Why is my horse's pupil uneven after an eye injury?
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Overview
An uneven pupil after an eye injury can happen for a few different reasons, including pain, inflammation, trauma to the eye, or a reaction to light. It’s not something to ignore, because pupil shape and size can change when the eye is irritated or damaged.
What you can check is whether the eye is open, watery, cloudy, swollen, painful, or changing over time. If the pupil stays uneven, the horse seems uncomfortable, or the eye looks worse rather than better, it’s sensible to get veterinary advice.
Things To Check
1. Compare both eyes in normal light and then again in shade, because pupil size can change with light levels.
2. Look for squinting, keeping the eye closed, tearing, rubbing, or repeated blinking.
3. Check for cloudiness, a bloodshot look, discharge, swelling, or any obvious scratch or bump around the eye.
4. Notice whether the pupil shape changes, stays uneven, or seems less responsive than the other eye.
5. Watch for signs the horse is unsettled, head shy, reluctant to move, or sensitive when you approach the injured side.
6. Think about what happened before the change, such as a knock, a branch strike, turnout, or grooming accident.
7. Check whether the horse is eating, behaving and moving normally, or seems dull or off-colour.
Common Causes
The most common causes are pain and inflammation after the injury, which can make the pupil look uneven or behave differently from the other eye. A direct knock can also cause swelling or bruising around the eye.
Other possibilities include a corneal scratch, an inside-eye inflammatory response, or damage to the structures that control the pupil. Less commonly, there may be bleeding inside the eye or more serious trauma that needs prompt veterinary assessment.
What To Do
Keep the horse calm and avoid any further work, turnout risk or situations where the eye could be bumped again. Don’t try to probe the eye or put anything in it unless your vet has told you to.
If you can do so safely, keep flies and dust away and observe the eye in good light a few times through the day. Make a note of whether the pupil stays the same, improves, or looks worse, and whether the horse becomes more uncomfortable.
When To Contact A Vet
An uneven pupil after an eye injury is a good reason to speak to your vet, especially if the eye is painful, cloudy, swollen, bleeding, or the horse is keeping it closed. Eye problems can change quickly, and it’s best not to wait if the appearance is worsening or the pupil isn’t returning to normal.
If the horse seems very uncomfortable, has reduced vision, or the injury was a direct blow to the eye, arrange prompt veterinary advice.
Products That May Help
If you’re dealing with a minor eye-area knock or want to keep nearby skin and hands as clean as possible while you monitor the injury, the Horse Care collection may be useful as part of your routine.
Related Questions
Can a horse’s pupil stay uneven after a minor eye injury?
What does a cloudy eye mean after a horse injury?
Should I keep my horse in or turnout if the eye looks injured?
Atlas is here to support owners with practical, easy-to-understand guidance. It is not a substitute for professional veterinary advice. If you're concerned about your animal's health, symptoms worsen, or something doesn't feel right, contact your vet.