What Is Strabismus (Crossed Eyes)?

It often shows up in a photograph first — one eye looking straight at the camera, the other drifting off to the side. Strabismus is the medical name for eyes that do not line up with each other: while one eye looks at what you are looking at, the other may turn inwards (the classic "crossed eyes"), outwards, upwards or downwards. You will also hear it called a squint, which is the word the surgical video at the top of this page uses.

First, what an eye check actually involves

If you or your child are referred for a suspected misalignment, expect the appointment to be unhurried and entirely surface-level — no needles, no scans in most first visits. The clinician will usually check vision in each eye separately, watch how the eyes move and line up as you follow a target, and check whether glasses are needed, because a strong focusing effort can itself pull an eye off line.

A fuller sense of a general eye appointment comes from another video on this site, "Eye and Vision Exam", which covers examination of the eye, vision, the retina and the field of vision. An alignment check builds on that same foundation — and an eye examination can also pick up unrelated problems, which is why our guide to what a cataract is and how it is removed sits in the same corner of the site.

The gentler options that usually come first

Not every strabismus goes anywhere near an operating theatre. Where glasses correct a focusing problem, wearing them can straighten the eyes on its own in some children. In young children there is a second concern: if one eye is consistently off line, the brain may start to favour the straight eye and let the other one's vision develop poorly — a related problem called amblyopia, or lazy eye. Patching the stronger eye for periods of the day is a commonly used way of encouraging the weaker eye to work, and it is one reason childhood misalignment is worth checking sooner rather than later.

When an operation is part of the plan

If alignment stays off despite glasses or patching, surgery on the eye muscles may be discussed. The idea is mechanical, not optical: the small muscles attached to the outside of the eye are repositioned or adjusted in strength so the two eyes pull in the same direction. Nothing is done inside the eye itself.

The video at the top of this page, "Squint Surgery Using Fugo Blade" (just under three minutes), follows exactly that kind of operation in a child — a strengthening procedure on the medial rectus, one of the muscles that moves the eye inwards, with the cutting done by a Fugo blade instrument. Watching it beforehand gives a fair sense of how small and precise the working area is, and your own surgeon can explain how the plan in an individual case compares.

Frequently Asked Questions

Is strabismus the same as a lazy eye?
No, although the two are often confused. Strabismus is the misalignment itself; a lazy eye (amblyopia) is reduced vision in an eye that can develop in childhood when a misaligned eye is ignored by the brain. One can exist without the other, and each is assessed separately.

Do children simply grow out of crossed eyes?
A brief, occasional crossing in the first few months of life can settle on its own, but a misalignment that persists, or is present most of the time, should not be waited out — it needs an eye examination, partly because of the lazy-eye risk described above.

Can strabismus be treated in adults?
Yes. Adults may have a long-standing misalignment from childhood, or develop a new one — sometimes with double vision. Either way it can be assessed, and glasses, exercises in selected cases, or eye-muscle surgery may be options depending on the cause.

Is squint surgery done inside the eye?
No. The surgery works on the muscles attached to the outside of the eyeball, adjusting their position or tension so the eyes align. The inside of the eye is not operated on.

MedicalVideos.com has published trusted medical videos since 2007. The site was founded by Dr. Mohamed Ibrahim, MD, PhD — physician-scientist.

Educational only — this article is general information about strabismus, not medical advice and not a diagnosis. An eye that persistently turns, or new double vision at any age, should be checked promptly by an eye specialist.