Tomographic measurements of in vivo cataracts by slit-lamp photography
N. H. Smith, W. H. Constad, P. N. Farnsworth and A. A. Cinotti
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.