Grading nuclear cataract: reproducibility and validity of a new method

Aims-To assess the reproducibility and validity of a new instrument for gra ding nuclear cataract-the laser slit lamp, by comparison with an establishe d method of lens grading-the Lens Opacities Classification System III (LOCS III). Methods-62 volunteers (113 eyes) were examined on two occasions. At each vi sit, a video image of the anterior segment was captured with the laser slit lamp and stored digitally. A measure of lens opacity for each laser slit l amp image was calculated using image analysis software. Each lens was also photographed on both visits for LOGS III grading of nuclear colour and nucl ear opalescence. Results-There was a linear increasing relation between the laser slit lamp measure of nuclear lens opacity and the LOGS III nuclear opalescence scores . The overall reproducibility of the laser slit lamp measurement was compar able with LOGS III (intraclass correlation coefficient of 95% (95% CI 92.9- 96.5) for the laser slit lamp method; 97% (95% CI 95.6-97.9) for the LOGS I II method). However, among healthy subjects, the reproducibility was lower (intraclass correlation for the laser slit lamp of 38.6% (95% CI 12.9-59.2) and 76.1% (95% CI 62.3-85.4) for LOGS III. Conclusion-The laser slit lamp appears to give a valid measurement of nucle ar cataract. The reproducibility of the instrument was high and similar to that of LOGS III. Modifications to the design would have to be made to impr ove its reproducibility among healthy subjects. It is simpler than other ob jective instruments, and could be useful in large scale studies of cataract .