What is sickle cell retinopathy?
Sickle cell retinopathy is a possible complication of sickle cell disease. It happens when abnormally shaped “sickled” cells block the blood vessels in the retina, a layer of cells in the back of the eye. The reduced blood flow can lead to abnormal blood vessel growth and vision problems.
Sickle cell disease affects your body’s ability to make hemoglobin, which is a protein in red blood cells that helps carry oxygen. Cells affected by this mutation become long and rigid, taking on the shape of a sickle. Sickling makes it easier for cells to become damaged or break. Sickled cells can get stuck in blood vessels, obstructing blood flow, and can also die sooner.
An unhealthy balance between the number of cells created and the number of cells destroyed can lead to anemia. Anemia is when your red blood cell count is too low, leading to fatigue, swelling and pain. The most severe cases of anemia in sickle cell disease are called sickle cell anemia.
The blocked blood flow can also cause pain and prevent oxygen and blood from reaching vital parts of the body, such as the lungs and brain.
When it comes to the eyes, blockage of the blood vessels in the retina is the most common. Although people with sickle cell disease retinopathy may not have symptoms, the blocked blood flow can lead to complications over time. These complications can affect your vision and may even lead to vision loss.
Sickle cell disease is an inherited disorder, so the type and severity will depend on the specific genes inherited from your parents. These genes contain codes for abnormal versions of hemoglobin. There are three main types of sickle cell disease:
- Hemoglobin SS – The hemoglobin S gene is inherited from each parent. This is the most severe form and is sometimes referred to as sickle cell anemia.
- Hemoglobin SC – The hemoglobin S gene is inherited from one parent and the hemoglobin C gene from the other parent. This version is typically mild to moderate.
- Hemoglobin beta thalassemia – The hemoglobin S gene is inherited from one parent and the beta thalassemia gene from the other parent. There are two subtypes, beta thalassemia plus and beta thalassemia zero. The plus subtype tends to be milder, while the zero subtype tends to be more severe.
The SS subtype is the most severe. Widespread pain and more serious complications, like blocked blood flow in the lungs, are more common with this form. However, people with the SC subtype are at higher risk of developing retinopathy.
How sickle cell disease hurts your eyes
Blood cells are normally round and flexible and fit easily through blood vessels. But when cells become sickle-shaped, they can get stuck. This is especially true in small blood vessels called capillaries.
Sickle cell retinopathy is the result of the retina not getting enough blood and oxygen. The medical term for this is ischemia. The retina senses light and delivers information to the brain to be processed into vision. Complications in this area can lead to visual impairment and even vision loss.
The body can also respond to ischemia with vascular changes, meaning changes in the blood vessels. These changes in the vessels in the eye can involve decreased blood vessel density and increased tortuosity (twisting or coiling). New, weaker blood vessels may also be formed.
These changes can then cause more complications.
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Types of sickle cell retinopathy
Generally, retinopathy in sickle cell disease is classified based on the extent of the vascular changes caused by blocked blood vessels. The non-proliferative version is an earlier stage, while the proliferative version is a more advanced stage.
Non-proliferative sickle cell retinopathy (early stage)
In non-proliferative sickle cell retinopathy, major changes haven’t happened yet. However, an eye doctor may be able to detect them. Signs of sickle cell retinopathy that tend to appear during this stage include:
- Salmon patches
- Iridescent spots
- Black sunburst spots
Salmon patches are caused by the rupture of a blood vessel due to build-up of sickle cells. This bleeding leads to a patch on the retina that fades from red to salmon-pink in color as the red blood cells break down. Eventually, they may even become yellow or white. This can leave a scar or a split area called retinoschisis.
This area may also have iridescent spots on the surface, caused by cells and byproducts underneath the internal limiting membrane. This membrane separates the retina from other tissues.
Black sunburst spots may also appear after bleeding. They are thought to be due to growth and movement of the retinal pigment epithelium, a layer of cells that separates the retina from the choroid. The choroid is another layer of the eye that surrounds the back of the eyeball between the retina and the white of your eye. Its primary job is to supply blood to the retina and optic nerve.
Although there are some vascular changes in non-proliferative sickle cell retinopathy, effects on vision don’t usually start until the later proliferative stages.
Proliferative sickle cell retinopathy (serious stage)
Proliferative sickle cell retinopathy happens when the restricted blood flow has been going on long enough to cause major changes and complications. These can include:
- Anastomoses – The formation of back-up connections between blood vessels
- Sea fan neovascularization – The growth of new blood vessels
- Vitreous hemorrhage – Bleeding inside the vitreous (a gel-like substance that’s solid enough to help the eye keep its shape)
- Retinal detachment – The retina is pulled away from its normal position
If the body isn’t getting enough oxygen, it will try to create new blood vessels. These new blood vessels take on the shape of a sea fan. They are also fragile and break easily, which can lead to more bleeding. This in turn leads to vitreous hemorrhage.
The vitreous is clear, so any blood in this area can block the light that normally passes through. This might interfere with your vision, but the bleeding is not usually obvious to an outside observer. In some cases, changes in vision might resolve on their own over time. This can make it difficult to recognize and diagnose a vitreous hemorrhage.
The most serious effect of proliferative sickle cell retinopathy is retinal detachment. This is normally a tractional detachment, meaning that the separation is caused by a pulling force. The pulling can come from membranes or new blood vessels formed in the vitreous or over the retina.
Vision loss can occur with either vitreous hemorrhage or retinal detachment, but retinal detachment is the primary cause.
Symptoms of sickle cell retinopathy
It is common not to experience symptoms at all. In many cases, there may be no symptoms until later stages, when the vascular changes start to affect vision. For example, with vitreous hemorrhage, your vision may deteriorate suddenly. These symptoms might only occur for a short time and may even resolve on their own over time.
When sickle cell retinopathy leads to retinal detachment, you still might not have any symptoms, especially if only some of your retina has detached. If there are symptoms, they can include flashes of light or shadows in the middle or the sides of your field of vision. You may also notice blind spots. An increase in eye floaters, which are small spots or lines that float across your vision, can also be a symptom.
Retinal detachment is a medical emergency. In the case of any visual changes — even if they only happen briefly — it is critical to visit the ER or a doctor to prevent any permanent vision loss.
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Checking your eyes for problems
In patients with sickle cell disease, regular screenings for retinopathy should start as young as age 10. Comprehensive eye exams should take place at least once a year. On average, retinopathy in sickle cell disease can start developing at age 13. This disease often shows progression, so early and regular screening is important.
Retinopathy can be difficult to recognize if it’s in early stages or there are no symptoms. However, recent imaging techniques have made it possible to recognize ischemia and retinal thinning.
- Spectral domain optical coherence tomography – This imaging technique uses light rays to show the retina in cross-sections. This makes it possible to identify areas where the retina is affected.
- Optical coherence tomography angiography – This light-based imaging lets examiners see changes in the vessels themselves.
- Fluorescein angiography – In this technique, a special dye is injected into the arm. This dye helps a camera see circulation in the back of the eye.
Ways to treat sickle cell retinopathy
There are treatments available once sickle cell retinopathy reaches an advanced stage. These range from laser to surgical treatments.
Laser treatment
Microscopic burns caused by laser treatment can help shrink the extra blood vessels in the retina and stop them from growing. Laser treatment such as laser photocoagulation can also help prevent the release of growth factors to stop their growth in the first place. The laser may be applied to a small portion of the new blood vessels or to the whole peripheral retina.
Laser treatment is considered to be a safe and effective way to prevent vision loss. However, studies differ on its exact effectiveness for preventing further proliferative changes in comparison to other techniques. Your doctor may choose to perform it alongside other treatments to increase effectiveness.
Anti-VEGF injections
Vascular endothelial growth factor (VEGF) helps your body form new blood vessels. Anti-VEGF refers to the injection of medications that can help block VEGF. These eye injections can help slow or even stop neovascularization in the retina. Anti-VEGF drugs are also sometimes injected before or after surgery to prevent hemorrhage.
Eye surgery
Sickle cell retinopathy can sometimes lead to retinal detachment. It is typically the tractional type (the retina is pulled from the back of your eye), which requires surgery. The surgeries your doctor may recommend include:
- Pneumatic retinopexy (noo-mat-ick RET-ih-no-pek-see) – In this technique, a small air bubble injected into your eye gently pushes the retina back in place.
- Scleral buckle – A tiny, flexible band is placed around the sclera (the white of your eye) to gently push your eye in the direction of the retina. This helps it reattach.
- Vitrectomy – In a vitrectomy, the vitreous is removed, which makes it easier for the surgeon to move the retina into position. It’s temporarily replaced by a gas, oil or salt water solution. Your eye will eventually replace the fluid with aqueous humor, a natural fluid it already makes for the front of the eye.
If there are also small tears in the retina, they may be repaired with laser or freezing (cryopexy) treatment before your surgery.
In general, treatment for a detached retina is highly successful — especially if you catch the detachment in its early stages. Treatment within the first few days generally shows the highest success and can prevent more of the retina from detaching. A detached retina is a medical emergency, so you should go to a doctor or the ER as soon as possible if you are experiencing sudden changes in vision.
READ RELATED: Detached retina recovery
Managing sickle cell disease
Treating sickle cell disease can help with the progression of sickle cell retinopathy. Some therapies help the body produce hemoglobin. Blood transfusions may also help by reducing the number of blood cells affected by sickle cell disease.
Some drugs may also help control the blood flow blockage that causes sickle cell retinopathy, such as:
- Hydroxycarbamide – Increases the levels of a hemoglobin that can carry oxygen.
- Crizanlizumab – Can help keep blood vessels from being blocked by stopping sickle cells from sticking to vessel walls.
Hyperbaric oxygen therapy can also help manage sickle cell retinopathy. This therapy involves exposure to oxygen in a room with special air pressure, which can increase the amount of oxygen in the blood and body.
While sickle cell disease can be managed, the options for curing it entirely are few. These treatments are limited to:
- Stem cell therapy – Transplanting healthy bone marrow (also called stem cells) from a matched donor (usually a sibling) that will then produce healthy red blood cells.
- Gene editing/therapy – Removing cells from the patient’s bone marrow and replacing them with the patient’s own stem cells that have been modified with gene therapy (this and other methods of gene therapy are currently in research).
Keeping your eyes safe
Problems related to the eye in sickle cell disease can be “silent,” so sometimes it’s hard to know when to see an eye doctor. The early stages, especially, may not cause symptoms, and some cases of retinopathy may even resolve on their own. But if there are sudden changes in your vision, you should see a doctor immediately.
Serious changes, like dark shadows or flashes of light in your field of vision, can indicate retinal detachment. Retinal detachment is a medical emergency, but treating it right away can help prevent permanent vision loss.
For patients with a sickle cell disease diagnosis, complete eye exams are recommended at least once a year. These exams should start as early as age 10. Regular eye examinations are the best method to monitor retinopathy and to prevent vision loss. If possible, a doctor who specializes in the retina should perform these screenings.
And remember to stay healthy! Regular consultations with your doctor and a healthy lifestyle can help avoid complications.
