Value is the dimension of lightness/darkness. In terms of a spectral definition of color, value describes the overall intensity or strength of the light. If hue can be thought of as a dimension going around a wheel, then value is a linear axis running through the middle of the wheel, as seen below:
Drusen are tiny yellow or white deposits in a layer of the retina called Bruchs membrane. They are the most common early sign of dry age-related macular degeneration. Drusen are made up of lipids, a type of fatty protein. They may be the result of a failure of the eye to dispose of waste products that are produced when the photoreceptors of the eye drop off older parts of the cell. There are several types of drusen with different levels of risk.
These are the most confusing and also the most worrisome. Drusen in the macula can be NORMAL and do NOT necessarily mean you have or will develop macular degeneration. Those lesions located within the macula are worrisome due to the association with macular degeneration, or ARMD. There are two types: hard and soft.