Glaucoma is an uncommon condition in dogs characterized by increased pressure inside the eyes (intraocular pressure, or IOP).
• When eyes do not properly drain aqueous humor (a type of liquid in the eye), pressure builds, which causes pain, damages ocular structures, and leads to vision loss
• Glaucoma may be genetic, secondary to another condition, or have no known origin
• Symptoms of glaucoma include enlargement of the affected eye, eye redness, squinting, and loss of vision
• A thorough ophthalmological exam including measurement of IOP detects glaucoma
• A diagnosis of glaucoma warrants emergency referral to a veterinary ophthalmologist
• Emergency treatment involves using medications to lower IOP
• Anti-glaucoma medications are available, but surgery is often also necessary
• Prognosis for protecting sight is variable, and prompt medical attention is the best chance for a favorable outcome
Glaucoma can be categorized as primary or secondary. Primary glaucoma develops spontaneously. Secondary glaucoma develops as a complication of another underlying condition.
Sometimes the initial symptoms are subtle and go undetected (i.e. “silent glaucoma”). Over time, additional symptoms may develop:
• Bulging of the eye (buphthalmos)
• Deformity of the eye
• White scars across the cornea
• Shrinking of the eyeball (if the eye has ruptured at some point)
Glaucoma can cause permanent vision loss, and is painful.
Timely intervention is crucial to have the best chances of protecting sight, and immediate veterinary assistance is required when a dog presents symptoms of glaucoma. Emergency referral to a board-certified veterinary ophthalmologist may be advised.
Glaucoma may affect one or both eyes. The anatomical conditions causing primary glaucoma are bilateral, but primary glaucoma almost always appears in only one at first, with the other eye developing it later. Secondary glaucoma is usually unilateral, but both eyes may be affected depending on the underlying cause.
Prolapsed eye lens and cataracts are examples of conditions that may form secondary glaucoma.
Primary glaucoma is an idiopathic condition, meaning it has no known origin, although some breeds appear to have a genetic predisposition.
Secondary glaucoma is more common. The pressure buildup comes secondary to other medical conditions, such as injury, tumor, or displacement (luxation) of the eye’s lens. Secondary glaucoma can also develop as a result of inflammation (uveitis), which itself has a multitude of causes including infectious diseases like Lyme, distemper, or blastomycosis.
Early in the course of the disease, ocular symptoms include:
• Excessive blinking (blepharospasm)
• Dilation of the pupil
• Constriction of the pupil
• Avoiding bright lights (photophobia)
• Vision loss (bumping into things), usually only if both eyes are affected
• The eyeball appears “sucked in” when compared to the other eye (enophthalmos)
• Elevation of the third eyelid (nictitans)
• Physical examination, including a thorough ophthalmologic exam:◦ Fluorescein stain ◦ Schirmer tear test ◦ Tonometry ◦ Gonioscopy
• Diagnostic imaging
• Referral to an ophthalmologist
Medications and surgery are used to decrease pressure by decreasing production of intraocular fluid along with drawing it out of the eye. If sight cannot be saved, the affected eye may need to be removed, as the pressure can be very painful.
The prognosis for primary glaucoma is guarded, and vision loss may occur in spite of aggressive treatment.
For secondary glaucoma the prognosis is more varied, depending on the underlying condition. While removal of affected eyes may become necessary, a dog can still live a good quality of life, even without sight, especially if their physical environment remains consistent.
Glaucoma cannot always be prevented. The risk of primary glaucoma can be minimized by not breeding dogs susceptible to the condition, but the variety of conditions which result in increased ocular pressure make it challenging to prevent secondary glaucoma.
Early detection of glaucoma is crucial in order to have the best chances to protect the animal's sight. Regular wellness exams (including tonometry) for early identification and treatment of conditions that lead to glaucoma may enable a vet to diagnose the condition before it reaches a critical stage.
Glaucoma is not contagious.
Glaucoma is uncommon in dogs.
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