Cataract classification systems, a critical review

Abstract

Abstract Purpose: Since the 1990s, large‐scale cataract epidemiologic studies have been conducted world‐wide by researchers from developed nations. Valuable data have resulted from these studies. However, cataract classification, the fundamental methodology for all studies, has not been closely scrutinized. This presentation reviews cataract classification of the past and present, and suggests future improvement.. Results: Past: The investigators often choose one classification system from, e.g., Oxford, Wilmer, LOCS, and some others. These were proposed since the late 1980s each with a unique design. However, to compare results from different studies, the cataract classification system must be standardized. By late 1990s, the WHO has recognized this necessity, and a new system was developed in 2000 by the WHO working group.Present: Dr H Sasaki and Dr S West were the first to use the new WHO‐sponsored system. Although a simplified classification system, it is highly quantitative when compared with previous systems. The new system is now beginning to be applied. Based on experience since 2000, the usefulness and characteristics of this new system will be presented.Future: In general, cataract grading agrees reasonably well with visual acuity. However, there is a specific type of lens opacification, i.e., “Retrodots”, that causes deterioration of vision and yet most ophthalmologists are still unfamiliar with it. Therefore, even the WHO‐sponsored system will require revisions as other subtle cataract sub‐types will also be detected in the future. It must be emphasized that further improvements in cataract classification, based on the investigators’ cumulative experience, are certain to continue.