Contact Lens Power Calculation, Selection, and Fitting in Optometry

Contact Lens Fitting Method Contact lenses are a widely used alternative to spectacles, offering better aesthetics, wider fields of vision, and convenience in certain cases. The process of determining the correct contact lens power, selecting the appropriate type, and fitting them properly requires precision and expertise. Below is a detailed explanation of these processes. 1. Contact Lens Power Calculation Since contact lenses sit directly on the cornea, unlike spectacles that rest a few millimeters away from the eye, the power required for contact lenses is often different from spectacle prescription. The following steps are followed: A. Convert Spectacle Prescription to Contact Lens Power Step 1: Identify the Spectacle Prescription The spectacle prescription (Rx) is measured in diopters (D) and given in the form: Spherical (SPH) Cylinder (CYL) Axis (if astigmatism is present) Step 2: Apply the Vertex Distance Correction Spectacle lenses sit about 12-14 mm away from the cornea. If the spectacle…