Abstract
Purpose:
Measurement of macular retinal nerve fiber layer thickness (mRNFLT) with optical coherence tomography (OCT) has become an important tool to diagnose glaucoma in its early stages and to detect decreased visual acuity in glaucoma patients. We investigated, in detail, the correlation between structure and function in the macula, and whether we could simulate the visual field with mRNFLT data.
Methods:
This study comprised 60 eyes of 34 patients with open angle glaucoma. To assess macular function, threshold, total deviation (TD), and pattern deviation (PD) from the Humphrey field analyzer (HFA, SITA-standard, 10-2 program) were used. To assess macular structure, we analyzed thickness data for the mRNFL, ganglion cell complex (GCC), and ganglion cell layer plus inner plexiform layer (GCL+IPL) from an OCT map of the macula (3D-OCT2000, Topcon, signal >50). An analysis was performed with Spearman’s coefficient of correlation to determine both the significance of the correlation between the HFA parameters and macular thickness at each of 68 test points (corresponding to the one grid of an OCT macular map), and also the formula for simulation. We then calculated a simulated threshold for each test point with the formula from the correlation between the thresholds and mRNFLT from the linear regression analysis.
Results:
For most test points, macular function and the layer-by-layer structure were significantly correlated. The levels of coefficient correlation in the significantly correlated test points were: threshold (r=0.26-0.87)≧TD (r=0.27-0.87)>PD (r=0.24-0.69) for function, and RNFL: (r=0.35-0.87)≧GCC (r=0.28-0.85)>GCL+IPL (r=0.24-0.81) for structure. The simulated grayscale map of the visual field based on the formula of the regression line between the mRNFL and the threshold was very similar to the actual visual fields. There was a significant correlation between the average simulated threshold of each of the 68 test points and the MD of the actual visual fields (r=0.76, p<0.0001).
Conclusions:
There was a significant correlation between structure and function in the macular area. The simulated visual fields generated from mRNFLT accurately reproduced the actual visual fields. Such a simulation of macular function generated from OCT parameters may be useful for glaucoma assessment in patients.
Keywords: 758 visual fields •
585 macula/fovea