Treatment of equine glaucoma by transscleral neodymium:yttrium aluminum garnet laser cyclophotocoagulation: a retrospective study of 23 eyes of 16 horses

Abstract

Contact neodymium:yttrium aluminum garnet (Nd:YAG) laser transscleral cyclophotocoagulation (TSCP) was performed on 23 eyes of 16 horses for treatment of glaucoma. The mean highest preoperative IOP was 51 +/- 17 mmHg. Follow-up evaluation was available for 19 eyes 1 day after surgery, 14 eyes from 1 to 2 weeks, 16 eyes from 4 to 6 weeks, 9 eyes from 12 to 16 weeks, and 10 eyes greater than 20 weeks after laser treatment. The mean intraocular pressure (IOP) the day following surgery was 34 +/- 13 mmHg. The mean IOP for each follow-up period was: one to two weeks postoperative, 23 +/- 9 mmHg; four to six weeks, 24 +/- 7 mmHg; 12-16 weeks, 28 +/- 10 mmHg; and >/= 20 weeks, 22 +/- 9 mmHg. IOP measurements were significantly different from pretreatment values for all follow-up intervals except for weeks 12-16 (P < 0.05). Treatment success was defined as maintenance of IOP < 30 mmHg. Treatment success was achieved in 93%, 88%, 78%, and 70% of the treated eyes at the 1-2 weeks, 4-6 weeks, 12-16 weeks, and the >/= 20 weeks re-evaluation, respectively. No significant difference was found between the number of eyes visual at presentation (52.2%) and visual at 20 weeks (60%). The most common laser complications were conjunctival hyperemia (21.7%) and corneal ulcers (13.0%). Results of this study indicate that Nd:YAG TSCP is an effective method of controlling IOP and preserving vision in horses with glaucoma. An effective Nd:YAG laser protocol for TSCP in the equine glaucomatous eye is a power setting of 11 W, duration of 0.4 s, applied 5 mm posterior to the limbus at 60 sites, resulting in a total energy dose of 264 J.

Surgical Treatment of Canine Glaucoma

“…15 Diode lasers have become the leading modality for CPC because of a more affordable cost, a better portability, and better absorption of their wavelength by melanin in the ciliary epithelium with less associated inflammation. [17][18][19][20][21][22] Endoscopic CPC (ECP) studies in veterinary ophthalmology are lacking, but studies comparing transscleral CPC (TSCP) and ECP in pediatric glaucoma did not show a significant difference in surgical outcome, both offering a moderate long-term IOP control (66.7% and 62% success respectively). 23 At present, diode laser glaucoma therapy, TSCP, and ECP are used for the treatment of primary and secondary glaucoma in canine, feline, and equine patients.…”

“…21 A contact mode application using scleral indentation enhances laser delivery and absorption by the pigmented epithelium, resulting in less total energy delivered to achieve the desired effect, and less collateral damage. 22 Contact diode TSCP can be performed with minimal instrumentation; the diode laser console and the delivery device or glaucoma probe.…”

A promising surgical approach to equine glaucoma

“…Options for surgical therapy in horses with glaucoma have historically been limited to cyclodestructive procedures such as TSCP (Whigham et al . ; Annear et al . ) and procedures terminal for vision such as enucleation.…”

Changes of Intraocular Pressure in Uveitic Horses

“…IOP is reported to be affected in diseases such as glaucoma and uveitis in dogs [7,11]. Tonometry has been also performed for diagnosis and prognosis of glaucoma in horses [3,4,8,26,27]. Glaucoma in the horse is being recognized with increased frequency by increased availability of applanation tonometers [3].…”