TL;DR: If your dog cannot blink one eye, it is likely caused by facial nerve paralysis and requires a veterinary exam within 24–48 hours to prevent painful corneal ulcers.
Why is my dog unable to blink one eye?
If your dog is unable to blink one eye, it is most commonly caused by facial nerve paralysis. This occurs when the nerve that controls the muscles of the face and eyelids is damaged or inflamed. You may also notice a drooping lip or ear on the same side. Common causes include middle ear infections, trauma, or idiopathic reasons where the cause is unknown.
Is it an emergency if my dog cannot blink?
- The urgency level for an inability to blink is generally Low to Moderate, requiring a veterinary appointment within 24 to 48 hours.
- The main risk is that the eye will become excessively dry (exposure keratitis), which can lead to painful corneal ulcers.
- If the eye itself looks very red, cloudy, or if your dog is pawing at it, you should seek care sooner.
How does sharing a photo help the veterinary team triage my dog?
- A clear, front-facing photo allows the team to assess the symmetry of the face.
- It helps identify subtle signs like drooping or changes in pupil size.
- By seeing the eye's current state, the team can provide better immediate advice on lubrication.
- The photo helps determine how quickly your pet needs to be examined in person.
Clinical Context (Merck Veterinary Manual)
In dogs, the inability to blink one eye, or unilateral paresis/paralysis, can be caused by idiopathic facial paralysis, trauma, ear disease, or brain-stem lesions. Clinical signs include an inability to blink, drooping ear, drooping upper lip, and drooling; however, facial sensation remains intact. Trauma from rough handling, automobile accidents, or surgery (e.g., bulla osteotomy, total ear ablation) may also result in facial paralysis. On the affected side, the palpebral fissure may appear slightly larger, and when the eyelids or cornea are touched, the eyelids do not close, though the eyeball will retract into the orbit if the trigeminal and abducent nerves are functioning. Corneal irritation may result in excessive tear production. In acute denervation, the ear carriage is often lower on the affected side.
Chapter: Neurology
Source: The Merck Veterinary Manual, 11th Edition (Page 1239)