Features flexible lens which changes its shape to provide true-to-life performance. Eyeball lengthens or shortens to demonstrate near and far sightedness, as well as normal vision. Your own eye focuses on near or distant objects by altering the thickness of its internal lens. This has been next to impossible to duplicate in a model – until now. Simulating the visual performance of the human eye, you can control the shape of the flexible silicone elastomer lens within this ingenious model, changing the focus of images projected onto its retina. You can also lengthen or shorten the eyeball itself to demonstrate nearsightedness (myopia), farsightedness (hyperopia), and normal vision (emmetropia). Vividly demonstrate: • accommodation (focusing on near objects by increasing lens curvature) • near-point of vision • yellow spot and blind-spot • presbyopia (age-related lack of accommodation due to loss of lens elasticity) • myopia • hyperopia (hypermetropia) •and use of corrective lenses. Complete with detailed instruction manual, external corrective lenses – one convex and one concave, lens holder, and projection object on stand.