Spherical Equivalent
Spherical equivalent = sphere + cylinder / 2 (the axis is dropped); lands the eye at the circle of least confusion.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Sphere
- 2.5 D
- Cylinder
- -0.5 D
Result: Spherical equivalent 2.25 D.
The tool opens with these values already filled in. Replace them with your own.
What the result means
- SE = S + C/2
- Half the cylinder is added to the sphere (axis dropped); lands the eye at the circle of least confusion. An optical value, not a diagnosis.
What you enter
- Sphere
- Cylinder
How this is calculated
Corboy JM, et al. The Retinoscopy Book. (Spherical equivalent identity; see also StatPearls "The Spherical Equivalent", NBK589657.) Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.