Ocular Hypertension and Corneal Thickness: A Long-Term Prospective Study. Results after Two Years

Abstract

Purpose

To study the importance of the central corneal thickness (CCT) in patients with ocular hypertension in a 2-year follow-up.

Methods

A total of 110 subjects with ocular hypertension (intraocular pressure [IOP] >21 mmHg and normal automated visual field test) were admitted to the study. All patients periodically underwent the following tests: 1) circadian IOP curve; 2) standard automated perimetry (SAP, Humphrey 30–2 SITA test); 3) short wavelength automated perimetry (SWAP); 4) frequency doubling technology perimetry (FDT, N-30 threshold test); 5) nerve fiber layer analysis with GDx; 6) ibopamine test; 7) ultrasonic pachymetry. Patients were divided into three groups, based on corneal thickness. The frequency of abnormal tests within these groups was evaluated with the Pearson's χ² test. Baseline IOP was corrected using the Doughty and Zaman formula. CCT was also considered as a continuous variable. A control group of 48 normal subjects was also considered.

Results

The mean CCT was 562.8 um ± 37.7. The difference with respect to normal subjects was statistically significant (p<0.01). Using the correction formula, 43 eyes (39.1%) had an IOP <21 mmHg. Abnormal test results were more frequently found with FDT. The percentage of abnormal results was found to be inversely proportional to CCT. The other tests gave inconsistent or conflicting results. Using the values of CCT as a continuous variable, no significant association was found with the GDx number and the visual field indices.

Conclusions

The results of our 2-year study confirm the importance of CCT measurement in the evaluation of the risk of developing glaucomatous damage.