Evaluation of the Therapeutic Efficacy of Local Anesthetics Used in the Removal of Corneal Foreign Bodies

Corneal injuries, including foreign body (FB) penetration, represent a significant portion of ophthalmic pathology, particularly among the working-age population. Successful FB removal requires the use of effective and safe topical anesthetics that not only minimize patient discomfort but also reduce the risk of complications such as keratitis, ulceration, or secondary infection. The safety profile of anesthetics is of particular importance, as their toxic effects on the cornea can delay epithelial regeneration and exacerbate postoperative complications. In clinical practice, instillation anesthetics such as proxymetacaine 0.5 % (Dropsthetic) and oxybuprocaine 0.4 % (Inocaine) are widely used. However, their comparative efficacy, effects on corneal status (including central thickness), and impact on tear film stability — particularly in patients with dry eye syndrome — remain insufficiently studied. Key aspects requiring evaluation include the speed of anesthesia onset, duration of action, influence on corneal thickness, and effects on tear film stability, especially in dry eye patients. This study aims to conduct a comparative analysis of these anesthetics in terms of therapeutic efficacy, safety, and patient-reported tolerability. The findings will help to optimize the choice of anesthetic for corneal foreign body removal, which is particularly relevant in emergency ophthalmic care settings.

Purpose. A comparative study of the therapeutic efficacy and safety of topical anesthetic instillations — Dropsthetic (proxymetacaine 0.5 %) versus Inocaine (oxybuprocaine 0.4 %) — in patients with corneal foreign bodies.

Patients and methods. This open-label prospective randomized study included 60 patients (60 eyes) with superficial corneal foreign bodies (metal — 60 %, concrete — 25 %, wood — 15 %). Patients were divided into two groups: Group 1 (n = 30) received proxymetacaine 0.5 %, Group 2 (n = 30) received oxybuprocaine 0.4 %. Parameters assessed included: оnset of anesthesia, duration of complete and total anesthesia, tear film stability (NIBUT), central corneal thickness (CCT), subjective tolerance (questionnaire).

Results. Proxymetacaine 0.5 % demonstrated statistically significant advantages in: faster anesthesia onset (22.0 ± 12.1 sec vs 30.0 ± 15.0 sec; p < 0.001), longer duration of effect (40.0 ± 1.3 min vs 35.0 ± 1.4 min; p < 0.001). Both anesthetics showed no clinically significant changes in tear film stability (NIBUT: p > 0.05), though oxybuprocaine significantly reduced breakup time at 1 hour (p < 0.001). Proxymetacaine caused less burning sensation upon instillation (3.3 % vs 30 %; p < 0.01). Proxymetacaine group showed less corneal edema in the optical zone (p < 0.001). Patients rated proxymetacaine higher for comfort (8.8 vs 7.1 points; p = 0.0001). In addition, DropSthetic was rated by the majority of patients as more comfortable (8.8 vs. 7.1 points; p = 0.0001), possibly due to its selective effect on unmyelinated nerve fibers, which leads to rapid suppression of the generation and conduction of nerve impulses.

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