What this means
Avoiding light shows up in different ways. A dog may sit in the shade on a sunny day, walk around the edge of a room by the curtains, squint, or turn its head away from a lamp or car headlights. Some dogs do not want to go out only in bright daylight but behave normally in the evening. Notice whether it happens with one eye or both, and whether your dog also blinks, waters or rubs its face.
Sensitivity to light can point to different eye problems: inflammation of the eye surface or the inside of the eye, an injury, raised pressure, or changes in the lens or iris. Some are present from birth and some appear later. Only a vet who examines the eyes can find the cause, and some of these conditions are painful and can quickly damage sight.
Note down when the light avoidance began, whether it was sudden or grew slowly, and whether one eye looks different, red or cloudy. Notice whether your dog plays, how it copes in the dark, and whether it has knocked its head. Do not put any drops in the eyes and do not use home remedies while the cause is not known.
Possible causes
These are things that can cause this sign. It is not a diagnosis, and they are not equally likely for your dog.
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Damage to or inflammation of the eye surface
A scratched or inflamed front surface of the eye hurts, and light makes the pain worse. The dog squints, waters and may rub its face.
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Inflammation inside the eye
When inflammation affects the inside of the eye, light becomes unpleasant. The eye may be red or cloudy and the pupil unusual.
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Raised pressure in the eye
Higher pressure inside the eye causes pain and sensitivity to light. The eye may look red or bigger than the other one.
About the condition: Glaucoma -
A lens that has moved out of place
When the lens no longer stays where it should, the eye can hurt and light can irritate it. The dog may squint or avoid bright light.
About the condition: Primary lens luxation -
An inherited difference in the iris or pupil
If the iris has developed unevenly, too much light enters the eye and a bright day is irritating. The dog may keep looking for shade.
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Injury or a foreign body in the eye
A speck of dust, a thorn or a blow can irritate the eye so that light becomes unpleasant. The dog often rubs its face a lot.
What else to watch for
These observations help your vet build the picture faster. Note down what you saw and when.
- When the light avoidance began and whether it was sudden
- Whether one eye or both are affected
- Whether the eye is red, cloudy or watering
- Whether your dog squints, rubs its face or blinks
- Whether your dog bumps into things or seems unsure in the dark
- Whether the pupils are the same size
When to book a routine visit
Sudden or lasting light avoidance is a reason to see a vet the same day, because eye problems can quickly damage sight. Say when it began and what else you have noticed.
Related conditions
Conditions whose entries mention this sign. The list is somewhere to read on, not a way to reach a diagnosis.
- Eye problems Eyes A dog's eyes can be affected by many different problems: faults of the eyelids and lashes, inflammation, injuries, corneal ulcers, clouding of the lens or diseases of the retina. Eyes are sensitive and some kinds of damage can get worse quickly and affect sight, so changes in the eyes are not something to wait out. If an eye suddenly turns red, seems painful or has been injured, the dog needs to see a vet immediately.
- Iris coloboma Eyes Iris coloboma is an inborn eye defect in which the iris, the coloured part of the eye, does not form completely and is left with a gap or notch. Because of this the pupil may look irregular in shape and cannot close down properly in bright light. The defect itself does not grow with age, but other changes in the eye can occur alongside it, so it is worth having the eyes checked by a vet.
- Primary lens luxation Eyes This is an inherited eye disease in which the fine fibres that hold the lens in place weaken, so the lens shifts or comes loose entirely. If the lens slips into the front of the eye, it can block the drainage of fluid and cause a sudden rise in eye pressure, which is very painful and threatens sight. In that case the dog needs a vet immediately.
Body systems: Eyes