Signs and Symptoms of Glaucoma in Dogs & Treatment Options Available at UVS
January 20th, 2015 | Posted in Medical Articles
What is Glaucoma?
Glaucoma is defined as increased pressure within the eye that causes degenerative changes in the optic nerve and retina with subsequent blindness.
What Causes Glaucoma?
Cells inside the eye behind the iris, called the ciliary body epithelium, continuously make the fluid (“aqueous humor”) that fills the front portion of the eye. Glaucoma develops when the normal flow of this fluid out of the eye is impaired. In most cases, this is caused by a hereditary defect where the filtering mechanism (“drainage angle”) around the periphery of the iris is blocked off. This is referred to as “primary glaucoma” and is most commonly seen in purebred dogs such as the Cocker Spaniel, Basset Hound, Bouvier, Springer Spaniel, Beagle, Shar Pei, Chow Chow, as well as many others. “Secondary glaucoma” refers to increased pressure in the eye due to other ocular diseases such as uveitis (inflammation inside the eye), lens luxation (dislocation of the lens from its normal position), and hyphema (bleeding inside the eye).
What are the signs of Glaucoma?
The signs associated with glaucoma may include all or some of the following: red eye, bluish/cloudy cornea, pain, dilated pupil, discharge from the eye, blindness, or enlargement of the eye.
How is Glaucoma Treated?
The goals of glaucoma treatment are to save as much vision as possible for as long as possible and to keep the patient comfortable. The treatment program is determined by the type of glaucoma, the severity and duration, the pet’s other medical problems, and the possibility of saving vision. Treatment ranges from using eye drops at home, to hospitalization for intense therapy, to possible surgery. A treatment plan for your pet will be discussed with you as the pet is evaluated and as the response to treatment is noted.
Surgical Options for Glaucoma:
If vision is present or there is a chance vision will return:
- Transscleral or Endoscopic Diode Laser Cyclophotocoagulation – A laser is used to destroy cells of the ciliary body, which is the tissue located inside of the eye behind the iris that produces fluid. This procedure is estimated to control eye pressure in 60-70% of patients for a period of 6 months. Complications include post-operative pressure spikes, intraocular bleeding, significant uveitis (inflammation) and corneal ulcers.
- Aqueous shunt implant (gonioimplant) – A small tube is implanted inside the eye. This tube, or shunt, sits partially inside the eye and partially outside the eye under the conjunctiva to allow fluid to leave the eye when pressure increases above a specific level. The success rate for this procedure to control pressure is similar to laser surgery, however a shunt doesn’t last forever and may be effective for only a few weeks, or up to a few months. Complications include scarring around the shunt causing back-up of the fluid in the eye and dislocation of the shunt. General anesthesia is required along with overnight monitoring.
If there is no chance for vision return, there is minimal to no response to medical therapy and the main goal is pain relief:
- Enucleation (eye removal) – The eye is removed and the eyelids are permanently closed. Provided there is not an infection or cancer present within the orbit, a silicone implant is may be placed in the eye socket to prevent a sunken appearance. General anesthesia is required. This procedure rarely requires overnight hospitalization. Immediately following surgery you can expect to see some swelling and minor bruising around the surgical site. Oral antibiotics and pain medications will be given for the first week. Sutures are removed after 10 to 14 days when the incision has healed. While the risk is low, there is a potential for infection to develop around the orbital implant (despite prophylactic treatment with antibiotics) or the body may reject the prosthesis. Should an infection or rejection develop, a second surgery would likely be necessary to remove the prosthesis.
- Evisceration with Intrascleral Prosthesis – This surgical procedure provides a cosmetic alternative to enucleation. In order to be a candidate for the surgery, the eye must have normal tear production and have a healthy cornea. The surgery involves making an incision through the conjunctiva and sclera (the white shell of the eye) and removing the contents within the eye. A silicone sphere (prosthesis) is then placed within the eye, and the conjunctiva and sclera are sutured closed. The patient has what appears to be a functional, though non-visual, eye. They are able to move the eye and blink as before. Post-operative therapy includes oral and topical antibiotics and an oral anti-inflammatory / analgesic with the use of an Elizabethan collar. Many corneas develop a cloudy or bluish haze during the healing process, some of which may be permanent. Patients with an intrascleral prosthesis will usually require routine lifelong care to maintain optimal corneal health. Long-term topical therapy may be necessary which includes lubricating eye drops, gels or ointments applied 1-3 times daily. Some patients experience a decline in tear production (dry eye syndrome) months to years following surgery and require topical medications to stimulate tearing. It is important to be aware that these patients can accidentally injure their corneas and require treatment even though the glaucoma will never return.
What can I expect after Treatment?
Unfortunately, the only thing predictable about glaucoma is that it usually gets worse (either quickly or gradually) and that each patient requires careful and frequent follow up so the treatment program can keep pace with the disease. However, in many patients vision loss can be postponed or prevented and, in virtually all situations, the patient can remain comfortable with medication and/or surgery.
