Evaluation of Goldmann applanation tonometry, rebound tonometry and dynamic contour tonometry in keratoconus

Abstract

PurposeTo compare the intraocular pressure (IOP) measurements obtained with the rebound tonometry (RT), dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT) in keratoconic corneas and to investigate the effects of central corneal thickness (CCT) and corneal radius of curvature (CR) on IOP measurements.MethodsSixty-three eyes of 63 keratoconus patients were enrolled in this cross-sectional study. IOP was measured on each subject always in the same order, ICare RT-Pascal DCT-GAT, after a minimum interval of 10 min between measurements. CCT and CR were measured using a rotating Scheimpflug camera before the IOP measurements in all subjects. One way repeated measures ANOVA and Pearson correlation coefficient analysis was used for the statistical assessment.ResultsMean IOP for all enrolled eyes was 11.72 ± 2.59 mm Hg for GAT, 9.34 ± 3.29 mm Hg for RT, and 15.42 ± 3.31 mm Hg for DCT. There were statistically significant differences among the three tonometers; GAT and RT (P < 0.001), GAT and DCT (P < 0.001), and RT and DCT (P < 0.001). GAT and RT were significantly positively correlated with CCT (r = 0.288, P = 0.025 and r = 0.483, P < 0.001, respectively). RT was also significantly positively correlated with CR (r = 0.550, P < 0.001). DCT was not significantly correlated with CCT (r = 0.115, P = 0.377) nor CR (r = −0.179, P = 0.168).ConclusionsDCT has overestimated but RT has underestimated IOP readings according to GAT measurements in keratoconic corneas. DCT may be the most appropriate tonometer to use in keratoconus for the measurements of IOP, because DCT do not appear to be dependent upon CCT and CR.

A Study for Parametric Morphogeometric Operators to Assist the Detection of Keratoconus

“…The deviation of the apex on the posterior surface of the cornea was larger in the eyes with keratoconus (0.19 ± 0.11 mm), and there was also a slight deviation in healthy corneas (0.08 ± 0.03 mm, effect size: −1.19) according to the toricity manifested in the subjective refraction [35]. The aforementioned presence of an irregular corneal surface, which created a protrusion in the keratoconic eye, also led to an increased corneal curvature [42] and, therefore, to an increase in the deviation of the point of minimum thickness (maximum curvature) of the posterior corneal surface (average distance from the minimum thickness point of the posterior surface to the Z-axis). These deviations were greater in the eyes with keratoconus (1.02 ± 0.35 mm) compared with healthy eyes (0.80 ± 0.26 mm, effect size: −0.88).…”

Aktueller Stellenwert der Druckmessung: Messverfahren und Fehlerquellen

“…Im Vergleich zur GAT fällt der IOD bei der Re-bound-Tonometrie systematisch um ca. 1-2 mmHg höher aus [38][39][40][41]. Bei anomaler Kornea ist trotz des Einflusses der zentralen Hornhautdicke eine Rebound-Tonometrie in einigen Fällen eine gute Alternative, in denen eine GAT oder eine dynamische Konturtonometrie nicht möglich ist [42].…”

Biomechanik und Augeninnendruck bei Hornhauterkrankungen

“…Özcura et al konnten diese Übereinstimmung in einer weiteren Arbeit jedoch nicht bestätigen. Hier zeigten sich deutliche Abweichungen der iCare-Messung von der GAT im Sinne einer falsch niedrigen Messung [17].…”