Correlation between visual cortex activation and macular parameters in patients with Stargardt disease.

Abstract

Purpose : Primary visual cortex (VC) contains a retinotopic map in which the central visual field (CVF) is highly magnified with respect to the peripheral field. Several studies have used functional magnetic resonance imaging (fMRI) to assess the reorganization of visual processing and correlation with the extrafoveal preferred retinal locus (PRL) in macular degenerations. We evaluated the functional response in VC and its correlation with macular parameters in patients with Stargardt disease due to ABCA4 mutations (STGD1).

Methods : 24 patients (aged 29.2±11.8 years; 8F) with STGD1 were enrolled and underwent ocular examination: best corrected visual acuity (BCVA) measured with ETDRS chart; microperimetry to assess mean macular sensitivity (MS), dense scotoma size (DSS) and PRL eccentricity (PRL-E); full field standard electroretinogram (ERG); optical coherence tomography to measure retinal pigmented epithelium atrophy area (RPE-A). Furthermore, patients underwent fMRI to assess cerebral activation during visual stimulation by a flickering checkerboard in four VC subdivisions, corresponding to 0°-5° (V1), 5°-10° (V2), 10°-15° (V3), and 15°-40° (V4) of CVF. Linear regression analysis was performed to estimate the relationship between VC activation and ophthalmological parameters (significant p-value if < 0.05). The study adhered to Declaration of Helsinki and received approval by the Local Ethics Committee; each patient gave informed consent.

Results : The regression analysis showed that higher values of ERG responses (i.e., b-wave 0.01 dark adapted, b-wave light adapted 3.0 and 30 Hz Flicker amplitudes) were significantly (p<0.001) associated with larger functional cerebral response in V1, V2 and V3 subdivisions. Moreover, activation in V1 subdivision was significantly associated with higher value of MS (p=0.004) and smaller DSS (p=0.003). No significant relationship was observed between VC activation and PRL-E. Finally, larger RPE-A was significantly (p<0.05) associated with smaller VC activation in V1, V2 and V3 subdivisions.

Conclusions : Our results show stronger VC activation in patients with a more preserved retinal function and macular structure. Furthermore, our study data support the hypothesis proposed by the recent literature of lack of neuronal reorganization in macular degeneration.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.