# Why Is My Dog Not Opening One Eye? Causes and When to Worry A dog not opening one eye is almost always a sign of discomfort, and the eye is one of the few places where hours matter. Some causes, like a scratch on the cornea or a piece of grass stuck under the eyelid, get worse quickly without treatment. Others, like a mild allergy or a bit of dust, may settle on their own. Your job is to figure out which one you are likely dealing with and how fast to act. This article is educational and is not a substitute for veterinary diagnosis or treatment. ## Quick Answer - A dog who holds one eye closed, squints, or keeps the third eyelid up is telling you the eye hurts. - Common causes include corneal ulcers, foreign bodies, dry eye, conjunctivitis, and glaucoma. - Sudden, severe signs (a hard bulging eye, a cloudy cornea, a dog who will not let you near the face) need emergency care the same day. - Do not use human eye drops or leftover pet medications unless your veterinarian tells you to. - If the eye is not fully open again within a few hours, or if it looks worse, call your vet. ## What a Partially Closed Eye Looks Like in Dogs When owners say a dog eye is not opening, they usually mean one of a few things. The dog may squint, blink constantly, or hold the lid mostly shut. The upper eyelid may droop. You might see the third eyelid (the pinkish membrane in the inner corner) slide across part of the eye. Some dogs paw at the face or rub the eye along furniture or carpet. A dog not blinking normally is another version of the same problem. Blinking spreads tears across the cornea, the clear dome on the front of the eye [1]. When blinking hurts or stops, the surface dries out and the problem can snowball. It helps to know what normal looks like. A healthy dog's eyes are bright, open, and roughly symmetrical. The whites are white, not red or yellow. There is little to no discharge. The pupils are the same size on both sides and shrink in bright light [1]. A puppy not opening one eye deserves special attention. Young dogs explore with their noses and mouths, and they are prone to injuries from other pets, toys, and plants. A closed eye in a puppy is not something to watch for a few days. ## Main Causes of a Dog Not Opening One Eye The table below groups the most common reasons a dog eye is not opening fully. Urgency is a general guide, not a diagnosis. | Cause | Typical clues | How urgent | |---|---|---| | Corneal ulcer or scratch | Squinting, tearing, pawing at the face, redness, a hazy spot on the cornea | Same day, emergency if sudden and severe | | Foreign body (grass seed, hair, grit) | Sudden onset, one eye only, dog resists having the eye examined | Same day | | Conjunctivitis (bacterial or allergic) | Red, puffy lids, yellow or green discharge, both eyes often affected | Within a day or two | | Dry eye (keratoconjunctivitis sicca) | Thick, sticky discharge, dull cornea, chronic squinting, often both eyes | Within a few days | | Glaucoma | Hard, painful eye, cloudy cornea, dilated pupil, head shy, sometimes vomiting | Emergency now | | Uveitis (internal eye inflammation) | Pain, light sensitivity, small pupil, cloudiness inside the eye | Same day | | Trauma (blunt injury, cat scratch, chemical) | Visible wound, blood, sudden swelling, known event | Emergency now | | Eyelid or lash problem (entropion, rolled lid, extra lashes) | Lid rubs the eyeball, chronic tearing, squinting that comes and goes | Within a few days | | Systemic disease affecting the eye | Eye signs plus weight loss, lethargy, appetite change, or other body signs | Within a few days, sooner if the dog is unwell | Eye problems in dogs often mirror the ones people get, including cataracts and glaucoma [1]. Some eye diseases are linked to problems elsewhere in the body. Diabetes, low blood calcium, Cushing disease, and low thyroid levels can all show up in the eyes, and so can infections, blood vessel disorders, and cancer that has spread [2]. That is one reason your vet may ask about the whole dog, not just the eye. Brachycephalic breeds (flat-faced dogs like Pugs, French Bulldogs, and Shih Tzus) have extra risk because of their skull shape. In one clinical series, keratoconjunctivitis sicca and corneal ulcers were the most common eye diagnoses in brachycephalic dogs [3]. If you own one of these breeds, a closed eye should lower your threshold for calling the vet. Dry eye is an immune-mediated condition in dogs. It causes poor tear production, surface inflammation, and a risk of vision loss [4]. It tends to build up slowly, so owners may notice a dog not opening one eye fully for weeks before anything dramatic happens. Less common causes exist too. A dog can lose vision from optic nerve inflammation, which may show up as dilated pupils that do not respond to light and sudden blindness [5]. Rare tumors of the skull can also press on structures around the eye and cause discharge or asymmetry [6]. These are uncommon, but they are reasons a vet exam matters when signs do not fit the usual pattern. If your dog is also off food, that combination changes the picture. See [My Dog Won't Eat: When to Worry](/knowledge/veterinary-medicine/vet-visit-decisions/dog-wont-eat-when-to-worry) and [Dog Not Eating for One Day: When to Start Worrying](/knowledge/veterinary-medicine/vet-visit-decisions/dog-not-eating-one-day) for guidance on appetite changes. ## Red Flags That Mean Emergency Care Now Some eye signs cannot wait for a morning appointment. Go to an emergency clinic now if you see any of these: - The eye looks bigger than the other one, or the surface looks cloudy or blue-white. This can signal glaucoma, which damages the optic nerve quickly. - The dog is in obvious pain: crying, pacing, refusing to be touched near the head, or pressing the face into walls or furniture. - There is a known injury, such as a cat scratch, a stick to the face, a chemical splash, or a blow to the head. - The eye is bleeding, or the eyeball looks out of place. - The dog suddenly cannot see, bumps into things, or has pupils that stay wide in bright light [5]. - The dog is vomiting, weak, or collapsed along with the eye problem. A cloudy cornea, a fixed dilated pupil, or a hard eye on gentle touch are all reasons to skip the wait. Glaucoma and deep ulcers can cost a dog its vision in a short time. ## What You Can Safely Do at Home While You Wait You cannot diagnose an eye problem at home, but you can avoid making it worse. Do not put anything in the eye unless your veterinarian prescribed it. Human eye drops, saline, and leftover antibiotics can irritate the cornea or mask signs your vet needs to see. Never use a steroid drop on an eye that might have an ulcer, because steroids can make an ulcer much worse. Do not try to remove a foreign body yourself. If you can see a grass seed or hair under the lid, leave it alone. A steady hand and good light are not enough, and you risk scratching the cornea. Keep your dog calm and away from other pets. A dog with a painful eye may snap when another animal comes close. A quiet room with dim light is often more comfortable. Use a soft cloth or cotton ball dampened with warm water to gently wipe discharge from the outside of the lids. Wipe away from the eye, and use a fresh piece each time. Do not press on the eyeball. If your dog will tolerate it, take a photo of the eye in good light. This helps your vet see how it looked earlier if things change. Watch for the signs above and be ready to drive to the clinic. If your dog is squinting and otherwise bright and eating, a same-day vet visit is usually enough. If any red flag appears, treat it as an emergency. ## What Your Veterinarian Will Check and Test Your vet will start with a full exam, not just the eye. They will look at both eyes, the eyelids, the tear film, and the pupils. They will compare the two eyes for size, symmetry, and response to light [1]. They will also check the rest of the body, because eye signs can point to disease elsewhere [2]. Expect a few specific tests. A fluorescein stain is a dye that shows scratches and ulcers on the cornea. It is quick and does not hurt. A Schirmer tear test measures tear production. A small strip of paper sits under the lower lid for a minute. Low numbers point to dry eye, which is common in some breeds [4][3]. Tonometry measures pressure inside the eye. High pressure suggests glaucoma. A close look with an ophthalmoscope lets the vet see the inside of the eye, including the lens and the back of the eye. This is how conditions like optic neuritis are found [5]. Depending on what they find, your vet may recommend blood tests, x-rays, or other imaging. They may also refer you to a veterinary ophthalmologist for specialized testing. Treatment depends on the cause. A simple ulcer may need antibiotic drops and pain relief. Dry eye usually needs lifelong tear-stimulating medication. Glaucoma needs pressure-lowering drugs, sometimes surgery. Your vet will calculate any medication dose from your dog's weight and health, so never guess at a dose yourself. ## Preventing and Monitoring Eye Problems You cannot prevent every eye injury, but you can lower the odds. Keep grass seeds, foxtails, and sharp plants away from your dog's face on walks. Check the eyes after hikes, especially in tall grass. Trim hair around the eyes of long-haired breeds so it does not rub the cornea. Use a harness instead of a neck collar if your dog has eye or neck problems, since pulling can raise pressure around the head. Schedule routine exams. Many eye diseases start quietly. A vet can spot early changes before your dog shows obvious signs. If your dog has a chronic eye condition, keep every recheck. Dry eye, glaucoma, and chronic keratitis all need monitoring over time. Some treatments for chronic corneal inflammation are still being studied, and your vet will tailor the plan to your dog [7]. Track your dog's appetite, energy, and water intake along with the eye. Changes in those areas can point to a body-wide problem that shows up in the eyes [2]. If your dog stops eating, see [Dog Not Eating: When to Worry and What to Do](/knowledge/veterinary-medicine/digestive-and-urinary-care/dog-not-eating-when-to-worry). ## Limitations and When to Contact a Veterinarian This article cannot tell you what is wrong with your dog's eye. Only an exam can do that. Individual cases need a veterinarian, and eye problems can change fast. Contact your veterinarian the same day if your dog is squinting, holding one eye closed, or has discharge that is new or getting worse. A same-day visit is also right if the eye looks red or the dog is rubbing it. Go to an emergency clinic now if the eye is bulging, cloudy, bleeding, or clearly painful, if there was a known injury, or if your dog suddenly seems blind [5]. A routine visit is fine if the eye looks normal now but your dog has had repeated episodes of squinting, chronic discharge, or a known breed risk. Flat-faced breeds and dogs with a history of dry eye fall into this group [3]. ## Frequently Asked Questions ### Should I wait to see if my dog's eye opens on its own? No, not if the eye is squinting or held shut. A closed eye means pain, and pain rarely resolves without treatment. Call your vet the same day. ### Can I use human eye drops on my dog? No. Human drops can irritate the cornea or hide signs your vet needs to see. Some ingredients, like steroids, can make an ulcer worse. Wait for your vet's instructions. ### Is a dog not blinking as serious as a dog not opening the eye? Yes, it can be. Blinking keeps the cornea moist and healthy. A dog that stops blinking normally may be in pain or may have a nerve problem, and the eye surface can dry out and ulcerate. ### My puppy is not opening one eye. Is that different from an adult dog? The causes overlap, but puppies are more likely to have injuries from play, foreign bodies, or infections. Do not wait to see if it improves. Puppies can lose vision quickly from untreated eye disease. ### Will my dog need to see a specialist? Many eye problems are handled by your regular veterinarian. If the diagnosis is unclear, if the eye does not improve with treatment, or if surgery may be needed, your vet may refer you to a veterinary ophthalmologist. ## Related Articles - [My Dog Won't Eat: When to Worry](/knowledge/veterinary-medicine/vet-visit-decisions/dog-wont-eat-when-to-worry) - [Dog Not Eating for One Day: When to Start Worrying](/knowledge/veterinary-medicine/vet-visit-decisions/dog-not-eating-one-day) - [Dog Not Eating: When to Worry and What to Do](/knowledge/veterinary-medicine/digestive-and-urinary-care/dog-not-eating-when-to-worry) - [Why Is My Dog Suddenly Scared of the Dark?](/knowledge/veterinary-medicine/anxiety-and-behavior-support/dog-suddenly-scared-of-dark) - [Why Are My Dog's Eyes Red?](/knowledge/veterinary-medicine/symptom-guides/why-are-my-dogs-eyes-red) - [What to Do If Your Dog's Medication Is Causing Lethargy: When to Worry](/knowledge/veterinary-medicine/pet-medication-guide/what-to-do-if-your-dogs-medication-is-causing-lethargy-when-to-worry) - [Why Is My Dog's Eye Watering? Causes and When to Worry](/knowledge/veterinary-medicine/symptom-guides/dog-eye-watering) - [Third Eyelid Showing in Dogs: Causes and When to Worry](/knowledge/veterinary-medicine/symptom-guides/third-eyelid-showing-dogs) - [Dog Eye Not Producing Tears, Blinking, or Dilating](/knowledge/veterinary-medicine/symptom-guides/dog-eye-not-tearing-blinking-dilating) ## References 1. [Eye Structure and Function in Dogs - Dog Owners](https://www.merckvetmanual.com/dog-owners/eye-disorders-of-dogs/eye-structure-and-function-in-dogs). Merck Veterinary Manual. 2. [Eye Disorders Resulting from Generalized Diseases - Dog Owners](https://www.merckvetmanual.com/dog-owners/eye-disorders-of-dogs/eye-disorders-resulting-from-generalized-diseases). Merck Veterinary Manual. 3. [Ocular disorders in brachycephalic cats and dogs: A clinical study from Türkiye](https://pubmed.ncbi.nlm.nih.gov/42460135/). Canadian journal of veterinary research = Revue canadienne de recherche veterinaire, 2026. 4. [Tear Protein Alteration in Dogs with Keratoconjunctivitis Sicca](https://pubmed.ncbi.nlm.nih.gov/41594350/). Animals : an open access journal from MDPI, 2026. 5. [Disorders of the Optic Nerve in Dogs - Dog Owners](https://www.merckvetmanual.com/dog-owners/eye-disorders-of-dogs/disorders-of-the-optic-nerve-in-dogs). Merck Veterinary Manual. 6. [Case Report of a Rare Clinical Presentation of Craniomaxillofacial Osteosarcoma in an Adult Male Dog](https://pubmed.ncbi.nlm.nih.gov/42655745/). Veterinary sciences, 2026. 7. [Topical Application of Preserved and Unpreserved Bevacizumab Eye Drops Improves Ocular Surface Parameters in Dogs with Chronic Keratitis: A Pilot Study](https://pubmed.ncbi.nlm.nih.gov/42076760/). Veterinary sciences, 2026. ## Further Reading - [American Veterinary Medical Association: First Aid Tips for Pet Owners](https://www.avma.org/resources-tools/pet-owners/emergencycare/first-aid-tips-pet-owners) - [Merck Veterinary Manual: Dog Owners](https://www.merckvetmanual.com/dog-owners) - [Cornell Richard P. Riney Canine Health Center: Canine Health Information](https://www.vet.cornell.edu/departments-centers-and-institutes/riney-canine-health-center/canine-health-information)