Seeing well requires both eyes to work properly. Some children, however, have a «lazy eye», or amblyopia, which prevents visual acuity from developing normally and leads to loss of vision in that eye. The problem is easily solved if it is picked up in time.
If a lazy eye is not treated in time it causes an irreversible loss of visual acuity beyond a certain age, usually between seven and nine — roughly when the visual system matures — because the brain cells responsible for vision that were not stimulated during childhood cannot develop later.
Causes
Amblyopia is caused by:
- In most cases (around 80 % of those detected), a difference in prescription between the two eyes, from myopia or, more often, hyperopia or marked astigmatism. The brain favours the development of vision in the better eye and stops using the other, which becomes lazy.
- In other cases, a squint (strabismus), which causes double vision and leads the brain to suppress the information from the deviated eye and use only that from the eye working correctly.
- Sometimes the cause is a congenital problem that clouds vision, such as a cataract or an opaque cornea. In these cases surgery is needed as early as possible to prevent loss of visual acuity.
Warning signs
The main signs that a child may not be seeing well are:
- Holding the page unusually close or unusually far away when reading or drawing.
- Looking away from what they are doing too often.
- Closing or screwing up the eyelids to look at something.
- Rubbing the eyes constantly.
- Tilting the head to one side to read the board at school.
- Watery or red eyes.
- Frequent headaches.
- Discomfort in sunlight or difficulty adapting to the dark.
Treatment
Most cases of amblyopia are easy to treat. Treatment means giving the lazy eye the best possible image by correcting its refractive error with glasses or contact lenses, and at the same time forcing it to work by patching the eye that functions normally.
The challenge is early detection — ideally before the age of two — because at that stage the visual system has not finished developing and is still adaptable. The proof is that amblyopia in an infant can be corrected in a matter of weeks, whereas in a five- or six-year-old it may take several years.
Recommended check-ups
For this reason, specialists advise all parents to have their children's eyes checked annually from an early age:
- A first check at six months.
- A second at one year.
- And another before the child's second birthday.
This provides good protection against amblyopia, since at that age it has not yet become irreversible and is easy to correct. From the age of two, an annual check-up is enough.