Abbe value: why some lenses show colour fringes

A different number from index

White light contains different wavelengths. A material can bend these by slightly different amounts; this is dispersion. The Abbe value is a way to describe that tendency under specified reference conditions. Off-centre viewing can make coloured edges more noticeable, especially around a high-contrast border. It is an optical trade-off, not a direct measurement of how well a person reads a vision chart.

Refractive index and Abbe value describe different properties. Abbe value relates to how much a material separates light into colours. Lower values mean greater dispersion, which some wearers notice as coloured edges when looking away from the lens centre.

The situation matters

ABDO describes colour fringes around high-contrast details and peripheral blur as possible effects. People vary in sensitivity. This does not mean that everyone will dislike a particular material, or that a single Abbe number predicts the entire wearing experience.

Make the complaint reproducible

Our suggested example is to tell the dispenser what object shows a fringe, which direction you are looking and whether the same effect occurs with your old glasses. Keep the comparison in ordinary viewing conditions; there is no need to invent a home pass-or-fail test.

Choose with the whole pair in mind

Ask how an alternative material would affect your specific pair’s thickness, weight, cost and intended use. A practical comparison is more useful than selecting the largest number from a chart. Keep a record of materials you have worn comfortably for future orders.

A worked example

If white text on a dark screen shows a coloured edge only when you look through the lens side, tell the dispenser the viewing direction and task. Ask them to check positioning and compare materials using the actual specification. Do not diagnose the material from a phone photograph alone: the camera, screen and lighting can add their own colour effects.