iVIS Ray Tracing in Keratoconus: Analysis, Role and Limits

What Happens in Keratoconus Optics

The weakened cornea bulges irregularly, producing irregular astigmatism and distorted ray paths. Hence the classic complaint: "I see with glasses, but the picture is never sharp" — with ghosting and halos, especially in dim light.

Where Ray Tracing Fits

Instead of asking only "how many dioptres?", ray tracing asks: what happens to light entering this eye, and how do corneal shape and aberrations affect the retinal image? That matters because the link between corneal shape and image quality is complex in irregular corneas.

What It Does Not Do

• It does not stop keratoconus — cross-linking is the stabilising procedure where progression is proven.
• It does not replace examination, Pentacam, refraction, surface assessment or history.
• Platform and device availability (including the iRES excimer platform) are discussed in clinic according to what is installed and approved — no device claim is made here.

Why It Matters After Cross-Linking

After stabilisation, irregular astigmatism and aberrations often remain: the disease stopped, but quality did not normalise. Advanced optical analysis then helps plan the second stage — visual rehabilitation with lenses or rings in selected eyes.

Refractive Surgery and Complex Cases

Keratoconus is never handled as "−4 dioptres, correct −4". In selected stable eyes after full assessment, advanced optical data may help design customised correction — but decisions rest on the complete dataset (Pentacam, examination, refraction, surface, acuity, history), never on ray tracing alone. In complex cases needing specialty lenses, understanding the optical system also guides expectations.