal apex) and mid-peripheral corneal thickness (MPCT) (within 2 mm – 5 mm of the corneal apex) were taken using the Optovue iVue 100 OCT. Measurements were obtained using the standard iVue 100 corneal pachymetry map. One drop of oxybuprocaine was then instilled using a sterile technique in the right eye (RE) of each participant. Central and MPCT measurements were obtained using the OCT at time intervals of 30 s for the first 2 min and then for 60-s intervals up until 5 min. Baseline central and MPCT were then measured for the left eye (LE) using the OCT. The effect of two drops of oxybuprocaine on CCT was also investigated on the left eye only using the same procedure as on the right eye.

Results: There were minimal fluctuations of the CCT and MPCT in the 5 min following instillation of either one or two drops of oxybuprocaine. The fluctuation of both the CCT and MPCT was within 10 µm irrespective of dosage and returned to baseline thickness after 5 min.

Conclusion: Clinically, short-term CCT and MPCT changes following the instillation of oxybuprocaine are not large enough to affect the accuracy of Goldmann applanation tonometry.