What should an optician check if a consumer reports their old glasses give better vision than their new ones with the same prescription?

When a consumer reports that their old glasses provide better vision than their new ones with an identical prescription, it is crucial to consider several optical factors that can affect the visual experience. Vertex distance and base curve play significant roles in how lenses interact with a wearer's vision.

Vertex distance refers to the distance from the back of the lens to the wearer's eye. If the vertex distance is different between the old and new glasses, it can significantly influence the perceived strength of the prescription and overall clarity of vision. For example, a longer vertex distance can make a prescription appear weaker, while a shorter distance can make it seem stronger.

Base curve, on the other hand, relates to the curvature of the lens. Different base curves can alter the way light enters the eye, affecting peripheral vision and overall image distortion. If the base curve of the new lenses differs from that of the old pair, it can lead to discrepancies in visual clarity, even if the prescriptions are the same.

Therefore, checking both the vertex distance and base curve is essential in determining why the consumer is experiencing better vision with their old glasses. This assessment can help ensure that the new lenses are optimized for the individual's visual needs and fit correctly.