Analysis of retro-illumination photographs for use in longitudinal studies of cataract.

Retro-illumination photography has potential for the monitoring of cortical and posterior subcapsular cataract formation. Variations in the individual illumination results have limited accurate quantification of opacities within such images. We present a new image analysis technique which minimises the effect of uneven and varying retro-illumination. The new technique has been tested for variation between photographers and over a short time period. We believe it is of value in lens assessment in combination with a semi-quantitative grading system.