Structural and Functional Assessment of the Macular Inner Retinal Layers in Multiple Sclerosis Eyes Without History of Optic Neuropathy

Background: Considering the lack of studies regarding the localized evaluation of the macular inner retina in multiple sclerosis patients without optic neuritis (MSnoON eyes), we investigated the structure and function of retinal ganglion cells (RGCs) located in different macular areas. Methods: In 24 MSnoON patients (mean age: 45.22 ± 5.57 years; 14 females and 10 males; mean MS disease duration: 11.07 ± 5.88 years) and in 30 age-similar (mean age: 45.09 ± 5.08 years) control subjects, complete ophthalmological examination, optical coherence tomography (OCT) and multifocal photopic negative response (mfPhNR) were performed. The ganglion cell layer thickness (GCL+-T) via OCT and the response amplitude density (RAD) through mfPhNR were measured from localized macular regions, including rings and Early Treatment of Diabetic Retinopathy Study (ETDRS) sectors. Results: When comparing MSnoON data from all tested areas with respect to the controls, macular GCL+-T and mfPhNR RAD mean values were found to be significantly (ANOVA, p < 0.01) reduced. In the MSonON group, considering both rings and sectors, the GCL+-T values were significantly and linearly correlated (Pearson’s test, p < 0.01) to the mfPhNR RAD values. Conclusions: In MS, even in the absence of optic neuritis, potential primary morpho-functional involvement of the inner macular elements can occur. This impairment widely involves all macular areas and sectors.