Acute ocular complications in sickle cell disease are medical emergencies that warrant prompt and aggressive management to preserve vision. These may arise following trauma, infection, or vaso-occlusive episodes. It may lead to eye vessels being occluded or culminating in proliferative sickle retinopathy (PSR).
Acute ocular complications that occur in sickle cell disease include; hyphema, central retinal artery occlusion (CRAO), orbital and periorbital infections, orbital infarction, and orbital compression syndrome (OCS). Let’s briefly have a look at them.
We define hyphema as the presence of blood in the anterior chamber of the eye; it is usually due to blunt trauma. A patient with hyphema typically presents with haemorrhage that covers the lower part of the iris and visual abnormalities like floaters or flashers, light sensitivity, and blurry vision. The hypoxic and acidotic nature of the anterior chamber of the eye makes hyphema very dangerous. It is because these changes in pH and O2 promote sickling of the red blood cells in the aqueous humour to go through the trabecular network. It leads to an increase of pressure in the entire eye, which then impedes blood flow in the central retinal artery, which can ultimately result in central retinal artery occlusion and optic nerve infarction. It is worth noting that people with sickle cell disease poorly tolerate increased intraocular pressure, and hyphema size doesn’t correlate well with the risk of visual loss. People with sickle cell disease can have prolonged hyphema and are at a high risk of secondary haemorrhage. When increased intraocular pressure secondary to hyphema isn’t amenable to medical interventions, anterior chamber paracentesis or surgical evacuation of the clot is needed to preserve vision.
Formation of a thrombus in the central retinal artery leads to central retinal artery occlusion (CRAO), a rare cause of acute blindness, only seen in children and young adults with sickle cell anaemia. When the sickle red cells occlude the central retinal artery, the lack of blood supply to the inner retina leads to its infarction, and this culminates in macular ischemia with a possibility of macular infarction. Patients with CRAO report sudden, painless unilateral or bilateral loss of vision. Much as CRAO can occur spontaneously, people with sickle cell disease in association with acute chest syndrome, moyamoya syndrome, or increased intraocular pressure secondary to hyphema have developed it.
Orbital infarction is a rare but severe ocular complication that typically occurs in the vaso-occlusive crisis. It is believed to be caused by ischemia vessel wall necrosis and complicated by hematoma formation. Because of the limited space in the orbital cavity, the inflammation that arises due to bone infarction affects the surrounding eye structures leading to observed features such as eye protrusion, eye pain, and lid +/- orbital oedema. Patients have decreased visual acuity and extraocular motility upon examination.
Orbital infarction can mimic periorbital infection. Perform imaging to rule out its different causes. As mentioned earlier, if symptoms do not remit with medical interventions, surgical management is mandated to prevent visual loss.
The presence of compressive optic neuropathy and decreased extraocular motility is known as orbital compression syndrome or orbital apex syndrome. It is due to orbital inflammation after sphenoid bone infarction with subperiosteal hematomas. The decreased extraocular motility is due to compression of the branches of cranial nerves III and V.
Once you rule out periorbital infection, initiation of corticosteroids can reverse this condition. Magnetic resonance imaging (MRI) helps make a diagnosis. Once medical interventions fail, surgical interventions must be employed.
When you encounter any of the above conditions or mere having them in your differentials, the following recommendations will guide you in helping the patient’s vision become preserved.
Again, as with all other articles about sickle cell disease so far, these are adapted from the evidence-based management of sickle cell disease manual at NHLBI.
- Immediately examine for hyphema in anyone with sickle cell disease who presents with eye trauma. If hyphema is present, promptly refer to an ophthalmologist for further management.
- Promptly transfer anyone with sickle cell disease and has signs of eye disease to an eye specialist capable of performing a dilated eye exam to assess visual acuity, intraocular pressure, and the peripheral retina.
- Manage acute ocular complications in consultation with an ophthalmologist, and other sickle cell specialists.
In many instances, referring the patient on time is the best management plan you can offer; however, you cannot refer on time if you cannot suspect a few of these conditions. Thorough history taking as well as detailed, focused examination will guide on which differentials to generate.
Don’t forget to share this article with your colleagues, and come back next time as we demystify the chronic complications of sickle cell disease in our next article series.