What is the primary use of a shadowgraph in contact lens evaluation?

The primary use of a shadowgraph in contact lens evaluation is to inspect lens edges. This tool allows practitioners to view the profile of the lens and assess the quality and smoothness of the edges, which is crucial for ensuring comfort and proper fit on the eye. Smooth edges minimize friction against the eyelid and help prevent irritation, making this aspect vital for a successful contact lens prescription.

While measuring lens diameter, determining lens power, and calculating lens thickness are important aspects of contact lens evaluation, they are typically accomplished through different methods and tools. The shadowgraph specifically excels in providing a visual assessment of edge irregularities and potential manufacturing defects that could influence lens performance and patient comfort.