The ocular manifestations of sickle cell anemia come mainly from sickled red cells blocking the small blood vessels of the eye, especially in the retina. This can cause sickle cell retinopathy, bleeding inside the eye, retinal detachment, and occasionally sudden loss of vision. Many of these changes cause no symptoms early on, which is why regular dilated eye examinations are part of routine sickle cell care.
In this guide I explain why the eye is vulnerable, which patients are at highest risk, what the eye changes look like, and how they are found and treated.
Why Sickle Cell Disease Affects the Eyes
Sickle cell anemia is the most common and usually most severe form of sickle cell disease. It results from a single change in the HBB gene, which leads to production of abnormal hemoglobin S. When oxygen levels fall, hemoglobin S polymerizes and the red cell stiffens into the characteristic sickle shape.
Sickled cells are rigid and sticky. They adhere to the lining of blood vessels (the endothelium) and plug small vessels, a process called vaso-occlusion. The eye has some of the finest blood vessels in the body, and the outer (peripheral) retina has a relatively limited blood supply, so it is particularly exposed to repeated small blockages. The same mechanism drives many other complications of sickle cell anemia, from pain crises to stroke.
Which Patients Are at Highest Risk?
A point that surprises many families: the genotype with the most severe anemia is not the one with the most eye disease. Proliferative retinopathy is classically most common in hemoglobin SC disease, followed by sickle-beta-plus thalassemia, and it also occurs in HbSS. One explanation is that people with HbSC have a higher hematocrit and thicker blood, which favors sluggish flow in small vessels.
| Genotype | General anemia severity | Risk of proliferative retinopathy |
|---|---|---|
| HbSS (sickle cell anemia) | Usually more severe | Present, generally lower than HbSC |
| HbSC | Usually milder | Highest |
| HbS/beta-plus thalassemia | Variable, often milder | Increased |
| Sickle cell trait (HbAS) | No anemia | Rare; mainly a concern after eye injury |
Retinopathy tends to appear from later childhood onward and becomes more common with age, so screening is ongoing throughout life.
Types of Ocular Manifestations
Proliferative sickle retinopathy
This is the most important sight-threatening change. It is traditionally described in five Goldberg stages:
- Peripheral arteriolar occlusion — small arteries at the edge of the retina close off.
- Arteriovenous anastomoses — the retina forms shunts between arterioles and venules at the boundary of the non-perfused area.
- Neovascularization — fragile new vessels grow, often in a fan shape called a “sea fan.”
- Vitreous hemorrhage — the new vessels bleed into the gel that fills the eye.
- Retinal detachment — scar tissue pulls the retina away from the back of the eye.
Some sea fans close off on their own (autoinfarction), but others progress, so they are monitored closely.
Non-proliferative changes
These include salmon-patch hemorrhages (fresh bleeds within the retina), iridescent spots (glistening deposits left after those bleeds resolve), black sunbursts (pigmented scars), and tortuous, twisted retinal veins. They usually do not affect vision on their own but signal that vaso-occlusion is happening in the eye.
Other eye findings
- Conjunctival sickle sign — comma-shaped, interrupted vessels visible on the white of the eye.
- Central retinal artery occlusion — a rare cause of sudden, painless vision loss.
- Macular thinning — areas of thinning at the center of the retina, seen on imaging, sometimes without symptoms.
- Hyphema — blood in the front chamber of the eye after injury. In anyone with sickle cell disease or trait, this can raise eye pressure quickly and needs urgent specialist care.
Symptoms and Warning Signs
Early retinopathy is usually silent, because it affects the periphery of the retina rather than central vision. When symptoms occur, they often mean something has progressed:
- New floaters, especially a sudden shower of dark spots
- Flashes of light
- A curtain or shadow across part of the vision
- Blurred or sudden loss of vision
- Eye pain or redness after any eye injury
Diagnosis and Screening
The cornerstone is a dilated fundus examination by an eye specialist, looking carefully at the peripheral retina. Additional tests help map damage and plan treatment:
- Fluorescein angiography — dye injected into a vein shows areas of poor blood flow and leaking new vessels.
- Wide-field retinal imaging — captures more of the peripheral retina in a single picture.
- Optical coherence tomography (OCT) — cross-sectional scans that detect thinning of the macula.
- Ultrasound — used when a vitreous hemorrhage blocks the view of the retina.
Guidelines generally recommend starting regular retinal screening in childhood, around age 10, and repeating it every one to two years if normal, more often if changes are found. Your hematology and eye teams will set an interval that fits your genotype and findings.
Management and Treatment
Not every retinal change needs treatment; many are simply watched. When sea fans persist, grow, or bleed, laser photocoagulation to the non-perfused retina can help them regress and reduces the risk of vitreous hemorrhage.
A non-clearing vitreous hemorrhage or a retinal detachment may need vitrectomy, surgery to remove the blood-filled gel and repair the retina. Surgery in sickle cell disease needs careful planning with the hematology team to reduce the risk of a crisis.
Anti-VEGF injections, drugs that block the growth signal for abnormal vessels, are used in some cases, often alongside laser or before surgery. Hyphema is managed with close pressure monitoring and prompt treatment, avoiding certain eye-pressure medicines that can worsen sickling.
Overall disease control also matters. Disease-modifying treatments such as hydroxyurea, and newer curative approaches like stem cell transplantation and gene therapy, target the underlying problem, although their specific effect on eye outcomes is still being clarified. For the broader picture of how this condition fits among blood disorders, see our overview of hematologic disorders.
When to See a Doctor
Seek same-day eye care if you have sickle cell disease or trait and notice:
- Sudden new floaters, flashes, or a shadow in your vision
- Sudden blurring or loss of vision in one eye
- Any blow to the eye, even if vision seems normal
- A painful red eye
Even without symptoms, keep your scheduled retinal checks. Finding retinopathy early gives the best chance of protecting sight.
Frequently Asked Questions
Can sickle cell anemia cause blindness?
It can, but severe vision loss is uncommon when retinopathy is found and treated early. Blindness usually results from untreated vitreous hemorrhage or retinal detachment. Regular screening is the best protection.
Why is eye disease more common in HbSC than HbSS?
People with HbSC tend to have higher hemoglobin levels and more viscous blood, which slows flow in the tiny retinal vessels. That favors repeated blockages in the peripheral retina, even though their overall anemia is milder.
How often should someone with sickle cell disease have an eye exam?
Most specialists advise a dilated retinal exam starting in late childhood and repeating every one to two years if normal. If retinopathy is found, checks become more frequent.
Does sickle cell trait affect the eyes?
People with trait rarely develop retinopathy. The key exception is eye injury: blood in the front of the eye (hyphema) can cause dangerous pressure rises, so anyone with trait who injures an eye should say so and be seen promptly.
Is laser treatment for sickle retinopathy painful?
It is usually done in the clinic with numbing drops, and most people describe discomfort rather than severe pain. Your eye specialist will explain what to expect and how many sessions may be needed.
