Eye Refraction Lab: Myopia, Hyperopia & Accommodation

This simulator models the human eye as the reduced optical system optometrists actually use to reason about refractive error: a single dioptric power sitting in front of a fixed-length vitreous chamber, with the retina as the target image plane. Drag the axial-length slider and watch a normal-length eye (emmetropia) stretch into a myopic one, or shrink into a hyperopic one, exactly as happens in real eyes. The accommodation slider reproduces what the ciliary muscle does when focusing on something close, the object-distance slider changes how strongly diverging the incoming light is, and the corrective-lens control shows how a spectacle prescription in diopters cancels the eye's own defocus. Every number on the readout panel — total power, defocus in diopters, and where the light bundle actually converges versus where the retina sits — comes from the same vergence equation (L′ = L + P) used in clinical optics.