Disabling glare comes in two forms, "background" from the sun flooding through windows and "spot" from dazzling on-coming bright car headlights. Some patients are diabled more by one than by the other type of glare. This new Glaremeter tester measures both types of glare, each by a flick of a switch: Flood to Spot/Spot to Flood. Lens holder sold separately. To qualify for cataract surgery due to glare, the level of impairment must be documented. Patented technology. Consider 10 Year Extended Warranty.