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If your cat has loss of vision in one or both eyes without ocular vascular injection or other apparent signs of eye inflammation, it may be suffering from Blind Quiet Eye. This disease may occur due to abnormalities in retinal image detection, retinal focusing, optic nerve transmission, or simply the central nervous system's inability to interpret images correctly.

Symptoms and Types

Because Blind Quiet Eye directly affects the cat's vision, it may display several signs, including:

• Clumsy behavior (e.g., bumping into objects, tripping, falling)
• Decreased or absent menace response (i.e., does not blink when a hand is waved toward the eyes)
• Impaired visual placing responses (e.g., extends the paws incorrectly when trying to approach a nearby surface)

In addition, these problems may become more exaggerated when outside at night.

Causes

There are several causes for Blind Quiet Eye, such as cataracts, central nervous system lesions, and the lens' inability to focus correctly. Other common causes include:

• Retinal disorders:
  • Sudden acquired retinal degeneration syndrome (SARDS)
  • Shrinking of the retina (progressive retinal atrophy)
  • Separation of the eye's inner lining (retinal detachment)
  • Ivermectin toxicity
  • Taurine deficiency
  • Enrofloxacin (an antibiotic) toxicity

• Optic nerve issues due to:
  • Inflammation
  • Cancer
  • Trauma
  • Underdevelopment
  • Lead Toxicity

Diagnosis

You will need to give a thorough history of your cat’s health and the onset and nature of the symptoms to the veterinarian. He or she will then perform a complete physical examination (including an opthalmoscopic exam) as well as a biochemistry profile, urinalysis, complete blood count (CBC) to rule out potential systemic causes of the disease.

During the ophthalmic exam a penlight will be used to rule out potential systemic causes of the disease, such as cataracts or retinal detachment. (In cases of retinal detachment, the systemic blood pressure is often elevated.) Ophthalmoscopy, meanwhile, may reveal progressive retinal atrophy or optic nerve disease.

If the ophthalmic exam reveals nothing irregular, it may suggest sudden acquired retinal degeneration syndrome (SARDS), retrobulbar optic neuritis (inflammation of the optic nerve after it exits the eye toward the brain), or a central nervous system (CNS) lesion. If the diagnosis is still in doubt, electroretinography -- which measures the electrical responses of photoreceptor cells in the retina -- makes it possible to differentiate retinal from optic nerve or CNS disease. Ocular ultrasounds and CT (computed tomography) and MRI (magnetic resonance imaging) scans are also very helpful to visualize and diagnose orbital or CNS lesions.