Turn your retinoscopy findings into a refraction in seconds: working distance, technique and cycloplegic taken into account, in plus or minus cylinder, with a printout for your records.
Calculate a refractionNo account needed. Nothing you enter is sent or stored.
How the calculation works
- Working distance: the neutralising lens includes the working-distance lens: 2.00 D at 50 cm, 1.50 D at 67 cm, 1.00 D at 100 cm. It is subtracted from each meridian.
- Mohindra: near retinoscopy in a dark room; 1.25 D is subtracted instead of the working-distance lens.
- Cycloplegic: an allowance for the ciliary tonus: 0.25 D (tropicamide), 0.50 D (cyclopentolate) or 1.00 D (atropine).
- Result: the lower net meridian is the sphere, the difference is the cylinder (plus cylinder) and the axis is the axis of the lower meridian. The switch shows the same result in minus cylinder.
Example
At 50 cm the horizontal meridian (180) is neutralised with +1.00 D and the vertical meridian (90) with +2.50 D. Net: −1.00 D at 180 and +0.50 D at 90, so the result is −1.00 / +1.50 × 180, or +0.50 / −1.50 × 90 in minus cylinder.
Frequently asked questions
Which working distance should I choose?
The distance from your eye to the patient’s eye while you neutralise. Most practitioners work at about 67 cm (arm’s length) or 50 cm.
Why do the meridians have to be 90° apart?
The principal meridians of regular astigmatism are perpendicular. If the axes you enter are not 90° apart, the calculator asks you to check them; when you change one axis, the other follows 90° away.
Is anything I enter stored?
No. The calculator and the printout work in your browser; nothing, not even the optional patient details, is sent to us or saved.