In this VETgirl online veterinary CE blog, we demonstrate how to perform ciliary body ablation for the treatment of canine glaucoma. Canine glaucoma is a painful and most often blinding condition. There are a number of topical anti-glaucoma medications available for dogs to alleviate the discomfort of the elevated intraocular pressure (IOP). Unfortunately, many dogs either fail to respond to medications, or the drops eventually become ineffective. If a dog has a permanently blind and persistently painful eye, then surgery should be pursued. There are 3 main surgical options:
- Evisceration with intrascleral prosthesis
- Ciliary body ablation (CBA)
Ciliary body ablation involves the injection of a drug into the vitreous chamber. The drugs used for injection are toxic to the ciliary body, which is the structure responsible for production of aqueous humor. The primary goal of CBA is to eliminate aqueous humor production, and thus achieve a low IOP without the use of topical anti-glaucoma medications. The most commonly used drug for CBA injections is Gentamicin, however a recent study (see below) describes the use of an antiviral drug, cidofovir.
Ciliary body ablation has an approximately 75-85% success rate. The primary benefits of CBA include a reduced cost as compared to the other surgical options, a quick procedure time, and the patient's ability to retain the eye. The cosmetic outcome of CBA is variable - all dogs will develop cataracts, the corneal often develops a grey haze, and the globe may shrink to varying degrees. A primary complication of CBA is intraocular bleeding, and some dogs require long-term treatment for intraocular inflammation. Dogs with primary glaucoma are the best candidates for CBA. CBA should be avoided in cases of glaucoma secondary to intraocular infections or neoplasia. CBA should never be performed in cats due to the risk of lens damage and subsequent sarcoma development.
- The patient is heavily sedated or placed under general anesthesia.
- The conjunctival surface and periocular area is steriley prepared using a betadine solution.
- An eyelid speculum is placed and small forceps are used to stabilize the globe.
- A 30g needle is placed into the anterior chamber at the limbus to allow aqueous humor to exit during the injection.
- A 1 mL syringe with a 25g needle is used to inject 30 mg (0.3 mL) of gentamicin into the vitreous.
- The needle is inserted approximately 6 mm posterior to the limbus.
- The tip of the needle is directed caudally to avoid the lens and the vascular ciliary body.
- A long-acting steroid is then injected subconjunctivally.
- In this video, 4 mg of triamcinolone acetonide was used.
- Alternatively, 1 mg of DexSP could be used.
- It is also acceptable to combine the steroid with the gentamicin and inject both into the vitreous.
- The IOP is assessed immediately post-injection and the goal is < 15 mmHg Additional aqueous humor should be removed if the IOP > 30 mmHg post-injection.
- Topical anti-glaucoma medications are quickly tapered and stopped within 2 weeks of the procedure.
- Topical and / or oral anti-inflammatories and a topical antibiotic is used for the first 1-2 weeks post-injection.
The success of the injection (as determined by IOP measurement) is assessed 1 month post-injection.
1. Low MC, Landis ML, Peiffer RL. Intravitreal cidofovir injection for the management of chronic glaucoma in dogs. Vet Ophthalmol 2014;17(3):201-6.