In this VETgirl online veterinary continuing education blog, Dr. Shelby Reinstein, DVM, DACVO reviews surgical management of glaucoma in dogs and cats. Make sure to check out our general guide to veterinary glaucoma here along with medical options for glaucoma in these VETgirl blogs!
Multiple surgical options are available to address glaucoma when medical therapy can no longer control the IOP. As with medical therapy, the surgical procedures can be classified into procedures that reduce aqueous humor production or improve aqueous humor outflow. The chosen procedure will depend upon the patient’s visual status and the desired cosmetic outcome. Once vision has been permanently lost, surgical procedures can alleviate pain associated with end-stage glaucoma and eliminate the need for topical medications.
Enucleation is removal of the eye and is relatively inexpensive with few complications. The main benefits of enucleation include the potential for histopathologic examination of the globe, immediate pain control, and the lack of additional topical eye drops. The disadvantages may include the postoperative appearance of the patient for some owners, the need for general anesthesia, or the cost. The post-operative recovery is simple and there is no long-term monitoring necessary. Histopathology is recommended when the cause of the glaucoma is unknown.
Evisceration (removal of the intraocular contents) and placement of an intrascleral prosthetic, silicone ball is a technique performed by veterinary ophthalmologists to provide optimal cosmetic outcomes. Proper case selection is imperative for a good outcome and consists most often of dogs with primary glaucoma without significant buphthalmos. Globes with chronic uveitis, the potential for intraocular neoplasia, or chronic corneal disease are poor candidates. The post-operative recovery requires both oral and topical medications, and long-term follow up is necessary. Post-operative complications include corneal ulcers, implant rejection, and corneal scarring. Owners must be made aware that the remaining ocular tissues (eyelids, conjunctiva, cornea, third eyelid) are still susceptible to disease and can require therapy.
Ciliary Body Ablation
Chemical ablation, or pharmacologic destruction of the ciliary body, is accomplished by injecting a toxic drug (either gentamicin or cidofovir) into the vitreous cavity to cause necrosis of the ciliary body. To assist with treating the induced uveitis, often a steroid (dexamethasone or triamcinolone) is injected concurrently into the vitreous or subconjunctival at the conclusion of the procedure. This technique can often be performed with heavy sedation and is the least expensive option. Post-operatively, topical glaucoma therapy is tapered over 2-3 weeks, and treatment (both topical and oral) of the uveitis is slowly reduced. Generally, a 1-month IOP recheck performed, and should occur approximately 1-2 weeks after discontinuation of all topical glaucoma drops. The desired IOP is < 15 mmHg, but complete phthisis bulbi with IOP < 4 mmHg is not uncommon. Long term, most dogs develop cataracts, however the cosmetic outcome is usually acceptable. Complications include inadequate control of IOP, hyphema, uveitis, retinal detachment, and significant phthisis bulbi. Long term medical requirements are generally low, and often consist of a lubricant gel or anti-inflammatory drop.