Noncontact tonometry through soft contact lenses

Under some circumstances it is advantageous to measure intraocular pressure (IOP) without removing soft contact lenses. In this study comparisons have been made between IOP measurements [using a noncontact tonometer (NCT)] with and without soft contact lenses on the eye. The influence of lenses of different water content, lens design, lens power, method of manufacture, and lens center thickness was examined. The most important parameter affecting the results was center thickness. It was shown that reliable and valid IOP findings can be obtained using a NCT with soft lenses on the eye when center thickness is less than 0.15 mm. In glaucoma screening readings obtained with lenses thicker than 0.15 mm may be convenient and useful although such results would be achieved with increased sensitivity and concomitant reduced specificity.