What is a "lazy" eye?

This is a common term that parents use to describe what they see a child's eyes doing, and they most often use it in these settings:

• One eyelid may appear lower or the child may partly close an eye ('squinting' it shut, for want of a better term).
• It might look as if the eyes are not symmetrical or "straight" when your child looks at you, or as they look to the side.
• There may be a constant and very obvious misalignment of their eyes. When the child is looking directly at you it is clear that only one eye is focused on your face, the other is looking off in a different direction. You may also see this in photos, with a small bright point of light in the middle of one pupil, but off to the side in the other eye. All of these are very important, these problems need prompt treatment, they do not go away on their own!

The confusing thing is that saying the eye is "lazy" is a common way people describe an eye which can't see as well as the other. That could just indicate that one eye needs glasses more than the other (the vision is as good as the other eye when the glasses are on).

 In short, the term "lazy eye" means very little because it is used to try and explain too much!

It is a non-medical term, and is better off being replaced by one of the problems explained below. The key for parents is to simply explain what they see their child's eye doing, or better still, take a photo and show us. 

An eye that appears to be not looking the same direction as the other

If one (or the eyes may take turns to do this) of your child's eyes is clearly pointing inwards, outwards, or drifts upwards when they are looking straight ahead, then they probably have what is correctly known as "strabismus ". This simply means that the eyes point different directions.

Take a look at the picture on the left, it shows a bright star of light in the middle of each pupil, which is a reflection from the flash on a camera. 

This is one of the easiest ways to detect that a child's eyes are not aligned, when taking a flash photograph of their eyes. In the center of each eye, within the pupil, you should see a spot of white light. If one eye is misaligned this spot will be positioned in a different place to the other eye (see below). 

Many baby's faces have an arrangement of the nose and skin folds that curve around from the upper lids that gives an appearance as if an eye is turned in, when in fact it is  normal. This is known as a pseudostrabismus. 

Esotropia  

"Eso" means in, tropia is 'a turn', so "turned in". If you look at the picture on the right it shows a spot of reflected light within the pupil of the right eye, but the reflection on the left eye is well away from the pupil, and you can clearly see the left eye is turned inwards.

This is a common problem, and can occur in babies (diagnosed from 3 months of age) and older children. 

If you think a child's eye is crossing inwards all of the time, or whenever they look at things up close or that are detailed, it is very important that you arrange to see an eye specialist as soon as possible (from 3 months old if that tendency persists). Your optometrist should be confident examining children from about 6 to 12 months of age, and your GP can assess and refer you to see a specialist.

Don't delay being seen, early treatment can mean that the problem resolves quickly, and your child gain nearly normal vision. Once a constant turn has been present for 6 months or more there is not always a full recovery of normal vision, surgery is frequently required, and the whole process takes much longer.  

Exotropia

"Exo" means 'out', so this is the correct term to use if an eye is pointing outwards relative to the other. This often occurs intermittently, ie most of the time your child can use both eyes together, but when they loose concentration (such as when 'tired'), look into the far distance,  or have bright light shining in their eyes, one eye turns out. Often the child becomes aware of this and resumes concentration, so the eyes focus on something close and are straight again.

Intermittent exotropia is quite common, usually starts around age 18 months (range 1 to 4 years), and the child usually has good vision in both eyes as they are using them together most of the time. As a generalisation, 1/3rd of children will 'get better' on their own, 1/3rd will need non-surgical treatment (glasses), and 1/3rd get worse and may need surgery. 

If an eye is constantly out-turned, so the child can never look at you with both eyes 'straight' then they have a more important problem. The brain does not like to look at 2 images, and so 'blocks out' the input from the turned eye, this causes amblyopia.

Also, a constantly out-turned eye in a young child, especially under 1 year of age, may be a sign that the eye has severe problems. See your doctor and have them refer the child for a check by an ophthalmologist immediately.