High intensity focused ultrasound cyclocoagulation in dogs with primary glaucoma: a preliminary study

Objective: to assess the effect of high intensity focused ultrasound (HIFU) on intraocular pressure (IOP) in dogs with primary glaucoma (PG). Animals studied: seven dogs (13 eyes) presenting with PG as diagnosed by a raised IOP (> 20 mm Hg) associated with consistent gonioscopy and ultrasound biomicroscopy of the ciliary cleft, with no other ocular disease. Patients were divided into 3 groups, corresponding to their pre-operative IOP (group 1 ranging from 21 to 30 mm Hg, group 2 from 31 to 40 and group 3 for 40 and above). Procedure: ciliary process sonication was achieved with a probe containing one high-frequency transducer operating at 21 MHz during 5 seconds. Six sites were treated in patients from group 1, 8 in group 2, 10 in group 3, under general anesthesia. Post-operative treatment consisted of systemic meloxicam and topical carbonic anhydrase inhibitors, beta-blockers and prostaglandins analogues. Results: no intraoperative complications were observed. Conjunctival hyperaemia occurred in eyes from group 2 (66%) and 3 (100%). Conjunctival burns were visible in 2 patients from group 3. One patient from group 3 experienced a hypertensive spike during the first hours post-op with associated pain. The hypotensive effect of HIFU was observed in all groups. Normotensive IOP (ÂiAœ20 mm Hg) was reached in all patients until the last recheck at 6 months post op. Conclusion: despite the small number of patients included in the study, HIFU appears to be a promising option for the management of PG in dogs.