Glaucoma is a disease associated with elevated pressure within the eye. There are two main types of glaucoma: primary and secondary. Primary glaucoma is a hereditary disease that is very common in dogs. Primary glaucoma occurs with higher prevalence in certain breeds of dog including the Cocker Spaniel, Boston Terrier, Chinese Shar-Pei, Bassett Hound, Siberian Husky, Shiba Inu and Chow-Chow. Although dogs are born with the ocular defect that leads to primary glaucoma, the signs of glaucoma often do not appear until middle age. Glaucoma can also develop secondary to another problems within the eye such as inflammation, cataracts, hemorrhage, trauma, lens dislocation (luxation) and cancer. Untreated, glaucoma can result in irreversible blindness within 24 hours. Glaucoma is an emergency. Early detection and treatment are critical to prevent or reduce optic nerve damage.
Signs of early glaucoma
- Squinting or inability to open the eye
- Cloudiness of the cornea
- Redness of the conjunctiva and sclera (white part of the eye)
- Third eyelid elevated
- Lethargic, decreased appetite
Additional signs of glaucoma
- Dilated pupil
- Visual impairment or loss
- Enlargement of the eye
Note: Not all of these signs will be present in every glaucoma patient!
A thorough eye exam is necessary in order to diagnose glaucoma and to help determine it’s cause. Examination of the retina, and optic nerve in particular, are essential to help gauge the extent of eye injury from the elevated pressure. Intraocular pressure is measured routinely during exams with a tonometer. Gonioscopy involves placment of a special lens onto the eye to view the fluid drainage angle inside the eye. It helps determine the type of glaucoma, and helps gauge the risk of an eye to develop glaucoma in the future.
In early stages of glaucoma, medical and surgical management can be effective to help preserve vision as long as possible, and minimize discomfort associated with the disease. Unfortunately, other than surgery, there is no permanent cure for glaucoma. The long-term prognosis for maintaining vision in dogs with primary (heritable) glaucoma is poor. Patients require lifelong management, and there is variability in how well they will respond to these therapies. In patients with primary glaucoma in one eye, many will develop glaucoma in the opposite eye within 6 to 9 months. However, the use of prophylactic therapy (glaucoma eye drops), can slow the development. With therapy, the second eye often develops glaucoma in 18 to 24 months. Regular follow-up appointments are very important to monitor trends of the intraocular pressure.
There are several surgical options for glaucoma management. The ideal choice is dependent on the unique features of your pet’s eye, such as type and stage of glaucoma and whether vision is present or not. Each surgical option with be explained in detail by your ophthalmologist following a complete eye examination.
Laser cyclophotoablation and filtering implant
This surgical procedure is used in the treatment of visual eyes with primary glaucoma when medication alone does not adequately lower pressure. The most common complications from surgery are excessive inflammation and eye pressure fluctuations during the initial recovery period.
This surgery involves lasering of the ciliary body gland of the eye (tissue that produces fluid within the eye) to reduce fluid production. The first 6-8 weeks of post-op care can be intense, but many dogs ultimately become more responsive to glaucoma medications and the disease can be controlled for several months or more. This procedure is often combined with placement of a shunt (filter) inside the eye to help fluid to flow out of the eye during the initial recovery period.
For blind eyes with advanced stage and / or uncontrolled glaucoma, several treatment options are available to eliminate the pain of high intraocular pressures and progressive enlargement of the eye:
Intraocular injection (pharmacologic ciliary body ablation)
This is the least invasive option and can be performed under light sedation in most patients. It is successful in permanently reducing eye pressure in 75-85% of patients within 1 month of injection. With this procedure, the appearance of the eye is less predictable long term, as the eye can decrease in size, and will appear somewhat cloudy due to cataract development and /or corneal changes.
Enucleation (complete eye removal)
This is essentially 100% successful in resolving the glaucoma, and allows a biopsy to be performed. Potential complications can occur such as bacterial infection of the surgery site or the development of of fluid accumulation in the orbit, but this they are rare. An implant may be placed within the orbit to minimize sinking of the eyelids, but the eyelids are permanently closed. No long term medical therapy is required.
An implant, in the form of a silicone sphere, may also be placed within the scleral shell of the eye to create a “false eye”. This often results in the most cosmetic and natural appearing outcome. The prosthesis is permanent and does not require care. All glaucoma medications are discontinued, and patients are treated with daily lubricating eye drops or ointments to support surface ocular health. Some patients may not be candidates for this option, as it requires an otherwise healthy outer surface of the eye and good tear production.