Acuity Testing Infants

Preferential Looking Test

 How do you Check a Baby’s Eyes?


Last time I wrote about the value of having a baby’s eyes examined. Now I will address the question of how do you check a baby’s eyes?

Obviously an infant is not able to read the letters on the eye chart or perform subjective tests such as selecting the clearest image. An example would be when I ask “which is better 1 or 2” question. Fortunately, there are other ways to determine visual acuity. Measurements of visual acuity and refraction are intended to identify nearsightedness, farsightedness and astigmatism. All are risk factors for amblyopia. Amblyopia is caused from non-use or deprivation that negatively impacts the development of the visual system. Instead of an eye chart with letters  that I use on school age children or a chart with shapes that I would use on a preschooler, I use a preferential-looking technique. Humans prefer to look at interesting objects instead of plain ones. I have several paddles with different size gratings and one paddle that is only gray. I flash the paddles in front of the infant and watch his/her response. This tells me how small the baby can see at a given distance. The smaller the gratings, the better the acuity. If the baby doesn’t prefer the gratings to the solid gray, I know we have passed the acuity threshold.

Retinoscopy is the other technique I use to measure the refraction, how much correction is needed for the baby to see clearly. Retinoscopy is the same technique my staff uses to get a starting prescription on most of my patients. They use a computerized system that measures the light as it comes off the retina (back of the eye). I do the same thing for the babies, but with a hand-held scope and some lenses.

Other assessments for eye alignment, motility and binocularity are done with various penlights, small toys and puppets. These tests measure eye coordination, which is the ability of both eyes to work together as a team to create one three-dimensional image in the brain. Good eye coordination, a skill that is not innate and must be developed, keeps the eyes in alignment. Later in life, poor eye coordination can make reading for extended periods of time difficult and may result in avoidance of detail work, such as writing or artwork, poor reading comprehension and clumsiness.

To evaluate the overall health of the baby’s eyes I dilate the pupils. The dilation causes little to no discomfort for the infant and allows a much more thorough examination. With light and magnifiers I can see the anterior eye structures like the cornea, lens, lids and lashes and the posterior structures such as the retina, optic nerve and blood vessels.

As an InfantSee provider, I provide a complimentary comprehensive eye assessment to all baby’s less than a year. (Nine months old is perfect for the exam).

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