How to use the Retinoscopy Calculator

A free tool for eye-care professionals. It turns your retinoscopy findings into a prescription (sphere, cylinder and axis) with the spherical equivalent. No account is needed, and the calculation runs in your browser.

Step by step

1. Settings. Choose the working distance (50, 67 or 100 cm), the cycloplegic agent if you used one, and the technique.
2. Findings. For each eye, enter the lens that neutralised each of the two main meridians. The axes are set to 180 (horizontal) and 90 (vertical). For oblique meridians, type one axis and the other is set 90° away.
3. Calculate. The result shows SPH, CYL and axis for each eye, and the spherical equivalent.
4. Transpose switches the result between plus and minus cylinder.
5. Print. To print a report, open "Patient details for the printout" (optional), fill in what you need and press Print. "Clear form" empties all fields.

How the result is calculated

For each meridian, the calculator subtracts the working-distance lens and, if chosen, the cycloplegic allowance:

Net power = neutralising lens − working-distance lens − cycloplegic allowance

• Working-distance lens: 50 cm = 2.00 D, 67 cm = 1.50 D, 100 cm = 1.00 D.
• Cycloplegic allowance: tropicamide 0.5% = 0.25 D, cyclopentolate 1% = 0.50 D, atropine 1% = 1.00 D.
• Sphere is the less plus of the two meridians, the cylinder is the difference between them (plus cylinder), and the axis is the axis of the less plus meridian.
• Spherical equivalent = sphere + cylinder ÷ 2.

Example at 50 cm: +2.00 at 180 and +1.00 at 90
→ −1.00 / +1.00 × 90, spherical equivalent −0.50 D

The calculator warns you when the two axes are more than 20° away from perpendicular (recheck the measurement), and when the cylinder is above 6.00 D.

Techniques

• Static: distance fixation, accommodation relaxed. Uses the working distance.
• Mohindra: near retinoscopy in a dark room, often for young children. The calculator subtracts 1.25 D instead of the working distance.
• Dynamic and near: the result uses the working distance, as for static; the technique is noted on the printout.

Questions

Do I need an account? No. The calculator is free to use, without a time limit.

What happens to the patient details? They are optional and only fill in the printed report. The calculator does not store them.

Plus or minus cylinder? The result is written in plus cylinder. Press Transpose for minus cylinder.

Something missing or unclear? Contact us. You get a personal answer within 24 hours.