Vision Simulator — what the patient sees
On-screen sizes assume a typical viewing distance. Currently drawn at 55 px/°
Educational simulation
This simulator is an educational teaching aid, not a diagnostic or clinical tool.
A point of light imaged by a defocused eye lands on the retina as a filled disc.
In minus-cylinder notation S / C × A, the meridian lying along the axis carries the sphere.
A young eye can add positive power and focus through part of a hyperopic error.
A small pupil shrinks the blur disc; eventually diffraction takes over.
Disability glare is modelled as a veiling luminance laid over the retinal image.
Field loss is filled in perceptually; patients are usually unaware of it.
The colour simulations use the Machado, Oliveira & Fernandes (2009) matrices.
Blur and letter size are angles, and turning an angle into pixels needs a calibration.
The blur is a single best-fit ellipse, which is exact only at the circle of least confusion.
Blur and letter size are angles.
Hold a bank or ID card flat against the screen and drag until the outline matches its width.