Welcome back for Part 3 of my Pediatric Eye Exam series!
In the first two posts of this series, I discussed how to assess visual acuity in an infant and how to do some basic additional testing.
Today, however, I’m gonna jump into one of the most common questions that I get:
How do you determine the glasses prescription of an infant?! They can’t tell you which is better one or two!
Refraction, in an infant or young child, is admittedly a much different procedure than in an adult.
As I discussed in my second post of the “Why Does My Eye Doctor” series, refraction in an adult typically involves showing a variety of lenses in a phoropter, and asking which one is subjectively better.
In infants and young children, however, refraction is done in free space, using retinoscopy.
What does this mean?
First things first, retinoscopy is a procedure by which the eye doctor shines a light towards the back of the eye and observes the ensuing reflex. Lenses then may be added to try to neutralize, or minimize, the movement seen. The lens that corresponds to the least amount of reflex movement is recorded as the prescription.
Free space just means that this procedure can literally take place anywhere! Since most infants and young children are not particularly skilled at sitting still, this is a vital component. With loose lenses, it is possible to much more easily follow the child as he or she moves around the chair/room.
However, as infants and young children can’t necessarily be trusted to focus on a specific target, dilating drops are often used to paralyze the focusing system to ensure that there isn’t fluctuation in the prescription found.
As discussed in my post, Decoding the Numbers: Hyperopia, most infants are far-sighted when they are young, with some amount of astigmatism. However, just because a prescription is found does not mean that full, or even part-time glasses wear is necessary. Rather, lenses are only prescribed when the prescription falls outside of the normal bounds, posing a potential for reduced vision, or amblyopia.
When glasses are prescribed, though, since infants and young children often can’t vocalize visual improvements, they are followed more frequently – often at 6-8 week intervals. At these visits, vision and prescription are reassessed to determine prescription accuracy and visual improvement. Once the accuracy has been confirmed and visual stability achieved, the child may then return to a normal follow-up pattern.
And there you have it!
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