Effect of Volumes of Solutions on Intraocular Pressure During Intravitreal Injection of Low Dose Gentamicin in Horses With Recurrent Uveitis: A Randomized Controlled Study.
Authors: Launois Thomas, Hontoir Fanny, Dugdale Alexandra, Dedieu Marion, Vandeweerd Jean-Michel
Journal: Journal of equine veterinary science
Summary
# Editorial Summary Recurrent equine uveitis management via intravitreal gentamicin injection carries a significant risk: iatrogenic elevation of intraocular pressure (IOP) potentially triggering retinal damage. Launois and colleagues conducted a randomised controlled trial comparing two volumes each of retrobulbar lidocaine (5 versus 10 mL) and intravitreal gentamicin solution (0.15 versus 0.3 mL) to determine their respective effects on IOP across 40 injections. Whilst the 10 mL lidocaine block produced a statistically significant IOP increase, the clinical difference was negligible at merely +0.5 mmHg; notably, gentamicin solution volume had no meaningful impact on pressure dynamics. The affected eyes demonstrated predictably lower baseline pressures (−6.1 mmHg) and responded to sedation with further reductions (−9.4 mmHg), suggesting these factors may offer some protective buffering during the procedure. For practitioners performing intravitreal gentamicin therapy, the 5 mL retrobulbar block is now the preferred approach—delivering equivalent anesthetic efficacy with slightly better pressure control—whilst either 0.15 or 0.3 mL gentamicin volumes can be selected based on clinical preference without meaningful pressure consequences.
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Practical Takeaways
- •Use 5 mL rather than 10 mL lidocaine for retrobulbar blocks in horses receiving intravitreal gentamicin injections, as it reduces IOP elevation while maintaining adequate anesthesia
- •Either 0.15 mL or 0.3 mL volumes of gentamicin solution can be used interchangeably without clinically relevant differences in IOP response
- •Monitor that pathologic eyes with uveitis already have lower baseline pressures; the combination of sedation and retrobulbar block further reduces IOP, which may be protective against acute pressure-related retinal damage
Key Findings
- •Pathologic eyes had significantly lower baseline IOP (-6.1 mmHg) and post-sedation IOP (-9.4 mmHg) compared to contralateral eyes
- •Retrobulbar block with 10 mL lidocaine produced a small but significant IOP increase (+0.5 mmHg) compared to 5 mL
- •No significant difference in IOP following intravitreal injection of 0.15 mL versus 0.3 mL gentamicin solution
- •5 mL retrobulbar lidocaine block achieves adequate anesthesia while minimizing IOP elevation during intravitreal gentamicin injection