An update on corneal hydration control.

An account is provided of developments in our understanding of the mechanism of corneal hydration control, particularly as regards the possibility of an active system for its regulation. Emphasis is given to issues that are contentious, such as the role of bicarbonate in the endothelial pump and the significance of water channels in both corneal limiting cell layers.

Drug delivery to the posterior segment from drops.

The published evidence that instilled drugs can affect the blood supply to the retina and optic nerve head in humans is examined. As a background, seven techniques that have been used to measure flow are briefly described and criticized. For timolol, the corresponding measurements, obtained by a number of investigators are evaluated.