I was recently asked how we are able to determine a vision prescription for eyeglasses for a baby or toddler. After all, the usual questions about "Is this better, or this?" won't work with such young patients.
Correct . . . a toddler can't communicate with you. However, there is an instrument called a "Retinoscope" which we use to shine a light into the toddler's eye from a distance of about 17 inches. We can interpret the reflection that comes back from the back of the toddlers retina into the pupil area. As we move the instrument from side to side, the reflected light we are watching will move either in the same direction as our instrument or in the opposite direction. This tells us whether we are dealing with nearsightedness or farsightedness. The speed of motion of the reflected light is an indication of how much prescription power will be required.
In a seasoned practitioner's hands we are able to very precisely determine how much and what power is required without asking the toddler a single question.
We do the same with adults who can't communicate or are illiterate or can't speak the same language, as in third world countries where in some instances on field trips no communication is possible at all.
It's pretty neat.
Dr. Dhavid Cooper