= 零 Dcurvature of the lens more convex)-refractive power Achciary muscle contractionsupensory ligaments relaxation elasticity of the lens-more convex parasympathetic nerve ②near point眼能看清的最近距离elasticity of the lens 8 years old 8.6 cm 20 years old 10.4c 60 years old 83.3cm (6)Near response ①accommodation 2Pupil contraction near reflex of pupil
parasympathetic nerve ②near point 眼能看清的最近距离 μ elasticity of the lens 8 years old 8.6 cm 20 years old 10.4cm 60 years old 83.3cm (6) Near response ①accommodation ②Pupil contraction near reflex of pupil
Convergence convergence reflex (7)Errors of refraction *Emmetropia normal vision +Myopia Nearsightedness Characteristics:parallel light rays are focused in front of retina Causes too long eveball Tooch refractory power Correction concave lens *Hyperopia Farsightedness Characteristics:parallel light rays are focused behind retina Cause too shoot evehall too weak refractor powe Correction convex lens *Astigmatism Characteristics light rays are refracted to different focus Cause the currature of refractive system are not uniform Correction eylindrical lens *presbuopia Characteristics near point Cause elasticity of the lens Correction conves lens (8)visual field (9)binocular vision and stereopsis
③Convergence convergence reflex (7) Errors of refraction *Emmetropia normal vision *Myopia Nearsightedness Characteristics: parallel light rays are focused in front of retina Causes too long eyeball Too much refractory power Correction concave lens *Hyperopia : Farsightedness Characteristics: parallel light rays are focused behind retina Cause too shoot eyeball too weak refractory power Correction convex lens *Astigmatism Characteristics light rays are refracted to different focus Cause the currature of refractive system are not uniform Correction cylindrical lens *presbuopia Characteristics near point ↑ Cause elasticity of the lens ↓ Correction conves lens (8) visual field (9) binocular vision and stereopsis