Corneal thickness measurements and visual function abnormalities in ocular hypertensive patients

Abstract

Purpose It has been suggested that a considerable subset of patients currently classified as having ocular hypertension may have thicker than average corneas that result in an overestimation of the true intraocular pressure (IOP). As a consequence, ocular hypertension patients with greater corneal thickness may be at a lower risk for functional damage, such as that detected by short-wavelength automated perimetry (SWAP). The purpose of this study was to evaluate the frequency of SWAP deficits in ocular hypertension patients and to correlate these findings with corneal thickness measurements in the same patients. Design Cross-sectional observational study. Methods Sixty-eight ocular hypertension patients with normal optic disks and 63 normal subjects were included in the study. All participants underwent standard automated perimetry (SAP), SWAP, and central corneal thickness measurements using ultrasound pachymeter. Central corneal thickness measurements in ocular hypertension patients with abnormal visual field test results were compared with central corneal thickness measurements in ocular hypertension patients with normal visual field results. In addition, central corneal thickness measurements in ocular hypertension patients were compared with central corneal thickness measurements in normal subjects. Results Sixteen of 68 patients with ocular hypertension (24%) demonstrated SWAP abnormalities, whereas four of 68 (6%) showed a deficit on SAP. The mean central corneal thickness in ocular hypertension patients with abnormal SWAP results was significantly lower than the mean central corneal thickness in ocular hypertension patients with normal SWAP results (545 ± 25 μm vs 572 ± 35 μm; P = .006). The mean central corneal thickness in the normal group was 557 ± 33 μm. The mean central corneal thickness in ocular hypertension patients with normal SWAP results was significantly higher than in normal subjects ( P = .02). There was no significant difference between mean central corneal thickness in normal subjects and in ocular hypertension patients with abnormal SWAP results ( P = .19). Conclusions The patients classified as having ocular hypertension but with visual field loss detected by SWAP had significantly lower central corneal thickness measurements than the ocular hypertension patients with normal visual field results. These results suggest that central corneal thickness should be taken into account when assessing risk for the development of glaucomatous damage among ocular hypertension patients.