Diode laser treatment for primary glaucoma in 18 dogs

Abstract

OBJECTIVE: To evaluate a higher total energy protocol for diode laser transscleral cyclophotocoagulation (TSCP) for the treatment of primary glaucoma in dogs. PROCEDURES: Diode laser TSCP was performed on 24 eyes of 18 dogs (six dogs were treated bilaterally). A glaucoma probe with a spot size of 600 microns was applied in 25 sites 3-4 mm posterior to the limbus for dogs. A power of 1000 milliwatts (mW) for a duration of 5000 milliseconds (ms) to deliver an average 125 J of energy per eye, which is higher energy delivery than previously reported for the diode laser for the treatment of canine glaucoma. Anterior chamber needle paracentesis was performed using a 30-gauge needle until intraocular pressure (IOP) was measured to be less than 15 mmHg by applanation tonometry. Subconjunctival corticosteroids were administered in all cases and a temporary tarsorrhaphy was applied in 13 of the 24 treated eyes. Postoperative topical and systemic corticosteroids, and carbonic anhydrase inhibitors were administered as required to maintain an IOP of less than 25 mmHg. Intraocular pressure was measured at approximately 3 h postoperatively then at 1, 2, 3, 7, 14, 28, 60, 120, and 180 days. Adequate control of IOP was considered to be less than 25 mmHg on re-examination. RESULTS: Intraocular pressure was successfully maintained within the normal range in 22/24 eyes (92%). Three eyes required a second diode laser treatment within the first week postoperatively. Two eyes developed recurrence of glaucoma at 8 and 32 weeks postoperatively. Follow-up ranged from 8 to 21 months. Fourteen eyes were assessed by clinical examination and history to be potentially visual. Of these, seven eyes (50%) regained useful visual function. Mean IOP at 6 months was 11.0 +/- 7.6 mmHg and at 12 months was 11.0 +/- 8 mmHg. Postoperative complications included cataracts (six cases), corneal ulceration (three cases), and keratitis (three cases). Of 13 cases that were treated postoperatively with a temporary tarsorrhaphy, only one case (8%) developed corneal disease. Of the remaining 11 cases that were not treated with a temporary tarsorrhaphy, there were three cases of corneal ulceration and two cases of vascular keratitis (45% incidence of corneal disease). This was found to be statistically significant (P < 0.05). Postoperative complications of hyphema and phthisis bulbi were not seen in this series. CONCLUSION: Low energy, higher power laser cyclophotocoagulation was effective in the treatment of canine primary glaucoma, with 50% of potentially visual eyes regaining vision, but may cause an increased incidence of secondary cataracts.