An independent evaluation of the Lens Opacities Classification System II (LOCS II). The Italian-American Cataract Study Group.

The Lens Opacities Classification System II (LOCS II) has been offered for use in clinical studies of cataract. The system uses slit lamp and retroillumination photographic standards to grade lens opacities into classes of increasing severity. The authors evaluated the reproducibility and validity of LOCS II before its possible use in a natural history study of age-related cataract. The authors found excellent inter- and intraobserver reproducibility when the LOCS II standard photographs were used for clinical or photographic gradings of cataract. There was a tendency to underestimate posterior subcapsular cataracts on photographic gradings compared with slit-lamp gradings. The accuracy of the photographic gradings of posterior subcapsular opacities tended to decrease as the severity of coexisting opacities increased.