Medical condition
Sickle cell retinopathy can be defined as retinal changes due to blood vessel damage in the eye of a person with a background of sickle cell disease. It can likely progress to loss of vision in late stages due to vitreous hemorrhage or retinal detachment. Sickle cell disease is a structural red blood cell disorder leading to consequences in multiple systems. It is characterized by chronic red blood cell destruction, vascular injury, and tissue ischemia causing damage to the brain, eyes, heart, lungs, kidneys, spleen, and musculoskeletal system.
People affected by sickle cell disease are commonly of African or Asian descent. Emigration patterns towards the Western Hemisphere have led to increased numbers of persons affected by sickle cell disease in regions where it was previously uncommon. Knowledge and understanding of sickle cell disease and its management are now increasingly relevant in areas such as the European Union. At a young age, a great proportion of people living with sickle cell disease can develop retinal changes. Sickle cell disease consists of several subtypes; however, the Haemoglobin type C (HbSC) subtype carries the gravest prognosis for sickle cell retinopathy and vision changes.
Regular retinal examinations can aid in early detection and treatment, thus reducing the impact of the condition and the risk of vision loss. Development and progression of sickle cell retinopathy can be favorably modified through management of the underling sickle cell disease. Treatment of the general disease can ameliorate its systemic effects.
Classification.
Sickle cell retinopathy can be classified based on retinal changes into non-proliferative and proliferative subtypes.
Non-proliferative sickle cell retinopathy (NPSCR).
Non-proliferative sickle cell retinopathy (NPSCR) can feature the following retinal manifestations:
Proliferative sickle cell retinopathy (PSCR).
Proliferative sickle retinopathy is the most severe ocular complication of sickle cell disease. Even though PSCR begins in the first decade of life, the condition remains asymptomatic and unnoticed until visual symptoms occur due to vitreous hemorrhage or retinal detachment.
Goldberg classification.
Goldberg classified PSR into following 5 different self-explanatory stages:
Cause.
Normal adult hemoglobin A molecule comprises two α and two β globin chains associated with a heme ring. Mutation at the 6th position of the beta chain is the cause of sickle cell disease. Due to sickle cell disease, vascular occlusion may occur in the conjunctiva, iris, retina, or choroid. Retinal changes occur due to blockage of retinal blood vessels by abnormal RBCs.
Diagnosis.
Diagnostic Techniques.
Diagnosis is conducted in a multidisciplinary manner. The diagnosis of sickle cell disease can be confirmed by cation high performance liquid chromatography, haemoglobin electrophoresis in adolescents and adults and molecular genetic diagnosis in prenatal and neonatal populations. Anterior segment signs including the conjunctival sign and iris atrophy are ocular manifestations that are strongly indicative of sickle cell disease. Early stages of sickle cell retinopathy are asymptomatic. However, retinal changes that are diagnostic of sickle cell retinopathy can be visualized using fundoscopic examinations, retinography, fluorescein angiography and coherence tomography. Ultra Widefield Fluorescein Angiography is the gold standard for diagnosis of proliferative sickle cell retinopathy. It is an invasive method that assesses both anterior and posterior segment structures. Spectral Domain Optical Coherence Tomography and Coherence Tomography Angiography are non invasive methods of diagnosing proliferative retinopathy. Visual acuity and intraocular pressure assessments can also yield results that are diagnostic of sickle cell retinopathy.
Differential diagnosis.
Sickle cell retinopathy should be differentiated from other retinal conditions that arise due to similar pathologies. The following differentials are classified by those pathologies.
Prevention.
Screening.
Screening is an important pillar of prevention of sickle cell retinopathy as it provides the benefit of early detection and treatment thus reducing complications. Screening also provides an opportunity for education of families predisposed to retinopathy as a result of a family history of sickle cell disease. Screening can take the form of DNA screening at birth and Ophthalmology-related examinations later in life.
Care of systemic disease.
Sickle cell disease is a systemic disease that affects several organs in the body. Management of the underlying disease can therefore prevent the development of retinopathy and slow its progression.
Treatment.
Medical.
Vascular endothelial growth factor (VEGF) is known to be associated with sea fan lesions which are types of neovascularization. Bevacizumab is an anti-VEGF drug used in intravitreal injection that is known to cause reversal of sea fan lesions and reduce the duration of vitreous hemorrhage. Intravitreal injection of anti-VEGF drugs can also be used prior to surgery to aid separation of tissues involved in the sea fan lesion and to reduce intraoperative and postoperative hemorrhage. It is useful in combination with photocoagulation.
Laser.
Indications for laser photocoagulation include
There are two methods of photocoagulation mainly used; feeder vessel coagulation and scatter laser coagulation. The first method closes the vessels that supply the neovascularized areas using laser burns. Both the xenon arc and argon laser can be used however, the argon laser carries a reduced risk of complications. In comparison, scatter laser coagulation has an indirect effect. Ischemic retina produces vascular endothelial growth factor (VEGF) which promotes neovascularization. Scatter laser coagulation destroys this ischemic retina using laser burns thus preventing vitreous hemorrhage, retinal detachment and vision loss.
Surgery.
Surgical intervention is indicated for severely advanced disease that poses a threat to visual acuity. Indications include longstanding vitreous haemorrhage, vitreous haemorrhage in both eyes, vitreous haemorrhage in patients with only one eye, epiretinal membranes, macular holes and the various forms of retinal detachment. Scleral buckle was a previously popular surgical intervention however, its complications include anterior segment ischemia as a result of vascular occlusion. The vascular occlusion can in turn lead to phthisis bulbi. Pars plans vitrectomy is useful for the management of vitreous haemorrhage. Its complications include cataracts, hyphema, glaucoma and unresolved vitreous haemorrhage.
References.
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