Bleeding behind the retina, medically termed a retinal or subretinal hemorrhage, occurs when blood leaks from compromised vessels into the light-sensitive tissues at the back of the eye. This condition immediately threatens sight because the blood blocks light from reaching the photoreceptors. The retina converts incoming light into electrical signals sent to the brain. When a hemorrhage occurs, the blood acts as an opaque barrier, potentially causing permanent damage to the retinal cells. This sudden interference with vision, often presenting as floaters, a hazy dark spot, or sudden central sight loss, requires immediate assessment by an eye specialist.
Age-Related Macular Degeneration
Age-related macular degeneration (AMD) is the most frequent cause of new, severe bleeding beneath the retina in older adults. AMD has two forms, but the wet form is directly responsible for significant hemorrhage. Wet AMD is characterized by choroidal neovascularization (CNV), where fragile new blood vessels grow from the choroid through Bruch’s membrane. This erratic growth is often stimulated by Vascular Endothelial Growth Factor (VEGF), a protein released by oxygen-starved retinal tissue. These new vessels are structurally weak and prone to leakage.
When pressure within these delicate vessels becomes too high, they rupture easily, leading to an acute subretinal hemorrhage. This accumulation of blood under the macula separates the photoreceptor cells from their nutrient supply, causing rapid and severe central vision loss. The resulting clot and scarring can lead to a dense, permanent disciform scar, which destroys the specialized cells necessary for detailed sight.
Damage from Systemic Health Conditions
Chronic diseases affecting the circulatory system can severely compromise the integrity of retinal blood vessels, leading to hemorrhage over time. The two most prominent systemic causes are diabetic retinopathy and hypertensive retinopathy, which damage the retinal microvasculature through distinct long-term mechanisms.
Diabetic Retinopathy
Diabetic retinopathy arises from prolonged exposure to high blood sugar levels, which alters the structure and function of retinal blood vessels. Early damage involves the loss of pericytes, specialized cells that maintain capillary stability. Vessel walls weaken, leading to the formation of microaneurysms that leak fluid and blood into the retina.
The most advanced stage is proliferative diabetic retinopathy (PDR), a response to widespread oxygen deprivation (ischemia). In PDR, the eye releases high concentrations of growth factors, notably VEGF, to stimulate neovascularization. These new vessels are abnormally fragile and grow on the inner surface of the retina or extend into the vitreous gel. Their delicate nature makes them highly susceptible to rupture, often resulting in a large vitreous hemorrhage that causes sudden vision loss.
Hypertensive Retinopathy
Hypertensive retinopathy results from chronic high blood pressure stressing the retinal arteries and arterioles. Over time, the sustained force causes structural changes, including intimal thickening and hyaline degeneration. This narrows the vessel lumen and stiffens the artery walls.
This chronic damage eventually compromises the blood-retina barrier, the protective layer controlling substance passage between the blood and the neural retina. When this barrier breaks down, blood components are forced out of the damaged vessels into the retinal tissue. This leakage often presents as “flame-shaped” hemorrhages located in the superficial nerve fiber layer, reflecting acute vessel wall failure.
Vascular Blockages and Physical Injury
Acute events, such as blockages within the eye’s vascular network or sudden physical trauma, can be direct and immediate causes of hemorrhage. These mechanisms involve mechanical disruption rather than the slow deterioration seen in chronic diseases.
Retinal Vein Occlusion
A retinal vein occlusion (RVO) occurs when a vein draining blood from the retina becomes blocked, often by a clot or compression from a hardened artery. The blockage prevents blood from exiting the retina, causing a rapid backup of blood volume into the venous system. This immediate congestion significantly increases the hydrostatic pressure within the affected capillaries.
This severe pressure buildup overwhelms the capillary walls, forcing blood and fluid to leak into the surrounding retinal tissue. The resulting bleeding is typically widespread, covering the area drained by the blocked vein, and may be accompanied by significant swelling of the central macula. RVO is considered an acute form of “eye stroke.”
Physical Injury
Direct physical impact to the eye or head can cause immediate bleeding from the rupture of otherwise healthy vessels. This is referred to as ocular trauma, ranging from blunt force impact to penetrating injuries. A severe blow to the eye can transmit a shock wave that physically tears the choroid, the vascular layer beneath the retina, causing a choroidal rupture.
This mechanical tearing leads to an immediate and often large subretinal hemorrhage as the highly vascular choroidal tissue bleeds profusely. Penetrating injuries, such as those caused by sharp foreign bodies, can directly lacerate retinal or choroidal vessels, leading to bleeding into the vitreous cavity or the retinal layers. In younger patients, severe concussive head trauma or sudden increases in intracranial pressure can also cause vessel rupture and hemorrhage.