[The application of digital photography with retroillumination for lens in cataract study]

To evaluate the reliability of digital photography with retroillumination for lens as a tool to assess the degree of lens opacity, and to study the morphological features of some lens diseases using the digital images.

The cataract screener (Neitz CT-S) was connected to a computer capable of acquiring digital images of lens. The digital lens retroillumination and slit lamp images were collected in 64 eyes. Three independent separate examiners took three sets of different CT-S digital photographs in four cataract subjects. The area of lens opacification in the images was measured and analyzed using threshold adjustment in PhotoShop software and a customized program in Matlab software.

The distinct digital images of lens cortical opacity, posterior subcapsular opacity and other lens diseases were obtained with CT-S computer digital photography, which images were much better than slit lamp sectional digital images. The sensitivity and specificity of measuring lens opacification with CT-S digital images were 90% and 94% respectively. However, the digital lens retroillumination images were not as sensitive as the slit lamp images for nuclear cataracts. The variation coefficients of lens opacity area in the three sets of CT-S digital images in the same subject, which were taken by the independent examiners, were from 2.23% to 10.86%. The cortical opacification in CT-S digital images was linear, cuniform or clustered aggregate shadow configuration. The posterior subcapsular opacification was discal vacuolar or granular appearance.

The reproducibility of the CT-S digital images taken by the independent examiners is excellent. This technique can objectively show cortical or posterior subcapsular opacities, but nuclear cataracts.