A serous retinal detachment (SRD) occurs when the neurosensory retina lifts away from the underlying tissue due to the accumulation of clear, or serous, fluid in the subretinal space. This fluid accumulates without a tear or break in the retina itself. Unlike other forms of retinal detachment, SRD is not caused by scar tissue or a retinal hole. The detachment of this light-sensitive tissue can lead to significant vision problems.
The Mechanism of Serous Retinal Detachment
The separation of the retina occurs because a natural barrier function in the eye fails, allowing fluid to leak into the space between the retina and the retinal pigment epithelium (RPE). The RPE is a layer of cells that acts as a pump, constantly moving metabolic waste and fluid from the outer retina back toward the choroid, the vascular layer beneath it. This active transport system maintains the retina’s adhesion.
A serous detachment develops when the RPE’s barrier function is compromised, often due to inflammation or vascular changes in the choroid. Fluid from the choroidal blood vessels leaks out and overwhelms the RPE’s ability to pump it away, pooling in the subretinal space and pushing the neurosensory retina away from the RPE.
Underlying Conditions That Cause Fluid Buildup
The most frequent cause of serous retinal detachment is Central Serous Chorioretinopathy (CSR), a condition strongly linked to high levels of endogenous or exogenous corticosteroids and psychological stress. In CSR, a localized dysfunction of the choroidal blood vessels leads to hyperpermeability, causing serum to leak through a damaged RPE. This leakage point creates the characteristic dome-shaped fluid pocket beneath the macula.
A serous detachment can also be a symptom of severe systemic or inflammatory diseases that affect the choroid. Vogt-Koyanagi-Harada (VKH) disease, an autoimmune condition targeting melanocytes, causes widespread inflammation in the choroid. This inflammation significantly increases vascular permeability and protein leakage, resulting in large, often multi-lobed, detachments that can affect both eyes.
Severe hypertension, such as that seen in preeclampsia or eclampsia during pregnancy, can also trigger SRD. The high blood pressure causes intense vasospasm, or constriction, of the choroidal arterioles, leading to ischemia in the choriocapillaris. This disruption damages the RPE barrier, and the resulting leakage causes serous detachment, which often presents bilaterally in affected pregnant women.
Tumors, such as choroidal melanomas or metastases, may also cause SRD. They do this by directly compressing or disrupting the choroidal and RPE layers, leading to exudation of fluid into the subretinal space.
Visual Symptoms Associated with SRD
The specific symptoms of SRD occur when the fluid bubble lifts the macula, the central part of the retina responsible for fine detail vision. Patients typically experience distorted central vision, known as metamorphopsia, where straight lines appear wavy or bent. This distortion is caused by the physical displacement and stretching of the photoreceptor cells over the fluid dome.
Objects may also appear smaller than their actual size, a symptom called micropsia, which results from the increased spacing between the photoreceptors in the detached macula. A central blind spot, or scotoma, can also be present, corresponding to the area of the retina that is separated from its nutrient supply.
Management Strategies and Prognosis
Management of SRD is determined by the underlying cause and the chronicity of the fluid accumulation. Many cases of acute CSR-related SRD resolve spontaneously within a few months without intervention, requiring only careful observation. For cases that persist or recur, specific treatments are necessary to prevent permanent damage to the photoreceptors and RPE.
Oral medications, particularly mineralocorticoid receptor antagonists such as eplerenone or spironolactone, may be prescribed, especially for chronic CSR. These medications are thought to reduce the hyperactivity and hyperpermeability of the choroidal vessels. When a focal leak is identified outside the macula, a low-intensity thermal laser can be used to seal the point of leakage.
Photodynamic Therapy (PDT) uses a light-activated drug injected into the bloodstream, which is then activated by a cold laser to selectively close down the leaky choroidal vessels. PDT is often the preferred treatment for persistent or recurrent SRD, as it targets the abnormal circulation without causing significant damage to the overlying retina. The prognosis is generally favorable for acute SRD, especially in preeclampsia and CSR, with most patients recovering good vision; however, chronic or recurrent fluid can lead to irreversible RPE atrophy and long-term visual impairment.