Influence of age, central corneal thickness, and quality score on dynamic contour tonometry

Abstract

To compare the IOP measurements obtained with dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT), and to analyse the influence of central corneal thickness (CCT) and age on both measurements, and the influence of the quality score on DCT readings. A total of 500 healthy subjects with no prior history of glaucoma or ocular hypertension (age: 7-86 years) were consecutively recruited. GAT, DCT, and CCT measurements were obtained from both eyes of each individual, in this order, by three observers. The mean of five CCT measurements was used for analysis. DCT measurements were accepted when quality scores varied between 1 (higher quality) and 3 (lower quality). Mean DCT measurements were 3.2 mmHg higher than GAT readings. CCT values varied between 449 and 653 microm. IOP measured by GAT correlated strongly with CCT (r(2)=0.28, P=<0.001), whereas DCT readings correlated poorly with CCT (r(2)=0.01, P=0.017). Both DCT (r(2)=<0.01, P=0.044) and GAT (r(2)=0.01, P=<0.001) measurements correlated poorly with age. Bland-Altmann analysis revealed disagreement between DCT and GAT readings, with 95% confidence intervals of +/-6.7 mmHg. Quality scores for DCT measurements were 1 (n=369, 36.9%), 2 (n=340, 34.0%), and 3 (n=291, 29.1%). DCT readings with quality score of 3 (18.8+/-3.4 mmHg) were significantly higher than those with quality scores of 1 (16.7+/-2.9 mmHg) and 2 (17.4+/-2.9 mmHg; P=<0.001). DCT is not influenced by CCT, unlike GAT. Both DCT and GAT measurements are not influenced by age. DCT measurements with lower quality scores are associated with higher readings.