Toxicity of topical ophthalmic anesthetics

Topical ocular anesthesia has been part of ophthalmology for more than a century. The most commonly used drugs today are proparacaine, tetracaine, benoxinate (oxybuprocaine) cocaine and lidocaine. Although generally well tolerated, all these can be toxic, particularly when abused. The most common toxicities are to the ocular surface, but abuse can cause deep corneal infiltrates, ulceration and even perforation. Fortunately, systemic side effects are rare. Cocaine is unique for its higher incidence of systemic side effects and high abuse potential, both of which impede its clinical use. When used appropriately, all these drugs are remarkably safe. They are generally not prescribed for home use, as prolonged abuse of these drugs can be expected to result in serious complications.

To evaluate the clinical course, treatment modality, factors affecting the epithelization period, and visual outcome in patients with topical anesthetic abuse keratopathy. The medical records of 19 patients with a confirmed diagnosis of topical anesthetic abuse keratopathy were retrospectively examined; occupation, initiating event, biomicroscopic findings, treatment modality, epithelization period, and best-corrected visual acuity (BCVA) were noted. The Wilcoxon signed rank test was used to compare BCVA before and after treatment; P values <0.05 were considered statistically significant. In all, 26 eyes in 19 men aged 21-44 (mean age: 31 ± 6) years were included. Initiating events included exposure to arc welding flash (8 patients), metallic foreign body injury (8 patients), and chemical injury (3 patients). On admission to hospital, 10 patients (52.6%) reported that they were using topical anesthetics. Upon admission to the hospital, 10 patients (52.6%) self reported that they were using topical anesthetics. The remaining 9 subjects were discovered to be using topical anaesthetic drops during hospitalization. Twelve patients (63.2%) were found to continue using these agents during their hospitalization. Oval corneal epithelial defect, stromal infiltrate, ring-shaped keratitis, and hypopyon were noted in 100%, 46.2%, 57.7%, and 42.3% of the eyes, respectively. Topical antibiotics (fluoroquinolones or combined fortified cephalosporins and aminoglycosides), preservative-free lubricants/autologous serum, and bandage contact lens/eye patches were used for treatment. Mean epithelization period was 19.96 ± 11.16 days (range: 6-50 days). Mean pretreatment and posttreatment BCVA was 0.12 ± 0.16 (range: 0.001-0.7) and 0.66 ± 0.30 (range: 0.0-1.0), respectively (P < 0.001). Ophthalmologists should be suspicious of topical anesthetic abuse keratopathy in young male manual laborers specialized in welding business and foundry work presenting with persistent epithelial defects, ring-shaped keratitis, and accompanying severe ocular pain.

To determine whether the use of lidocaine gel prior to povidone-iodine antisepsis is associated with increased microbial survival.