Causes of Sudden Blindness
Understanding Sudden Blindness in Dogs
Sudden blindness in dogs can be alarming for pet owners and often indicates a serious underlying medical issue. Prompt veterinary attention is critical to determine the cause and preserve any remaining vision, if possible. Here are several common causes of acute vision loss in dogs:
Bilateral Retinal Detachment
Retinal detachment occurs when the retina separates from the back of the eye, interrupting the transmission of visual signals. This condition can develop due to trauma, hypertension, or systemic illnesses such as ehrlichiosis. It is typically diagnosed using an indirect ophthalmoscope. In some cases, immediate medical treatment or surgical intervention can allow the retina to reattach and restore vision.
Sudden Acquired Retinal Degeneration Syndrome (SARDS)
SARDS is most frequently seen in middle-aged female dogs. Affected dogs suddenly lose vision, often accompanied by increased thirst, hunger, and urination. Their pupils are typically dilated and unresponsive to light. An indirect ophthalmoscope can help rule out retinal detachment, and an electroretinogram (ERG) is used to confirm the diagnosis.
There is no treatment for SARDS, and the resulting blindness is irreversible. Over time, the retina degenerates and exhibits signs of atrophy. Interestingly, the systemic signs (increased thirst and hunger) tend to fade over time. The exact cause of SARDS remains unknown, but it is suspected to involve an internal release of a steroid-like compound that is toxic to the retina and mildly harmful to the liver.
Acute Onset Glaucoma
Glaucoma is characterized by increased intraocular pressure due to impaired drainage of fluid from the eye. This pressure damages the optic nerve and, if untreated, leads to permanent blindness. Certain breeds—including Samoyeds, Cocker Spaniels, Poodles, Chow Chows, and Siberian Huskies—are genetically predisposed.
There are two primary types of glaucoma: primary and secondary. In cases of acute primary glaucoma, symptoms can include elevated eye pressure, redness, squinting, cloudiness of the cornea, a dilated and unresponsive pupil, and vision loss. Even with treatment, approximately 40% of affected dogs will lose vision in the affected eye within one year.
Anterior Uveitis
Anterior uveitis refers to inflammation of the uvea, the vascular layer of the eye that includes the iris and surrounding tissues. This painful condition can threaten vision if not treated promptly.
Symptoms include squinting, redness, excessive tearing, eye discharge, changes in pupil shape or size, swelling of the eyeball, and changes in iris color or clarity. Causes range from trauma and autoimmune disease to cancer, metabolic conditions, and infections (bacterial, fungal, parasitic, or viral—such as canine distemper).
Optic Neuritis
Optic neuritis involves inflammation and swelling of the optic nerve, which transmits visual signals from the eye to the brain. This condition can lead to partial or complete sudden vision loss in one or both eyes.
Clinical signs include dilated pupils unresponsive to light, diminished or absent light reflexes, and a swollen optic disc visible on examination. Some dogs may also show signs of systemic neurological involvement depending on the underlying cause.
Central Nervous System Disease
Blindness caused by diseases of the brain or spinal cord often presents with additional neurological signs. These may include head tilt, seizures, nystagmus (involuntary eye movements), or weakness in the limbs. A thorough neurologic exam and advanced imaging (such as MRI) may be required to determine the source.
Conclusion
Sudden blindness in dogs is always a medical concern, that requires immediate care. A veterinarian should be consulted immediately for primary assessment, however, an ophthalmologist may be required for a complete diagnosis. Because the causes are varied—ranging from eye-specific conditions to systemic and neurologic diseases—a full veterinary evaluation is essential. Early intervention can make a significant difference in preserving vision, managing pain, and addressing underlying health issues.
If your dog suddenly loses vision or shows signs of visual impairment, contact your veterinarian or a veterinary ophthalmologist immediately.
Adapted from lecture by Valerie Hayden, LVT, CVT, RVT
