Routine vision screening is important, because many abnormalities are treatable if discovered early, and untreated, can lead to vision loss and blindness. Among the vision problems that your Pediatrician will evaluate your child for include:
- strabismus - a misalignment of the two eyes, affecting about 4% of children. Strabismus is usually described by the direction of misalignment, which can be outward (exotropia), inward (esotropia), upward (hypertropia) or downward (hyotropia). A child may also have a phoria, with eye deviation only when one of the eyes is covered or when he is tired or sick.
- amblyopia - reduced vision in an eye, which can be secondary to strabismus, anisometropia (unequal refractive errors in both eyes, for example, if one eye is more farsighted than the other eye), congenital cataracts, etc.
- refractive errors - such as myopia (nearsightedness) and hypermetropia (farsightedness).
Other testing may include the corneal light reflex test, in which a light is directed at the bridge of the nose and the light reflex is examined to make sure it is symmetrical or shines in the same spot on both eyes. If the light reflex is off-center or not symmetrical in both eyes, then it might indicate a misalignment of the eyes. This is useful to differentiate pseudostrabismus, a condition in which the eyes appear to be misaligned because of prominent epicanthal folds or a broad nasal bridge and which doesn't require treatment, from true strabismus.
The unilateral cover test can be used to determine if an infant or young child will follow an object while one of the eyes is covered. For example, your Pediatrician can see if your child can fix on and follow a toy with both eyes, and then cover the left eye and see if he continues to follow it with his right eye. Then, the right eye is covered to see if he will follow the toy with his left eye. If he gets really fussy or refuses to follow the object when you cover one of his eyes, then that may indicate that the vision in the other eye is reduced.
In older children, the unilateral cover test is also useful to check for strabismus. While the child is looking at a distant object, such as an eye chart or toy, cover one of his eyes. If the other eye moves outward or inward, then that might indicate that his eyes are misaligned and that he has strabismus. The test is then repeated by covering the other eye.
Other problems that indicates the need for further evaluation include parents noticing that their child's eyes are crossing, that their eyes aren't straight or if they just don't seem to be seeing well. It is important to keep in mind that younger children usually don't report problems with their vision, especially if the problem is in just one eye and the other eye is accomodating for it. Older, school age children, may report that they can't see the board, or they may have frequent headaches, double vision or are frequently squinting. Formal testing of visual acuity is usually possible once a child is three years old, although 2 year olds may be able to be tested with picture cards. The Allen chart includes easily recognized pictures, including a cake, hand, bird, horse, and telephone.