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Background
In previous study, peripheral retinal nerve fiber layer (RNFL) thickness is considered to be the earliest structural changes which can be detected.3D-OCT can measure the thickness of macular ganglion cell complex (mGCC), which makes the detection of primary glaucoma possible in the early stage.
Objective
This study was to measure the thickness of mGCC and disc-peripheral RNFL in early stage of primary glaucomous eyes by 3D-OCT and assess the anatomic basis of glaucoma-induced optical nerve damage.
Methods
3D-OCT images from 10 patients with advanced stage primary glaucoma in one lateral eye and early stage glaucoma in fellow eye from December 2010 to December 2012 were prospectively analyzed in China-Japan Friendship Hospital.The patients were diagnosed based on the recommended standard of National glaucoma group (1987 version) and received routine eye examination.3D-OCT scanning was performed using 3D-macular mode, 3D-macular Wide mode and 3D-disc mode with TOPCON 3D-OCT 2000 system, and the images at macular 6 mm×6 mm area were analyzed.The posterior pole area was divided into 5 concentric rings from fovea toward periphery and equally subdivided into 100 small checks, with the area of 0.6 mm×0.6 mm for each.The probable values in each check were calculated as the ratio of each figure and corresponding normal value.The probable values were expressed as red color (P<1%), yellow color (P<5%) and gray color (P≥5%). Then the disc-periphery RNFL thickness and disc cup were evaluated.
Results
No evident abnormality was found in the thicknesses of photoreceptors layer and bipolar cell layer in both advanced glaucomous eyes and the early stage of glaucomous eyes in the 10 patients.Serious damage of visual field was seen in the advanced glaucomous eyes and presented with red color in the parapapillary RNFL area, mGCC area and macular RNFL area, showing an evidently attenuation of the thicknesses of parapapillary RNFL, mGCC and RNFL.However, the visual field was close normal in the early stage glaucomous eyes, and mGCC and macular RNFL showed yellow color, while green or yellow color was exhibited in the parapapillary RNFL area, indicating mGCC and macular RNFL thickness was reduced, but parapapillar RNFL thickness was near normal.
Conclusions
The change of mGCC thickness is earlier than that of peripheral RNFL at optic disc in primary glaucomaous eyes, which may imply that the disappear of macular ganglion cell body is earlier than that of the axon.