Abstract
Purpose: :
To determine if both normal and abnormal areas in the peripapillary retinal nerve fiber layer (RNFL), as measured by optical coherence tomography (OCT) correlate topographically with both normal and abnormal areas of visual function identified by frequency–doubling technology (FDT) perimetry.
Methods: :
We prospectively identified subjects with ocular hypertension or glaucoma. OCT scans of the peripapillary RNFL of both eyes were obtained with the Stratus OCT using the 3.4 mm Fast RNFL protocol. Subjects underwent perimetry with the FDT Matrix 24–2 full–threshold algorithm. Each of the 54 testing areas on the FDT Matrix visual field pattern deviation plot was assigned a score based on the degree of abnormality at that location compared to the normative database. A total score for each hemifield (superior and inferior) was calculated.
The Stratus OCT printout includes the average peripapillary RNFLT at each clock hour, and compares these data to its normative database. Each clock hour was assigned a score based on the degree of abnormality at that location, compared to the normative database. The 3 and 9 o'clock positions straddle the superior and inferior halves of the peripapillary retinal nerve fiber layer; accordingly these clock hours were assigned to both the superior and inferior nerve fiber layer for purposes of topographic correlation.
The total score of the superior 7 clock hours and the inferior 7 clock hours, based on the OCT–derived RNFL thickness measurements were correlated with the total score of the inferior 27 points and the superior 27 points on the FDT Matrix visual field, respectively
Results: :
We studied 52 eyes. For the FDT Matrix, the mean score was 15.4 ±21.5 in the superior hemifield and 8.1 ±11.6 in the inferior hemifield. For the OCT, the mean score was 1.3 ±2.2 in the superior clock hours and 2.3 ±2.9 in the inferior clock hours. There was moderately strong correlation between the inferior OCT score and the superior FDT score r=0.66, p<0.0001 (Pearson) and r=0.62, p<0.0001 (Spearman). There was weak correlation between the superior OCT score and the inferior FDT score r=0.38, p=0.005 (Pearson) and r=0.42, p=0.002 (Spearman).
Conclusions: :
The results of OCT–derived measurements of the inferior peripapillary RNFL are moderately strongly correlated with topographically corresponding FDT Matrix–derived visual function findings. However, there is relatively weak correlation between superior RNFL measurements and their corresponding FDT Matrix findings.
Keywords: nerve fiber layer • perimetry • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)