Subretinal fluid (SRF) refers to the accumulation of fluid beneath the retina, the light-sensitive tissue of the eye. This condition often signals an underlying issue. Prompt evaluation by an eye care professional is important if any new or worsening vision problems arise.
What is Subretinal Fluid?
Subretinal fluid is a collection of serous fluid that gathers in the space between the neurosensory retina and the retinal pigment epithelium (RPE). The retina is a thin layer of tissue responsible for converting light into electrical signals that are sent to the brain. This conversion relies on the precise arrangement of specialized cells called photoreceptors within the retina.
When fluid builds up, it lifts the retina away from its underlying support structures, including the choroid and retinal pigment epithelium. This separation disrupts the normal functioning of the photoreceptors and can interfere with the retina’s ability to process visual information clearly.
Common Causes of Subretinal Fluid
Subretinal fluid frequently develops as a manifestation of several distinct eye conditions, with age-related macular degeneration (AMD) being a common culprit. Specifically, the “wet” form of AMD, also known as neovascular AMD, involves the growth of abnormal, fragile blood vessels from the choroid, a layer beneath the retina. These new vessels, termed choroidal neovascularization (CNV), are prone to leaking fluid and blood into the subretinal space. This leakage can damage the photoreceptors and lead to rapid vision decline.
Another prevalent cause is Central Serous Chorioretinopathy (CSCR), a condition characterized by fluid leakage from the choroid through a weakened retinal pigment epithelium. This fluid collects under the neurosensory retina. CSCR is often linked to elevated levels of corticosteroids, either from medical use or the body’s own stress response, suggesting a connection to psychological stress and certain lifestyle factors. The fluid accumulation in CSCR typically affects the macula, the central part of the retina responsible for sharp, detailed vision.
Less common causes of subretinal fluid include various inflammatory conditions that affect the eye, such as uveitis. Certain rare genetic disorders can also lead to fluid accumulation beneath the retina. Additionally, some benign or malignant tumors within or near the eye’s posterior segment may lead to SRF by disrupting normal fluid dynamics or causing direct leakage.
How Subretinal Fluid Affects Vision
Subretinal fluid impacts a person’s vision, primarily affecting the central visual field. Individuals often report experiencing blurred central vision, making it difficult to discern fine details. Another common symptom is metamorphopsia, where straight lines appear wavy or distorted. This distortion can make everyday tasks like reading or recognizing faces challenging.
Blind spots, known as scotomas, may also develop in central vision, appearing as dark or missing areas. Some individuals perceive a general dimness or grayness. These symptoms arise because the fluid lifts and displaces the photoreceptors from their normal position on the retinal pigment epithelium. This disruption interferes with the precise alignment needed for light to be converted into neural signals, leading to garbled or incomplete information.
Diagnosis and Treatment Options
Diagnosing subretinal fluid typically begins with a comprehensive eye examination, which includes assessing visual acuity and a dilated fundus examination. The primary diagnostic tool to confirm and monitor SRF is Optical Coherence Tomography (OCT). This non-invasive imaging technique provides high-resolution cross-sectional images of the retina, allowing eye care professionals to visualize the fluid collection and assess the layers of the retina. OCT scans can detect even small amounts of fluid and track changes over time.
Another diagnostic procedure, Fluorescein Angiography (FA), may identify the source of leakage. During FA, a fluorescent dye is injected into a vein, and photographs are taken as the dye circulates through the retinal and choroidal blood vessels. This technique highlights areas where blood vessels are leaking fluid or are growing abnormally, providing information about the underlying cause of the SRF.
Treatment for subretinal fluid focuses on addressing the specific underlying condition causing the fluid accumulation, rather than merely draining the fluid itself. For wet Age-related Macular Degeneration, the standard treatment involves anti-VEGF (vascular endothelial growth factor) injections. Medications such as aflibercept, ranibizumab, and bevacizumab are administered directly into the vitreous gel of the eye. These agents work by inhibiting the activity of VEGF, a protein that promotes the growth and leakage of abnormal blood vessels, thereby reducing fluid and preventing further vision loss.
In cases of Central Serous Chorioretinopathy, observation is often the initial approach, as the fluid can spontaneously resolve in many individuals within a few months. If the fluid persists, recurs, or significantly impacts vision, other treatments may be considered. These include photodynamic therapy (PDT), which uses a light-activated drug and a cold laser to close leaky vessels, or focal laser photocoagulation, which uses a thermal laser to seal specific leaking points. Oral medications may also be prescribed. Ongoing monitoring and regular follow-up appointments with an ophthalmologist are important to manage subretinal fluid and preserve vision.