Distance Rx to Reading & Computer Glasses Converter

Turn a distance prescription and its ADD into single-vision reading and computer prescriptions for both eyes.

Reading and computer prescriptions from the distance Rx

Select Distance SPH, CYL, Axis, and Reading Addition (ADD).

1. Distance Prescription (Distance Rx)
Right Eye (OD)
Left Eye (OS)
2. Select Reading Addition (ADD)
Typical ADD range: +1.00 D to +2.50 D based on patient age.
Reading Glasses Rx (Focal ~40cm) 100% ADD Applied
OD (Right Eye) 0.00 -0.75 x 180
OS (Left Eye) +0.50 -0.50 x 90
Computer Glasses Rx (Focal ~65cm) 50% ADD Applied
OD (Right Eye) -1.00 -0.75 x 180
OS (Left Eye) -0.50 -0.50 x 90
Dispensing Guidance: Single-vision reading lenses provide maximum reading field at 40cm. Computer lenses use 50% ADD to reduce neck strain at desk & monitor distances (60–75cm).

Worked example

Distance prescription OD −2.00 −0.75 × 180, OS −1.50 −0.50 × 90, with an ADD of +2.00. These are the values the calculator opens with.

Right eye (OD)Left eye (OS)
Distance−2.00 −0.75 × 180−1.50 −0.50 × 90
Reading, full ADD+0.00 -0.75 x 180°+0.50 -0.50 x 90°
Computer, half ADD-1.00 -0.75 x 180°-0.50 -0.50 x 90°

Only the sphere changes. The right reading sphere comes out at +0.00, so that lens is plano with the cylinder alone.

A hyperopic example: OD +1.50 −0.50 × 90 and OS +1.75 with no cylinder, ADD +2.50. The calculator gives reading +4.00 -0.50 x 90° and +4.25 +0.00 x 90°, computer +2.75 -0.50 x 90° and +3.00 +0.00 x 90°. Where the cylinder is +0.00, write the left eye as a sphere on the order.

The ADD is usually written once under the distance powers, or in its own column; the guide on how to read an eye prescription shows the common layouts.

The formula

Reading SPH = distance SPH + ADD

Computer SPH = distance SPH + ADD ÷ 2

CYL, AXIS
Unchanged. Astigmatism is the same at every viewing distance.
ADD
The near addition from the prescription, +0.75 to +4.00 D in the calculator.

The ADD is prescribed for a reading distance of about 40 cm. A screen at 60 to 70 cm needs less, and half the ADD is the usual starting point for computer glasses. Some practitioners use up to two thirds for a nearer screen; the working distance decides.

Before you order single-vision readers

  • Centre reading lenses on the near PD, usually 3 to 4 mm less than the distance PD, or the wearer gets base-in prism they did not need.
  • Reading glasses blur the distance. They are not for walking about or driving.
  • Ask what the wearer does: sheet music, a laptop and a desktop monitor sit at different distances, and one pair may not suit them all.

Limits. The calculator does simple addition. It does not know the wearer's working distance or accommodation, and it does not check the axis you type. See the medical disclaimer.

Questions

Do the cylinder and axis change for reading glasses?

No. Only the sphere changes. The cylinder and axis are copied from the distance prescription.

What distance are the two results for?

The reading result, with the full ADD, is for about 40 cm. The computer result, with half the ADD, is for about 60 to 70 cm.

Can I make readers from a progressive prescription?

Yes. A progressive prescription is a distance prescription plus an ADD, which is exactly what this calculator takes.