Evaluation of macular ganglion cell analysis compared to retinal nerve fiber layer thickness for preperimetric glaucoma diagnosis

Purpose: To compare the diagnostic ability of the ganglion cell analysis (GCA) and retinal nerve fiber layer (RNFL) protocol on optical coherence tomography (OCT), to diagnose preperimetric glaucoma. Methods: A prospective, cross-sectional study of 275 adult patients including 47 early glaucoma (mean deviation better than -6.0 D), 150 glaucoma suspects (106 with suspicious discs and 44 ocular hypertensive (OHT), and 78 normal controls was done. Eligible participants were scanned with the spectral domain CirrusTM OCT (Carl Zeiss Meditec, Dublin, CA). Average peripapillary RNFL thickness and GCA measurements were obtained. Area under receiver operating characteristic (AROC) curves were used to evaluate discriminant value of both protocols to diagnose likely preperimetric glaucoma among glaucoma suspects. Results: Average RNFL and GCA were significantly thinner in glaucoma patients compared to glaucoma suspects and normal controls (P < 0.001). The RNFL was 92.26 ± 8.8 ? in normal controls, 87.9 ± 12.12 ? in glaucoma suspects and significantly thinner in POAG (70.29 ± 10.18 ?; P < 0.001). The GCA was 81.94 ± 6.17 ? in normal controls, 77.69 ± 9.03 ? in glaucoma suspects, and significantly thinner in POAG (69.36 ± 11.06 ?; P < 0.001). AROCs for discriminating glaucoma suspects from normal were modest, with no difference in AROC of average RNFL or GCA measurements (DeLong; P = 0.93). Average RNFL thickness had significantly greater AROC values than average GCA for discriminating glaucoma suspects (both suspicious discs and OHT) from glaucoma (P = 0.03 and 0.05, respectively. AROC for diagnosing glaucoma was significantly better (P = 0.02) for RNFL (0.88 ± 0.03) than GCA (0.77 ± 0.04). Conclusion: In the present time, GCA measurements, as provided by the SD-OCT, do not appear to outperform RNFL measurements in the diagnosis of preperimetric glaucoma.