Purpose: To correlate Humphrey visual field mean sensitivity and peripapillary nerve fiber layer thickness as measured by scanning laser polarimetry.
Methods: The authors studied 54 eyes of 34 patients who visited a university-based glaucoma clinic and had undergone scanning laser polarimetry and Humphrey perimetry within 6 months. The study population included normal patients and those with glaucoma, ocular hypertension, and glaucoma suspect. The authors correlated visual field sensitivity with peripapillary nerve fiber thickness, and visual field mean deviation with the average deviation from the normal nerve fiber layer thickness. They also correlated the visual field mean deviation with all available GDx Nerve Fiber Analyzer parameters.
Results: The visual field mean sensitivity and deviation showed a bilinear correlation to peripapillary nerve fiber layer thickness. The visual field mean sensitivity changed little when the nerve fiber layer thickness was greater than 70 microm. The nerve fiber layer thickness below this level was associated with a rapid decrease in the visual field sensitivity. Similarly, the visual field mean deviation was close to 0 dB when the nerve fiber layer was within -10 microm of the normal value; below this thickness, the mean deviation became substantially more negative. There was a large individual variability around the bilinear fit. Of the scanning laser polarimetry parameters, a calculated index, referred to as the number, had the highest correlation with the Humphrey mean deviation.
Conclusion: The bilinear correlation and its variability between the scanning laser polarimetry and visual field parameters make it difficult to predict the result of one from the other. In general, the correlation between the two is better when there is a significant visual field defect than when the visual field is close to normal.