Goldmann tonometry tear film error and partial correction with a shaped applanation surface

Figures & data

Figure 1 Schematic of tear film adhesion modeling.

Figure 2 CATS tonometer prism cross section of the modified applanating surface.

Abbreviation: CATS, correcting applanation tonometry surface.

Figure 3 Photograph of the CATS tonometer prism and GAT prism applanating surfaces.

Abbreviations: CATS, correcting applanation tonometry surface; GAT, Goldmann applanation tonometer.

Figure 4 Illustration of Goldmann applanation tonometry tear film adhesion.

Notes: Upper right inset: illustration of tear film meniscus and angle theta between the cornea and the prism applanation surface. Lower right inset: illustration of applanation mires imaged through the tonometer prism demonstrating mire thickness and measurement applanation end point.

Figure 5 Photograph of applanation tonometry tear film adhesion measurement setup with Perkins tonometer, acrylic hemisphere, scale, and mire imaging microscope.

Figure 6 Photograph of applanation tonometry tear film adhesion measurement setup with Perkins tonometer and cadaver eye apparatus.

Figure 7 Tear film adhesion force error (mmHg) comparing the CATS and GAT prisms on PMMA-simulated cornea.

Notes: Box-and-whisker plots of measured film adhesion for when using artificial tears and fluorescein as tear film stimulants and when using the GAT and CATS tonometers. The figure also includes the difference of the mean values between groups and the p-value corresponding to a two-sample difference of mean t-test.
Abbreviations: CATS, correcting applanation tonometry surface; GAT, Goldmann applanation tonometer; PMMA, polymethyl methacrylate.

Figure 8 Cadaver globe tear film adhesion force error (mmHg) comparing the CATS (blue) and GAT (red) prisms demonstrating curvilinear fits from GLME analysis along with 95% confidence intervals.

Abbreviations: CATS, correcting applanation tonometry surface; GAT, Goldmann applanation tonometer; GLME, general linear mixed-effects; IOP, intraocular pressure.

Figure 9 Tear film adhesion error versus applanation meniscus mire thickness in CATS and GAT prisms using GLME multivariate analysis output.

Abbreviations: CATS, correcting applanation tonometry surface; GAT, Goldmann applanation tonometer; GLME, general linear mixed-effects.