Crossed eyes or lazy eyes? Differences between Strabismus and Amblyopia

11 July 2019

Author: Kate Green

Difference between strabismus (crossed eyes) and amblyopia (lazy eyes)

Functional vision problems

Strabismus and amblyopia are frequently confused with each other, and people often use the terms interchangeably. They are, in fact, two different eye conditions, albeit with some shared characteristics. Put simply, strabismus is a problem with the alignment of the eyes and is informally called “crossed eyes”. The eyes do not look in the same direction at the same time, as they should. Amblyopia, however, is essentially a problem with a person’s eyesight. It’s also known as a “lazy eye” and typically means that they cannot see an image clearly in one (or sometimes both) of their eyes. Strabismus and amblyopia are functional vision problems, stemming from issues with how the eyes work together, known as “eye teaming”. In most cases, there are also problems with areas of eye focusing and eye movement, highlighting issues between the eyes, brain and visual pathways.


What is strabismus?


Strabismus, also called a “squint”, is a condition whereby the eyes do not look in the same place simultaneously. Either one or both eyes can point up, down, in or out. This can be either constant or intermittent, but both types make it difficult for the brain to process images from each eye separately into one singular image. Symptoms tend to range from headaches, eye fatigue and strain, to poor depth perception and blurry or double vision. This is particularly common in cases of intermittent strabismus where the eyes take turns in pointing to different places, forcing the brain to work hard to process the images. In cases of constant strabismus, the symptoms tend to be less severe as the brain gets used to only relying on one eye. It begins to ignore images from the misaligned eye, and so there is no effort required to combine the two. This results in reduced headaches and minimal blurry vision, but can lead to more severe problems like amblyopia. Strabismus can also be either small-angle or large-angle, referring to whether or there is a slight or significant misalignment of the eyes.


Can strabismus be cured?


Strabismus is usually treated with a combination of techniques, most commonly vision therapy and surgery. The surgery typically shortens the muscles which hold the eyeball in place by severing and shortening them, and then reattaching them in a different position. This pulls the eye round into the correct position in an aesthetic sense, but does not actually address the underlying reason for the strabismus in the first place. Vision therapy is a non-invasive solution which can treat the root cause of the strabismus, rather than just its physical appearance. Vision therapy can even be carried out at home, with affected patients completing sets of exercises involving different levels of eye focusing. This can strengthen the eye and, if carried out while the child is young enough (ideally before the age of 8), result in normal vision.


What is amblyopia?


Amblyopia is also known as a lazy eye and is a problem with a person’s development of vision. With this disorder, the eye does not achieve normal visual acuity and often cannot be fixed with glasses or contact lenses. Amblyopia usually develops as a result of strabismus. If the angle of the strabismus is particularly large, and especially if it’s a case of constant strabismus, the brain forgets to use the affected eye to see. This causes it to become extremely weak, with all visual signals ignored. Essentially, the condition is when the brain suppresses information from either one or both eyes.


Strabismus is the most common cause of the condition, as discussed above. Refractive disorders can also cause amblyopia; for example, if one eye is extremely long-sighted, while the other is extremely short-sighted, the brain will rely more on the eye which is less impaired. The eye which is used less becomes “tuned out” and, over time, will experience blurred vision from disuse. This phenomenon is also present in a third type of amblyopia: deprivation amblyopia. This is usually caused by congenital cataracts – where a child is born with cataracts in either one or both eyes. As light cannot enter the baby’s eye, they do not use the eye, again causing the brain to ignore any visual signals from it, resulting in amblyopia.


Can you get rid of a lazy eye?


Amblyopia does not cure itself, so treatment is required early in life in order to avoid permanent visual problems. In some cases, strong prescription glasses can help improve the condition, especially when combined with “patching”. This is where the stronger eye is covered in order to force the weaker, amblyopic eye to work harder in transferring visual signals. While this doesn’t always address the underlying cause of a lazy eye, it can help with the symptoms. Patching is usually combined with vision therapy, a non-invasive technique. It focuses on developing “vision teaming skills” to promote cohesion between both eyes, and encourages the patient to practise different types of focusing. Even once the symptoms have reduced, the patient should still persevere with the exercises to prevent regression.


As with strabismus (before it develops into Strabismic Amblyopia), some forms of amblyopia can be treated with a surgical procedure. Again, the muscles are severed and reattached at different places in the eye, to pull the eyeball round into a front-facing position. This doesn’t, however, treat the underlying cause of amblyopia, nor does it improve the poor visual acuity that comes as a result of amblyopia.


Does laser eye surgery help?


Strabismus, or crossed eyes, doesn’t necessarily mean that a patient requires vision correction. They may have 20/20 vision, but just suffer with eye alignment. Amblyopia, on the other hand, occurs when an eye doesn’t have normal visual acuity. Provided that spectacles or contact lenses correct their vision to an acceptable level, laser eye surgery would help the patient improve their sight.


Strabismus and amblyopia have both been found to be psychologically damaging, negatively impacting people’s confidence – both in terms of their physical appearance and feeling unconfident in their visual abilities. Laser eye surgery can certainly help with the latter, meaning that you’ll rely less on glasses and contacts, and achieve more visual balance across both eyes. Get in touch with us to hear about how treatment has changed thousands of people’s lives, or to book in for your free consultation.

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