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Causes of Sudden Blindness in Dogs

Sudden Blindness in Dogs

Sudden blindness in dogs can stem from several underlying disorders with some affecting the eyes directly and others presenting as secondary manifestations due to underlying systemic conditions. Whether the blindness is temporary or permanent, may depend on the underlying condition and how quickly the issue is tackled. Some types of eye disorders are a emergency as permanent loss of vision may be the consequence if left untreated. Dogs suffering from certain types of sudden blindness may be referred to a veterinary opthamologist for deeper evaluation.

 Causes of sudden blindness in dogs

Causes of sudden blindness in dogs

Sudden Blindness in Dogs 

Although blindness in dogs can be heartbreaking, dogs do not rely on their vision to the extent that humans do. Because dogs live in an olfactory world, dogs therefore appear to adjust better to their blindness than expected. Regardless, acute visual impairment is distressing to both owners and dogs.

Although the visual impairment seems to be indicative of an issue primarily affecting the dog's eyes, it's important to point out that several underlying medical disorders affecting the whole body may be the cause. The vet will therefore gain a detailed history of the dog and run some tests so to identify possible underlying systemic diseases.

Possible systemic conditions known to lead to visual impairment or sudden blindness in dogs include malignant lymphoma causing uveitis and retinal detachment, hypertension, meningitis, brain lesions and renal disease.

It also important to consider that, although it may appear as if the dog sustained sudden onset of blindness, in reality the condition may have been affecting the dog insidiously for quite some time, only that the dog was able to compensate before the vision was totally lost.

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Signs of sudden blindness in dogs include dilated pupils that do not respond to light, dogs walking clumsy, often bumping into furniture, dogs who suddenly aren't interested in eating or drinking, lethargy and not moving around much. Not always these signs though are readily recognized. Dog owners can try to test their dog's vision to gain an insight, but the vet should be seen at once as some forms of blindness may be reversible if the the vet is seen on time.

A Case of Retinal Detachment 

retinal detachment

A dog's retina is the blood supply to the eye. In retinal detachment, the retina "peels away" from the back of the eye. Affected dogs develop severe visual impairment or blindness suddenly. A lack of the dog's pupil reaction to light may be possibly witnessed based on the extent and duration of the lesion.

The underlying causes of retinal detachment in dogs may be several, ranging from trauma, a complication of cataract surgery, a hereditary predisposition in brachycephalic breeds, some forms of cancer and as a result of high blood pressure.

To precise, retinal detachment in dogs with high blood pressure results from high systolic pressures. Unlike humans, there are no known conditions in dogs that may cause an elevated diastolic pressure. In humans, elevated diastolic pressures are associated with atherosclerotic disease, a condition that doesn't typically occur in dogs. A high systolic blood pressure in dogs is seen as a result of underlying disease processes such as chronic kidney disease or hyperthyroidism unlike the primary hypertension seen in people.

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Sudden blindness in dogs caused by high blood pressure may be reversible if the high blood pressure is quickly addressed and the underlying cause of the high blood pressure is treated. Retinal hemorrhage and detachment can be easily detected by a vet using an ophthalmoscope.

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Optic Nerve Problems 

Optic neuritis is the inflammation of the optic nerves that innervate the eyes. The presence of inflammation around the optic nerve can be due to the presence of a brain lesion such as a tumor affecting the optic nerve. Other possible causes include infections such as toxoplasmosis, exposure to toxins, autoimmune disorders and trauma.

Affected dogs exhibit acute, sudden onset of blindness affecting both eyes. The pupils are widely dilated and the pupils no longer respond to light.

An abnormal optic nerve can be detected through an eye exam with the slit lamp. Optic neuritis is treated with steroids in high doses, and then, afterward, in lower doses and the underlying cause needs to be addressed. Antibiotics may also be indicated.

Blindness can occur secondary to diabetes.

Blindness can occur secondary to diabetes.

SARD-Sudden Acute Retinal Degeneration

SARD, stands for sudden acute retinal degeneration, and as the first word "sudden" in this acronym implies, it's a condition known for causing a very rapid onset of blindness in dogs.

The vision loss doesn't happen over the course of several weeks or months, but rather more likely it happens over the course a few of days up to 1 to 2 weeks. The loss of vision is complete and irreversible.

Affected dogs are generally between the ages of 7 and 14 years of age, with females affected more than males. Symptoms, interestingly, include increased appetite, increased water intake and increased urination. Generally, these signs are seen in the couple of months prior to the onset of vision loss. The pupils are moderately to widely dilated.

Recent research seems to suggest that SARDS may be a form of an immune-mediated disease, where the retina is subject to atrophy and there is cell death of the photoreceptor cells. The retina in affected dogs upon examination tends to appear normal initially. SARDS is typically detected by chromatic pupillary light activity testing with a definitive diagnosis attained by electroretinography (ERG).

Unfortunately, there is currently no treatment for this condition, but research is being conducted on finding a treatment. Iowa State University School of Veterinary Medicine has been working on creating an intravenous immunoglobulin treatment (IV-Ig) for SARDS in dogs. This treatment though has gained mixed results and can have significant complications.

Other Causes of Sudden Blindness in Dogs 

Progressive Retinal Atrophy (PRA) is a genetic condition affecting the rods and cones of the eye. The retina at the back of the eye degenerates leading to irreversible blindness. It starts with gradual progression of night blindness that ends up eventually affecting the dog's vision in bright light. Affected dogs are around 6 to 8 years of age and show dilated pupils. Diagnosis is obtained by retinal/ funduscopic examination. Unfortunately, there is no treatment for this condition.

Other causes of sudden blindness include cerebral hypoxia after general anesthesia, acute cataract, toxicities such as ivermectin, enrofloxacin, retinal hemorrhage, acute uveitis and glaucoma (sustained elevated pressure within the eye).

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