What Is Epiretinal Membrane?

Membrane preretinal membrane is an age-related proliferative disease, which is manifested by secondary changes caused by the formation of the macular preretinal membrane and its contraction. Most patients are asymptomatic, and a few have slowly progressing visual impairment.

Anterior retinal membrane

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Membrane preretinal membrane is an age-related proliferative disease, which is manifested by secondary changes caused by the formation of the macular preretinal membrane and its contraction. Most patients are asymptomatic, and a few have slowly progressing visual impairment.

nickname

Idiopathic macular anterior membrane,

Common locations

eye

Common symptoms

Decreased vision, reduced vision, deformed vision, and diplopia

Nature

Age-related proliferative disease

Preretinal membrane, alias: idiopathic macular anterior membrane, idiopathic macular anterior membrane, idiopathic macular anterior membrane, idiopathic premacular fibrosis, primary retinal folds.

(I) Cause of the disease 1. The cause of the disease is unknown. The nature of the membrane is caused by

1. Symptoms Common symptoms of anterior retinal membrane include decreased vision, reduced vision, deformed vision, and diplopia. The disease may be asymptomatic early. Visual changes can occur when the premacular membrane affects the foveal fovea, usually with a slight or moderate decline, rarely less than 0.1. When the macular edema and wrinkles appear, it can cause obvious vision loss or visual deformation. Amsler grid table can detect visual deformation. When complete vitreous detachment occurs and the premacular membrane separates from the retina, symptoms can resolve on their own and vision is restored, but this is rare.
The reasons for the affected visual function include the following aspects: cloudiness of the anterior macula masking the foveal center; the retina of the macular region is deformed by traction; macular edema; ischemia due to traction of the anterior membrane. The severity of the symptoms is related to the type of premacular membrane. If the premacular membrane is thin, 95% of the eyes can maintain vision above 0.1, usually around 0.4.
2. Signs The ocular changes of the anterior retinal membrane are mainly in the fundus macular. Most cases are accompanied by complete or incomplete vitreous detachment. In addition, the idiopathic macular anterior membranes occur mostly in the elderly, and often have varying degrees of lens opacity or lens sclerosis.
In the early stages of the disease, the premacular membrane is a transparent membrane that attaches to the surface of the retina, manifesting as a silk-like, flickering, or drifting retinal light reflection in some areas of the posterior pole. The lower part of the retina is slightly edema and thickened, and sometimes the projection of large vessels on the surface of the retina onto the retinal pigment epithelium can be seen obliquely with slit light. At this time, the macular fovea is generally not invaded, and most of it does not affect vision.
When the premacular tissue thickens and contracts, the retina can be pulled to cause wrinkles on its surface. These wrinkles have different shapes, which can be represented by thin linear stripes that are scattered radially from one or more centers; they can also appear as irregularly arranged broad-banded stripes. The thickened premacular membrane gradually changes from an early translucent to opaque or off-white, crawling on the surface of the retina in a mass or band. Sometimes these bands can be seen leaving the retina, suspended in the posterior vitreous space, or adhered to the retinal surface in the form of a bridge.
After the retina is pulled, small vessels in the temporal vascular arch of the optic disc are deformed and distorted, and even the vascular arch is concentrically contracted, and the area of the macular nonvascular area is reduced. In the later stages, the great retinal veins can become darkened, dilated or deformed. Sometimes there are small cotton wool spots, bleeding spots, or microaneurysms in the retina of the macula. If the premacular membrane is off-center, its traction will cause the macular area to shift. If the thickened premacular membrane is incomplete, a pseudomacular hole can be formed, and the defect site has a dark red appearance.
Most of the premacular membranes are confined to the optic disc and vascular arch, and very few cases can go beyond the vascular arch and even reach the equator.
The diagnosis can be confirmed based on fundus changes and fundus angiography.

1. FFA examination FFA can clearly show the morphology of capillaries in the macular area, deformation and distortion of small vessels in the lesion, and abnormal strong fluorescence, fluorescent shielding or point-like, irregular leakage of fluorescence from the diseased area.
In the early stage of the idiopathic macular anterior membrane, the fundus showed only cellophane or silk-like reflections, and no changes caused by retinal traction had occurred. At this time, fluorescent angiography generally showed no obvious abnormal changes. See-through fluorescence from RPE damage is sometimes found.
With the development of the disease, the retina of the macular region is pulled and a series of pathophysiological changes appear. The main manifestations of fluorescent angiography are:
(1) The small blood vessels in the macula are stretched by the anterior membrane of the macula, meandering or straightening. The macular arch becomes smaller, deformed, or displaced. According to the degree of vascular traction, Maguire et al. Classified the fundus fluorescein angiography of the idiopathic macular anterior membrane into 4 grades, which represented the affected blood vessels in 1 quadrant, 2 quadrant, 3 quadrant, and 4 Quadrants. Large retinal vessels rarely show abnormalities.
(2) In progressive idiopathic macular anterior membrane, the vascular barrier is damaged due to the stretching of the membrane, dye leakage occurs, and membrane staining is sometimes seen.
(3) Those with macular cystoid edema show a star-shaped or petal-shaped leakage. Due to the traction of the macular area, the macular cystoid edema is more atypical and shows irregular fluorescence accumulation.
(4) If the premacular membrane is thick, it can appear as a different degree of fluorescent shielding. In rare cases, the local superficial retinal layer is accompanied by tiny hemorrhage spots, which also appear as fluorescent obscuration.
2. OCT optical coherence tomography is a new non-contact, non-invasive tomography technology developed in the 1990s. Measured by light reflection, its axial resolution is as high as 10µm, which can display the microscopic morphology of the posterior segment of the eye, similar to the histopathological observation of a living body. The OCT examination of the idiopathic macular anterior membrane is very intuitive and accurate, and the display rate is more than 90%. It can diagnose the thin and transparent macular anterior membrane, provide the characteristics of the macular anterior membrane and its deep retinal section, and analyze the premacular membrane. Location, morphology, thickness, and relationship to the retinal vitreous, determine the presence of macular cystoid edema, full-thickness, lamellar, or pseudomacular holes, and the presence of superficial detachment of the macula.
OCT examination can confirm the diagnosis of premacular membrane, especially in the early clinical manifestations are slight, only when the fundus examination only vitreous membrane-like reflection, OCT can show the premacular membrane. The main manifestations in OCT inspection are:
(1) The medium-high-enhanced and widened light band connected to the inner layer of the macular retina, sometimes the anterior membrane is widely adhered to the inner surface of the retina and it is difficult to distinguish the boundaries, and sometimes it can be convex to the vitreous cavity in a mass.
(2) Thickening of the retina, if accompanied by macular edema, it can be seen that the fovea depression becomes shallow or disappears.
(3) If the premacular membrane is concave around the center, a concentric contraction occurs, and the center fove has a steep or narrow shape, forming a pseudomacular hole.
(4) If part of the neuroepithelial layer is missing, a lamellar macular hole is formed. OCT examination can also quantitatively measure the thickness of the premacular membrane. Wilkins et al. Measured the anterior macular membrane in 169 eyes with an average thickness of (61 ± 28) µm.
3. Visual Field Examination As a method of psychophysical examination, visual field examination can accurately reflect the early changes of macular disease by measuring the macular threshold. With the automatic perimeter, the corresponding regional light sensitivity analysis can be performed according to the scope of the macular lesion. Early idiopathic macular anterior membrane may be free of visual field abnormalities, and late visual field changes are mostly reduced in light sensitivity to varying degrees. Using the fluctuations of light sensitivity and light threshold, the visual progress of the course of the idiopathic macular anterior membrane and the surgical effect can be evaluated.
4. Visual electrophysiological examinationsThe visual electrophysiological examinations commonly used to determine macular function include photopic electroretinograms, scotopic red light and photopic red light electroretinograms, scintillation electroretinograms, and local macular electroretinograms. , Multifocal electroretinogram (mfERG), visual evoked potential, etc. Among them, the multifocal electroretinogram has the characteristics of objectiveness, accuracy, localization and quantification, and can more accurately, sensitively and quickly determine the visual function within 23 ° of the posterior pole retina. Idiopathic macular anterior membranes have little effect on electrical activity of the retina. Early visual electrophysiological examinations generally show no significant abnormalities. Late local macular electroretinograms and multifocal electroretinograms may show varying degrees of amplitude reduction. It is thought that it may be related to the stretching of the retinal tissue by the premacular membrane, causing the arrangement of cone cells to change, and the decrease of the refractive interstitial transparency. These two tests, as objective and sensitive indicators for evaluating visual function, are of great significance for analyzing disease progression and surgical effects.
5. The composition of cell fibrous preretinal membrane is mainly composed of cell components and collagen fibers produced by these cells.
(1) Cellular components: All studies so far have confirmed that the cellular components of the anterior membrane are multigenic. In the simple preretinal membrane, glial cells are the most important cellular component. The cellular components of the complex anterior retinal membrane are much more complex, mainly including glial cells, pigment epithelial cells, and fibroblasts, as well as vitreous cells, inflammatory cells, and macrophages. It is sometimes difficult to identify cells in the proliferative membrane even with an electron microscope, so sometimes it is necessary to identify them by immunohistochemistry. The main cell morphological characteristics are briefly described as follows:
Glial cells: It is not only the main component of the simple anterior membrane, but also one of the most common cellular components in the composite anterior membrane. There are two types of glial cells, namely Müller cells and astrocytes, both of which are larger. Müller cells have horned nuclei, nuclear chromatin is dense, polar, with cytoplasmic protrusions, microvilli, and basement membranes. There are abundant cytoplasmic intermediate filaments (10nm) in the cytoplasm, as well as microfilaments. In addition, the endoplasmic reticulum, glycogen, free ribosome, mitochondria, and Golgi apparatus of the sliding surface can be seen. Astrocytes have elliptical nuclei, long cytoplasmic protrusions, basement membranes can be seen around blood vessels, and major organelles and abundant intermediate filaments can also be seen in the cytoplasm.
Pigment epithelial cells: It is one of the main cellular components in the composite preretinal membrane, especially for those with pore-derived retinal detachment, which is considered to be the most important cellular component.
(2) Intercellular substance: The intercellular substance of the cell fibrous preretinal membrane mainly contains a large number of collagen fibers with a diameter of 20 to 25 nm, which is about 1 times thicker than normal vitreous collagen fibers. It is thought to be produced by cells in the anterior membrane. Retinal pigment epithelium, glial cells, and fibroblasts can all synthesize collagen fibers. In addition, there are some proteins in the intercellular substance, the most important of which is fibronectin, which has been confirmed to be abundant in the anterior membrane by immunohistochemical staining. It plays an important role in promoting cell migration, cell recognition, contact, spread and aggregation. Fibronectin can be produced by cells in the anterior membrane of the retina, or it can be directly infiltrated into the anterior membrane tissue from plasma due to the breakdown of the blood-retinal barrier.
6. New blood vessels In the vascular fibrous preretinal membrane, in addition to the cell fibrous preretinal membrane, there are many cellular components and collagen fibers, as well as more new blood vessels. Among cell components, glial cells are the most common. In addition, there are also many spindle cells. It has a homogeneous nucleus, is rich in cytoplasm, and is eosinophilic. There are new blood vessels scattered in the anterior membrane, which can originate from the optic disc or other retinal parts. There can be cracks in the inner retinal membrane and vitreous posterior boundary membrane that the new blood vessels pass through. New blood vessels are often dilated and the walls are thick. The surrounding vitreous body is often concentrated and often adheres to the retina. The retina near the adhesion may have detachment and atrophic changes. There are also more fibronectin in the intercellular substance. The retinal tissue itself also has pathological changes in the primary retinal disease, such as diabetic retinopathy and vein occlusion.

Anterior retinal thickening can cause retinal deformation, edema, small bleeding spots, cotton wool spots, and local serous retinal detachment.

Indications and timing of surgery: There is no uniform standard for surgical treatment of the anterior retinal membrane. Whether or not the operation depends on the patient's symptoms, vision loss, vision requirements, whether accompanied by other eye diseases, age, and contralateral eye conditions.
The following situations can consider surgery:
1. Vision is 0.1 or below, without permanent macular damage.
2. Visual acuity of 0.4 or more, but with severe diplopia, deformed vision and other symptoms (for patients who require better visual effects, surgery can be attempted by a skilled surgeon).
3. Visual acuity is better, but fluorescein imaging shows fluorescein leakage or macular edema.
4. The macular anterior membrane after retinal detachment should be stabilized, and there can be no surgery before active contraction.

The prognosis of surgical treatment of the anterior retinal membrane is generally good. Factors that affect the prognosis include the irreversible damage of the macular pre-existing, obvious visual loss and / or deformation of the visual object, and the duration and presence of macular cystoid , The thickness of the membrane, the morphological characteristics of the membrane, whether there is damage during the operation, the degree of residual membrane, and whether there are postoperative complications.