Correlation between retinal nerve fiber layer thickness and central corneal thickness in patients with ocular hypertension: An optical coherence tomography study

PURPOSE: To correlate the retinal nerve fiber layer (RNFL) thickness and optic nerve head (ONH) parameters measured by optical coherence tomography (OCT) with central corneal thickness (CCT) measurements in patients with ocular hypertension (OHT). DESIGN: Observational cross-sectional study. METHODS: SETTING: Tertiary care referral teaching institute. STUDY POPULATION: Fifty,one eyes of 51 patients with OHT and 35 eyes of 35 normal subjects. Both groups were stratified into thin (CCT <= 555 mu m) and thick (CCT > 555 mu m) cornea subsets. Ocular hyper-tensives were further stratified by CCT into <= 555 mu m, 556 to 588 mu m, and > 588 mu m subsets. OBSERVATION PROCEDURE: RNFL thickness (average, superior average, and inferior average) and ONH parameters were measured by OCT. CCT was measured by ultrasonic pachymetry. MAIN OUTCOME MEASURES: Correlation between CCT and OCT measurements of RNFL and ONH parameters. RESULTS: In the OHT group, CCT correlated significantly with all three RNFL measurements (Pearson's coefficient r = 0.412, 0.484, and 0.380, respectively) but with only four ONH parameters (cup-to,disk area ratio, cup area, rim area, and horizontally integrated rim width; r = -0.459, -0.283, 0.421, and 0.436, respectively). The RNFL in ocular hypertensives with CCT <= 555 mu m was significantly thinner than in those with thick corneas (analysis of variance, post hoc Bonferroni comparisons, P < .001). RNFL thickness of normal subjects and ocular hypertensives with CCT > 555 mu m were similar. CONCLUSIONS: Ocular hypertensives with CCT <= 555 mu m may represent patients who have either very early undetected glaucoma or an inherent structural predisposition to glaucomatous damage. This may in part explain the higher risk of these patients for progression to glaucoma.