Glaucoma is one of the leading causes of blindness in small animals.

Glaucoma is an increase of intraocular pressure within the eye.

Most pets with glaucoma will develop a red, painful eye.

After the initial diagnosis of glaucoma is made, the patient is treated with medical therapy and/or surgery.

Once the pressures have been controlled, maintenance levels of medications are prescribed for long-term therapy.

What is Glaucoma?

• Glaucoma is one of the leading causes of blindness in small animals.
  
• Glaucoma is an increase of intraocular pressure within the eye.
  
• Intraocular fluid, termed aqueous humor, is produced behind the iris (the colored part of the eye) in the ciliary body. This fluid flows through the pupil and drains from the eye at the drainage angle, a sieve-like network. Aqueous humor is produced and passes from the eye at approximately the same rate, resulting in a stable intraocular pressure within a range of 15-25 mm of Hg. Glaucoma is a consequence of a blockage of the outflow of fluid and a buildup of pressure within the eye.
  
• High pressure damages the retina and optic nerve and if the pressure is elevated for several hours, permanent damage or blindness can result.
  
• In general, there are considered to be two broad categories of glaucoma.
  • Primary glaucoma occurs without any previous ocular disease while secondary glaucoma is a consequence of some other ocular disease.
  • Primary glaucoma is caused by the decreased outflow of fluid caused by abnormal function of the drainage angle.
    
  • Primary glaucoma is known to occur within certain breeds of dogs and is thought to have an inherited basis. This type of glaucoma is more common in certain breeds such as the Beagle, Poodle, Norwegian Elkhound, Cocker Spaniel, Basset Hound, Samoyed, Shar Pei and Chow Chow, but can occur in any breed.
    
  • Secondary glaucoma is the result of some other ocular disease that interferes with the natural flow of ocular fluid. Diseases that commonly cause secondary glaucoma include ocular inflammation, lens dislocation, ocular trauma and intraocular tumors.
• With early medical and surgical therapy, vision may be restored. But once the optic nerve has been permanently damaged, restoration of vision is unlikely. Frequently with extreme elevations of pressure, the eye becomes permanently blind and painful. The aim of therapy at this point is to maintain a pain-free and cosmetic eye.

Symptoms & Diagnosis

• Most pets with glaucoma will develop a red, painful eye. Your pet may also exhibit pain by loss of appetite, excessive sleeping or a decrease in activity. A decrease of vision is usually not recognized unless both eyes are affected.
  
• The diagnosis of glaucoma is based on history, clinical signs, tonometry and gonioscopy. Clinical signs of glaucoma include a "red-eye" with a fixed and dilated pupil. In the later stages, the eye may become enlarged.
  
• Tonometry is the measurement of intraocular pressure.
  
• Gonioscopy is a technique used to evaluate the drainage angle. The technique is essential to evaluate the pre-glaucomatous eye for risk of future attacks or predisposition.

Treatment

• Patients with glaucoma usually exhibit some level of pain or discomfort related to the elevated intraocular pressure. After the initial diagnosis of glaucoma is made, the patient is treated with medical therapy and/or surgery. This may require a brief period of hospitalization.
  
• Once the pressures have been controlled, maintenance levels of medications are prescribed for long-term therapy. Medications that are commonly used include those that are aimed at improving the outflow of aqueous humor or decreasing its production.  
  
• In many instances of primary glaucoma, it is impossible to control the pressure with medications alone and a variety of surgical techniques have been developed to aid in the control of pressure.
  
• Laser surgery and cryosurgery are surgical procedures designed to damage the fluid producing cells and decrease fluid production in the eye. Both laser and cryosurgery are minimally invasive but recurrence of glaucoma may occur following these procedures. Significant temporary post-operative swelling develops following cryosurgery.
  
• Patients that have secondary glaucoma related to lens luxation may require surgery to remove the lens.
  
• An intraocular prosthesis (called intrascleral prosthesis) is performed on patient’s eyes that are blind due to pressure elevations. This technique salvages a cosmetic, pain-free eye and involves removal of the intraocular contents and the implantation of silicone prosthesis within the eyeball. The shape of the eye is maintained and the normal eye movements continue. Following this procedure, minimal care is needed and the eye usually remains pain-free and cosmetic. The eye does not look exactly like your pet’s original eye, but is considered more cosmetically pleasing than enucleation (removal of the eye).
  
• In some patients enucleation is warranted. Although the surgery may seem drastic, enucleation is a reliable way to alleviate the source of your pet’s pain. The eye is removed and a silicone globe is placed in the socket and the eye lids are permanently sutured over the silicone globe. This prevents the skin over the eye socket from sinking in.

Prognosis

• Glaucoma is seldom diagnosed early enough to restore vision in the eye affected first. Therefore, during the initial examination, time will be spent to evaluate the "good" eye.
  Prognosis is dependent upon early diagnosis, appropriate medical therapy, and regular re-examinations.
• Examinations three to six times per year are often required to monitor pets with a predisposition for glaucoma.