Fig. 2. Brunescent (brown) nuclear cataract using (A) narrow beam slit illumination and (B) retroillumination. The cataract is best seen by direct slit illumination. In retroillumination, as seen in this image, the outline of the nuclear cataract may be seen due to its increased refractive index, although the cataract does not cast any shadows. Because of its central location, this cataract may cause distortion of images early in their development.