Peripapillary distribution of Muller cells within the retinal nerve fiber layer in human eyes

The purpose of this study was to describe the distribution of Muller cell within the peripapillary retinal nerve fiber layer (RNFL) in human eyes. Eleven unpaired normal postmortem eyes were recruited into this study. Each eye was sectioned using the "umbrella technique" to obtain a concentric peripapillary ring centered on the optic disc, with a diameter of 3.0 mm. Immunohistochemistry with anti- CRALBP stained Muller cell within each ring. The RNFL thickness measurements around the peripapillary ring were: 262.5, 339.4, 285.4 and 347.5 μm for the temporal, superior, nasal and inferior quadrants, respectively. Muller cell were found to be unevenly distributed in the peripapillary RNFL of normal eyes. The relative Muller cell staining to the thickness of each measured segment (16.6%, 15.2%, 21.3%, and 17.9% for the temporal, superior, nasal and inferior quadrants, respectively) showed a significant increase in the nasal quadrant. The RNFL thickness measurements obtained using imaging techniques reflect the amount of axonal tissue present in this layer. In this study we highlight that around 20% of RNFL thickness is composed of non-axonal contents which do not represent neuronal tissue, nor are they necessarily lost in the glaucomatous process. More so, the ratio of the Muller cell component to the total RNFL thickness varies around the peripapillary RNFL ring, demonstrating the lowest relative content of Muller cell superiorly and the highest content nasally. Further studies should compare the amount and distribution of Muller cell in normal versus glaucomatous eyes.