Lazy Eye: Symptoms, Causes and Treatment of Amblyopia
Lazy eye (or amblyopia) is an early childhood condition where the eyesight doesn’t develop properly in one eye. It’s a cognitive vision problem because the brain puts more emphasis on the information coming from the good eye while virtually ignoring the lazy eye. So its not really the eye that’s being lazy – but the brain.
Symptoms of Lazy Eye
Amblyopia affects about 3% of all children in the USA, making it the most common cause of vision problems in young children. The symptoms include:
- Blurred or double vision
- Poor depth perception
- Eyes that turn in or out
- Eyes not working together
- A permanent squint
It most often affects just one eye although it is possible to have amblyopia in both eyes.
What Causes Lazy Eye?
The main cause of lazy eye is an underdeveloped nerve pathway from the eye to the brain. It’s not an intrinsic problem in the eyeball – but a developmental problem arising when the part of the brain receiving images from the affected eye is not stimulated properly and so can’t develop to its full visual potential.
There are multiple causes for this underdevelopment, including:
- Strabismus – the eyes are misaligned causing blurred overall vision
- Childhood cataracts – a cloudy lens causing blurred overall vision
- Farsightedness – a shorter eyeball causing blurred close-up vision
- Nearsightedness – a longer eyeball causing blurred distant vision
- Astigmatism – a squashed cornea causing blurred overall vision
The term lazy eye came about because in each of these scenarios leading to amblyopia, one eye is often much weaker than the other. As a result, the weaker eye sends a blurred image to the brain which is confusing, causing double-vision.
Over time, the brain learns to ignore the faulty image from the weaker eye, which no longer attempts to focus correctly with the good eye. If left untreated the condition becomes severe and the older the child, the poorer the recovery.
Treatment of Underlying Conditions
Eye doctors first need to treat the underlying cause of the lazy eye.
For instance, childhood cataracts are treated with eye surgery under general anesthetic to remove the cloudy lens and replace it with an artificial lens. Mild cataracts in babies and children may be treated by wearing glasses or contact lenses so cataract surgery is not required.
Vision problems that lead to lazy eye – such as uneven nearsightedness or farsightedness – can be corrected by wearing glasses which enable the eyes to focus together. At first your child may feel they can see better without the glasses. Because their eyes have become used to working hard to focus, they find it alien to let the glasses create a different kind of focus for them. They will need lots of encouragement to wear the glasses permanently and re-train the eyes.
Lazy Eye Treatment
The amblyopia may have corrected itself after treatment of the underlying eye condition. If not, doctors can treat the lazy eye using the most common approach of an eye patch on the good eye – called occulation. This forces the brain to accept and recognize the image coming from the weaker eye.
The eye patch should be worn for several hours a day, during which time the child should do close-up activities like coloring or reading. The length of time needed to wear the patch overall depends on the age of the child, the severity of the lazy eye, and how much they co-operate with wearing the patch. A follow-up check after three months will help determine progress.
Sometimes atropine eye drops are used to blur the vision of the good eye instead of wearing an eye patch. They dilate the pupil and blur close-up vision to encourage the proper use of the lazy eye. Deciding whether to use an eye patch or eye drops is a matter of preference for the child.
Children who receive lazy eye treatment before the age of 5 years usually see a good recovery in their natural vision, albeit with some lack of depth perception.
However, delaying amblyopia treatment can lead to permanent vision problems: a child of 10 years may only ever experience a partial recovery.
There are risks involved in both treatments for lazy eye:
- Using an eye patch can overpenalize the stronger eye which can create a condition called reverse amblyopia. Patches can also irritate the skin and cause hypopigmentation. There is also a social stigma with wearing an eye patch which school-age children may suffer with psychologically.
- Using eye drops to blur the good eye can have the unwanted side-effect of creating nodules in the eye. They may also cause eye irritation, headaches, mood swings, rapid heart rate and reddening of the skin.