What is Lazy Eye?
What is “Lazy Eye”?
“I think I have a lazy eye”, “I think my child has a lazy eye” or “his eye is a bit lazy”. Lazy Eye is a commonly used phrase or description but it can mean different things to different people. Regardless of the condition it is used to describe, early detection and treatment is recommended. However it’s good to understand what lazy eye means.
Lazy eye is used to describe:
- One eye that doesn’t see as well as the other ie things look blurrier through one eye – AMBLYOPIA
- An eyelid that tends to droop or close particularly as the person gets tired – PTOSIS
- One eye that wanders in or out – STRABISMUS
- One eye just doesn’t feel right, particularly when doing concentrated close work – CONVERGENCE INSUFFICIENCY/CONVERGENCE EXCESS
Optometrists tend to use the term “lazy eye” to describe the first one in this list, AMBLYOPIA. This describes a situation where one eye has reduced vision compared to the other one, even when the person is wearing their best sight correction. The following information will discuss this specifically. However, anyone experiencing or noticing any of the signs or symptoms on this list should have a vision examination.
Understanding Amblyopia (Lazy Eye)
Primarily amblyopia is diagnosed when one eye does not see as well on a distance letter chart compared to the either eye, even when the best correction is in place, and there is no sign of eye disease. Up to 1 in 20 people are affected1.
Amblyopia is often associated with a higher prescription like hyperopia or astigmatism in one eye, although both eyes can often need correction to see clearly. Sometimes amblyopia is associated with an eye that turns, usually an inward turning eye. Often it is an eye-turn or STRABISMUS that alerts parents that something amiss. Children who have amblyopia but no eye-turn may not be consciously aware that anything is wrong as the other eye provides clear vision.
Lazy Eye is not a “One Eyed” Problem
Amblyopia is often talked about that it makes it seem that there is a problem with the eye itself and that it is somehow “weak” or has weak muscles. While it is true that the amblyopic side often has a higher degree of prescription, the eye itself is healthy and the eye muscles usually work fine.
For many years, some have questioned the notion that amblyopia is a problem with one eye, and instead have looked at amblyopia arising out of a problem of the two eyes working together. Recent research in “two-eyed” methods of amblyopia treatment, help confirm aspects of this alternative theory2,3. Essentially, the poor vision results from an active process of shutting down vision in one channel, a process called suppression to avoid confusion. An eye-turn can also be considered as a process of “pushing” one eye out of the way to assist in this shutting down process. Not all of the information is shut down, so the eye is not “useless” or “lazy” but is operating at a reduced level function.
Lazy Eye is not just an “Eye Problem”
When one eye is not seeing well or turning, it is easy to get overly focused (no pun intended) on just those aspects of the situation. However, there are often other visually-related skills and abilities that are affected when amblyopia or lazy eye is present that need to be considered as they impact on other aspects of quality of life. There is an increasing body of evidence that indicates even when the unaffected side is “in charge”, some other skills are not as good as expected. These include:
- eye-hand co-ordination
- eye tracking
- reading speed
- depth judgement
- visual perception
How Is Lazy Eye Treated?
Every case is different, but broadly amblyopia treatment involves one or more of the following – spectacles or contact lenses, patching and eye exercises.
How Do I Know If My Child Has a Lazy Eye?
Often a child might not show strong outward signs and it is during a screening that a problem is found. Other signs might include:
- excessively clumsy
- squinting one eye, particularly in bright light
- one eye turns
- shutting one eye or head turning
- one pupil looks different in photo’s compared to the other
Optometry Australia recommends routine eye exams at 6 months, 3 years and before school. This is a good way to detect problems early. A family history of eye problems would be another reason to consider having a precautionary examination.
What to Do If You Think that You or Your Child has a Lazy Eye
While it appears that treatment is possilble even in adults, the key message is that early treatment is best. While we now know that age is not necessarily a barrier to treatment, treatment is considered to be better and more effective the younger you are. The first step is to have a comprehensive assessment with an optometrist.
1. Carlton J and Kaltenthaler E. Amblyopia and quality of life: a systematic review. Eye (2011) 25, 403-413.
2. Hess RF1, Babu RJ, Clavagnier S, Black J, Bobier W, Thompson B. The iPod binocular home-based treatment for amblyopia in adults: efficacy and compliance. Clin Exp Optom. 2014 Sep;97(5):389-98.
3. Zhou, J., Thompson, B. & Hess, R.F. A new form of rapid binocular plasticity in adult with amblyopia. Sci. Rep. 3, 2638; DOI:10.1038/srep02638 (2013)