WHAT CAUSES DRUSEN?
'Drusen' are the metabolic by-products of vision.
When light energy hits the retina, it is converted into an electrical impulse by the retinal cone cells, which are like fingers. In the process of converting the light energy into an electrical impulse, the fingertips (of the cone cells) slough off. These should then drain down into the deeper layers of the eye, and be flushed out of the eye through the circulatory system.
Unfortunately the membrane at the bottom of the eye through which the fingertips of the cones should drain can become blocked. It is like a sieve, and is called Bruch’s membrane. Hence the “fingertips” accumulate in the basement layer of the retina, being unable to pass through the sieve. These deposits, when they coalesce, are known as drusen. They continue to accumulate, and given the right circumstances they disturb the layer of retinal cone cells and prevent them from functioning properly.
This is the beginning of dry macular changes.
Drusen are seen on OCT scanning, which is why the OCT has become the instrument of choice in all hospitals treating macular degeneration. This instrument is starting to be seen in Optometric practice also, being in around 10% of Optometry practices throughout the UK.
It is an invaluable tool in the detection and treatment of AMD in both its forms. I use it routinely in eye examinations here.