Clinical RGP calculator

Clinical Input Parameters

1. Keratometry (K) Values (D or mm)

K Flat (D / mm) @ Axis (°)

K Steep (D / mm) @ Axis (°)

2. Spectacle Prescription

Sphere (D)

Cylinder (D)

Axis (°)

Back Vertex Distance (BVD) (mm)

3. Trial RGP Lens Parameters

BC Flat (mm) @ Axis (°)

Flat Meridian Power (D)

BC Steep (mm) @ Axis (°)

Steep Meridian Power (D)

3b. Lens and Corneal Geometry

Overall Diameter (OAD/TLD) (mm)

Optical Zone Diameter (OZD) (mm)

Corneal Eccentricity (e-value)

Asphericity relation: `Q = -(e-value)^2`

Intermediate Curve Single-sided Width (ICW) (mm)

Peripheral Curve Single-sided Width (PCW) (mm)

Intermediate Curve Radius (BC + Δ) (mm)

Peripheral Curve Radius (BC + Δ) (mm)

Intermediate Curve End Diameter (mm)

Computed Radii (Flat / Steep)

IC: —

PC: —

Current Segments

OZD / IC End / OAD: —

4. Base Curve Adjustment (Optional)

Flat Meridian BC Adjustment (mm)

Steep Meridian BC Adjustment (mm)

-0.05mm (steeper)=+0.25D tear lens → RGP power -0.25D; +0.05mm (flatter)=-0.25D tear lens → RGP power +0.25D

OR Sphere (D)

OR Cylinder (D)

OR Axis (°)

Includes BVD conversion (5-20mm)

Bitoric Clinical Inputs

1. Keratometry (K) Values (D or mm)

K Flat (D / mm) @ Axis (°)

K Steep (D / mm) @ Axis (°)

Spectacle Sphere (D)

Spectacle Cylinder (D)

Axis (°)

Back Vertex Distance (BVD) (mm)

Base Curve Adjustment (0.05mm Step)

Flat Meridian BC Adjustment (mm)

Steep Meridian BC Adjustment (mm)

-0.05mm (steeper)=+0.25D tear lens → RGP power -0.25D; +0.05mm (flatter)=-0.25D tear lens → RGP power +0.25D

OR Sphere (D)

OR Cylinder (D)

OR Axis (°)

Includes BVD conversion (5-20mm)

Low Toric Stimulation bitoric RGP Clinical Inputs

1. Keratometry (K) Values (D or mm)

K Flat (D / mm) @ Axis (°)

K Steep (D / mm) @ Axis (°)

Spectacle Sphere (D)

Spectacle Cylinder (D)

Axis (°)

Back Vertex Distance (mm)

Toricity Factor (%)

Base Curve Adjustment (0.05mm Step)

Flat Meridian BC Adjustment (mm)

Steep Meridian BC Adjustment (mm)

-0.05mm (steeper)=+0.25D tear lens → RGP power -0.25D; +0.05mm (flatter)=-0.25D tear lens → RGP power +0.25D

OR Sphere (D)

OR Cylinder (D)

OR Axis (°)

Clinical Reference

Key Formulas

BC ↔ Diopter: D = 337.5 / BC (mm)

Tear Lens: Tear D = Adjusted BC (D) - K (D)

Back Vertex: Ocular Rx = Spect Rx / (1 - d × Spect Rx) (d=BVD in meters)

BC Adjustment: 0.05mm = 0.25D tear lens change

Precision Tip

4 sig figs for clinical accuracy. Critical for high-power prescriptions.

Key Formulas

Back Vertex: Ocular Rx = Spect Rx / (1-d × Spect Rx)

Units: d = BVD (m), 5-20mm range

D (Diopter) = 337.5 / Corneal Curvature (mm)

Tear Lens = Lens BC - Corneal K

Fit Factors (ΔK)

ΔK (D)	Flat	Steep
2.0	On K	0.50D Flatter
2.5	0.25D Flatter	0.50D Flatter
3.0+	0.25D Flatter	0.75D Flatter

Precision Tip

OAD: 8.800-9.200mm | All calculations use 4 sig figs (3 decimals)

Fluorescein Pattern Simulation (2D)

Optimal Fit

Flat Δ(BC-K): 0.0000mm (Optimal Fit)

Steep Δ(BC-K): 0.0000mm (Optimal Fit)

Flat Tear C / I / P: —

Steep Tear C / I / P: —

Clinical RGP calculator

Clinical Input Parameters

1. Keratometry (K) Values (D or mm)

2. Spectacle Prescription

3. Trial RGP Lens Parameters

3b. Lens and Corneal Geometry

4. Base Curve Adjustment (Optional)

Clinical Calculation Results (4 Significant Figures)

BVD Conversion Calculator

Spectacle Prescription

Corneal Plane Conversion (4 Sig Figs)

Bitoric Clinical Inputs

1. Keratometry (K) Values (D or mm)

Base Curve Adjustment (0.05mm Step)

Bitoric Calculation Results (4 Sig Figs)

Low Toric Stimulation bitoric RGP Clinical Inputs

1. Keratometry (K) Values (D or mm)

Base Curve Adjustment (0.05mm Step)

Low Toric Stimulation bitoric RGP Calculation Results (4 Sig Figs)