When these vessels are blocked, abnormal blood vessel growth can occur and the retina thins. Over time, vision becomes impaired.
Types of Sickle Cell Retinopathy
There are two types of sickle cell retinopathy:
Non-proliferative sickle retinopathy (NPSR): Because the sickle-shaped red blood cells create blockages in the blood vessels, the retina suffers from a lack of blood flow and cannot receive important nutrients and oxygen. Initially, this occurs on the peripheral retina, causing initial findings known as salmon patches due to the leakage of blood from vessels. Over time, these leaks are resorbed and the area appears normal with iridescent spots. Eventually, this leads to the development of black sunburst spots in response to the bleeding. Proliferative sickle retinopathy (PSR): In PSR, long-term deprivation of oxygen and lack of blood flow cause the body to produce vascular growth hormone. This leads to the growth of blood vessels. Most of these newly formed blood vessels, however, are irregularly shaped, and instead of promoting blood flow, they cause further leakage of blood and increase the bleeding behind the retina. Eventually, this results in vitreous hemorrhage, blood in the jelly-like filling in the back part of the eye, or tractional retinal detachment, which causes vision loss.
There are five stages of PSR:
Stage 1: Peripheral arterial occlusions, the obstruction of blood flow from the heart to the legs due to narrowing or blockage of the vessels, occur. Stage 2: To allow blood flow around the peripheral arterial occlusions, the body attempts to create alternate pathways for blood flow. These alternate pathways, called arteriovenous anastomoses, allow for aberrant blood flow and create bigger areas of non-perfusion, where blood cannot be delivered to retinal tissue. Stage 3: Areas of non-perfusion create larger areas with a lack of blood flow and oxygen flow, creating a sea fan appearance that is visualized using fluorescein angiography. This medical procedure uses a special dye and camera to look at blood flow in the retina and choroid. Stage 4: Vitreous hemorrhage occurs. Stage 5: Tractional retinal detachment occurs.
Causes
People affected by sickle cell disease undergo a chemical change in their hemoglobin, which is a protein that carries oxygen and attaches to red blood cells. This change makes the hemoglobin become stiff rods, which then alters the shape of the red blood cells. Normally, red blood cells are round and can move easily throughout the body’s vessels.
In a person affected by sickle cell disease, the stiff hemoglobin rods contort the red blood cell shape from a round to a crescent or sickle shape. As a result, these red blood cells cannot easily pass through the body’s vessels and can become stuck, creating blockages.
Diagnosis
A diagnosis of sickle cell retinopathy is usually made by an optometrist or ophthalmologist. Findings that can lead to a diagnosis of sickle cell retinopathy include:
The presence of comma-shaped blood vessels in the sclera, or the white part of the eye, is common in sickle cell retinopathy. The sclera will also show signs of inflammation, which is known as bulbar conjunctiva. Some people may have narrow, irregular lines deep in the retina, which are configured in a circular pattern around the optic disc. These are called angioid streaks. Fluorescein angiography, to examine blood flow in retina and choroid, may reveal vessel blockages from the sickle cells. Spectral domain optical coherence tomography is a test that shows cross sections of the retina and can detect thinning of the retina in sickle cell retinopathy. Optical coherence tomography angiography is a type of imaging used to visualize blood vessels in the retina. It shows changes in the retinal and choroidal vessels, and is useful for detecting blocked vessels as a result of sickle cell disease.
Treatment
The goal of treatment is to identify sickle cell retinopathy early and preserve vision. Even with extensive retinal thinning, it’s possible to maintain visual acuity.
For people with NPSR, there is no treatment. For PSR, there are a few therapies available:
Laser: For large areas of blocked blood vessels, a laser can reduce the size of the blockage and prevent the release of the vascular growth hormone and therefore creation of new but abnormal blood vessels. Anti-vascular endothelial growth factor (Anti-VEGF): This medication is injected using a very thin needle into the eye. It blocks the release of the vascular growth hormone and prevents the body from creating new but abnormally shaped blood vessels. Surgery: This may be needed to treat vitreous hemorrhage. It is also needed for retinal detachment to reattach the retina and prevent vision loss.
Prognosis
NPSR, especially when diagnosed early by an eye specialist, does not tend to cause loss of vision. Individuals who have NPSR may notice black spots or floaters in peripheral vision, but otherwise can maintain visual acuity.
PSR can have a significant impact on visual acuity and can even lead to total vision loss. Current recommendations are to have anyone diagnosed with sickle cell disease aged 10 and older be evaluated by an eye specialist at least annually so PSR can be detected in the early stages. Once PSR progresses to stage 4 or 5, the damage to the retina is significant and prevention of vision loss is more challenging.
Summary
Sickle cell retinopathy is one of the potential complications of sickle cell disease. It occurs when sickle cell disease causes blockage of the blood vessels in the retina and choroid, both of which are important to visual processing. When these vessels are blocked, abnormal blood vessel growth can occur and cause the retina to thin and become detached.
A Word From Verywell
Sickle cell disease affects many parts of the body. One of them is the eyes. When it does, it’s called sickle cell retinopathy. Left untreated, it can lead to vision loss. Understanding the sickle cell disease process and establishing routine care with an eye specialist can help you identify sickle cell retinopathy early and minimize visual loss with early treatment.
