Abstract
Background: :
Topical anaesthesia is widespread used in anterior segment surgery. Ethanol or cocaine have widely been used for PRK and for creating epithelial flaps in LASEK. In view of recent clinical evidence regarding ocular toxic effects of alcohol and local anaesthetics, we wished to assess the impact of these locally applied drugs on ocular surface wound healing using an ex vivo whole globe wound healing model.
Materials and Methods: :
Standardized corneoepithelial lesions, 5.0mm in diameter and 40µm in depth, were created with an Excimer laser in freshly enucleated porcine eyes. These were then exposed to control solutions [basic saline solution (BSS; pH 7.4; baseline) and tissue–culture medium (positive control)] and to the test agents [ethanol 2–99%, cocaine 2–10%, novocaine 0.4%, tetracaine 0.5–1% and lidocaine 2%]. The wound–healing response and toxic effects were monitored after 20 to 26 hours by comparing lesion sizes after fluorescein staining.
Results: :
According to baseline data obtained using BSS (4.44±0.15mm), ethanol 2–10% did not interfere with wound healing, whereas higher concentrations delayed wound healing (lesion size 24h after exposure to ethanol 20%: 4.58±0.20mm; p=0.035). Even in low concentrations, cocaine (4.83±0.25mm; p<0.001), tetracaine (5.59±0.35mm; p<0.001) and novocaine (5.76±0.18mm; p<0.001) induced toxic effects with an increase of lesion size above baseline whereas lidocaine 2% exhibited a moderate negative effect on wound healing with only moderate toxicity (lesion sizes after 20h and 24h: 5.01±0.17mm and 4.78±0.14mm, respectively; p<0.001).
Conclusions: :
The herein presented data support the clinical impression of a negative impact of local anaesthetics and ethanol on ocular surface wound healing. The experimental set up allows to systematically assess the impact of local anaesthetics and other drugs routinely used in anterior segment surgery on ocular surface wound healing.
Keywords: wound healing • cornea: epithelium • refractive surgery