Can cats see in the dark? How feline night vision works
Not in total darkness: with no light at all a cat cannot see, just like us. But in very dim light it sees far better than a person, because its retina is packed with cells that work in low light and has a reflective layer behind it that uses the light twice.
The short answer: dim light yes, pitch black no
Every animal’s eye needs light to see, and the cat’s is no exception. In a sealed room without the faintest chink of light, a cat finds its way by hearing, smell, its memory of the space and its whiskers, but it cannot see. What makes it special is that total darkness hardly ever exists in real life: at night there is always a little light from the moon, the street lamps, the standby light on the TV or the window. With that tiny amount of light, which to us looks almost black, a cat can make out shapes and movement with considerable ease. The usual estimates in the veterinary literature put the light it needs to see at around a sixth of what we need, although the exact figure depends on how it is measured.
A retina built for twilight
The retina contains two kinds of light-sensing cells: cones, which work in bright light and handle colour and detail, and rods, which are extremely sensitive and work in low light but cannot tell colours apart. A cat’s retina has a far higher proportion of rods than ours. It is the legacy of a twilight hunter: its wild ancestor hunts mainly at dawn and dusk, when rodents are on the move, and its eye is tuned for those hours. The price is that in broad daylight it sees colours more faintly and in less detail than a person does.
The tapetum lucidum: the mirror behind the eye
Behind the retina, a cat has a layer of cells that acts like a mirror, called the tapetum lucidum. Light that passes through the retina without being absorbed bounces off this layer and travels back through the sensitive cells, giving them a second chance to catch it. That is why a cat’s eyes glow green, yellow or bluish when a torch beam or a camera flash hits them. Many nocturnal and twilight animals have this layer; we do not. In blue-eyed cats and some very pale-coated cats the reflection sometimes looks reddish instead, because their tapetum contains less pigment.
Pupils that open almost all the way
A cat’s pupil is a vertical slit that narrows to a hairline in bright light and widens in the gloom until it fills almost the whole eye. That range is far greater than a round pupil like ours can manage, and it lets the cat go from a dark hallway to a sunny balcony without being dazzled. On top of that, a cat’s eye is very large for the size of its head, with a wide cornea and lens that let in more light. Pupils that stay widely dilated in bright light, or that differ in size between the two eyes, are not normal and should be checked by a vet.
What a cat sees worse than you
All that sensitivity comes at a cost. A cat’s visual acuity, its ability to see fine detail, is considerably poorer than ours: something a person sees clearly at 30 m (about 100 ft), a cat sees as a blur from much closer. Nor can it focus well on anything right in front of its nose, closer than about 25 to 30 cm (10 to 12 in), which is why it sometimes fails to find a treat that is practically under its chin; for things that close it relies on smell and its whiskers. In return, its field of view is slightly wider than ours and it is superb at spotting movement, even out of the corner of its eye. It struggles to see an object that is perfectly still, but picks up one that moves even slightly.
The other senses that work the night shift
Good as a cat’s eyesight is in dim light, it does not work alone at night. Its hearing picks up far higher-pitched sounds than we can hear, such as the ultrasonic squeaks of mice, and it can swivel each ear independently to pinpoint exactly where a noise is coming from. Its sense of smell is vastly sharper than ours and tells it who has passed by and how long ago. And its whiskers, or vibrissae, detect air currents and contact with nearby objects, letting it weave between furniture without touching it when there is not enough light. That is why a cat that gradually goes blind can carry on living an almost normal life in a home it knows: it has a map of the space built with all its senses at once, not just its eyes.
Why this matters at home
Understanding how your cat sees explains a lot. The early-morning sprints down the hallway are not whims: it is the cat’s most active time of day and it can see perfectly well by the light coming through the window. Toys that move slowly and unpredictably appeal far more than a ball sitting still. And if it sometimes cannot see the food you have put right in front of it, it is not being clumsy. There is no need to leave lights on for it at night, unless it is an older cat with failing eyesight, in which case a soft light and furniture that always stays in the same place help it find its way around.
When to suspect your cat’s eyesight is failing
Cats are very good at making up for vision loss with their other senses, so the problem is often noticed late. Warning signs: it bumps into furniture someone has moved, hesitates before jumping or misses jumps it used to make, is more disoriented at night than during the day, has dilated pupils in bright light, or the eye looks cloudy or a different colour. In older cats, a common cause of sudden blindness is high blood pressure, which can detach the retina and is often linked to kidney disease or hyperthyroidism. If it is treated early, some sight can be recovered, so sudden blindness means seeing the vet the same day.
Cats cannot see in total darkness, but in very dim light they see far better than we do, thanks to a rod-rich retina, pupils that open almost all the way and the tapetum lucidum, which reflects light and makes their eyes glow. The trade-off is that they see less detail, focus poorly on things very close up and perceive colours as more muted.
Educational content from Michipedia, translated from the Spanish original. It does not replace the advice of a vet or a feline behaviour specialist. Every cat is an individual.