Tomographic measurements of in vivo cataracts by slit-lamp photography.

A practical method for detecting in vivo cataracts has been developed using a commercially available slit-lamp camera and by utilizing a measuring grid photographic technique. The basis of the method is to photograph a series of slit-beam sections through a lens at varying angles to the optic axis. The areas of opacity show up as localized regions of light back-scatter where the opacities intersect the path of the beam. A set of measuring grids compensated for angle distortion have been prepared. These are superimposed on the appropriate photograph. By taking a sufficient number of sections through a cataractous lens, a tomographic representation of the opacities can be constructed using a lens map. An example of the procedure of three-dimensional mapping is presented using actual lens pictures. The photographic parameters used in this method are explained in detail. The method achieves the goals of ease of use, reproducibility, and applicability to research and clinical studies.