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 < or =555 microm) and thick (CCT >555 microm) cornea subsets. Ocular hypertensives were further stratified by CCT into < or =555 microm, 556 to 588 microm, and >588 microm 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 < or =555 microm 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 microm were similar.

Conclusions

Ocular hypertensives with CCT < or =555 microm 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.