Dogs have quite poor vision, up to eight times worse than humans at seeing detail. Scientists think this is because dogs struggle to tell red and green apart, much like colour blind humans. Dogs only have two types of cells (called cones) in the back of the eye/retina responsible for seeing colour while most humans have three. Cones work best in bright light so humans fair better in those conditions.

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How have dogs evolved to see in darker conditions?

Dogs’ wild ancestors were more active at dusk and dawn so eyes that work better in lower light are an evolutionary advantage. Therefore, they have evolved to have more light-sensitive cells called ‘rods’ than humans. Consequently, they see better than us in dimmer light.

Dogs have other adaptations to help them see in low light; a larger pupil which lets in more light; a lens that is closer to the retina, making the image on the retina brighter; and finally the tapetum. The tapetum is a mirror-like structure in the back of the eye that reflects light giving the retina another chance to register light. It is also what causes a dog’s eyes to glow at night, which if you have ever caught it on camera, looks very spooky!

What does this have to do with anything?

Our vision is different to our canine friends’. For us, vision impairment is most obvious in dim light, but for dogs this may not be the case.

If your dog has sight issues, they may still struggle in dim light but they will probably show signs during the day. A dog’s main sense is smell. The percentage of the dog’s brain devoted to analysing smells is 40 times larger than a human’s. Their second best sense is hearing. Consequently, if dogs become slowly vision-impaired they often cope with this better than we would. Most vision-impaired dogs can go on to live a happy life.

Signs your dog may have issues with vision

If you suspect your dog has a problem with their eyes or vision, it’s important to see your vet who can perform an examination. If poor vision is the cause of your dog’s dislike of the dark there may be other signs such as:

  • clumsiness.
  • hesitation before entering unfamiliar areas (including dark spaces).
  • difficulty finding familiar objects like food and water bowls.
  • increased sleeping.
  • enlarged eyeball(s).
  • change of pupil colour.
  • startled or aggressive behaviour, even around familiar people.
  • rubbing their eyes or head.
  • watery or inflamed eyes.
  • discharging or crusty eyes.

There are many causes of visual issues in dogs such as: cataracts, glaucoma, corneal injury (caused by dry eye or ulcers, for example) or problems with the retina. Many of these can be treated or at least improved.

Could dogs be scared of the dark?

Fear of darkness has been recognised in people for decades. Researchers as early as Sigmund Freud linked it to separation anxiety in humans. It’s now thought that as sight is our most powerful sense, darkness makes humans feel vulnerable, and our creative brains work overtime wondering what could be there. Certainly, anxiety disorders are diagnosed and treated in dogs regularly but there are no real studies showing pet dogs get the same fear of the dark as us.

Dogs can suffer separation anxiety, which may manifest at night given this is the time your dog may be separated from you. Surveys suggest that between 13% and 18% of owners report problem behaviours with dogs left alone. Common signs include destruction, toileting, barking or howling. There are different reasons for this condition but most commonly it’s because the dog has never learned that being alone can be okay.

Start young by making sure your dog has a place they like to be on their own. Only leave them for a few minutes, associating your departure with something positive (like treats) before building the time alone slowly. A pheromone (a chemical released by animals for communication) called dog-appeasing pheromone has been produced in the form of collars, sprays and diffusers. This sends comforting signals to dogs, which can also help in stressful, or anxious situations alongside behaviour modification.

Indication of cognitive dysfunction syndrome

Cognitive dysfunction syndrome (CDS) is a disorder of older dogs that shares some similarities with Alzheimer’s in people. Signs such as disorientation and confusion are often worse at night, so may be interpreted as a dark/night phobia. Reportedly, 28% of dogs 11 to 12 years of age and 68% of dogs 15 to 16 years of age show at least one sign associated with CDS. Signs include:

  • disorientation, restlessness, staring and appearing confused.
  • new phobias, or separation anxiety.
  • changes in social interaction such as becoming more needy or maybe more aloof.
  • changes to the sleep–wake cycle, such that daytime sleeping and night time wakefulness occurs.
  • passing urine or faeces in the house when previously house-trained.
  • changes in activity (decreased or increased).

An examination is needed by your vet to check for other causes of some of the signs such as neurological disease, hormone conditions, metabolic issues (e.g. liver disease), pain, medications, and loss of sensation (hearing or sight, for example). Further testing may be needed to help eliminate other issues. Although there is no cure for CDS, diet, medications, and environmental and behavioural modifications can help.

Negative associations with the dark

If your dog has suffered trauma while in darkness, theoretically they may develop a fear linked with darkness. For example, if your dog has been attacked by another dog, involved in a road traffic accident or been exposed to frightening fireworks while out in the dark, they may be reluctant to go out in the dark again. If the cause of the trauma is known then behaviour modification may help. Desensitisation CD programmes, plus use of pheromones would be a good first step for noise phobias.

If your dog seems to suddenly be afraid of the dark, there’s usually a reason which shouldn’t be ignored. The first step is to arrange an appointment with a vet to discuss your concerns so they can perform a thorough examination to look for possible causes.

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