Background: Cataract surgery requires prolonged anaesthesia, concomitant with permanent hydration and lubrication of the cornea, in order to provide a clear view of the operation area.
Aims: The primary objective of the study was to assess several formulae of a soluble ophthalmic insert: TOPICSERT [bupivacaine (Bupi) + hyaluronic acid (HA) or sodium hyaluronate] in terms of complete and long-lasting anaesthesia of the cornea. The hydration properties of HA were not assessed in this study.
Methods: In a prospective double-blind, cross-over, randomized study, with latin-square allocation of treatments, 16 healthy volunteers received a single dose of each formula (A, 1 mg Bupi and 0.1 mg HA; B, 0.5 mg Bupi and 0.1 mg HA; C, 1 mg Bupi and 0 mg HA, and D acting as a placebo) via the ocular route with 1 week of wash-out between each period. Corneal anaesthesia was measured using a Cochet-Bonnet esthesiometer.
Results: There was a statistically significant difference between treatments with regard to the main criterion (complete anaesthesia lasting at least 20 min) when general association statistics were used (Mantel-Haenzel test, P < 0.0001): 68.75% (n = 11) of subjects receiving treatment A, 37.5% (n = 6) receiving treatment B, and 87.5% (n = 14) on treatment C reached complete and satisfactory anaesthesia, while this was not achieved in any of the subjects receiving placebo. Ninety-five percent confidence intervals of the difference between treatments were as follows: treatment A vs. B (-0.03, 0.66), treatment A vs. C (-0.47, 0.10), treatment B vs. C (-0.84, - 0.16). Only the difference between B and C was statistically significant (adjusted probability by the method of Bonferroni, P < 0.001). When complete anaesthesia was reached, mean (+/-SD) duration of anaesthesia was as follows: 20.7 (+/-6.5), 15.3 (+/-11.4) and 24.7 (+/-7.6) min for treatments A, B, C, respectively.
Conclusions: Bupivacaine 1 mg seems to be the efficient and safe dose. The value of hyaluronic acid as a corneal hydration agent and used in association with bupivacaine will be the subject of further studies.