Question 1

How accurate is this astigmatism simulator?

Accepted Answer

The simulator models a single cylindrical refractive error as a directional Gaussian blur — the same point spread function used in optical research (Atchison et al., 2009). It approximates the visual effect of uncorrected astigmatism at a given cylinder power and axis. However, real astigmatism varies by type (corneal vs. lenticular), accommodation, viewing distance, and individual eye anatomy, so the simulation is an educational approximation rather than a clinical tool.

Question 2

What do the diopter and axis sliders control?

Accepted Answer

The diopter slider (0–3D) controls the severity of the simulated astigmatism — higher values produce more blur. The axis slider (0–180°) controls the direction of the blur using the TABO convention: 0° produces horizontal blur, 90° produces vertical blur, and intermediate values produce diagonal blur. Together they define the cylindrical component of a prescription.

Question 3

Can I use my actual prescription?

Accepted Answer

Yes. Open the "Use my prescription" section in the controls panel and enter your cylinder (CYL) power and axis, or paste your full prescription text — the parser recognizes common formats like "-1.50 × 90" and "OD: -2.00 -1.50 x 90". Only the cylinder component is modeled; sphere (SPH) and add power are not simulated since they affect overall focus rather than directional blur.

Question 4

Is my data private? Are images uploaded?

Accepted Answer

Everything runs locally in your browser using WebGL2. No images, webcam frames, or prescription data are sent to any server. If you use the webcam mode, the video stream stays entirely on your device. The only data that leaves your browser is the URL parameters (diopter, axis, source type) if you share a link.

Question 5

How is the simulator different from real astigmatism?

Accepted Answer

The simulator applies a uniform directional blur across the entire image. Real astigmatism interacts with accommodation (your eye's focusing mechanism), varies with pupil size and lighting conditions, and may differ between your two eyes. People with astigmatism also develop neural adaptations over time that partially compensate for the blur. The simulator shows the optical effect in isolation — useful for understanding and explaining the condition, but not a substitute for a clinical eye exam.

Astigmatism simulator

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