Pediatric Autorefractor Measuring principle
The measuring principle of the plusoptix A09 is based on eccentric photo-retinoscopy. Infrared light is projected through the pupils onto the retina. Depending on the refractive error, the reflected light forms a specific brightness pattern within the pupil. The spherical refraction is calculated based in this crescent pattern. To determine cylinder and axis the same measurement is repeated in three meridians.
The measurement with infrared light is completely innocuous. Infrared light is also contained in daylight and not visible.