Abstract
Abstract: :
Purpose: It has been demonstrated that ocular hypertensive (OHT) patients with thinner corneas are at a higher risk for development of glaucomatous visual field loss than OHT patients with thicker corneas. We then speculated that OHT patients with thinner corneas would be more likely to show abnormal results in tests designed to detect early retinal nerve fiber layer (RNFL) damage. The purpose of this study was to examine the relationship between RNFL measurements obtained using scanning laser polarimetry with variable corneal compensation and CCT measurements in OHT patients. Methods:The study included one eye each of 44 ocular hypertensive patients and 48 healthy control subjects of similar age. All patients had normal optic disc and normal standard automated perimetry visual fields. OHT patients had intraocular pressure (IOP) measurements higher than 22mmHg in more than one occasion. All patients underwent imaging with the GDx VCC (Laser Diagnostic Technologies, Inc., San Diego, CA) scanning laser polarimeter. We examined the relationship between GDx VCC RNFL measurements and previously determined risk factors for development of visual field loss among OHT patients, namely central corneal thickness, age, IOP and vertical cup–to–disk–ratio. Results:CCT measurements in OHT patients were significantly higher than in healthy subjects [575 ± 30 µm vs. 555 ± 32 µm; P = 0.002]. Higher GDx VCC parameter Nerve Fiber Indicator (NFI) scores, indicating more RNFL damage, were significantly correlated with thinner CCT measurements in OHT patients (r = –0.502 ; P = 0.001). OHT patients with thinner corneas (n=22; mean CCT = 553 ± 21 µm) had significantly higher NFI scores than OHT patients with thicker corneas (n=22; mean CCT = 598 ± 18 µm) and healthy control subjects (NFI mean ± SD: 27 ± 9.5, 21 ± 9.8 and 20 ± 7.0, respectively; P = 0.004; ANOVA). NFI values were not significantly different between OHT patients with thicker corneas and healthy subjects. In multivariate analysis, only age and CCT were significantly associated with GDx VCC RNFL measurements in OHT eyes. Conclusions: OHT patients with thinner corneas had significantly more RNFL damage than OHT patients with thicker corneas and healthy control subjects. These findings support the notion that RNFL loss as assessed by the GDx VCC may represent early glaucomatous damage in ocular hypertensive eyes.
Keywords: imaging/image analysis: clinical