(I) Nature of low vision It is a state of inhibitory sleep or dysplastic atrophy (i.e., sleeping, atrophy state) of visual cells caused by certain congenital causes (e.g., congenital cataract, strabismus, nystagmus or high myopia and high hyperopia, high binocular refractive error, etc.). (II) Basic principle of treating low vision Remove the cause, wake up the sleeping cells with special color light, and forge the atrophied vision with threshold icons. (C) various therapeutic devices to improve low vision vision enhancement principle 1, the function of attracting attention: the most important, if the child can not look at the icon or color light for a longer period of time, any vision enhancement function may fail due to the lack of a certain amount of visual stimulation. Attention-attracting features include: (1) closed head a mask (such as Dr. Eye 3-5 generation instrument and eye mask low vision amblyopia treatment instrument, etc.), in this type of equipment, the child is in front of the training icons or color light, the eye around the dark, can effectively prevent things around the distraction; (2) moving, zoom icons or color light: changing targets than static targets more attractive to children’s attention. (3) Children’s interest in colors and patterns, etc.: Wolffy, Pleasant Goat, cats, dogs, 3D stereograms, etc. The docked hood, flying dots, bifocal flying dots and color light pursuit in Dr. Eye 3-5 generation amblyopia devices are all attention-getting vision enhancement functions. 2, threshold icon vision enhancement function: is the most effective direct vision enhancement function, “threshold” is the threshold, that is, the child can just see clearly but there is a certain difficulty of the threshold, cross this hurdle, vision will improve. (1) Threshold “E” or “C” icon: suitable for children over 3 or 5 years old (see Dr. Eye 3-5 generation amblyopia instrument) (2) Threshold grating (visual physiology) icon: suitable for children under 2 or 5 years old, non-cooperative (see Dr. Eye eye mask type low vision instrument) (3) Threshold image icon: suitable for children aged 2.5 to 3.5 years old who can recognize images (see Dr. Eye Mask Low Vision Amblyopia Instrument for details) 3. It can wake up three kinds of RGB vision cells (sensitivity) on the retina in the fundus of the eye and increase vision indirectly (such as RGB color light vision enhancement in Dr. Eye amblyopia apparatus) 4. RGB eye sensitivity vision enhancement: use RGB color light to wake up sleeping vision cells and use color light position change to train focusing sensitivity.