A subretinal hemorrhage describes bleeding that occurs in the space between the light-sensitive neurosensory retina and the supporting layer beneath it called the retinal pigment epithelium (RPE). This event can lead to sudden and significant changes in vision, including blurriness, distortions, or blind spots. To visualize and diagnose this condition, eye care specialists use an imaging technique called Optical Coherence Tomography (OCT). This non-invasive scan provides a detailed, cross-sectional view of the retina’s intricate layers, which allows for precise identification and management of the hemorrhage.
The Role of OCT in Retinal Imaging
Optical Coherence Tomography functions much like an “optical ultrasound,” using light waves instead of sound waves to capture high-resolution, cross-sectional images of the retina. By analyzing reflected light, the OCT machine generates a detailed map of the retina’s distinct layers, which are only micrometers thick. This provides a level of detail that cannot be achieved with a standard clinical eye exam or fundus photography alone.
The imaging process is non-invasive and takes only a few minutes. The patient rests their chin on a support and looks into a lens while the machine scans the eye with a safe, invisible light source. The resulting image reveals the retinal anatomy with exceptional clarity, showing its precise thickness and structure.
Identifying a Subretinal Hemorrhage on an OCT Scan
On an OCT scan, a subretinal hemorrhage has a distinct appearance. The accumulated blood appears as a “hyperreflective” area, meaning it shows up as a bright, dense signal on the image. This is due to blood cells and fibrin scattering the OCT’s light beam more intensely than surrounding retinal tissues. This bright material occupies the space between the neurosensory retina and the underlying RPE, causing a visible separation of the retina from its normal position.
The scan clearly delineates the hemorrhage’s boundaries, showing its thickness, shape, and exact location relative to the fovea, the center of the macula responsible for sharp vision. The OCT can also distinguish a subretinal hemorrhage from other types of bleeding. A sub-RPE hemorrhage occurs when blood collects underneath the RPE layer, creating an elevation of the RPE itself, which presents a different visual pattern.
The texture of the hemorrhage on the OCT can also offer information. Fresh blood may appear more uniformly hyperreflective, while an older, resolving hemorrhage might show changes in its reflectivity or signs of organization. Intraretinal hemorrhages are also distinct, appearing as pockets of hyperreflectivity confined within the layers of the retina itself.
Key OCT Findings and Their Clinical Significance
Beyond simply identifying the presence of blood, an OCT scan reveals specific details that have direct clinical significance for a patient’s prognosis and treatment strategy. A primary assessment is the health of the photoreceptor cells, the specialized neurons that detect light. These cells are located in the outer retinal layers, directly adjacent to the space where a subretinal hemorrhage occurs. The OCT image can show if these photoreceptor layers are intact, compressed, or disrupted by the mechanical pressure and toxicity of the blood.
Clinicians examine the integrity of the external limiting membrane (ELM) and the ellipsoid zone (EZ), which are bands on the OCT scan that correspond to photoreceptor structures. Disruption or absence of these bands in the area of the hemorrhage suggests damage to the photoreceptors, which can correlate with a poorer visual prognosis. The presence of subretinal fluid alongside the blood is another common finding that the OCT can quantify, as this can also contribute to photoreceptor stress.
The OCT scan is also used to identify the underlying cause of the bleeding. In many older adults, a subretinal hemorrhage is a complication of wet age-related macular degeneration (AMD). This condition involves the growth of abnormal blood vessels from the choroid, a formation known as a choroidal neovascular membrane (CNV). An OCT can often detect the presence of a CNV, which helps confirm the diagnosis and guide treatment.
Monitoring Treatment and Recovery with OCT
OCT imaging is used for monitoring the progression of a subretinal hemorrhage over time, both during natural resolution and in response to medical or surgical intervention. Clinicians use serial OCT scans at regular intervals to track changes in the hemorrhage’s size, thickness, and location. This monitoring allows for an objective assessment of whether the bleed is shrinking, stabilizing, or expanding. After treatments like intravitreal injections of anti-VEGF agents, the OCT can show a reduction in associated fluid and a gradual clearing of the blood.
In cases where a procedure called pneumatic displacement is performed—which involves injecting a gas bubble into the eye to move the blood away from the macula—follow-up OCT scans are used. The scans confirm the successful displacement of the hemorrhage and the subsequent re-flattening of the retina against the RPE. This information helps doctors determine if the intervention was effective or if additional steps are needed.
Ultimately, these follow-up scans provide insights into the potential for visual recovery. As the blood clears and the retina returns to its proper anatomical position, the OCT can show the extent of any residual structural damage. The restoration of the normal layered appearance of the retina, particularly the recovery of the photoreceptor layers, is a positive prognostic indicator. This ongoing assessment helps manage patient expectations and guides long-term care.