The effect of cataract severity and morphology on the reliability of the Lens Opacities Classification System II (LOCS II).

Data collected from 3646 eyes in the Italian-American Natural History Study of Age-Related Cataract were used to investigate whether the reliability of the Lens Opacities Classification System II (LOCS II) by the severity of the opacity that is being graded or is influenced by the presence and severity of coexisting opacities. Reliability was assessed by comparing the slit-lamp gradings of two clinical examiners (346 eyes) and the gradings performed at the slit lamp with gradings of photographs (3646 eyes). The severity of cortical and nuclear opacities did not affect the reproducibility of slit-lamp gradings, but clinical grading of posterior subcapsular opacities became more reliable as the severity of the posterior subcapsular opacities increased. More advanced coexisting opacities decreased the agreement in the slit-lamp diagnosis of nuclear, but not cortical or posterior subcapsular, opacities. Comparisons of clinical and photographic gradings showed very good to excellent agreement for nuclear and cortical opacities, regardless of the severity of the specific opacity or the severity of the coexisting opacities. Agreement in diagnosing posterior subcapsular opacities was decreased in eyes with milder posterior subcapsular opacities and in eyes with more severe coexisting nuclear and/or cortical opacities. The effect of the severity of the opacity being graded and the severity of coexisting opacities on the reliability of the LOCS II must be considered in studies that use the system to classify and grade cataracts.