The relation of individual variation in total retinal ganglion cell layer thickness to post-retinal anatomy

Abstract

Introduction: There is individual variation in both the thickness of the retinal ganglion cell (RGC) layer of the eye, and in the relative size of anatomical components of the post-retinal visual pathway. In ophthalmologic disease, congenital RGC loss shrinks the geniculo-striate pathway (although increases apparent V1 thickness). We tested if normal variation is shared in retinal and post-retinal visual anatomy. Methods: Forty subjects were studied with SD-OCT, anatomical MRI scanning, and ocular biometry. Macular OCT was performed on the right and left eye, and with horizontal and vertical B-scan orientations (width 30° visual angle). The RGC+IPL layer (hereafter “RGC”) was segmented and edited using OCT-Explorer v5.0. The acquisitions were combined into a single, pseudo-right eye. The mean RGC layer thickness was obtained for each subject. T1 brain images were acquired at 3T and analyzed with the HCP pipeline. We obtained the volume of the optic chiasm and lateral geniculate nucleus, and the surface area and thickness of area V1 gray matter. Results: The correlation between the left and right eye RGC thickness was r=0.98, suggesting low measurement noise. As has been reported previously, axial length was negatively related to RGC thickness, accounting for 26% (+−9% quartile by bootstrap resampling) of across-subject variance in RGC thickness. There was no effect of subject age in these data. The volume of the optic chiasm and LGN, relative to total supra-tentorial volume, were positively related to RGC thickness (13+−4% additional variance explained). There was no relationship between RGC thickness and either V1 surface area or thickness. Conclusion: There is a modest relationship between individual differences in total RGC layer thickness and the size of the optic chiasm and LGN. It remains to be seen if differences in the distribution of RGC density across the retina, independent of overall thickness, are related to post-retinal organization.

Acknowledgement: U01EY025864