Effect of Central Corneal Thickness on Iop Measurements Obtained With Dynamic Contour Tonometry and Goldmann Applanation Tonometry in Aphakic Eyes Post Congenital Cataract Surgery

Abstract

Purpose: : To analyze the influence of central corneal thickness (CCT) on intraocular pressure (IOP) measurements obtained with dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT) in aphakic eyes post congenital cataract surgery.

Methods: : Forty nine eyes of 32 patients (12.5 ± 4.7 years old) with aphakia post congenital cataract surgery were examined. GAT (Haag Streit R900, Switzerland), DCT (SMT Swiss Micro Technology, Switzerland), and CCT (Sonomed Micropach 200P+, USA) measurements were obtained, in this order, by three examiners (one examiner per instrument). The mean of 5 CCT measurements was used for analysis. DCT measurements were accepted only when quality scores were 1,2, or 3. Linear regression analysis was performed to test the correlation between CCT, DCT and GAT measurements. Bland Altmann analysis was performed to evaluate the agreement between DCT and GAT measurements.

Results: : Mean CCT was 624.78±61.39 µm. Mean IOP measurements were 18.78 ± 4.31 mmHg for GAT and 17.68 ± 2.96 mmHg for DCT (P=0.07, paired t test). Spearman correlation tests showed IOP measurements by DCT to have poor correlation with CCT (r² = 0.001, P=0.89). GAT IOP measurements showed a strong correlation with CCT (r² = 0.22, P=0.001). IOP measurements by GAT displayed a strong correlation with those obtained with DCT (r² = 0.157, P=0.005). Bland-Altmann analysis revealed poor agreement between DCT and GAT readings, with 95% confidence intervals of ± 8.30 mmHg.

Conclusions: : In aphakic eyes post congenital cataract surgery, GAT readings tend to be higher than DCT measurements, with poor agreement between them. DCT measurements were not influenced by CCT in this series, whereas GAT measurements were influenced by CCT.

Keywords: intraocular pressure • cataract • cornea: clinical science