Spectacle lenses lose approximately 8% of the available light through reflection from the external and internal surfaces of the lens. This has two main consequences for glasses wearers – their eyes don’t receive as much light as they otherwise would, and their eyes aren’t as visible to others because they are ‘hidden’ behind distracting reflections.
Anti-reflection coating the lenses vastly reduces the amount of light lost by surface reflection – often to under 1%.
Cosmetically this significantly improves their appearance – the picture illustrates the difference that coated lenses (on the right in the picture) can make. Not only is it more flattering, but it also aids ‘non-verbal’ communication.
The optical advantage of the coating is most noticeable in low lighting, when the eyes need as much of the available light as possible. Night driving is probably the activity that benefits most from anti-reflection coated lenses – the effects of oncoming headlight glare (see the comparison below), the presence of ‘ghost’ images (bright light sources repeated more faintly elsewhere on the lens as a result of internal reflections) and visual contrast are all areas where coated lenses can help the wearer significantly.