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Ocular toxicity of subconjunctival gentamicin
1Department of Ophthalmology, Medical College of Georgia, Augusta 30912-3400.
Abstract:
The subconjunctival injection of commercial gentamicin, given either as a single dose or as repeated injections, caused a hyperemic conjunctival response. Simultaneously there was a toxic myopathy induced in the extraocular muscles. The overall response, followed with light microscopy, occurred as a focal infiltrate of polymorphonuclear leukocytes with progression over a few days to a mononuclear cell infiltrate that accompanied fiber degeneration. Injections of each ingredient of commercial gentamicin individually showed that only gentamicin caused the muscle response; methylparaben, EDTA, and sodium bisulfite were without effect. The pH of the solution was eliminated as a contributing factor as was osmolarity of the injection. Increasing recognition is being given to post-operative complications caused by the prophylactic subconjunctival injection of gentamicin following cataract, and other intraocular surgery. The present data offer a mechanistic explanation for many of these toxic findings.
Insights
Subconjunctival gentamicin injections cause eye muscle damage and inflammation. This study identifies gentamicin as the sole cause, explaining post-operative complications after eye surgery.
Area of Science:
- Ophthalmology
- Toxicology
- Muscle Physiology
Background:
- Subconjunctival gentamicin is used prophylactically after intraocular surgery.
- Post-operative complications linked to gentamicin injections are increasingly recognized.
Purpose of the Study:
- To investigate the toxic effects of subconjunctival gentamicin on extraocular muscles.
- To elucidate the mechanism behind gentamicin-induced myopathy.
Main Methods:
- Subconjunctival injections of commercial gentamicin (single and repeated doses) in animal models.
- Light microscopy to examine extraocular muscle tissue.
- Individual component testing of gentamicin, methylparaben, EDTA, and sodium bisulfite.
Main Results:
- Gentamicin injections induced hyperemic conjunctival response and toxic myopathy in extraocular muscles.
- Histopathology revealed polymorphonuclear leukocyte infiltration progressing to mononuclear cell infiltrate and fiber degeneration.
- Only gentamicin, not its excipients (methylparaben, EDTA, sodium bisulfite), caused the myopathy.
- pH and osmolarity were ruled out as contributing factors.
Conclusions:
- Gentamicin is the causative agent of subconjunctival injection-induced myopathy.
- The findings provide a mechanistic explanation for observed toxicities following prophylactic gentamicin use.
- Highlights potential risks associated with gentamicin prophylaxis in ophthalmic surgery.