To calculate the Spherical Equivalent (SE):
\[ SE = C + \left( \frac{S}{2} \right) \]
Where:
A Spherical Equivalent is a simplified, single number representation of a person’s refractive error, or the power of an eyeglass prescription. It is calculated by adding half of the cylinder power to the sphere power in an eyeglass prescription. This measurement is often used in large population studies of refractive error, or when prescribing contact lenses, as it provides a general idea of the degree of nearsightedness or farsightedness.
Let's assume the following values:
Using the formula:
\[ SE = -1.50 + \left( \frac{-2.00}{2} \right) = -1.50 + (-1.00) = -2.50 \text{ diopters} \]
The spherical equivalent is -2.50 diopters.