When you look at the lens of an elderly patient through the slit lamp, you will notice that the reflection from the anterior capsule is blue-white, whereas the reflection from the posterior capsule is a golden yellow. The double passage of light through the lens has resulted in a loss of blue light due to light scattering, producing the yellow reflection. The more nuclear sclerosis present, the yellower is the reflection. Thus we can think of the crystalline lens as a minus blue filter, because of both its yellow pigment and its preferential scattering of blue light.
This concept of the lens as a minus blue filter was suggested by Dr. Aran Safir2 and helps to explain why the optic nerve looks more yellow in the phakic eye than in the aphakic eye. In fact, to the medical student, the blue-white appearance of the optic nerve in the aphakic eye may be confused with optic atrophy.
This concept of the lens as a minus blue filter was suggested by Dr. Aran Safir2 and helps to explain why the optic nerve looks more yellow in the phakic eye than in the aphakic eye. In fact, to the medical student, the blue-white appearance of the optic nerve in the aphakic eye may be confused with optic atrophy.
