A Surgical Technique for Removal of Setaria digitata From the Anterior Chamber Under Standing Sedation: Outcomes in 12 Horses.

OBJECTIVE

To describe a rapid surgical technique for removal of the intraocular nematode Setaria digitata from the anterior chamber of horses under standing sedation and to report clinical outcomes.

ANIMALS STUDIED: Twelve client-owned horses (2021-2026) presented with a motile intracameral worm.

PROCEDURES: All surgeries were performed under field conditions using standing sedation (xylazine 1.1 mg kg-1 and butorphanol 0.1 mg kg-1 IV), regional nerve blocks (lidocaine 2%), and topical anesthesia (proparacaine). A 2.8 mm uniplanar oblique (~45°) corneal incision was created ventrolaterally approximately 2 mm from the limbus using a keratome. The anterior chamber was filled with dispersive hydroxypropyl methylcellulose (HPMC), and controlled viscoelastic egress facilitated atraumatic extrusion of the worm. The incision was left unsutured.

RESULTS

Worm removal was successful in 11/12 eyes (91.7%). In one chronically affected eye, the worm was suspected to be adherent to the iris and could not be removed. Median incision-to-extraction time was 2 min (range 1-3 min). Nine eyes (75%) retained or regained vision within 7 days; three remained non-visual due to pre-existing end-stage glaucoma or suspected retinal detachment. Postoperative complications included transient peripheral corneal edema in one horse, which resolved with medical management, and anterior chamber fibrin formation in one eye in which viscoelastic was not used.

CONCLUSIONS

Although not a substitute for surgery under general anesthesia, viscoelastic-assisted removal of S. digitata through a small self-sealing corneal incision is a rapid, minimally invasive, and field-applicable technique when performed by appropriately trained ophthalmic surgeons.