Correlation of central visual field sensitivity and GC/IPL thickness in glaucoma

Abstract

 

Purpose

 

To explore regions of highest correlation on macular retinal ganglion cell/inner plexiform layer (GC/IPL) thickness maps derived from spectral domain optical coherence tomography (SD-OCT) with local loss in visual field sensitivity as measured with 10-2 standard automated perimetry in patients with glaucoma.

 

Methods

 

One hundred thirty seven eyes of 125 subjects with glaucoma and available Macular Cube 200x200 scans (Cirrus HD-OCT) and 10-2 standard achromatic perimetry VFs were included. The macular scans were centered with relation to foveal center. Total deviation at each test location of 10-2 VFs (expressed as 1/Lambert values) was correlated with the GC/IPL thickness at 20,000 A-scan locations in the corresponding inferior or superior hemiretinas and color maps of the resulting correlations were constructed demonstrating only correlation coefficients with p <0.05. The main outcome measure was the topographic correspondence between single 10-2 VF locations and the area of highest correlation on the correlation maps.

 

Results

 

Test locations from the 10-2 VFs correlated significantly with GC/IPL thickness in localized arcuate pattern mostly limited within the central 4.8 x 4.0 mm oval area (highest Spearman’s rho = 0.426-0.744, p<0.05). The correlated region was more extensive superiorly (6.90±0.84 degrees) compared to the inferior region (5.84±0.55 degrees, p<0.001) whereas the correlated inferior region of GC/IPL was wider inferiorly (10.00±0.42 vs 9.34±0.45 degrees, p<0.001). No visual field test location demonstrated any correlation with OCT pixel measurements beyond the central oval area. Overall, our approach confirmed the displaced correlation between VF test locations and corresponding macular locations. One notorious finding was the correlation of test locations nasal to the fixation along the horizontal meridian with OCT measurements located nasal to the fovea near the horizontal meridian. The highest correlations were seen with thickness measurements located about 3 degrees from the foveal center especially along the vertical meridian.

 

Conclusions

 

The results of this study indicate that structure-function relationships are not one-to-one in the macula but have localized characteristics in the distribution pattern. The ganglion cell layer damage associated with local visual field sensitivity loss of each test point is arcuate in nature.