 # Ophthalmic Spherical equivalent Calculator Online

## Ophthalmic Calculators

Ophthalmic Spherical equivalent Calculator Online

The spherical equivalent is calculated by adding the sum of the spherical power with half of the cylinder power

Formula for the calculate spherical equivalent

Spherical equivalent Formula = SPH Power + Half of CYL power

For example, with a spectacle correction of -4.00/ -1.00 x 180, the spherical equivalent = -4.00D + ½(-1.00D) = -4.00D + (-0.50D) = -4.50D spherical equivalent.

## What is spherical equivalent ?

The spherical equivalent typifies the optical (spherical) prescription, which places the astigmatic eye in a refractive state of meridional balance within the circle of least confusion.

A Spherical Equivalent is an estimate of your eyes’ refractive error, calculated independently for each eye. It is calculated by merging the spherical (nearsightedness or farsightedness) and cylindrical (astigmatism) components of your refractive error but is usually not accurate enough for ordering glasses that would provide the sharpest vision. An analogy would be converting a football-shaped surface where half of the surface is steeper than the rest into a completely spherical surface like a basketball. It is not an exact fit, but the idea is to get as close as possible.

Spherical equivalents are often used by eye doctors to prescribe contact lenses for patients with low astigmatism or patients who want colored contact lenses (very few colored contact lens brands are able to correct astigmatism), to reduce the astigmatism in an eyeglass prescription for patients who have trouble adapting, or to compare overall changes in prescriptions.