• Inner Nuclear Layer Thickness, Metamorphopsia, and Tangential Retinal Displacement

    By Lynda Seminara
    Selected By: Richard K. Parrish II, MD

    Journal Highlights

    American Journal of Ophthalmology, September 2018

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    Metamorphopsia is a common early feature of macular diseases such as central serous chorioretinopathy, age-related macular degeneration, and epiretinal membrane (ERM). In a retrospective clinical study, Ichikawa et al. looked at inner nuclear layer (INL) thickness in relation to metamorphop­sia and tangential retinal displacement in ERM. They found INL thickness to be a useful biomarker for metamorph­opsia, as well as an indicator of tangen­tial retinal displacement in ERM.

    The study was a consecutive interventional series of 50 patients (50 eyes) who received surgery for ERM. M-charts were used to measure metamorphopsia. Measurements of INL thickness, outer retinal layer (ORL) thickness, and distances between the intersections of 2 sets of retinal vessels were obtained from Spectralis optical coherence tomography (Heidelberg Engineering) and infrared images.

    Outcomes of interest were correla­tions of INL and ORL thickness with M-chart scores and retinal displace­ment distances.

    The authors noted strong cor­relations between preoperative INL thickness and the metamorphopsia scores obtained preoperatively and 3 months postoperatively. Moreover, INL thickness at baseline and its change from baseline to 3 months correlated significantly with vertical retinal dis­placement observed 3 months post­operatively (both p < .001). Neither preoperative nor postoperative ORL thickness was found to correlate with preoperative or postoperative meta­morphopsia scores.

    Therefore, the authors proposed the utility of INL thickness as a biomarker for the degree of metamorphopsia both before and after ERM surgery. Their findings suggest that changes in the inner retinal layer, which cause distor­tion of Müller cells, play a large role in the development of metamorphopsia, thus providing further evidence that Müller cells function as optical fibers in the retina. However, the precise mech­anisms by which retinal layer shrinkage generates metamorphopsia have not been determined.

    Even when ERM surgery is successful, many patients will experience aniseikonia and metamorphopsia after­ward. Hence, the authors recommend exploration of more efficient ways to correct irregular positions of retinal Müller cells.

    The original article can be found here.