Ocular toxicity of subconjunctival gentamicin

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.