## 2 Materials and Methods
### Grading of ERM and CB Alterations  
We used the classification systems of [PERSON] et al. for describing CB alterations and ERM (Figures 1 and 2).  
Figure 1: Tractional abnormalities of the central bouquet. Panels **(A1–C1)** and the corresponding magnifications (yellow boxes) **(A2–C2)** show SD-OCT scans through the fovea the different stages of central bouquet (CB) alterations, as proposed by [PERSON] et al. [7]. **(A1,A2)** Stage 1 CB alteration: a small, fuzzy hyperreflective area (cotton ball sign, green arrowheads), associated with a stage 3 epiretinal membrane (ERM) (white arrowhead). **(B1,B2)** Stage 2 CB alteration: a central hyporeflective pocket of subretinal fluid under the interdigitation zone (green arrowheads), associated with a stage 2 ERM (white arrowhead). **(C1,C2)** Stage 3 CB alteration: a thick, dome-shaped, hyperreflective, acquired vitelliform lesion between the retinal pigment epithelium and the ellipsoid zone (green arrowheads), associated with a stage 3 ERM (white arrowhead). Scaling is identical in all images. Scale bars are displayed in the bottom right corners of panels **(A1–C1)**. For improved readability, units are only shown once in panel **(C1)**. CB = central foveal bouquet; ERM = epiretinal membrane; RNFL = retinal nerve fiber layer; INL = inner nuclear layer; ONL = outer nuclear layer; Ch = choroid.  
Figure 2: Staging scheme for epiretinal membranes. Panels **(A1–D1)** show near-infrared images, **(A2–D2)** display the corresponding OCT-B scans of ERM stages [4]. **(A1,A2)** Stage 1. Mild ERM (white arrowhead) with few anatomical changes. The foveal depression is preserved, and all retinal layers are well identified (selected layers labeled). **(B1,B2)** Stage 2. ERM with more advanced anatomical alterations. The foveal depression is lost, but all retinal layers are well defined. **(C1,C2)** Stage 3. The foveal floor is covered by continuous ectopic inner foveal layers (EIFL, teal arrowhead). As in Stage 2 ERMs, foveal depression is lost, but all retinal layers are well defined. **(D1,D2)** Stage 4. Advanced ERM with complete foveal disorganization. Thick EIFLs cover the foveal area, there is no foveal depression and all retinal layers are disrupted [30]. Scaling is identical in all images. Scale bars are displayed in the bottom right corner of panels **(A2–D2)**. For improved readability, units are only shown once in panel **(D2)**.  
CB alterations were graded by severity from stage 1 to stage 3. A small, fuzzy hyperreflective area (cotton ball sign) between the interdigitization zone (IZ) and the ellipsoid zone (EZ) was classified as stage 1. At stage 2 a central hyporeflective pocket of subretinal fluid under the IZ was observed. Stage 3 depicts a larger collection of hyperreflective material somewhere between the retinal pigment epithelium and the EZ (Figure 1).  
ERM qualified as stage 1; only mild morphological changes were seen. Foveal depression had to be preserved, and all retinal layers had to be identifiable. At stage 2, a more progressive retinal distortion with loss of the foveal depression was present. In stage 3, ERM was continuous with ectopic inner foveal layers (EIFL) anomalously crossing the central foveal area along with loss of the foveal depression. Finally, in stage 4 significant retinal thickening and remarkable anatomic disruption of the macula was shown (Figure 2).