Creating smaller eyedrops by reducing eyedropper tip dimensions.

The risk of toxicity and adverse systemic effects from eyedrops is increased because of the large size of conventional eyedrops. Although the tear film normally contains only 7 to 10 microliters, commercial eyedrops are 50 to 70 microliters. Much of the excess is pumped into the nasolacrimal system where it is systemically absorbed and capable of causing toxicity. A smaller eyedrop can achieve a maximal tear film concentration with far less systemic absorption. We found that changes in the outer and inner diameters of an eyedropper tip can alter eyedrop volume markedly. By selecting appropriate tip dimensions we produced eyedrops of less than 25 microliters; in some cases they were as small as 11 microliters.