Crossed eyes, known medically as strabismus, affect roughly 2% of people worldwide. The most obvious sign is one eye pointing in a different direction than the other, but the misalignment isn’t always easy to spot. Some cases are subtle, intermittent, or only show up when you’re tired. There are simple checks you can do at home, and knowing what visual symptoms to watch for can help you figure out whether your eyes are truly misaligned.
What Crossed Eyes Actually Look Like
Strabismus isn’t just eyes turning inward toward the nose, though that’s the most common image people have. Eyes can drift in four directions. Inward turning (esotropia) is what most people picture when they hear “cross-eyed.” Outward turning (exotropia) is sometimes called “wall-eyed.” Eyes can also shift upward or downward, though vertical misalignment is less common.
The misalignment can be constant or intermittent. Some people’s eyes only drift when they’re fatigued, stressed, or focusing on something very close. Others notice it mainly in photographs. If the turning comes and goes, you might not realize it’s happening at all unless someone else points it out or you catch it in a mirror during a tired moment.
Visual Symptoms That Signal Misalignment
You don’t always need a mirror to suspect strabismus. Your vision itself gives clues. Double vision is one of the strongest indicators in adults. When your eyes aren’t pointing at the same target, your brain receives two different images and may struggle to merge them. You might see two overlapping versions of a sign, a face, or a line of text.
Other signs include difficulty judging distances (parallel parking becomes harder, you misjudge how far away a cup is when reaching for it), eye strain or headaches after reading or screen work, and a habit of closing or squinting one eye in bright light. Some people unconsciously tilt or turn their head to compensate for the misalignment, finding a position where their vision feels more comfortable. If you notice yourself doing this regularly, it’s worth investigating.
Two Simple Checks You Can Try at Home
The Light Reflection Test
This is a simplified version of a clinical screening tool called the Hirschberg test. Dim the lights in a room, then hold a small flashlight or your phone’s light about an arm’s length from your face (or from the person you’re checking). Have them look directly at the light. Look closely at both eyes: you should see a tiny bright dot reflected on the surface of each eye. If the eyes are properly aligned, that dot appears in the same position on both corneas, typically near the center of each pupil. If one reflection is centered and the other is off to one side, that eye is likely misaligned.
This test works especially well for checking young children or infants who can’t describe what they see. It’s also useful for spotting misalignment in photos. If you notice the camera flash consistently reflects in different spots on your child’s eyes, that’s worth a professional evaluation.
The Cover Test
Pick a small target across the room, like a letter on a poster or the corner of a picture frame. Focus on it with both eyes open. Now cover one eye with your hand or a piece of cardboard. Watch what the uncovered eye does. If it stays perfectly still and keeps staring at the target, that eye was already aimed correctly. If it shifts to “pick up” the target (moving inward, outward, up, or down), it wasn’t aligned while both eyes were open.
Repeat with the other eye covered. The direction of the shift tells you the type of misalignment. If the uncovered eye jumps inward to find the target, the eye was drifting outward. If it jumps outward, the eye was turned inward.
There’s a second part to this test that checks for a subtler problem. Cover one eye for a few seconds, then remove the cover and watch that eye as it’s revealed. If it makes a small corrective movement to realign with the other eye, you may have a latent deviation, one that only appears when binocular vision is interrupted. This type of misalignment (called a phoria) is extremely common and often doesn’t cause problems, but in some people it contributes to eye strain and intermittent double vision.
Crossed Eyes in Babies and Young Children
Many parents panic when their newborn’s eyes appear crossed, but in most cases what they’re seeing is pseudostrabismus, a false appearance of misalignment. Babies have flat nasal bridges and small folds of skin near the inner corners of their eyes (epicanthal folds) that cover some of the white part of the eye on the nose side. This makes the eyes look turned inward even when they’re perfectly straight. The illusion is most noticeable in photos, especially when the child is looking to one side.
Most babies outgrow this appearance as their face develops and the nasal bridge becomes more prominent. However, pseudostrabismus and true strabismus can look identical to an untrained eye. A child who has pseudostrabismus can also develop real strabismus later on. The light reflection test described above is one of the most reliable ways to tell the difference at home: if the reflections are symmetrical, the alignment is likely fine regardless of how the eyes look.
True strabismus in children is a more urgent concern than in adults because of how the developing brain responds to it. When a child’s eyes send mismatched images, the brain often solves the problem by suppressing the input from one eye entirely. Over time, the neural pathways serving that eye weaken, leading to amblyopia (lazy eye). Research using brain imaging has confirmed that this suppression causes measurable structural changes in the visual cortex. If caught early, amblyopia is treatable. If left too long past the critical period of visual development, the vision loss in the affected eye can become permanent, even if the alignment is later corrected.
When Crossed Eyes Appear Suddenly in Adults
Strabismus that develops in adulthood is a different situation from childhood strabismus. It’s frequently caused by something affecting the nerves that control eye movement. Thyroid eye disease, diabetes-related nerve damage, stroke, head trauma, and neurological conditions can all cause one or more eye muscles to stop working properly. When the onset is sudden, especially with new double vision, it signals something that needs prompt medical attention. Doctors typically order brain imaging to rule out serious causes like stroke or a tumor pressing on a nerve.
There’s also emerging evidence linking heavy smartphone and digital device use to a specific type of acquired inward-turning in younger adults. Prolonged close-range screen time may overtax the focusing system, and some case reports suggest that reducing device use improves or resolves the crossing. The research is still limited to case reports and small studies, but clinicians are increasingly asking patients with new-onset esotropia about their screen habits as a first step.
What a Professional Eye Exam Adds
Home checks can raise a red flag, but they can’t measure the degree of misalignment or identify the cause. An eye doctor uses prisms, clear triangular tools that bend light, to measure exactly how far off the eye is. They hold prisms of increasing strength in front of the misaligned eye until the deviation is neutralized, giving them a precise number. This measurement guides treatment decisions, whether that’s corrective lenses, vision therapy, prism glasses, or surgery.
A full evaluation also tests how well your eyes work together as a team, checks for any underlying vision loss in the weaker eye, and assesses whether the misalignment changes when you look in different directions. That last detail matters because it helps distinguish between problems with the eye muscles themselves and problems with the nerves controlling them.
If you’ve done the home checks and something looks off, or if you’re experiencing double vision, frequent headaches with near work, or a head tilt you can’t explain, a comprehensive eye exam with an ophthalmologist or optometrist trained in binocular vision is the logical next step.