GOLDMANN APPLANATION TONOMETRY USING STERILE DISPOSABLE SILICONE TONOMETER SHIELDS

Purpose: Placement of a sterile single-use cover over the tonometer ti p may be a convenient and safe alternative method to repeated chemical disinfection. This study was undertaken to evaluate the accuracy and performance of Goldmann applanation tonometry using a sterile disposab le silicone tonometer shield over the biprism tip. Methods: The same i nvestigator measured intraocular pressure in 120 eyes with and without the shield. The eyes were tested randomly first with either the uncov ered or the covered tonometer to control for the possible effects of r epeated tonometry influencing measurement differences. Readings were r ecorded independently in a masked fashion. Results: The intraocular pr essure measurements evaluated with the silicone shield caused an avera ge overestimation of the true intraocular pressure of 1.9 +/- 1.9 mmHg (P = 0.0001). Covered and uncovered readings correlated well (r = 0.9 1, P = 0.0001). The sensitivity and specificity of the covered tonomet ry in detecting intraocular pressures of 21 mmHg or higher (as measure d without the shield) were 96.3% and 68.8%, respectively. Minor distor tions of the normal-appearing fluorescein bands were seen in 5% of the tonometries, and the shield had to be replaced because of bubbles or wrinkles on the applanating surface in 3.3% of the measurements, which means that care must be taken when fitting the shield. Conclusions: A lthough covered and uncovered tonometry readings correlated well, an o verall trend for a slightly increased measured intraocular pressure as a result of using the silicone shield over the Goldmann tonometer tip was found. The outstanding sensitivity of this procedure in detecting increased intraocular pressure suggests that it can be useful in scre ening for ocular hypertension and glaucoma.