Why are my cat’s eyes different sizes (one bigger than the other)?
Expert Answer
A cat’s uneven eyes can be caused by many things, including genetics, irritant stimulation, injury, conjunctivitis, or herpesvirus infection. Injury to one eye causes pain and tearing that keep it from opening fully, and irritants or herpesvirus can do the same.
Rinse the eye with saline and apply some anti-inflammatory eye drops to see if symptoms ease. If they do not improve, take the cat to a vet promptly.
My cat's one eye stayed squinty and it was a herpes flare, saline rinses and vet eye drops opened it back up. Uneven eyes can be a simple irritant or something like conjunctivitis or injury, so rinse and watch first. If it doesn't improve or he's in pain, a vet can catch herpes or a scratch before it scars. Don't ignore a suddenly smaller or swollen eye, eyes are easy to damage permanently if left.