Retinal ganglion cell layer thinning within one month of presentation for optic neuritis

Background: Spectral domain optical coherence tomography (SD-OCT) reveals retinal ganglion cell layer plus inner plexiform layer (GCL+IPL) and peripapillary retinal nerve fiber layer (pRNFL) thinning in chronic optic nerve injury. At presentation, swelling of the pRNFL confounds evaluation of early axon loss. Objective: We studied whether the GCL+IPL thins before the pRNFL, the trajectory of GCL+IPL loss and relationship to vision. Methods: We prospectively evaluated 33 eyes (study) with new optic neuritis, using perimetry and SD-OCT with investigative three-dimensional layer segmentation and commercial two-dimensional segmentation to compute the GCL+IPL and pRNFL thickness. Results: At presentation, GCL+IPL thickness (82.4±8.8 μm) did not differ from unaffected fellow eyes (81.2±6.7 μm), via the three-dimensional method, while the two-dimensional method failed in 9% of study eyes. At 1-2 months, there was thinning of the pRNFL in 10% and of the GCL+IPL in 93% of study eyes. GCL+IPL reduction was greatest during the first 2 months. GCL+IPL thinning at 1-2 months correlated with GCL+IPL thinning at 6 months (r=0.84, P=0.01) and presentation visual acuity (r=0.48, P=0.006) and perimetric mean deviation (r=0.52, P=0.003). Conclusion: GGL+IPL is an early biomarker of structural injury in optic neuritis as thinning develops within 1-2 months of onset, prior to pRNFL thinning.