Purpose
To obtain the macular grid sectors of optical coherence tomography (OCT) by an approach with a high correlation between macular retinal nerve fiber layer (mRNFL) or ganglion cell-inner plexiform layer (mGCL+IPL) and the clockwise circumpapillary RNFL (cpRNFL) in the patients with normal tension glaucoma (NTG).
Methods
This study comprised 101 eyes of 101 patients (mean age: 59.4 ± 14.7 years, 40 male and 61 female) with mild and moderate stage of NTG (mean deviation of Humphrey Field Analyzer, MD≧-12.0 dB). The thickness of cpRNFL, mRNFL, and mGCL+IPL was assessed with spectral-domain OCT (3D OCT-2000, Topcon Corporation, Tokyo, Japan). The data was excluded if the image quality was less than 60. The region of interest (ROI: 6×6 mm square area) was centered on the fovea, corresponding to the 20×20 degrees, and measured the layer thickness at each 10×10 grids separated by two degrees. The Spearman’s rank correlation coefficient was determined between each temporal clockwise sectors (7, 8, 9, 10, 11 o’clock-sector) of cpRNFL and each grid of mRNFL and mGCL+IPL, respectively. The macular sectors derived from the clockwise cpRNFL were set where the correlation coefficient was over 0.4. For the validation, the topographic macular sectors was confirmed with superimposed on the swept-source OCT image (12 x 9 mm, EnView software, Topcon) showing the anatomical trajectory defect of nerve fibers.
Results
The macular sector with a high correlation coefficient (r≧0.4, p<0.05) to clockwise cpRNFL was obtained. The number of grids in mRNFL and mGCL+IPL was 40 and 18 (7 o’clock), 43 and 22 (8), 33 and 44 (9), 39 and 39 (10), and 18 and 19 (11) (r= 0.40-0.79). Interestingly, the distribution of mRNFL sectors were well matched with the RNFL defect of OCT image, however, the sectors of mGCL+IPL was different and the distribution was close to the fovea than that of mRNFL.
Conclusions
These macular sectors and displacement of mRNFL and mGLL+IPL may help us the accurate clinical research in NTG, which is major type of glaucoma in Asia.
Keywords: 585 macula/fovea