Cats close their eyes for several distinct reasons, from communicating trust and affection to simply shifting their sensory focus. The most well-known reason is the “slow blink,” a deliberate narrowing of the eyes that functions as a form of positive emotional signaling between cats and the people or animals around them. But eye closure in cats can also indicate relaxation, pain, sensory adaptation, or a medical problem, depending on the context.
The Slow Blink: A Social Signal
When your cat looks at you and slowly narrows or closes their eyes, they’re not just being sleepy. A 2020 study published in Scientific Reports tested this behavior in two controlled experiments. In the first, cats produced significantly more eye-narrowing movements when their owners slow-blinked at them compared to when no interaction took place. In the second experiment, cats were more likely to approach an unfamiliar person after that person slow-blinked at them than when the person maintained a neutral facial expression.
This tells us two things. Cats mirror the slow blink back when they receive it, and they interpret it positively enough to approach a stranger who does it. The researchers concluded that slow blink sequences function as a form of positive emotional communication between cats and humans. Whether the behavior triggers a genuinely pleasant internal state in the cat or simply signals that the person is non-threatening isn’t fully settled, but the effect is real either way.
You can try this yourself. Look at your cat with a relaxed face, then slowly close your eyes for a second or two before opening them again. Many cats will return the gesture. Among cat behaviorists, the slow blink is sometimes called a “cat kiss.”
Why Eye Contact Feels Threatening
The slow blink works partly because of what it replaces. In feline body language, a direct, unblinking stare is confrontational. Cats in conflict lock eyes with each other, and an unbroken gaze from a human can feel the same way. Closing or narrowing the eyes is the opposite signal: it communicates that the cat doesn’t perceive a threat and isn’t issuing one. By voluntarily giving up visual awareness, even briefly, a cat demonstrates that it feels safe enough to let its guard down.
This is also why cats in shelters or unfamiliar environments tend to keep their eyes wide open and fixed on nearby movement. They’re on alert. A cat that half-closes its eyes in your presence is telling you it has no reason to watch you closely.
Sleep and Drowsiness
Cats sleep between 12 and 16 hours a day, and much of that time is spent in light drowsiness rather than deep sleep. Researchers studying feline sleep have identified four distinct states: wakefulness (including drowsiness), light slow-wave sleep, deep slow-wave sleep, and REM sleep. Cats can spend 3 to 8 hours per day in REM sleep alone.
During light sleep, you’ll often see your cat with eyes partially closed or flickering. Their ears may still rotate toward sounds, and they can snap awake instantly. This “cat nap” state accounts for a large chunk of their day, so half-closed eyes in a relaxed posture usually just mean your cat is drifting in and out of a light doze.
Closing Eyes While Eating
Some cats close their eyes while eating, which can look odd but is perfectly normal. When food is directly under a cat’s nose and not moving, vision becomes the least useful sense. Cats shift their focus to smell and whisker contact to navigate the food in front of them. Their whiskers detect the shape and position of objects at close range, and their sense of smell confirms what they’re eating. Closing the eyes at that point is simply part of concentrating on other senses.
There’s a comfort component too. A cat that closes its eyes while eating feels secure enough in its environment to stop visually scanning for danger. It’s a subtle sign of trust, similar in spirit to the slow blink.
Light Sensitivity and Pupil Anatomy
Cat eyes are built to gather light efficiently, which makes them exceptional hunters in dim conditions but also means bright light can be intense. Their vertical slit-shaped pupils can expand and contract rapidly to adjust to changing light, but in very bright environments, squinting adds an extra layer of light reduction beyond what the pupil alone can handle. If your cat squints when stepping into direct sunlight or when you turn on a bright overhead light, that’s a normal physiological response.
The Third Eyelid
Cats have a nictitating membrane, a translucent third eyelid that sits in the inner corner of each eye. Its primary jobs are protecting the cornea and producing tears. The gland at the base of this membrane produces 25% to 40% of a cat’s total tear output, keeping the eye moist and forming a protective film over the surface.
You’ll sometimes catch a glimpse of the third eyelid when your cat is falling asleep or just waking up. It slides partway across the eye during drowsiness and retracts when the cat is fully alert. If the third eyelid stays visible while your cat is awake and active, that’s worth paying attention to. A persistently protruding third eyelid can indicate pain, illness, dehydration, or a problem behind the eye itself.
Squinting as a Sign of Pain or Illness
Not all eye closing is benign. Cats are notoriously good at hiding discomfort, but their faces give clues. The Feline Grimace Scale, a validated tool for assessing pain in cats, includes orbital tightening (squeezing around the eyes) as one of its key indicators. A cat in pain often holds its eyes partially shut in a tense, sustained squint that looks different from the soft, relaxed narrowing of a slow blink or a drowsy cat.
Involuntary squinting or rapid blinking in one or both eyes can also signal eye-specific problems: a corneal scratch, an infection, a foreign object, or inflammation. This type of squinting tends to look asymmetric (worse in one eye), and the cat may paw at its face, produce excessive tears, or avoid light. If the squinting came on suddenly, persists for more than a day, or is accompanied by discharge, redness, or behavioral changes like hiding or loss of appetite, something medical is likely going on.
How to Read the Context
The key to interpreting your cat’s eye closure is the rest of their body. A cat that slow-blinks while lounging on the couch with a loose, relaxed posture is content. A cat that squints while hunched, with ears flattened or whiskers pulled back, is uncomfortable. A cat that closes its eyes and purrs while you scratch its chin is savoring the moment. A cat with one eye held shut and watering needs a closer look.
Cats communicate constantly through their eyes. Once you start watching for the differences between a trust signal, a nap, a light adjustment, and a pain response, their behavior becomes much easier to read.