In the late 1960s, studies by George Duncan explained many of the basic principles that
underlie lens ion homeostasis. The experiments pointed to a permeability barrier close to
the surface of the lens and illustrated the requirement for continuous Na, K-ATPase-
mediated active sodium extrusion. Without active sodium extrusion, lens sodium and
calcium content increases resulting in lens swelling and deterioration of transparency. Later,
Duncan's laboratory discovered functional muscarinic and purinergic receptors at the …