Pigment Epithelial Detachment (PED) is commonly associated with various disorders of the retina, especially age-related macular degeneration (AMD). This condition involves the retinal pigment epithelium (RPE), a delicate layer of cells that sits beneath the light-sensing cells of the retina.
Understanding Pigment Epithelial Detachment
The RPE is a single layer of cells that performs many functions, including nourishing the retina and removing waste products. It rests on Bruch’s membrane, which acts as a barrier separating the RPE from the blood vessels of the choroid beneath it.
A Pigment Epithelial Detachment occurs when a collection of material separates the RPE from the underlying Bruch’s membrane. This separation creates a dome-like or blister-shaped elevation of the RPE layer. The contents of this raised area determine the specific type of PED and its implications for vision.
When a PED forms in the macula, the central part of the retina responsible for sharp, detailed vision, patients may notice changes in their sight. A common symptom is metamorphopsia, where straight lines, such as door frames or utility poles, appear wavy or distorted. Patients may also experience central blurring or a dim area in the middle of their vision.
Classifying the Types and Underlying Causes
The classification of a PED is based on the material accumulating under the RPE, which informs the prognosis and treatment strategy. In the context of AMD, three primary types of PED are recognized: serous, drusenoid, and fibrovascular.
A Serous PED is characterized by the presence of a clear, watery fluid that accumulates beneath the RPE, creating a smooth, domed elevation. This type of detachment is often seen in Central Serous Chorioretinopathy (CSR), particularly in younger patients, and may also occur as a feature of non-exudative (dry) AMD. In some cases, serous fluid accumulation is caused by leakage from abnormal blood vessels that have not yet fully broken through the RPE.
A Drusenoid PED is composed of soft, accumulated waste material, known as drusen, which builds up between the RPE and Bruch’s membrane. This type is strongly associated with dry AMD, resulting from the RPE’s failure to effectively process and eliminate cellular debris. The drusenoid material causes the RPE to elevate in a dome shape, which may eventually lead to vision loss through atrophy.
The Fibrovascular PED indicates the presence of new, abnormal blood vessels growing beneath the RPE, a condition called choroidal neovascularization (CNV). These new vessels are leaky, often causing a mixture of serous fluid, blood, and scar tissue to accumulate, linking this type to the “wet” or exudative form of AMD. The irregular, notched appearance of this detachment on imaging reflects the underlying neovascular membrane.
Modern Diagnostic Tools
Optical Coherence Tomography (OCT) is the non-invasive standard for visualizing the retina and is used for diagnosing and monitoring PEDs. This tool uses light waves to create high-resolution images that clearly show the separation of the RPE from Bruch’s membrane, allowing clinicians to measure the height and diameter of the detachment.
The internal characteristics seen on OCT help differentiate between the types, such as the clear space of a serous detachment versus the more reflective, homogenous material of a drusenoid one. Fluorescein Angiography (FA) is a supplementary test that involves injecting a dye into the bloodstream to highlight areas of leakage. For a serous PED, FA will show the dye pooling rapidly within the dome-shaped elevation.
Indocyanine Green Angiography (ICG) is another tool used to identify the underlying choroidal circulation, which is helpful in detecting CNV, especially in cases of fibrovascular PED. More recently, OCT Angiography (OCTA) has emerged, offering a non-invasive way to visualize blood flow within the retina and choroid. This allows for the detection of abnormal neovascular networks associated with fibrovascular PEDs without the need for injectable dyes.
Management and Treatment Strategies
The approach to managing a PED depends entirely on its classification and the presence of new blood vessel growth. For small, non-symptomatic Serous PEDs or stable Drusenoid PEDs, the initial strategy involves careful observation. Regular monitoring with OCT is performed to watch for changes in size, height, or the development of CNV.
If a PED is classified as fibrovascular, indicating the presence of active choroidal neovascularization, the primary treatment is anti-VEGF therapy. These medications, such as Lucentis, Eylea, and Vabysmo, are injected directly into the eye to block Vascular Endothelial Growth Factor (VEGF). VEGF is a protein that stimulates the growth and leakage of the abnormal blood vessels. By inhibiting VEGF, these injections aim to dry up the leakage, stabilize or reduce the size of the PED, and prevent further vision loss.
In cases of Serous PEDs linked to Central Serous Chorioretinopathy, other focused treatments may be considered. These can include certain types of laser therapy or photodynamic therapy (PDT), which seals the area of leakage.