What is Glaucoma in Dogs?
Glaucoma in dogs is a condition characterized by heightened pressure inside the eye, also known as intraocular pressure (IOP). It stems from an imbalance between the production of fluid within the eye and its drainage.
Aqueous humor, a fluid vital for nourishing ocular structures, is produced by the eye’s ciliary body. After feeding these structures, the surplus fluid should be efficiently drained through the iridocorneal angle, the region between the cornea and the iris.
When drainage and production aren’t in equilibrium, pressure builds up behind the eye, leading to glaucoma. The condition arises from reduced drainage of aqueous humor rather than excessive production.
Glaucoma manifests in two forms:
- Open-angle glaucoma: It progresses slowly, gradually causing blindness.
- Closed-angle glaucoma: This type is characterized by a sudden surge in IOP, causing acute pain and rapid blindness.
Elevated IOP damages crucial components of the eye:
- The optic nerve, responsible for transmitting visual messages from the eye to the brain.
- The retina, which detects light and sends signals to the brain for image formation.
- The optic disk, the entry point of the nerve into the eye.
Glaucoma often induces pain and can lead to blindness either swiftly or gradually due to ongoing optic nerve damage. However, prompt diagnosis can help prevent or delay blindness.
Symptoms
Symptoms of glaucoma in dogs vary depending on whether the onset is acute or gradual. Acute glaucoma presents more noticeable changes and signs of discomfort, making it easier for dog owners to identify. However, the gradual onset of glaucoma can go unnoticed as the clinical signs may be subtle.
For dogs experiencing acute severe glaucoma, the following clinical signs may be observed:
- Dilated pupils unresponsive to direct light
- Redness in the whites of the eye
- Eye swelling or bulging
- Rubbing or scratching at the affected eye
- Increased lethargy or subdued behavior
- Squinting or avoiding touch near the affected eye
- Decreased appetite
- Excessive watery discharge from the eye
- Sudden blindness, evident through bumping into objects, reluctance to move around, and sudden anxiety
In cases of mild to moderate chronic glaucoma, the following clinical signs may be present:
- Cloudy or hazy bluish appearance in the outer layer of the eye
- Slightly dilated pupils slow to respond to light
- Enlarged or distended eye veins in the white of the eye
- Minor eye enlargement
Prolonged elevation of intraocular pressure (IOP) can lead to the eyeball appearing very large and feeling firm to the touch. It may also cause displacement of the lens, the small structure behind the iris responsible for focusing light. If left untreated, elevated IOP can eventually result in the rupture of the eye due to sustained pressure.
Causes
The causes of glaucoma in dogs vary and can be categorized into primary and secondary types.
Primary glaucoma results from increased intraocular pressure (IOP) in an otherwise healthy eye, often stemming from genetic abnormalities affecting the eye’s drainage angle. Goniodysgenesis, an inherited condition, heightens the risk of closed-angle glaucoma and necessitates regular eye exams for affected dogs. Genetic testing aids in diagnosing primary open-angle glaucoma, characterized by a gradual rise in IOP and slow vision loss.
Secondary glaucoma, the most prevalent type in dogs, arises from elevated IOP due to eye injury or underlying medical conditions:
- Lens luxation occurs when the lens displaces in front of the iris, obstructing the drainage angle or pupil and causing fluid retention.
- Uveitis, an inflammation of the eye’s interior components, results in debris, inflammation, or scar tissue that obstructs the drainage angle, leading to fluid buildup.
- Cataracts affect the lens and may induce inflammation or debris that obstructs the drainage angle, causing fluid accumulation.
- Tumors can physically block or inflame the drainage system, hindering fluid drainage.
- Bleeding in or around the eye, stemming from trauma or retinal detachment, can impede fluid drainage from the iridocorneal angle.
Diagnosis
When suspecting glaucoma in your dog, prompt veterinary attention is crucial as it’s deemed a medical emergency. Upon visiting the vet, a thorough physical examination will be conducted, considering the onset of symptoms and any pertinent medical history, particularly if eye trauma has occurred.
To diagnose glaucoma, intraocular pressure is assessed and compared between both eyes using a tonometer. Elevated pressure in one or both eyes indicates glaucoma. Subsequently, referral to a board-certified veterinary ophthalmologist may be recommended. The ophthalmologist can perform a gonioscopy to assess the drainage angles of the eyes, providing further insights into the condition.
Depending on the presentation and severity of symptoms, the specialist may also consider ocular ultrasound and/or electroretinography to aid in diagnosis and treatment planning. These diagnostic tools help in evaluating the extent of the condition and guiding appropriate management strategies.
Treatment
Treating glaucoma in dogs requires immediate action to reduce intraocular pressure (IOP) and mitigate the risk of blindness and optic nerve damage. Given the urgency, treatment commences promptly, with an emphasis on identifying and addressing any underlying causes contributing to glaucoma.
Typically, a combination of ophthalmic medications is prescribed to swiftly lower IOP to within the normal range. These medications facilitate fluid drainage from the eye and may include:
- Eye drops containing carbonic anhydrase inhibitors (e.g., Orzolamide), prostaglandins (e.g., Latanoprost), and beta-adrenergic blocking agents (e.g., Timolol) to alleviate fluid buildup behind the eye and reduce IOP.
- Analgesics are administered to manage the discomfort associated with the condition.
In severe cases where optic nerve damage is minimal, cyclocryotherapy might be considered. This treatment involves using extremely cold temperatures to target and eliminate the cells in the ciliary body responsible for fluid production within the eye.
Alternatively, specialized medication can be injected directly into the eye to achieve a similar effect of reducing fluid-producing cells. Early diagnosis allows for these procedures to potentially slow down the progression of the disease.
In instances where the optic nerve sustains irreversible damage, surgical removal of the affected eye may be recommended. This procedure not only alleviates pain but also eliminates the need for ongoing glaucoma therapy. Most dogs adapt well to their environment following surgical eye removal.
Living and Management
Recovery and ongoing management of glaucoma in dogs typically involve lifelong treatment. Regular veterinary visits are essential for monitoring intraocular pressure (IOP) and making necessary adjustments to medication, particularly during the initial stages of therapy.
It’s common for most pets with glaucoma to experience bilateral involvement, affecting both eyes. In cases where glaucoma is detected in only one eye, measures are usually taken to safeguard the unaffected eye. This proactive approach is particularly crucial in instances of primary glaucoma (inherited), as more than 50 percent of dogs develop glaucoma in the unaffected eye within eight months following diagnosis in the affected eye.
Glaucoma in Dogs FAQs
Can dogs survive with glaucoma?
Yes, dogs can survive with glaucoma.
Do dogs experience pain with glaucoma?
Severely elevated intraocular pressure, whether from acute severe glaucoma or chronic gradual glaucoma, often causes significant pain.