Middle-Inner Macular Layers Dysfunction in a Case of Stellate Foveomacular Retinoschisis Detected by Abnormal Multifocal Photopic Negative Response Recordings

Abstract

We describe the macular morpho-functional assessment of a 65-year-old man affected by stellate nonhereditary idiopathic foveomacular retinoschisis (SNIFR), studied by visual field, SD-OCT, autofluorescence, full-field electroretinogram (ffERG), multifocal electroretinogram (mfERG) and multifocal Photopic Negative Response (mfPhNR) recordings. The typical presentation consists of the foveal appearance of radial cartwheel pattern for the splitting of the retinal layers at the level of the Henle fiber layer (HFL) and the outer plexiform layer (OPL), perfectly seen by Spectral Domain-Optical Coherence Tomography (SD-OCT). Despite a normal function of the outer retina of the peripheral and central retina evaluated by ffERG and mfERG respectively, we observed a reduced function of the retinal elements involved in the retinoschisis by recording mfPhNR that assesses mainly inner retina function (retinal ganglion cells and their axons). Therefore, it is likely that the observed impaired mfPhNR responses reflect the signaling defects derived from the delaminated middle retina and transmitted to the innermost retinal layers.

Keywords: PhNR; SNIFR; electroretinogram; inner retina; retinoschisis.

Figure 1

Morphological evaluation of the right eye (RE) and left eye (LE) of a patient affected by stellate nonhereditary idiopathic foveomacular retinoschisis (SNIFR) (F.F.), showed in comparison with a representative normal eye (Control eye). (A) Autofluorescence exam shows a foveal hypoautofluorescence with a radial aspect in F.F RE and LE. (B) Spectral Domain-Optical Coherence Tomography (SD-OCT, Heidelberg Engineering, Heidelberg, Germany) scan shows typical foveomacular schisis cavities at the level of Henle Fibers Layer (HFL) and Outer Plexiform Layer (OPL) (red arrows) associated with intraretinal hyperreflective foci and mild retinal pigmented epithelium abnormalities in F.F RE and F.F LE.

Figure 2

We assessed the function of the outer and middle-inner retina of our patient affected by stellate nonhereditary idiopathic foveomacular retinoschisis (SNIFR) (F.F.), whose results are compared in this figure with a representative normal eye (Control eye). (A) The preganglionic elements (photoreceptors and bipolar cells) of the macular region (from 0° to 25° centered to the fovea) were investigated by multifocal electroretinogram (mfERG: Diagnosys UK, LTD; Histon, Cambridge, UK) recordings. MfERG averaged responses were obtained from five concentric annular retinal regions (rings) centered on the fovea: from 0° to 5° (ring 1, R1 in red), from 5° to 10° (ring 2, R2 in yellow), from 10° to 15° (ring 3, R3 in green), from 15° to 20° (ring 4, R4 in purple) and from 20° to 25° (ring 5, R5 in blue). We considered the mfERG peak-to-peak Response Amplitude Density (RAD), measured in nanoVolt/degree² (nV/deg²), between the first negative peak (N1) and the first positive peak (P1) and indicated by the arrow (↓) in five concentric rings (R) centered to the fovea with increasing foveal eccentricity. The values of N1-P1 RADs detected in all Rings of diseased eyes were within the normal limits that were extensively reported in our previously published paper [8]. Therefore, it can be observed that diseased eyes and control eyes showed similar traces. (B) We assessed also the macular function of localized middle-inner retinal layers containing ganglion cells and their axons and glial cells by measuring the RAD of the multifocal Photopic Negative Response (mfPhNR) (Diagnosys UK, LTD; Histon, Cambridge, UK) recordings. MfPhNR averaged responses obtained from rings 1 to 5 (R1 to R5, depicted by red, green, purple, blue and orange traces, respectively) are presented by measuring the RAD that is indicated by an arrow (↕). Reduced RADs were detected in all rings in OU as compared to our normal limits [9].