The role of Müller cells in tractional macular disorders: an optical coherence tomography study and physical model of mechanical force transmission

Abstract

BackgroundTo explore the role of foveal and parafoveal Müller cells in the morphology and pathophysiology of tractional macular disorders with a mathematical model of mechanical force transmission.MethodsIn this retrospective observational study, spectral-domain optical coherence tomography images of tractional lamellar macular holes and patients with myopic foveoschisis were reviewed and analysed with a mathematical model of force transmission. Parafoveal z-shaped Müller cells were modelled as a structure composed of three rigid rods, named R1, R2 and R3. The angle formed between the rods was referred to as θ . R1, R2 and R3 lengths as well as the variation of the angle θ were measured and correlated with best corrected visual acuity (BCVA).ResultsIn tractional lamellar macular holes, there was a significant reduction of the angle θ towards the foveal centre (p<0.001). By contrast, there were no significant differences in θ in myopic foveoschisis (p=0.570). R2 segments were more vertical in myopic foveoschisis. There was a significant association between lower θ angles at 200 µm temporal and nasal to the fovea and lower BCVA (p<0.001 and p=0.005, respectively). The stiffness of parafoveal Müller cells was predicted to be function of the angle θ , and it grew very rapidly as the θ decreased.ConclusionParafoveal Müller cells in the Henle fibre layer may guarantee structural stability of the parafovea by increasing retinal compliance and resistance to mechanical stress. Small values of the angle θ were related to worse BCVA possibly due to damage to Müller cell processes and photoreceptor’s axons.

Multimodal Imaging of Lamellar Macular Holes

“…Comparing en face OCT and fluorescein angiography findings, the authors speculated that the intraretinal splitting characteristic of ERM foveoschisis may be considered a subtype of macular edema in which intraretinal spaces are created by mechanical displacement of cells rather than disruption of the inner and/or outer retinal barriers. This assumption fits well with previously published studies on the biomechanics of the parafoveal Müller cells [ 24 ].…”

Distinctive Mechanisms and Patterns of Exudative Versus Tractional Intraretinal Cystoid Spaces as Seen With Multimodal Imaging

“…However, a recent report suggested a significant association between verticalized Henle fibers and lower BCVA, possibly due to an increase in the Müller cell's stiffness and consequent photoreceptor tractional damage. 6 Most of the eyes included in the present report were diagnosed with tractional lamellar macular hole, in which Henle fibers were mainly beveled, and not fully vertical. With such an anatomical configuration, Henle fiber may maintain a good reservoir of stiffness, which may protect the underlying photoreceptors.…”

“…A recent physical and mathematical model proposed that parafoveal Z-shaped Müller cells may increase retinal compliance and dampen the effect of mechanical forces due to the horizontal processes located in the Henle fiber layer, the preferred location of schisis in the retina. 6 Such horizontal processes may verticalize under the action of more severe tractional forces. Therefore, the intraretinal hyperreflective columnar elements illustrated with OCT may correspond to "beveled" or "verticalized" Henle fibers.…”

“…Recent reports have illustrated novel insights into the morphology and biomechanics of the macular region, with a distinctive focus on Müller cells, a cellular subtype considered to be a key player in the development of both exudative and tractional cystoid spaces. 6,7 Such a pathoanatomical approach coupled with multimodal imaging analysis may help to distinguish exudative and tractional forms of intraretinal cystoid spaces, providing a better understanding of the pathophysiology of these conditions. Therefore, we designed this retrospective study incorporating recent biomechanical theories and multimodal imaging with the aim to better characterize the different forms of macular edema and determine clear-cut distinctions between tractional and exudative intraretinal cystoid spaces using advanced retinal imaging.…”

Stellate nonhereditary idiopathic foveomacular retinoschisis resolution after vitreomacular adhesion release

“… 13 A recent publication proposed a physical model of mechanical force transmission for the Z-shaped parafoveal Müller cells in tractional macular disorders and found an association between the grade of verticalization of the horizontal processes of this cells and the BCVA. 14 The visual acuity in SNIFR patients could be majorly preserved due to a lower mechanical stress transmitted from the Müller cells to the photoreceptors which might explain a milder verticalization of Henle fibers when compared to other conditions in which vitreo-retinal interface mechanical forces are higher such as myopic foveoschisis.…”