🔷 Corneal Curvature & Light Focusing Simulator

Spherical vs Toric Cornea

A healthy cornea curves like a basketball; an astigmatic one curves like a football.

• Spherical: Normal shape (equal curvature all meridians)
• Toric: Astigmatic shape (football-like, two curvatures)
• ~1 in 3: Prevalence (people have notable astigmatism)
• Genetic: Common cause (shape of cornea or lens)

Why shape matters

Placeholder: curvature uniformity determines focus quality.

Two Meridians With Different Curvature

The steepest and flattest meridians are usually perpendicular to each other.

• Higher D: Steep meridian power (bends light more)
• Lower D: Flat meridian power (bends light less)
• 90°: Typical angle (apart between meridians)
• Keratometry: Measured by (or corneal topography)

Meridian mapping

Placeholder: topography maps power across the corneal surface.

Light Splitting Into Two Focal Lines

Instead of one focal point, astigmatism produces two separated focal lines.

• Conoid of Sturm: Structure name (classic optics model)
• Least confusion: Between the lines (blur circle midpoint)
• Perpendicular: Line orientation (to each meridian)
• Cyl power: Depends on (diopters of difference)

Two-line focus

Placeholder: each meridian focuses light at a different depth.

Blurred Image at All Distances

Because no plane holds a sharp point focus, images blur near, far, and in between.

• Blurred: Near vision (lines still separated)
• Blurred: Far vision (lines still separated)
• Least confusion: Best plane (still not sharp)
• Eye strain: Symptom (common complaint)

Everyday effect

Placeholder: streaking or doubling appears on fine detail.

Astigmatism Axis and Magnitude

Correction requires both a diopter magnitude and an axis in degrees.

• 0–180°: Axis range (standard notation)
• Diopters: Magnitude unit (cylinder power)
• Toric lens: Correction tools (glasses, contacts, LASIK)
• -2.00 x90: Notation example (cyl power at axis)

Reading a prescription

Placeholder: cylinder value and axis together define the fix.

Placeholder: toric correction flattens the steep meridian only.