Subretinal fibrosis is an eye condition characterized by the formation of scar tissue beneath the retina. This abnormal tissue growth can significantly impair vision, often leading to permanent central vision loss. Understanding its causes, diagnosis, and treatment is key to managing its impact on eye health.
Understanding Subretinal Fibrosis
Subretinal fibrosis involves the development of abnormal fibrous tissue in the subretinal space, the delicate area between the neurosensory retina and the retinal pigment epithelium (RPE). This scar tissue is formed by myofibroblasts, cells not typically found in a healthy retina. The fibrotic scar can damage photoreceptors, the RPE, and the choriocapillaris, all crucial for proper vision. This damage disrupts the normal microenvironment of the eye, leading to cell death. The presence of subretinal fibrosis is a common outcome of chronic tissue injury and inflammation in the eye.
Causes and Contributing Factors
Subretinal fibrosis can arise from several underlying conditions, often representing an exaggerated wound healing response to tissue damage. A primary cause is age-related macular degeneration (AMD), particularly its wet form (neovascular AMD or nAMD). In nAMD, abnormal blood vessels (choroidal neovascularization or CNV) grow under the retina, leading to fluid leakage and hemorrhage. This inflammatory process can trigger cells, including retinal pigment epithelium (RPE) cells, to transform into myofibroblasts, which then produce the scar tissue. Studies indicate that subretinal fibrosis occurs in up to 36% of nAMD patients after one year and 45% after two years, even with regular anti-VEGF treatment.
Ocular trauma, such as penetrating eye injuries, can also lead to subretinal fibrosis. Such injuries cause inflammation and stimulate the proliferation of cells like RPE cells and glial cells, contributing to fibrous membrane formation. Inflammatory eye diseases, including uveitis, can also lead to subretinal fibrosis. For example, in punctate inner choroiditis (PIC), inflammation can result in new blood vessel formation, which can progress to subretinal scarring if untreated.
Previous retinal surgeries, such as those for retinal detachment, can sometimes be associated with subretinal fibrosis due to the body’s healing response. Surgical manipulation and subsequent inflammation can lead to the proliferation of glial cells and the deposition of extracellular matrix. In some instances, subretinal fibrosis can be idiopathic, meaning it develops without a clear identifiable cause. These cases may involve spontaneous changes in the vitreous, where fibrous tissue settles on the macula and initiates membrane formation.
Recognizing Symptoms and Getting a Diagnosis
Individuals experiencing subretinal fibrosis may notice several changes in their vision, which often develop gradually. Common symptoms include blurred central vision, making it difficult to see fine details. Distorted vision, known as metamorphopsia, is another frequent complaint, where straight lines may appear wavy or bent. Patients might also report blind spots (scotomas) or a general decrease in vision quality. Sensitivity to light and the appearance of floating objects can also occur.
Diagnosing subretinal fibrosis involves a comprehensive eye examination by an ophthalmologist. This typically includes a dilated fundus examination, where the doctor directly visualizes the back of the eye. To confirm the diagnosis and assess the extent of the scar tissue, advanced imaging technologies are commonly employed. Optical Coherence Tomography (OCT) is a non-invasive technique that provides high-resolution cross-sectional views of the retina, allowing specialists to visualize the subretinal hyperreflective material (SHRM) that indicates fibrosis.
Fluorescein angiography (FA) is another diagnostic tool where a dye is injected into a vein. As the dye circulates, a special camera takes pictures, revealing abnormal blood vessel growth, leakage, or staining of fibrotic scars. While FA is used, OCT provides more detailed structural information, helping differentiate fibrotic tissue from other subretinal materials like hemorrhage or neovascular tissue. These imaging modalities collectively allow for a precise assessment of the scar tissue’s impact on the retina.
Treatment Options
Managing subretinal fibrosis often involves a multi-faceted approach, with treatment choices depending on the underlying cause and severity of the scar tissue. Currently, there is no single, universally effective anti-fibrotic treatment available to completely eliminate subretinal scarring. However, various strategies aim to stabilize vision, prevent further loss, or, in some cases, improve visual outcomes.
Surgical intervention is a primary option, especially when the scar tissue causes significant retinal distortion or detachment. A common procedure is vitrectomy with membrane peeling. During a vitrectomy, the vitreous gel is removed through small incisions. Specialized micro-forceps are then used to carefully peel away the abnormal fibrous membrane from the retinal surface. This aims to reduce the traction exerted by the scar tissue on the retina, potentially improving vision or preventing further damage.
In cases where subretinal fibrosis is linked to wet age-related macular degeneration, anti-VEGF (vascular endothelial growth factor) injections may be used. These medications, such as bevacizumab, ranibizumab, aflibercept, and faricimab, are injected directly into the vitreous to inhibit the growth of abnormal blood vessels and reduce fluid leakage. While anti-VEGF therapy can stabilize or improve vision by targeting neovascularization, it may not always prevent the development or progression of subretinal fibrosis, which can still occur in a significant percentage of treated eyes.
Corticosteroids, either systemic or delivered locally via injections, may be considered, particularly for fibrosis associated with inflammatory eye diseases like uveitis. These medications reduce inflammation, a contributing factor to fibrosis. Corticosteroids might also be used in combination with other therapies, such as anti-VEGF injections, to manage both inflammation and vascular leakage. The goal of these treatments is generally to manage the condition and preserve existing vision.