Earlier studies put under debate the predictive value of various morphologic details of the retina, concluding that retinal thickness and photoreceptor layer and external limiting membrane integrity are the most important in estimating the outcome of idiopathic epiretinal membrane (ERM) surgery. However, a recent meta-analysis revealed that many discrepancies exist between studies, and the need for a good predictive model still remains.

Swept-source optical coherence tomography (SS-OCT) is an emerging technology that offers simultaneous, high-resolution, wide-field cross-sectional imaging of the vitreous, retina, and choroid. In a recent study we confirmed that in addition to the retina being altered in idiopathic ERM, the choroid is affected as well. We confirmed that choroidal thickness was decreased 3 months after surgery. Further study is required to determine whether this decrease is long lasting.

Furthermore, we have previously noted several novel findings of the choroidal architecture, such as the suprachoroidal layer, suprachoroidal space, and possible irregularities of the outer choroidoscleral boundary. The meaning of those findings was not exclusively studied.

The suprachoroidal layer consists of 2 bands, an inner hyperreflective band and an outer hyporeflective band. The hyporeflective band of the suprachoroidal layer probably corresponds to the suprachoroidal space. The suprachoroidal space was historically observed only in choroidal effusion syndrome. Recently, this layer was reported to be more frequently visible in hyperopia. Furthermore, we confirmed this layer to be more often visible in macular diseases than in healthy eyes. In patients with ERM without metamorphopsia and without vision complaints, we did not observe this layer in any of 20 analyzed eyes. In another retrospective study of 21 eyes, examined before and after vitrectomy for idiopathic ERM, we noted this layer in 4 cases. It was also observed that the suprachoroidal layer is even more often visible in eyes with full-thickness macular holes and vitreomacular traction syndrome. The factors correlating with the visibility of this layer are still not precisely understood. With the advent of new technology enabling the introduction of drugs to the suprachoroidal space, the role of the visualization of the suprachoroidal layer and suprachoroidal space might be of growing importance.

The aim of this prospective analysis was to estimate if there are factors associated with the visibility of the suprachoroidal layer in eyes with idiopathic ERM. An additional intention was to describe long-term changes in retinal and choroidal morphology, visualized with SS-OCT, before and after vitrectomy for idiopathic ERM.

Methods

This is a prospective consecutive case series of 29 eyes of 29 patients with idiopathic ERM operated on in the year 2013. Inclusion criteria were symptomatic ERM scheduled for vitrectomy. We excluded eyes with membranes secondary to other pathologies such as retinal detachment, laser photocoagulation, or vascular occlusion and also excluded patients with previous ocular surgery (except noncomplicated cataract surgery performed at least 12 months before the beginning of the study), coexisting age-related macular degeneration, nicotine abuse, diabetes or glaucoma, or refractive errors above +2 and −2 diopter before cataract surgery. We obtained institutional ethics committee approval (Centrum Zdrowia Matki Polki, Lodz, Poland) and the study complied with the Declaration of Helsinki. Patients were recruited from the authors’ outpatient department and signed informed consent for the study.

In all eyes we measured visual acuity (Snellen charts) and performed a complete ophthalmic examination and SS-OCT (DRI-Atlantis; Topcon, Tokyo, Japan) before surgery at 2 time points: 9–12 months and then 1 week before vitrectomy. Postoperatively, we examined the patients at 1 week, 6 months, and 12 months. In all cases, we performed a single line scan with a resolution of 1 μm, with a length of 12 mm. Focal central retinal thickness was measured manually as the distance between the internal limiting membrane (ILM) and the retinal pigment epithelium (RPE). Choroidal thickness was measured manually (by Z.M. and K.O.) on black-and-white images, between the line representing RPE (the outermost hyperreflective retinal layer) and the outer choroidoscleral boundary (the outer hyperreflective line of the choroid). The software included a caliper for manual measurements. Irregularities of the inner and outer plexiform layers were categorized as either striae or waves ( Figure 1 ). The extent of adhesion between ERM and the retina surface was categorized as either multiple adhesion points to the retina ( Figure 1 , Top; Figure 2 , Center top) or flat adhesion without evident anteroposterior traction ( Figure 1 , Top; Figure 3 ). Additionally, we analyzed the visibility of the suprachoroidal space ( Figure 3 ), the regularity of the outer choroidoscleral boundary (regular vs irregular) ( Figure 4 ), defects of the photoreceptors, and central hyperreflective deposits ( Figure 1 , Bottom, star). We used SigmaStat (Systat, London, UK) for Windows for statistical analysis.

Hyperreflective striae (A) vs hyperreflective waves (B) of the outer plexiform layer in swept-source optical coherence tomography (SS-OCT) in idiopathic epiretinal membranes. (A-Top) SS-OCT of an 82-year-old man with idiopathic epiretinal membrane. Visual acuity was 0.52 logMAR (0.3 Snellen) before surgery and central retinal thickness was 388 μm. Hyperreflective striae are visible (arrows). These striae have similar reflectivity to outer and inner plexiform layers, but seem to infiltrate the nuclear layers. ONL = outer nuclear layer; OPL = outer plexiform layer. (B-Bottom) SS-OCT of a 41-year-old man with idiopathic epiretinal membrane. Visual acuity was 1 logMAR (0.1 Snellen) before surgery and central retinal thickness was 841 μm. Nasal to the fovea, hyperreflective striae are visible (arrows). These striae have similar reflectivity to plexiform layers, but seem to infiltrate the nuclear layers. Additionally, temporal to the fovea, the plexiform layers have a wavy, irregular contour. The white star indicates a subretinal hyperreflective deposit.

Swept-source optical coherence tomography of idiopathic epiretinal membrane with multiple adhesion points to the retina (black stars). The suprachoroidal layer is visible. (Upper) Twelve months before surgery. (Center top) One week before surgery. (Center bottom) One week after surgery. (Lower) Twelve months after surgery. OPL = outer plexiform layer; SCL = suprachoroidal layer.

Preoperative follow-up of a 67-year-old woman with idiopathic epiretinal membrane with flat adhesion to the retinal surface. (Top) Swept-source optical coherence tomography 12 months before surgery. Visual acuity was 0.15 logMAR (0.7 Snellen). Striae at the outer border of the outer plexiform layer are visible (box). (Bottom) Swept-source optical coherence tomography 1 week before surgery. Visual acuity decreased to 0.82 logMAR (0.15 Snellen). No photoreceptor defects are observed. Striae at the outer border of the outer plexiform layer progressed and formed waves. Irregularities of the inner plexiform layer are seen (box). The enlarged box presents suprachoroidal layer (SCL) and suprachoroidal space (SCS). OPL = outer plexiform layer; ONL = outer nuclear layer; IPL = inner plexiform layer; INL = inner nuclear layer.

Swept-source optical coherence tomography in idiopathic epiretinal membranes in 2 eyes: (Right column) eye with an irregular choroidoscleral boundary; and (Left column) eye with a regular outer choroidoscleral boundary. (Upper images) Twelve months before surgery; (Center top images) 1 week before surgery; (Center images) 1 week after surgery; (Center bottom images) 6 months after surgery; (Bottom images) 12 months after surgery.

Surgical Technique

Two experienced surgeons (J.N., Z.M.) performed all of the operations. Core vitrectomy and Membrane Blue Dual staining (0.06% solution for 1 minute) were performed. ERM peeling within the vascular arcades followed. Then, a second staining was performed for 30 seconds. If present, the second layer of the ERM was then peeled. If not, the ILM was grasped with ILM forceps and peeled off in a circular fashion ( Supplemental Video , available at AJO.com ). In cases of multilayered membranes, staining was applied until the ILM was peeled. No tamponade was used in any case.