Every aspect of advanced retinal imaging laser eyewear: principle, free focus, resolution, laser safety, and medical welfare applications

Retinal imaging laser eyewear has a miniature laser projector inside the frame which provides the wearer with digital image information through the pupil using the retina as a screen. Its principle is based on the geometric optics of the Maxwellian view combined with a parallel and narrow RGB laser beam. A prototype with the trademark of RETISSA® was invented with a miniature laser projector inside the glasses frame using a non-axisymmetric free-surface reflecting mirror. The image resolution was measured based on the visual acuity testing using a retinal projected image of Landolt ring for four subjects with the different naked visual acuity of 0.04, 0.5, 0.9 and 1.2. Also, the theoretical image resolution was studied based on the beam propagation simulation under the eyeball model. The results show how to achieve high resolution and free focus in proper balance by adjusting the laser beam characteristics of the beam diameter and divergence. On the laser safety, RETISSA® was found to be in the Class I category, which has the safety factor of over 700 in the RGB radiation intensity under the international standard of IEC60825-1. RETISSA® also met the thousand times more strict Class I criteria of FDA/CDRH 21CFR1040.10 with the total RGB radiation intensity of less than 0.37 μW, indicating its laser radiation is not considered to be hazardous as stated in the definition of FDA Class I. The experimental evidence that the radiation of RETISSA® is equal to or weaker than displays of conventional digital devices also provide its proof of safety, including its long-term use as one of daily digital devices. The potential of retinal laser imaging is mentioned for use in ophthalmology medicine. The current activity on the medical welfare applications as low vision aids and ophthalmic testing equipment is reviewed including clinical research and trials in Japan and Europe.