Analysis of test questions: in the picture: ① ciliary muscle ② cornea ③ lens ④ iris ⑤ choroid ⑤ retina ⑤ vitreous body. (1) The cornea is the structure shown by numeral ② in the figure. (2) The light reflected by external objects passes through cornea, aqueous humor, lens and vitreous body in turn, and is refracted by lens, finally forming an inverted object image on retina. Photosensitive cells on the retina receive the stimulation of the object image, which transforms the object image information into nerve impulses, and then transmits them to the visual center of the brain through the optic nerve, thus forming vision. Because the brain can process the received information, what we see is always an upright image. The pathway can be summarized as follows: light reflected by external objects → aqueous humor (cornea) → pupil → lens → vitreous body → retina → optic nerve → visual center of cerebral cortex (forming vision). (3) Only when the object image falls on the retina can we see the clear object image, which requires the adjustment of the intraocular lens and other structures. If you don't pay attention to eye hygiene, or read a book at close range for a long time, the lens will become excessively convex and can't be restored to its original state, or even the anterior and posterior diameter of the eyeball is too long, and the object image formed by the distant object falls in front of the retina, making the distant object unclear and forming myopia. Wearing concave lenses can correct myopia.