Glaucoma is characterized by increased intraocular pressure as a result of compromised intraocular fluid overflow.
If your pet is developing glaucoma you may notice increased tearing, squinting, ocular redness or cloudiness, enlargement of the eye(s), a tendency to rub the eyes, drooping of the eyelids, compromised vision, and decreased appetite and energy levels.
However, these are generalized signs of ocular pain, and are not necessarily specific for glaucoma. Your veterinarian or veterinary ophthalmologist can diagnose glaucoma by measuring your pet’s intraocular pressure using an instrument called a tonometer.
The eye produces intraocular fluid, or “aqueous humor,” that flows through the eye, then drains. In a normal eye, aqueous humor production and draining is constant and equal. In glaucoma, the outflow drainage pathway is obstructed.
Since the aqueous humor production is constant, the rate of the fluid production is higher than the rate of fluid drainage. Since the eye is a closed space, constant filling with compromised drainage will lead to increased intraocular pressure.
Glaucoma is a progressive condition, meaning it has a natural tendency to worsen over time. When uncontrolled, glaucoma is both painful and potentially blinding. It is therefore critical for your pet’s well being that they receive glaucoma therapy. All glaucoma cases benefit from receiving topical glaucoma medications (eye drops) as soon as possible. Any additional therapy will depend on whether or not the glaucoma is primary or secondary.
As mentioned above, all glaucoma cases require glaucoma medications in the form of eye drops. Therapy beyond that depends on whether or not the eye is still visual. If so, then surgery may be considered with the aim of maintaining vision and comfort for as long as possible. If not, a salvage procedure to help restore long-term comfort should be considered.
Surgical therapies (performed under general anesthesia) for visual eyes:
One way to relieve the pressure of glaucoma is to try to restore the balance between fluid production and fluid drainage. Remember, it is the drainage that is compromised. We can try to slow the rate of fluid production by “ablating,” or shutting-down, the tissue that creates the fluid – the ciliary body epithelium. Laser energy can be applied to the ciliary body epithelium to ablate it.
Another way to restore the balance between fluid production and fluid drainage is to provide an accessory drainage (fluid outflow) pathway. This can be accomplished by placing a “goniovalve.” A goniovalve is a device that shunts fluid from inside the eye to the tissue space surrounding the eye. From there the fluid is naturally absorbed by the body.
Both laser therapy and goniovalve therapy can maintain vision and control glaucoma quite effectively for months to years, but unfortunately they are not permanent cures. Furthermore, they are not meant to replace glaucoma medications, but are therapies performed as additions to medical therapy.
Factors that are critical to maintaining control of glaucoma for as long as possible are:
If your pet has an eye that is already blind from glaucoma, then a salvage procedure should be considered to restore long-term comfort. Salvage procedures are meant only for blind eyes, as they are irreversible procedures aimed at restoring comfort (not vision).
Though they may seem drastic the first time you learn of them, rest assured that pets with blind and painful eyes are simply much happier once the pain is relieved. This is evidenced by a rapid return of their energy levels and appetites.
Most owners report that their pet is back to their “usual self” or even “like a puppy again” within days after a salvage procedure. In addition, the permanent glaucoma relief means your pet will no longer need glaucoma medications.
Salvage surgical procedures for blind and painfully glaucomatous eyes include the following:
Which salvage procedure is best for your pet is largely a matter of personal preference. While the intrascleral prosthesis allows for a more cosmetic appearance, there is a slightly higher chance of complications that may require future therapy. Your veterinary ophthalmologist can discuss with you in more detail the pros and cons of these procedures.
For more information on this subject, speak to the veterinarian who is treating your pet.