Epimacular membrane

Introduction to the macular anterior membrane The vascular fibroproliferative membrane on the inner surface of the retina occurs in the macular epiretinal membrane, which is called the macular epiretinal membrane. Among them, there is no exact cause, called the macular anterior membrane patient. Occurs in rhegmatogenous retinal detachment and its reduction surgery (such as photocoagulation, condensation, electrocoagulation, intraoperative or postoperative bleeding, postoperative uveal inflammatory response), chorioretinal inflammation, retinal vascular occlusion, diabetic retinopathy, ocular trauma , glass volume of blood, said secondary macular anterior membrane. Common symptoms of the macular anterior membrane are decreased vision, blurred vision, visual distortion, and monocular diplopia. Early symptoms can be asymptomatic. Visual acuity changes can occur when the macular anterior membrane affects the fovea of the macula, usually mild or moderate, rarely below 0.1. When the macular edema folds, it can cause significant vision loss or visual distortion, and the Amsler checklist can detect visual distortion. When the vitreous body completely detaches and the macular membrane is separated from the retina, the symptoms can be relieved by itself and the vision is restored, but this is rare. Surgical indications and timing of surgery: There is no uniform standard for surgical treatment of the macular anterior membrane. Surgery depends on the patient's symptoms, the degree of vision loss, vision requirements, whether it is accompanied by other diseases of the eye, age, and contralateral eye conditions. basic knowledge The proportion of illness: 0.001% Susceptible people: no specific population Mode of infection: non-infectious Complications: retinal detachment

Cause of macular epiretinal membrane

Causes

The cause of the macular anterior membrane is unknown. The essence of the membrane is composed of cells derived from the retina and various derivatives or metabolites thereof. According to clinical and cytological studies, the formation of the primary macular anterior membrane is mainly related to the posterior vitreous detachment and the migration of cells from the retina to the macular area, which can form a fibrous membrane with contractile ability.

Cell migration factors (55%):

The cells and extracellular components of the macular membrane were analyzed by immunohistochemistry and electron microscopy. The main cellular component in the primary macular epiretinal membrane is the Müller cells, which traverse the intact inner limiting membrane. This is followed by pigment epithelial cells, which may have the ability to cross the non-porous retina or migrate through the peripheral fine pores to the inner surface of the retina. Other cells include fibroblasts, myofibroblasts, glial cells, clear cells, pericytes, and macrophages, which may be derived from the retinal blood circulation, and some belong to the cell components of the vitreous itself. Extracellular matrices (such as fibronectine, vitronectin, and thrombospondine, etc.) are derived from plasma at the blood-retinal barrier lesion or by pigment epithelium that migrates to the surface of the retina. Preretinal cells are connected to each other by these substances and form fibrous membrane tissue. The contraction of myofibroblasts can cause contraction of the membrane, thereby pulling the retina, causing a series of pathological changes and clinical symptoms. The treatment of the macular anterior membrane is not good. Blind danger.

Pathogenesis

1. The role of posterior vitreous detachment in the formation of macular anterior membrane. The incidence of posterior vitreous detachment (PVD) in elderly people over 65 years old is more than 60%, from 60 to 70 years old, the incidence rate is 20 % increased to 52%. In patients with macular epiretinal membranes, posterior vitreous detachment is the most common ocular accompanying change, with an incidence of 57% to 100%, mostly complete posterior vitreous detachment. Also in patients with posterior vitreous detachment, the incidence of macular anterior membrane is also high. It is speculated that when the vitreous is detached, the local retinal anatomy changes accordingly, making the retina more susceptible to damage. When the vitreous body is detached, traction is generated on the posterior pole portion, and the weak region of the inner limiting membrane is pulled by this, which is liable to cause damage, which is the beginning of cell proliferation on the surface of the retina and formation of the macular epiretinal membrane. If the vitreous body is incomplete and the detachment persists, it will cause continuous vitreous macular traction, resulting in macular damage such as cystoid macular edema.

Although posterior vitreous detachment is closely related to the anterior macular membrane, there is still a considerable part of the macular anterior membrane patient with no posterior vitreous detachment. The relationship between the occurrence of the macular anterior membrane and posterior vitreous detachment needs to be explored.

2, cell migration and the development of the macular anterior membrane, it is generally believed that glial cells originate from the inner layer of the retina, through the damage of the inner limiting membrane to the inner surface of the retina, and along the surface of the retina, and migrate to the periphery. From an anatomical point of view, the inner limiting membrane on the surface of the optic disc and the large blood vessel is relatively weak, which is prone to breakage and provides a passage for the migration of glial cells. Under electron microscopy, it can be observed that the proliferative macular epiretinal tissue directly continuates with the inner membrane rupture, confirming this theory.

Another cell component of the macular membrane - retinal pigment epithelial cells may migrate to the inner surface of the retina by:

(1) Entering the inner surface of the retina through a subclinical retinal tear or autistic retinal tear.

(2) Retinal pigment epithelial cells may be transformed from glial cells.

(3) Various physical and chemical factors in the vitreous produce chemotaxis to retinal pigment epithelial cells, so that they can complete trans-retinal migration. Under the influence of various factors in the vitreous cavity, the retinal pigment epithelial cells undergo morphological changes, and the outer layer of the retina migrates to the inner surface of the retina through cell deformation. Retinal pigment epithelial cells can release chemokines and attract astrocytes.

(4) In addition, there may be resting primitive retinal pigment epithelial cells on the inner surface of the retina, which are activated by various factors.

3. The pathophysiological changes of the retina caused by the macular anterior membrane. The observation under the electron microscope confirmed that the contraction of the cellular components in the anterior macular membrane caused the retina to be pulled to form a anterior membrane with various shapes. The contraction of the macular anterior membrane is mainly in the tangential direction of the retina, so the chance of causing cystoid edema of the macula is small. If the macular anterior membrane is accompanied by vitreous macular traction, it is prone to macular cystic edema and even lamellar macular holes.

The fovea of the macula is pulled and will be deformed and displaced. Small blood vessels around the macula are pulled and compressed by the anterior membrane, resulting in dilatation, deformation, venous return disorder, and decreased capillary blood flow velocity, which may lead to vascular leakage and bleeding spots. Clinical symptoms such as deformation, enlargement or contraction, and visual fatigue may occur.

Macular anterior membrane prevention

Patients should be prevented from receiving radiation for a long time, especially long-wave ultraviolet rays, which may cause chronic lens damage, which may lead to age-related macular degeneration to accelerate the development of lesions. Therefore, patients should not be exposed to strong sunlight, light, and a variety of other radiation. When doing activities outside, wear sunglasses or a sun visor to prevent radiation from reaching your eyes.

Macular anterior membrane complications Complications

Thickening of the macular anterior membrane can cause retinal deformation, edema, small bleeding spots, cotton mottling and local serous retinal detachment.

Macular anterior membrane symptoms Common symptoms Visual impairment Visual distortion Double vision

symptom

Common symptoms of the macular anterior membrane are decreased vision, blurred vision, visual distortion, and monocular diplopia. Early symptoms can be asymptomatic. Visual acuity changes can occur when the macular anterior membrane affects the fovea of the macula, usually mild or moderate, rarely below 0.1. When the macular edema folds, it can cause significant vision loss or visual distortion, and the Amsler checklist can detect visual distortion. When the vitreous body completely detaches and the macular membrane is separated from the retina, the symptoms can be relieved by itself and the vision is restored, but this is rare.

The reasons for the visual function are affected by the following aspects: 1 The opaque macular anterior membrane blocks the fovea. 2 The retina of the macula is deformed by traction. 3 macular edema. 4 local retinal ischemia due to traction of the macular anterior membrane. The severity of the symptoms is related to the type of macular anterior membrane. If the macular anterior membrane is relatively thin, 95% of the eyes can maintain a visual acuity of 0.1 or more, usually around 0.4.

Sign

The ocular changes in the macular anterior membrane are mainly in the macula of the fundus. Most cases are accompanied by complete or incomplete detachment of the vitreous. In addition, the macular anterior membrane occurs mostly in the elderly, often with varying degrees of lens opacity or lens nucleus hardening.

In the early stage of the disease, the macular anterior membrane is a transparent membrane tissue attached to the surface of the retina, which appears as a silky, scintillating or drifting retinal light reflection in some areas of the posterior pole. The local retina below is slightly edematous and thick, and sometimes the projection of large blood vessels on the surface of the retina on the retinal pigment epithelial layer can be seen by oblique light. At this time, the fovea of the macula is generally not invaded, and does not affect vision.

When the macular anterior membrane tissue is thickened and contracted, the retina can be pulled to form wrinkles on its surface. These wrinkles have different shapes and can be expressed as slender linear stripes which are radially dispersed by one or more centers. It can also be expressed as irregularly arranged broadband stripes. The thickened macular anterior membrane gradually changes from an early translucent to an opaque or grayish white, crawling on the surface of the retina in a lumpy or strip shape. It is sometimes seen that these strips leave the retina, are suspended in the posterior space of the vitreous, or are bridged to the surface of the retina at a distance.

After the retina is pulled, the small blood vessels of the radial arch of the optic disc are deformed and distorted, and even the vascular arch is concentrically contracted, and the area of the macular avascular area is reduced. In the advanced stage, the great retinal veins may become dark, dilated or deformed. Sometimes the macula retina can also see tiny cotton spots, bleeding spots or microaneurysms. If the macular anterior membrane is centered, its traction will cause the macular area to shift. If the thickened macular anterior membrane is incomplete, a pseudo-macular hole can be formed, and the defect has a dark red appearance.

Most macular anterior membranes are confined to the optic disc and vascular arch, and in very few cases they can extend beyond the vascular arch and even reach the equator.

Macular anterior membrane examination

1, FFA inspection

FFA can clearly show the morphology of the macular arch in the macular area, the deformation and distortion of small blood vessels, and the abnormally strong fluorescence, fluorescent obscuration or spot-like, irregular fluorescent leakage from the lesion.

In the early stage of the macular anterior membrane, there is only cellophane or silk-like reflection in the fundus, and no changes in the retina are caused by traction. At this time, there is no obvious abnormal change in fluorescein angiography. Translucent fluorescence caused by RPE damage can sometimes be found.

With the development of the disease, the retina of the macula is pulled and a series of pathophysiological changes appear. The main manifestations of fluorescein angiography are:

(1) The small blood vessels in the macular area are pulled by the anterior membrane of the macula, and the snakes are twisted or straightened. The macular arch ring becomes smaller, deformed or displaced. According to the degree of vascular grafting, Maguire et al. classified the fundus fluorescein angiography of the macular anterior membrane into 4 grades, representing the affected vessels as 1 quadrant, 2 quadrants, 3 quadrants and 4 quadrants. There are few abnormalities in the large blood vessels of the retina.

(2) In the progressive development of the macular anterior membrane, the vascular barrier is impaired due to the pulling of the membrane, dye leakage occurs, and sometimes membrane staining is observed.

(3) There is a star or petal-like leakage in patients with cystoid macular edema. Due to the traction of the macular area, cystoid edema of the macula is more atypical and exhibits irregular fluorescence accumulation.

(4) If the anterior membrane of the macula is thick, it can show different degrees of fluorescent occlusion. In rare cases, the local superficial retina is accompanied by tiny bleeding spots, which also appear as fluorescent obscuration.

2, OCT inspection

Optical coherence tomography is a new type of non-contact, non-invasive tomography developed in the 1990s. It is measured by light reflection and its axial resolution is up to 10 m, which can show the microscopic morphology of the posterior segment of the eye, similar to the pathological observation of living tissue. OCT examination of the macular anterior membrane is very intuitive and accurate. The display rate is over 90%. It can diagnose the opaque transparent macular anterior membrane, provide the characteristics of the macular anterior membrane and its deep retinal section, and analyze the location and shape of the macular anterior membrane. Thickness and relationship with the vitreous of the retina to determine the presence of cystoid macular edema, full-thickness, lamellar or pseudo-macular hole, and the presence of shallow detachment of the macular area.

The diagnosis of the macular anterior membrane can be confirmed by OCT examination, especially in the early clinical manifestations. OCT can show the macular anterior membrane when the fundus examination only shows hyelinosis. In the OCT inspection, its main performance is:

(1) A medium-high-enhanced and widened light band connected to the inner layer of the macula, sometimes the anterior membrane and the inner surface of the retina are widely adhered and it is difficult to distinguish the boundary, and sometimes it may be agglomerated to the vitreous cavity.

(2) thickening of the retina, if accompanied by macular edema, it can be seen that the fovea sag becomes shallow or disappears.

(3) If the macular anterior membrane is surrounded by the fovea, a concentric contraction occurs, and the fovea has a steep or narrow shape, forming a pseudo-macular hole.

(4) If the neuroepithelial layer is partially missing, a lamellar macular hole is formed. The thickness of the macular anterior membrane can also be quantitatively measured by OCT examination. Wilkins et al. measured 169 eyes of the macula anterior membrane with an average thickness of (61 ± 28) m.

3, visual field examination

Visual field examination As a psychophysical examination method, the early changes of macular diseases can be accurately reflected by measuring the macular threshold. With the automatic perimeter, the corresponding regional light sensitivity analysis can be performed according to the range of macular lesions. The early macular anterior membrane may have no visual field abnormalities, and most of the late visual field changes have different degrees of light sensitivity decrease. Using the fluctuation of light sensitivity and light threshold, the visual function of the macular anterior membrane and the surgical effect can be evaluated.

4, visual electrophysiological examination

Visual electrophysiological examinations commonly used to determine macular function include clear electroretinogram, scotopic red light and bright red electroretinogram, scintillation electroretinogram, local macular electroretinogram, multifocal retina Electrogram (multifocal electroretinogram, mfERG), visual evoked potential, etc. Among them, the multifocal electroretinogram has the characteristics of objective, accurate, localized and quantitative, and can more accurately, sensitively and quickly determine the visual function within 23° of the posterior pole retina. The macular epiretinal has little effect on the electrical activity of the retina. Early visual electrophysiological examinations generally have no obvious abnormalities. Late local macular electroretinograms and multifocal electroretinograms may have different amplitudes. It is thought that it may be related to the traction of the macular anterior membrane to the retinal tissue, causing the orientation of the cone cells to change and the transparency of the refractive interstitial to decrease. These two tests, as objective and more sensitive indicators for evaluating visual function, are important for analyzing disease progression and surgical outcomes.

5, the composition of the cell fibrotic retinal membrane

It is mainly composed of cellular components and collagen fibers produced by these cells.

(1) Cellular composition: All studies to date have confirmed that the cellular components of the anterior membrane are multi-sourced. The simple preretinal membrane, glial cells are the most important cellular components. The cellular components of the composite preretinal membrane are much more complex, including glial cells, pigment epithelial cells and fibroblast-like cells, as well as vitreous cells, inflammatory cells and macrophages. Identifying cells in a proliferating membrane is sometimes very difficult even with an electron microscope, and therefore it is sometimes necessary to identify it by immunohistochemistry. The main cell morphology features are briefly described as follows:

1 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 stellate glial cells, both of which are large in size. Müller cells have an angular nucleus with dense nuclear chromatin, polar, cytoplasmic processes, microvilli and basement membrane. The cytoplasm is rich in cytoplasmic intermediate filaments (10 nm) and may also have microfilaments. In addition, the smooth endoplasmic reticulum, glycogen, free ribosome, mitochondria and Golgi apparatus can be seen. Stellate glial cells have an elliptical nucleus with long cytoplasmic processes. The basement membrane is visible around the blood vessels. The main organelles and abundant intermediate filaments are also visible in the cytoplasm, but the smooth endoplasmic reticulum is less than Müller cells.

2 Pigment epithelial cells: It is one of the main cellular components in the composite preretinal membrane, especially for rhegmatogenous retinal detachment, which is considered to be the most important cellular component.

(2) Intercellular substance: The intercellular substance of the cell fibrotic preretinal membrane mainly contains a large number of collagen fibers having a diameter of 20 to 25 nm, which is about 1 times thicker than normal vitreous collagen fibers. Therefore, it is thought to be produced by cells in the anterior membrane. Retinal pigment epithelial cells, glial cells and fibroblasts can 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 abundantly present 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 by plasma due to destruction of the blood-retinal barrier.

6, new blood vessels

In the vascular fibrotic epiretinal membrane, in addition to the cellular fibrotic retinal anterior membrane, there are many kinds of cellular components and collagen fibers, and there are many new blood vessels. Among the cellular components, glial cells are the most common. In addition, there are many spindle-shaped cells, which have homogeneous nuclear, cytoplasmic, eosin staining positive. There is a new blood vessel in the anterior membrane, which can be seen from the optic disc or other retinal parts. The retinal inner membrane and the posterior vitreous membrane of the new blood vessels can be seen to have a breach. The neovascularization is often dilated and its wall is thick. The surrounding vitreous is often concentrated and often adheres to the retina. The retina near the adhesion can be detached and atrophic. There is also more fibronectin present in the intercellular substance. The retinal tissue itself also has pathological changes in primary retinal diseases such as diabetic retinopathy and venous obstruction.

Diagnosis of macular epiretinal membrane

diagnosis

Diagnosis can be confirmed based on fundus changes and fundus angiography.

Differential diagnosis

Retinopathy: This disease is an arcuate, exudative chorioretinal lesion that occurs in and around the macula, accompanied by subretinal neovascularization and hemorrhage. Generally caused by capillary rupture, according to the bleeding site, can occur in the retina, pre-retinal and vitreous parts. Generally, it is caused by monocular disease, and the age is more than 50 years old. Retinopathy mainly occurs in photoreceptor cells and pigment epithelial cells.

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