How is prescription strength for glasses determined for small children and special needs individuals who can’t communicate?
In: Biology
It is possible to do an objective refraction without asking the patient ‘which is better, 1 or 2’. It involves a device called a streak retinoscope and basically you ‘streak’ a narrow slit of light across a dilated pupil. You observe if the cat eye red reflex moves on the same direction as the streak or opposite. Then you grab a hand-held lens lens from your tray assortment of lenses and do it again to see how the reflection has changed. Add dioptric power, subtract power until you neutralize the movement. The power of lenses you used to get to that endpoint will guide you to the prescription. In babies and toddlers, they have very high amounts of focusing power so you have to dilate the pupils which also immobilizes their accomodation or focusing power which allows you to prescribe based on their actual resting optical power of the eye. It can be done at any age but it can be a challenge.
It does not involve photos, puffs of air or other exam methods. It is old school skill.
The part of the eye exam that goes “whats better… 1… or 2…?” Is actually just fine tuning the prescription. A moderately accurate guess can be made based on other, physical tests they do. This includes looking at how your eye reacts to stimuli, photos of the eye, and puffs of air. These can usually get close enough
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