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Ophthalmology > RETINA
Epimacular Membrane
Article Last Updated: Oct 27, 2008
AUTHOR AND EDITOR INFORMATION
Section 1 of 11  
Author: Kean Theng Oh, MD, Consulting Staff, Associated Retinal Consultants, PC
Kean Theng Oh is a member of the following medical societies: Alpha Omega Alpha, American Academy of Ophthalmology, American Society of Retina Specialists, and Association for Research in Vision and Ophthalmology
Coauthor(s):
Bradley M Hughes, MD, Assistant Professor, Department of Ophthalmology, Retina and Vitreous Service, University of Arkansas for Medical Sciences;
John H Drouilhet, MD, FACS, Clinical Professor, Department of Surgery, Section of Ophthalmology, University of Hawaii, John A Burns School of Medicine
Editors: V Al Pakalnis, MD, PhD, Professor of Ophthalmology, University of South Carolina School of Medicine; Chief of Ophthalmology, Dorn Veterans Affairs Medical Center; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Steve Charles, MD, Director of Charles Retina Institute; Clinical Professor, Department of Ophthalmology, University of Tennessee College of Medicine; Lance L Brown, OD, MD, Ophthalmologist, Affiliated With Freeman Hospital and St John's Hospital, Regional Eye Center, Joplin, Missouri; Hampton Roy Sr, MD, Associate Clinical Professor, Department of Ophthalmology, University of Arkansas for Medical Sciences
Author and Editor Disclosure
Synonyms and related keywords:
epimacular membrane, EMM, epiretinal membrane, cellophane maculopathy, preretinal macular gliosis, preretinal macular fibrosis, macular pucker, preretinal vitreous membranes, epiretinal astrocytic membranes, surface wrinkling maculopathy, internoretinal fibrosis, silk-screen retinopathy
Background
Epimacular membranes (EMMs) are collections of collagenous cells that occur on the inner surface of the central retina. These membranes have contractile properties and can lead to visual changes and metamorphopsia because of their effect on the underlying retina.
This ocular pathology was first described by Iwanoff in 1865, and it has been shown to be a relatively common entity, occurring in about 7% of the population. EMMs have been called a variety of names, including epiretinal membranes, cellophane maculopathy, preretinal macular gliosis, preretinal macular fibrosis, macular pucker, preretinal vitreous membranes, epiretinal astrocytic membranes, surface wrinkling maculopathy, internoretinal fibrosis, and silk-screen retinopathy; all of which pertain to clinico-anatomic descriptions of pathologic findings produced by EMMs of varying severity and differing morphologic characteristics. EMMs can be associated with a variety of ocular conditions, such as posterior vitreous detachments (PVD), retinal tears, retinal detachments, retinal vascular occlusive diseases, ocular inflammatory diseases, and vitreous hemorrhage. However, a large proportion does not occur in the context of any associated disease or known history and therefore are classified as idiopathic epimacular membranes (IEMM). Idiopathic and postdetachment membranes are the most common EMMs and, as such, will be the focus of this article. See related CME at Retinal Disease.
Pathophysiology
EMMs are avascular, fibrocellular membranes that proliferate on the surface of the retina and can lead to varying degrees of visual impairment. These cells, once in contact and attached to the retina, may proliferate and form sheets of membranes over the surface of the retina. Through their contractile properties, the underlying retina is, in turn, distorted. The effect on vision is variable and determined by the severity of the distortion, the location, and other secondary effects on the retina. The source of the cells producing these membranes has been the source of great debate. Earlier reports proposed that glial cells (primarily fibrous astrocytes) from the inner layers of the neurosensory retina proliferated through breaks in the internal limiting membrane (ILM) produced after a retinal tear or a posterior vitreous detachment. Modern vitrectomy specimens have shown that epiretinal membranes comprise glial cells, retinal pigment epithelial cells, macrophages, fibrocytes, and collagen cells. These cells are found in varying proportions in accordance with the etiology of the membrane. Membranes associated with retinal breaks, previous retinal detachments, or cryopexy are composed mainly of dispersed RPE cells, while cells of glial origin predominate in the IEMM. Furthermore, these cells also possess the ability to change into cells with similar appearance and function. The incidence of associated PVD in cases of IEMM range from 75-93%, and PVD is present in virtually all eyes with retinal breaks or retinal detachments and subsequent EMM formation. It has been suggested that PVD may contribute to EMM formation in many ways. PVD can lead to retinal breaks that may liberate RPE cells that initiate membrane formation. Small breaks in the ILM after PVD also may provide retinal astrocytes access to the vitreous cavity, where they may subsequently proliferate. Finally, vitreous hemorrhage, inflammation, or both associated with a PVD also may stimulate EMM formation. EMM formation without PVD may predispose patients to vitreomacular traction syndrome (VMT). Chang et al evaluated patients with VMT using a spectral-domain ocular coherence tomography (SD-OCT) and ultrastructural correlation using samples obtained during surgery.1 They were able to document fibrocellular proliferation between the inner surface of the retinal and posterior surface of the vitreous, resulting in increased vitreoretinal adhesion.1 Bovey and Uffer observed a phenomenon of ILM tearing associated with EMM.2 They hypothesize that the presence of ILM tears and folds are more likely when the EMM forms prior to a posterior vitreous detachment, resulting in the subsequent cleavage plane being between the ILM and the inner retina rather than at the ILM surface.2
Frequency
United States
The frequency at which EMMs occur varies according to the underlying disease. The idiopathic variety of EMMs has been shown to be present in up to 7% of the population. Bilateral cases have been seen in as much as 30% of the population. Clinically significant EMMs occur in 3-8.5% of eyes after successful primary retinal detachment surgery. Patients noted to be at the greatest risk for EMMs are those with preoperative signs of proliferative vitreoretinopathy, including rolled retinal edges, star folds, and equatorial ridges. One study noted no significant difference in the frequency of EMMs in eyes that underwent subretinal fluid drainage compared to those that had nondrainage procedures. The possible risk of epimacular development in eyes that have undergone cryotherapy or laser photocoagulation for retinal tears is difficult to quantify because it is almost impossible to determine whether the cellular dispersion was caused by the retinal tear itself or the subsequent therapy for it. The incidence of EMM formation associated with other ocular pathologies, such as retinal vascular occlusive disease, ocular inflammation, or vitreous hemorrhage, is unknown.
Mortality/Morbidity
The visual loss depends on the severity of the distortion of the retina, the location of the wrinkling of the retina, and any other secondary effects of the membrane on the retina (eg, edema, hemorrhage).
Sex
Both sexes appear to be affected in relatively equal percentages.
Age
EMMs occur more frequently in the older population with postmortem studies showing 2% prevalence in individuals aged 50 years and as much as 20% prevalence in individuals aged 75 years.
History
The type and degree of symptoms experienced by the patient depends largely on the thickness of the membrane, the degree of retinal distortion it causes, the location of the wrinkling, and the presence or the absence of retinal detachment or edema.
- The usual symptoms caused by EMMs run the spectrum from no symptoms at all to severe visual dysfunction.
- Early on, EMMs cause little or no visual disturbance.
- As the membrane progresses, the visual disturbance is often vague and difficult for the patient to describe.
- Mild distortion or blurring is the most common symptom.
- Vision better than 20/50 is present in 78-85% of cases, while 56-67% have vision better than 20/30. Only 2-5% have vision poorer than 20/200.
- In more advanced cases, metamorphopsia, micropsia, or Amsler Grid abnormalities may be present.
- In contrast, vision is markedly reduced in patients with EMMs associated with retinal detachment. Vision is 20/60 or better in only 7% of cases and 56% have vision poorer than 20/200 after successful retinal reattachment surgery.
Physical
The clinical findings in EMMs vary according to the degree of severity of the membrane. Gass formulated a classification system based on the appearance of the membrane and the underlying retinal tissue and vessels. - Grade 0 membranes
- Grade 0 EMMs are translucent membranes not associated with any retinal distortion.
- These EMMs also are known as cellophane maculopathy owing to the cellophanelike sheen coming from the inner retinal surface as it is seen ophthalmoscopically.
- Grade 1 membranes
- Membranes causing an irregular wrinkling of the inner retinal surface are classified as grade 1 EMMs.
- The crinkled cellophane appearance is caused by the gathering of the inner retinal layers into folds following the contraction of the overlying membrane.
- Fine, superficial, radiating folds extend outward from the margins of the contracted membrane.
- Wrinkling may be sufficient to produce tortuosity of the paramacular vessels pulling them toward the fovea.
- Cystoid macular edema, retinal hemorrhage, exudates, and RPE disturbances are typically absent.
- Grade 2 membranes
- Membranes, especially those that develop after retinal detachment surgery, have an opaque, thick appearance.
- Gross, full-thickness puckering of the macula may be present along with retinal edema, small hemorrhages, cotton-wool spots, and, infrequently, a localized detachment of the retina.
- These membranes are labeled macular puckers or grade 2 membranes.
- Pseudoholes
Causes
See Pathophysiology.
Retinal Detachment, Tractional
Other Problems to be Considered
Retinal vascular occlusive diseases
Posterior uveitis
Cystoid macular edema
Imaging Studies
- Fluorescein angiography
- Performing an angiogram in cases of EMMs does not contribute anything significant in its diagnosis since the clinical picture is often specific enough. In less advanced cases, the angiographic picture is basically unremarkable. More significant findings, such as vessel tortuosity and macular edema, may be seen in more advanced cases.
- Perform fluorescein angiography to rule out other lesions that may mimic EMMs.
- Macular holes typically show early background fluorescence through the hole that disappears in the later phases.
- EMMs with pseudoholes typically do not exhibit this fluorescence since normal retinal tissue exists in the area.
- An exudative macular degeneration also may mimic the appearance of an EMM, but its angiographic picture of early fluorescence and leakage is easily distinguishable from EMMs.
- Fluorescein angiograms of EMMs can reveal subtle leakage of the perifoveal capillaries or evidence of ischemia due to capillary dropout, which can assist with counseling for postoperative expectations.
- Ocular coherence tomography
- Ocular coherence tomography (OCT) can elucidate the presence or absence of an EMM.
- OCT can objectively measure other effects of the EMM on the retina, such as macular thickening, presence or absence of macular edema (eg, cystoid macular edema), and any associated vitreous traction on the retina.
- OCT allows the monitoring of the postoperative return of the normal retinal architecture as well as the presence of persistent traction or folds of the retina.
- Gupta et al used combined OCT/scanning laser ophthalmoscopy (SLO) to evaluate 44 consecutive eyes with EMM.3
- Of the patients evaluated, 20 out of 44 demonstrated multiple foci of contracture within the EMM. They subdivided EMM into “simple puckers" and “complex puckers.”
- Complex puckers had a higher rate of intraretinal cysts and macular thickening than simple puckers.
- However, no difference in visual dysfunction existed between the two groups; the authors hypothesize that architectural differences in the retina may precede visual acuity loss.
Surgical Care
Isolate EMM as the main cause of a patient's visual impairment prior to planning a corrective procedure. Evaluate the patient carefully to rule out other pathologic conditions, such as macular holes, subfoveal choroidal neovascular membranes, cystoid macular edema, or retinal vascular occlusive disease, that may mimic the appearance of a true membrane. Surgical treatment of EMM is usually not an emergent procedure. Only when there is macular edema does it become a more urgent procedure. Several surgical techniques exist for the treatment of EMM. However, 3 basic stages of treatment exist. - Vitrectomy
- Pars plana vitrectomy is performed to excise the posterior and central vitreous in phakic patients and the remainder of the anterior vitreous in aphakic and pseudophakic patients. This step is especially important in cases where marked adherence of the vitreous to the macula is present.
- Lately, questions have been raised regarding the need for vitrectomy in EMM peeling, especially in those cases where no significant PVR exists.
- The main advantages of doing a vitrectomy are the prevention of vitreous contraction and elimination of vitreous traction on the macula. In addition, removal of the vitreous is believed by many to increase the safety of the mechanical aspects of the membrane removal.
- The main disadvantages of vitrectomy include cataractogenesis and increased possibility of creating iatrogenic retinal breaks. Vitrectomy has been shown to increase the rate of cataract formation through unclear mechanisms.
- Studies have shown that a 3-fold increase in the rate of significant cataract formation exists in patients that have undergone vitrectomy after a follow-up period of only 6 months.
- Some surgeons feel that the effectiveness of membrane peeling is negated significantly by the cataract formation such that they have foregone vitrectomy in selected cases, opting to perform no-infusion/no-vitrectomy membrane peelings. The main disadvantage of this technique is the persistence of floaters postoperatively, which may be very bothersome to some patients. Furthermore, some surgeons have seen no significant difference in either cataractogenesis or development of retinal breaks/detachments in their series comparing vitrectomizing and nonvitrectomizing techniques.
- While the vitrectomy can be performed using the standard 20-gauge system, surgeons are also using smaller gauge vitrectomy systems (eg, 23 gauge, 25 gauge) for surgical management of EMM.4, 5 These systems are transconjunctival with the potential to create self-sealing wounds. Complications appear low while affording the potential for more rapid surgical and visual recovery.
- Epiretinal membrane peeling
- From the time Machamer developed the concept of membrane peeling in the mid 1970s, several variations and refinements in both technique and instrumentation have been developed.
- This procedure basically involves identifying the outer edge of the membrane and creating a dissection plane with the use of a blunt-tipped pick or a bent needle.
- Once the edge of the membrane is seen, it may be gently lifted off the retinal surface with the use of a pick or fine forceps.
- The membrane should be lifted in a tangential rather than an anteroposterior fashion so as not to pull on the underlying retina and create tears. This maneuver is relatively straightforward if the edge of the membrane is visible.
- Charles developed a maneuver that approaches the membrane from inside out in cases where the edge is difficult to identify.6 It involves creating a slit on the thickest part of the membrane with a straight microvitreoretinal blade and using this opening as the edge with which to start the peeling. The peeling is performed moving the forceps in a circular fashion similar to capsulorrhexis. The freed membrane should be removed either by pulling it out with the forceps through the sclerotomy or by using the vitreous cutter.
- Internal limiting membrane (ILM) peeling
- Removal of the ILM at the time of EMM peeling is a current controversy.
- Vital stains, such as indocyanine green (ICG) dye and Trypan blue dye, have been used to assist ILM and EMM peeling. Dyes that stain the ILM highlight foci of EMM and potentially reduce the risk of recurrence or the persistence of symptoms.
- Similar to its use in macular hole surgery, the use of ICG has proponents and detractors on the basis of its potential toxic effects. Haritoglou et al suggested that ICG-assisted ILM peeling may adversely affect the functional outcome of surgery for EMM.7
- Hillenkamp et al prospectively evaluated the effect of ICG dye in the setting of EMM surgery.8 No difference or evidence of ICG toxicity was observed. Both visual function and macular morphology improved in patients with and without ICG dye use.
- However, Garweg et al suggested that ILM peeling with ICG dye, but not with trypan blue dye, may result in loss of the central visual field over time.9 No difference in visual acuity was noted. This study suggests that the ICG dye, not necessarily the ILM peeling, may have an adverse effect following EMM surgery.
- Management of retinal breaks
- Once the membrane is removed, it is imperative for the surgeon to look for any breaks in the retina, both in the posterior pole and in the periphery.
- Any maneuvers completed to remove the membranes, no matter how elegant, become irrelevant if the retina detaches because of missed breaks.
- Careful scleral depression of the anterior retina combined with indirect ophthalmoscopy should be performed to detect breaks in the periphery.
- Breaks without subretinal fluid accumulation can be treated by laser retinopexy or cryoretinopexy.
- The presence of significant amounts of subretinal fluid necessitates internal drainage under air, retinopexy, and gas tamponade.
Further Outpatient Care
- It is important to monitor patients long term because of reoccurrence of the condition.
Complications
- Intraoperative
- The most frequently encountered intraoperative complications with vitrectomy and membrane peeling include intraocular bleeding and the development of retinal breaks.
- Petechial hemorrhage along the internal retinal surface may be seen as the membrane is peeled off the retina but usually resolves within days of the operation.
- More significant bleeding is encountered when an underlying vessel is damaged as a strongly adherent membrane is being peeled. This bleeding usually can be controlled by raising the intraocular pressure temporarily and waiting for the vessel to stop bleeding spontaneously or by applying cautery on the offending vessel.
- The development of retinal breaks is the most important intraoperative complication that may be encountered. The incidence of intraoperative posterior pole breaks ranges anywhere from 0-15%, while that of peripheral breaks ranges from 5-6%.
- Meticulous peeling of the membrane and careful examination of the peripheral retina are the most effective means to minimize postoperative problems associated with these retinal breaks.
- Postoperative
- The most frequent postoperative complication that may be seen is the accelerated progression of nuclear sclerosis of the lens, which may occur in as many as 75% of eyes over time.
- Most patients have to undergo cataract extraction within 2 years to maximize the benefits afforded by membrane peeling.
- Postoperative retinal detachment may be caused either by a missed break or by a new break that developed after further contraction of the remaining anterior vitreous. This detachment happens in 3-6% of patients and nearly always is treated successfully by another operation.
- Recurrence of EMM happens in less than 5% of idiopathic cases but may be higher for postdetachment and postinflammatory cases.
Prognosis
- Numerous studies have addressed the potential benefit of surgery to remove the EMMs. These studies have looked at the quantification of the postoperative visual acuity improvement as well as the subjective improvements through postoperative quality of life questionnaires. They have also looked at other prognostic factors that may influence visual outcomes.
- Surgical removal of clinically significant EMMs usually results in improvement in both visual acuity and biomicroscopic appearance of the retina. Studies have shown that, postoperatively, 78-87% of patients with IEMM and 63-100% of patients with postdetachment membranes improved at least 2 Snellen lines. Patients with poorer preoperative vision tended to improve the most, but those patients with better preoperative vision obtained the best final results.
- Visual acuity has also been evaluated through the use of postoperative questionnaires. A large-scale study showed that surgery improved the symptom of distortion the most, with moderate-to-severe symptoms most improved. Improvement was also seen in other daily tasks, such as reading small print.
- Sometimes, however, the metamorphopsia may persist despite improvement in visual acuity. This is seen mostly in cases where there is incomplete peeling of the membrane. On the other hand, there are cases wherein the distortion is improved but the Snellen acuity remains unchanged. This mainly is encountered in cases where there is long-standing macular edema.
- The presence of new or accelerated cataract formation has been shown to occur in the surgical treatment of EMMs.
Medical/Legal Pitfalls
- Informed consent for surgery
- It should be emphasized that vitrectomy and membrane peeling for EMMs, idiopathic or otherwise, does not guarantee full visual recovery. Roughly 80% of cases do have at least a 2 Snellen line improvement, but this also depends on the duration and the severity of the membrane.
- Special mention of possible postoperative complications should likewise be emphasized, such as cataract progression, retinal breaks and detachment, and endophthalmitis.
The authors and editors of eMedicine gratefully acknowledge the contributions of previous author, Sherman O Valero, MD, to the development and writing of this article.
| Media file 1:
Grade 2 epimacular membrane causing striations in the retinal surface. Note the presence of a pseudohole. |
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| Media file 2:
Fluorescein angiogram demonstrating retinal vascular distortion. Note the leakage of the dye in the macular area, which represents secondary macular edema. |
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| Media file 3:
Very dense epimacular membrane with associated macular distortion. |
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Epimacular Membrane excerpt Article Last Updated: Oct 27, 2008
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