## About Residual Astigmatism Calculator (Formula)

The Residual Astigmatism Calculator is a tool used to calculate the residual astigmatism based on the refractive astigmatism at the corneal plane and the refractive astigmatism at the anterior corneal. Residual astigmatism refers to the remaining astigmatism after certain corrective procedures.

**The formula used to calculate the residual astigmatism is as follows:**

Residual Astigmatism (RA) = Refractive Astigmatism at Corneal Plane (RACP) – Refractive Astigmatism at Anterior Corneal (RAAC)

In this formula, the refractive astigmatism at the corneal plane and the refractive astigmatism at the anterior corneal are measured in units such as diopters (D). The residual astigmatism is determined by subtracting the refractive astigmatism at the anterior corneal from the refractive astigmatism at the corneal plane.

For example, if the refractive astigmatism at the corneal plane is 2.50 D and the refractive astigmatism at the anterior corneal is 1.75 D, the residual astigmatism can be calculated as:

Residual Astigmatism = 2.50 D – 1.75 D = 0.75 D

Therefore, in this example, the residual astigmatism would be 0.75 diopters.

The Residual Astigmatism Calculator simplifies this calculation process, allowing users to quickly determine the residual astigmatism based on the provided refractive astigmatism values. It is commonly used in ophthalmology and optometry to assess the effectiveness of corrective procedures and evaluate the remaining astigmatism post-surgery or other treatments.