Retinal nerve fiber layer thickness within the area of apparently normal visual field in normal-tension glaucoma with hemifield defect.

PURPOSE

To evaluate changes in nerve fiber layer (NFL) thickness in areas with apparently normal retinal sensitivity in eyes with normal-tension glaucoma (NTG) with hemifield dominant visual field defects.

METHODS

The prospective clinical study consisted of 17 eyes from 17 patients with NTG in whom superior or inferior hemifield dominant defects based on the Humphrey visual field of central 30 degrees were present, and 10 normal eyes from 10 control subjects matched in age and refractive error. The retinal NFL thickness was evaluated with a scanning laser polarimeter. Mean NFL thickness measurements in the defined ring in four quadrants (superior, inferior, nasal, and temporal) were obtained. To facilitate visual field and NFL thickness correspondence, the total deviation (TD) plot of the visual field was divided into four 90 degrees quadrants, using Wirtschafter's scheme to match the four quadrants examined by laser polarimetry.

RESULTS

The mean NFL thickness in the unaffected quadrant, i.e., the quadrant within the area corresponding to the hemifield with apparently normal visual field in eyes with NTG, was significantly thinner than the average NFL thickness of the superior and inferior quadrants in the normal eyes. In eyes with NTG, the NFL thickness in the affected quadrant also was significantly thinner than that in the unaffected quadrant. In the unaffected quadrant, visual field TD (the sum of the TD values within this quadrant) showed a significant correlation with the ratio of NFL thickness in the unaffected quadrant to that in the nasal quadrant.

CONCLUSION

Early changes in the retinal nerve fiber layer may already exist even in the unaffected area of the visual field in eyes with NTG with hemifield dominant visual field defects.