Tabby tackles your important medical questions…

A friend has asked me a couple of times how vision testing is undertaken in babies. I kept promising to look it up. Below is the answer, pilfered from various websites and reformatted to better meet our information needs:

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.

In very young children, vision evaluation usually consists of an examination for the red reflex (checks for cataracts and retinoblastoma), eye alignment (misaligned eyes may indicate strabismus) and eye movements. 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.

Until formal vision testing is possible after three years of age, younger children's vision can be assessed by observation of how they fixate and track objects and by the history of the child's parents. Visual milestones for infants include being able to follow an object to midline in the first 2-6 weeks, past midline by 1-3 months, and follow an object 180 degrees by 3-5 months.

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 identify pseudostrabismus, a condition in which the eyes appear to be misaligned because of prominent epicanthal folds or a broad nasal bridge.

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. 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.

Other problems that suggest 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.

hope this answers your question,

TT