Ear mites aren't to blame for your cat's weepy eye. It's possible your cat has ear mites and a weepy eye -- the former may even foster the latter in some circumstances -- but it's not a causal relationship. Both conditions are health issues, though, and your cat needs help.
Introducing ... Ear Mites
Cats don't usually have ear problems, but when they do, it's often because of ear mites. Cats, dogs and even humans can get ear mites. The most common culprits are members of the Otodectes cynotis species. (It's noteworthy that all mites and ticks are a subclass of the arachnid family, which is typically associated with spiders and scorpions.) Signs of infestation are obvious: your cat keeps scratching and shaking his head and he's constantly holding his inflamed ear against his head. Check his ears to confirm. You may not be able to see their pinhead-sized bodies, but the dark, gooey waste they strew about inside your cat's ear is hard to miss. In the short-term, they cause itchiness and irritation. If left untreated, they can cause infections and, eventually, deafness.
A Reason to be Weepy-Eyed
Cats cry to flush out their eyes. This is typically a response to eye irritation, allergies or clogged tear ducts. Epiphora, the medical term for excessive tears, is sometimes accompanied by squinting, inflammation, redness, discharge, sagging skin or corneal ulcers, all in and around the eye. Your cat may acquire epiphora because he has rhinitis, aka sinusitis; acute eye irritation; tumors and conjunctiva of the eye, eyelids, nasal cavity, maxillary facial bone or adjacent sinuses; or any condition that caused tear duct obstruction. Anthropomorphic anecdotes aside, there's no evidence that cats cry emotional tears. Emotional crying appears to be the sole domain of humans.
Why Your Cat May Have Both
Ear mites can't directly cause a weepy eye, but your cats response to them can. Once afflicted with ear mites, your cat will try to scratch, shake and groom them out of his head. This effort is in vain -- the mite's foothold is too deep within the ear -- but amid a frenzied assault, your cat may inflict collateral injury on himself. Outdoor cats are more likely to encounter ear mites as well as get into brawls that cause the kind of eye damage that results in epiphora. Ear mites are highly contagious to all cats, though. Those in close confines, such as feral collectives or animal shelters, have higher infestation rates than their domestic brethren.
What To Do
If your cat has ear mites, call a veterinarian. A diagnosis is usually confirmed via otoscope, and treatments involve topical, oral and systemic cleanings. If your cat has a weepy eye, try to figure out if it's cause is acute or chronic. In the case of the former, it should pass, unless it's the secondary result of behavior. (Remember how a weepy eye can be indirectly related to ear mites?) In the case of the latter, call a veterinarian. The treatment of epiphora is as diverse as its causes. Sometimes there's a simple fix; other times treatment involves surgery.
- Cornell Feline Health Center: Ear Mites -- Tiny Critters That Can Pose a Major Threat
- Purdue University College of Veterinary Medicine: Ear Mites
- PetMD: Watery Eyes in Cats
- PetMD: Eye Defects (Congenital) in Cats
- KittenCare.com: Eye Problems in Cats & Kittens
- The Daily Cat: Do Cats Cry Tears When They Are Sad?
- IPM North Carolina: Ear Mite
- Northern Virginia Community College Veterinary Technology Program: Lesson 11 -- Mites and Ticks
- Stanford Cat Network: Caring for Feral Cats
- The American Journal of Tropical medicine and Hygiene: A Human Case of Otoacariasis Involving a Histiomatid Mite (Acari: Histiostomatidae)
- Cat's Eye image by Erika_DC from Fotolia.com