Subretinal fibrosis is a severe complication of several eye diseases resulting in permanent central vision loss. This condition is characterized by the formation of scar tissue beneath the retina, specifically in the macular region responsible for sharp, detailed central sight. This fibrous scar represents an end-stage response to chronic injury and inflammation within the back of the eye. The scarring damages light-sensing cells and support structures, creating a blind spot that significantly impairs a person’s ability to read, drive, and recognize faces.
Anatomy and Definition of Subretinal Fibrosis
The eye’s interior structure involves several tightly arranged layers. The retina is the innermost layer, containing photoreceptor cells that convert light into electrical signals. Directly beneath the retina is the retinal pigment epithelium (RPE), which provides metabolic support to the photoreceptors. Separating the RPE from the blood-vessel-rich choroid is Bruch’s membrane.
The space between the neurosensory retina and the RPE is the subretinal space. Subretinal fibrosis involves the formation of a dense, pathological scar, often called a fibrovascular membrane, within this space or beneath the RPE. This fibrotic tissue is an accumulation of excessive proteins, such as collagen and fibronectin, deposited by cells that have transformed into myofibroblasts.
The scar tissue physically disrupts the organized layers of the retina. This fibrous plaque acts as a physical barrier, cutting off photoreceptors from the RPE and the choroid, their primary sources of nutrients and oxygen. This isolation and compression leads to the death of the light-sensing cells, resulting in irreversible vision loss.
Underlying Causes and Major Risk Factors
The most common cause leading to subretinal fibrosis is neovascular, or “wet,” Age-Related Macular Degeneration (AMD). Wet AMD is characterized by Choroidal Neovascularization (CNV), the abnormal growth of new, fragile blood vessels from the choroid. These vessels are leaky, causing fluid and blood to accumulate under the retina, which triggers a chronic, damaging wound-healing response.
This prolonged inflammatory process leads to scar formation. Cells, including retinal pigment epithelial cells and circulating macrophages, transform into myofibroblasts, which are the primary cells that produce the scar tissue components. Subretinal fibrosis is considered an end-stage outcome of CNV, often occurring despite initial treatments aimed at slowing the neovascular process.
Eyes with CNV lesions where abnormal vessels penetrate the RPE and grow directly in the subretinal space are more likely to progress to fibrosis. Cellular processes involving growth factors, such as Transforming Growth Factor-beta (TGF-\(\beta\)), drive the excessive production of extracellular matrix proteins. Up to 40% of eyes treated for wet AMD may develop some degree of subretinal fibrosis within two years.
Other Causes
Subretinal fibrosis can also result from other conditions causing chronic inflammation or damage in the back of the eye. These include severe eye trauma or infectious diseases, such as ocular toxoplasmosis, which induce a similar scarring response. Additionally, certain previous surgical interventions involving the retina or choroid can sometimes lead to a fibrotic reaction during the healing process.
Recognizing the Signs and Visual Impact
The presence of subretinal fibrosis causes noticeable visual symptoms for the patient. The most common complaint is a loss of central vision, described as a dense, fixed blind spot known as a scotoma. Patients may also experience metamorphopsia, which is the distortion or warping of straight lines, caused by the scar tissue physically pulling on the retina.
The condition is diagnosed using specialized non-invasive imaging techniques performed by an ophthalmologist. Optical Coherence Tomography (OCT) is the main tool used to visualize the retinal layers in cross-section. On an OCT scan, subretinal fibrosis appears as a dense, uniformly hyperreflective mound or mass located in the subretinal space, confirming the presence of scar tissue.
Fluorescein angiography is another diagnostic method where a dye is injected into the bloodstream to highlight the vessels in the back of the eye. A fibrotic scar typically shows blocked fluorescence early, followed by late staining as the dye collects in the dense tissue. OCT angiography can further reveal if the scar complex still contains an abnormal vascular network. The size and location of the lesion, particularly if it is under the fovea, correlate directly with the severity of permanent vision loss.
Current Treatment and Management Strategies
The primary focus of managing subretinal fibrosis is preventing its formation in patients with active neovascular disease. Aggressive anti-Vascular Endothelial Growth Factor (anti-VEGF) therapy is the standard of care for wet AMD. This treatment stabilizes abnormal blood vessels and reduces the inflammation that drives the scarring process. Optimizing the anti-VEGF regimen is the most effective strategy to mitigate the risk of progressing to a fibrotic end-stage.
Once a dense fibrotic scar has fully formed, current treatments are severely limited because the damage to photoreceptors is usually irreversible. Established scar tissue does not typically respond to anti-VEGF injections, as this treatment targets blood vessels, not the resulting scar. Research is underway to develop specific anti-fibrotic agents, but these are not yet clinically available.
Surgical intervention, such as vitrectomy and the attempted removal of the subretinal scar tissue, is a highly complex procedure. While surgery aims to peel the fibrous membrane away, it carries significant risks and often has variable success rates in restoring meaningful central vision. Treatment for established subretinal fibrosis therefore concentrates on stabilization, maximizing the function of the remaining healthy retina, and providing low-vision aids.