Color blindness as part of the retinal damage caused by diabetes. Vitamin A deficiency may also cause color blindness. Some subtle forms of color blindness may be associated with chronic solvent-induced encephalopathy (CSE), caused by long-time exposure to solvent vapors. Red–green color blindness can be caused by ethambutol, a drug used in the treatment of tuberculosis. The typical human retina contains two kinds of light cells: the rod cells (active in low light) and the cone cells (active in normal daylight). Normally, there are three kinds of cone cells, each containing a different pigment, which are activated when the pigments absorb light.
Retina bipolar cell inhibition and become active (depolarized), while the OFF bipolar cell loses its excitation (becomes hyperpolarized) and becomes silent. Rod bipolar cells do not synapse directly on to ganglion cells. Instead, rod bipolar cells synapse on to a Retina amacrine cell, which in turn excite cone ON bipolar cells (via gap junctions) and inhibit cone OFF bipolar cells (via glycine-mediated inhibitory synapses) thereby overtaking the cone pathway in order to send signals to ganglion cells at scotopic (low) ambient light conditions. OFF bipolar cells synapse in the outer layer of the inner plexiform layer of the retina, and ON bipolar cells