In vivo studies on cataracts using the Scheimpflug slit lamp camera

We conducted reproducibility studies on an in vivo objective method of documenting cataracts: Scheimpflug photography using the Topcon SL 45 camera. Normal and cataractous lenses were photographed and the photographs digitized and analyzed using a Perkin Elmer microdensitometer attached to a PDP 11 and Vax 11/780 computer. Linear densitometry was performed through the center of the lens. We found very good reproducibility. The intraclass correlation for the mean densities in the nucleus was 0.95: that is, intra- and interobserver variability accounted for only 5% of the overall variability. For the anterior cortex, intraclass correlation was 0.88 and for posterior cortex it was 0.84. This method may be useful, within limits, in future clinical trials of anticataract medications.