Abstract
Purpose: :
To compare structure-function correlations of macular ganglion cell complex (GCC) and peripapillary retinal nerve fiber layer (pRNFL) analyses as determined spectral-domain optical coherence tomography (SD-OCT).
Methods: :
We prospectively enrolled glaucomatous patients [glaucomatous optic neuropathy and reproducible visual field (VF)] with previous experience in VF testing (≥ 3 exams) from May 2010 to September 2010. Those with any ocular disease other than glaucoma were excluded. All patients underwent achromatic standard automated perimetry and SD-OCT imaging (RTVue-100; Optovue Inc., CA) using the conventional pRNFL scan (3.45 mm circular scan) and the ganglion cell complex scan (a 7x7mm macular grid, consisting of RNFL, ganglion cell layer and inner plexiform layer). Structure-function relationships were investigated by correlating average GCC thickness and pRNFL thickness with VF mean deviation (MD) and visual field index (VFI).
Results: :
A total of 52 eyes (52 patients; mean age, 57.6±13.4 years) were included. Mean (±SD) values for MD, VFI, PSD, average GCC thickness and average pRNFL thickness were -5.4dB, 87.3%, 4.2dB, 84.9µm and 92.3µm, respectively. A higher coefficient of determination was found between average GCC thickness and VFI (R2=0.44, p<0.0001) when compared to average pRNFL thickness and VFI (R2= 0.34, p<0.0001). Similar results were found when these analyses were performed using MD index values instead of VFI values (GCC vs MD, R2=0.44, p<0.0001; pRNFL vs MD, R2=0.34, p<0.0001).It was found that a decrease of 1.1µm in average GCC thickness corresponded to a 1% VFI reduction, while a decrease of 0.7 µm in the average pRNFL thickness resulted in the same VF sensitivity loss.
Conclusions: :
Both SD-OCT parameters correlated significantly with visual function indexes. A similar or even stronger correlation was found when the GCC analysis, a relative new SD-OCT parameter based on segmented macular evaluation, was considered. Differently from previous studies evaluating total macular thickness, our results highlight the importance of macular assessment in glaucomatous eyes.
Keywords: visual fields • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • ganglion cells