Pigment Epithelial Detachment (PED) is a separation in the back of the eye that occurs when the retinal pigment epithelium (RPE) lifts away from the underlying tissue. This separation is a common finding in various retinal diseases, most notably age-related macular degeneration (AMD). The lifting creates a dome-shaped space that can compromise the photoreceptor cells responsible for vision. Accurate diagnosis and classification are essential for determining proper treatment and prognosis. Optical Coherence Tomography (OCT) is the standard for visualizing and confirming the presence of a PED.
Understanding the Retinal Pigment Epithelium and Detachment
The Retinal Pigment Epithelium (RPE) is a single layer of cells positioned between the light-sensing retina and the blood vessels of the choroid. It forms the outer blood-retina barrier, regulating the passage of nutrients and waste products between the two layers. A major function of the RPE is to maintain the health of the photoreceptor cells—the rods and cones—by supplying them with nutrients and absorbing scattered light.
A Pigment Epithelial Detachment is the physical separation of the RPE cell layer from the underlying Bruch’s membrane. Bruch’s membrane is a thin layer that acts as a filter and scaffold beneath the RPE. When material (fluid, waste deposits, or new blood vessels) accumulates in this potential space, it exerts pressure, causing the RPE to dome or elevate. This detachment disrupts the close relationship between the RPE and the photoreceptors, which can lead to dysfunction and vision loss.
Optical Coherence Tomography (OCT) Imaging
Optical Coherence Tomography is a diagnostic tool that provides cross-sectional images of the retina, similar to how ultrasound creates images, but using light waves instead of sound. This technology allows clinicians to see the microscopic layers of the retina and choroid in detail. OCT offers micron-level resolution, enabling the non-invasive visualization of the sub-retinal structures.
On an OCT scan, a Pigment Epithelial Detachment appears as a characteristic dome-shaped or smooth elevation of the RPE line. The RPE, which normally appears as a single, bright, hyper-reflective line, is lifted away from the Bruch’s membrane beneath it. The space created beneath the elevated RPE is what the clinician analyzes to determine the type of PED. The specific reflectivity and contents of this sub-RPE space allow for accurate classification and guide subsequent treatment decisions.
Types of Pigment Epithelial Detachment
PEDs are classified based on the material that accumulates within the sub-RPE space, which helps determine the underlying disease process. The three main types are Drusenoid, Serous, and Vascularized, each carrying a different prognosis. The contents seen on OCT scans determine the category and the risk of progression to severe vision loss.
Drusenoid PEDs
Drusenoid PEDs are caused by an accumulation of drusen, which are lipid and protein waste products that deposit between the RPE and Bruch’s membrane. On OCT, these appear as elevations over a space filled with homogeneous, mildly hyper-reflective material. This type is associated with the dry form of AMD and tends to have a stable course, though it still carries a risk of progressing to late-stage disease.
Serous PEDs
Serous PEDs result from the leakage of fluid, usually from the choriocapillaris, which collects beneath the RPE. On OCT, these detachments appear as smooth, sharply demarcated, dome-shaped elevations over a homogenously dark, hypo-reflective space. Serous PEDs without associated new blood vessel growth (avascular) generally have a favorable natural course. However, most serous PEDs observed in age-related macular degeneration are actually vascularized.
Vascularized PEDs
Vascularized, or fibrovascular, PEDs are caused by the growth of new, abnormal blood vessels, known as choroidal neovascularization (CNV), underneath the RPE. This CNV tissue is prone to leaking fluid and blood, which lifts the RPE. On OCT, these detachments often show heterogeneous or irregular internal reflectivity due to the presence of neovascular tissue, blood, or serous fluid within the dome. These PEDs are a manifestation of wet AMD and carry the highest risk for rapid, severe vision loss.
Clinical Management and Prognosis
The management strategy for a Pigment Epithelial Detachment is determined by the underlying cause and the type identified through OCT imaging. A PED classified as drusenoid and stable often requires only close observation and frequent monitoring. Patients are typically advised to maintain regular follow-up visits, involving repeat OCT scans, to detect any signs of change or progression to a more aggressive form.
For serous or fibrovascular PEDs, where the underlying cause is often choroidal neovascularization, active intervention is necessary to prevent significant vision decline. The primary treatment involves intravitreal anti-VEGF (anti-vascular endothelial growth factor) injections. These medications, such as ranibizumab or aflibercept, are injected directly into the eye to inhibit the growth and leakage from the abnormal blood vessels.
The goal of anti-VEGF therapy is to reduce fluid and exudation, causing the PED to flatten. Vision improvement correlates with the resolution of fluid accumulation in the neurosensory retina overlying the PED. Fibrovascular PEDs are often resistant to treatment and may require more frequent injections than other forms of wet AMD. The prognosis varies significantly: drusenoid PEDs are associated with a slower, stable course. Vascularized PEDs have a poorer prognosis without treatment, and rapid dome reduction may sometimes lead to complications such as a retinal pigment epithelium tear.