Veterinary care should include diagnostic care and subsequent treatment recommendations.Diagnosis In-depth A complete medical history and physical examination should be obtained by your veterinarian. Medical tests are needed to establish the diagnosis, exclude other disease and determine the impact of glaucoma on your pet.
Diagnostic tests specific to the eye (other tests to evaluate general health may/may not be necessary as well). A variety of specialized instruments are used for an eye exam including a transilluminator and a biomicroscope (also known as a slit lamp), as well as a direct and an indirect ophthalmoscope. The examination can help to answer some of the following important questions that will help determine the cause of glaucoma and the prognosis:
Is the pupil mobile?
Where is the lens?
How much inflammation is inside of the eye?
Are there any indications of a tumor or of trauma?
Do the retina and optic nerve appear healthy?
Other tests may include:
Tonometry may be used to measure the pressure inside of the eye (intraocular pressure, IOP). This test is very important and it has to be frequently repeated to determine how well treatments are working. There are several instruments used to check pressures, the most common of which are the Tonopen® and the schiotz tonometer. They are simple tests done in the exam room with just a drop of topical anesthetic on your pet's eye.
Gonioscopy involves using a special lens placed on your pet's eye so that the drainage angle can be viewed. This test is especially important when determining if glaucoma is primary (because of a narrow or malformed drainage angle). With some tumors that grow slowly in the eye, gonioscopy is used to periodically evaluate how close a tumor is to invading the drainage angle. Depending on the temperament of your pet, this test is generally done with just topical anesthetic so that your pet doesn't feel the gonioscopic lens placed on the surface of the eye.
Treatment for glaucoma can be broken down into medical and surgical care. Depending on the cause determined for glaucoma, different options are more or less appropriate.
Injectable and oral medications are used on an emergency basis to lower pressure, not on a long-term basis to control glaucoma: mannitol, glycerin (hyperosmotics).
Oral products to decrease the production of fluid in the eye: methazolamide, acetazolamide, dichlophenamide (carbonic anhydrase inhibitors).
Topical products to decrease the production of fluid in the eye: dorzolamide, brinzolamide (carbonic anhydrase inhibitors); timolol, betaxolol, levobunolol (beta blockers).
Topical products (from different drug classes) that try to open the drainage angle: phospholine iodide, ecothiophate, demarcarium bromide, pilocarpine, carbachol, latanoprost.
Oral and topical anti-inflammatories to decrease inflammation in the eye: prednisone, methylprednisone, dexamethasone (oral steroidals); carprofen, aspirin (oral nonsteroidals); prednisolone acetate/phosphate, betamethasone, dexamethasone (steroidal topicals); diclofenac, flurbiprofen, suprofen, indomethacin (non-steroidal topicals).
All above medications are generally used in combination with the dosing adjusted as needed.
Laser or Cryocycloablation – This uses a laser or freezing probe to kill some of the cells in the eye that are producing the fluid. This is appropriate for either a visual or a blind eye (a visual eye is treated less aggressively to kill just enough cells to decrease the pressure, but not to destroy too much of the inside of the eye).
Gonioimplant or Goniovalve – This involves placing a small tube in the eye to filter the excess fluid produced to the outside of the eye. It is generally used for a visual eye.
Enucleation - This is removal of the eye and results in eyelids that are permanently sewn shut. This is appropriate if the eye is blind. If there is a tumor inside of the eye, this is typically preferred because a pathologist can have the eye to determine what type of tumor it is.
Intraocular prosthesis – This is the removal of the inside of the eye, but the "shell" of the eye is left and a black silicone ball is placed inside. This is appropriate if the eye is blind. This can be used if there is a tumor inside of the eye, but further surgery could be necessary depending on the report from a pathologist.
Intravitreal injection – This involves injecting a medication into the eye that kills all of the fluid producing cells; frequently the eye shrinks down after this procedure.
There are many subtleties to be taken into consideration so all of the surgical options are not appropriate for any given case.