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Sickle retinopathy results from aggregation of abnormal hemoglobin in the red blood cells in the retinal microcirculation, leading to reduced deformability of RBCs, stagnant blood flow in the retinal precapillary arterioles, thrombosis, and ischemia.
History:
Sickle cell disease (SCD) was first described in Africa under a variety of names that related to cultural spiritual beliefs. James B. Herrick was an American physician who made the first clinical discovery and reported in 1910 ‘peculiar elongated and sickle-shaped red blood corpuscles in a case of severe anaemia’ affecting a medical student from Grenada. Initially the disease was known as Herrick’s syndrome and it was not until 1922 when a fourth case reported by a medical student, Verne R. Mason, from Johns Hopkins Hospital that the term ‘sickle cell anaemia (SCA)’ was first used.
In 1937, Harden published the first retinal findings of SCR in two patients who had dilated and tortuous vessels which were at that time attributed to congenitally abnormal vessels. The next case series came from Accra, in what was then the Gold Coast, describing unusual changes in retinal vessels with peripheral small aneurysms in one case and vitreous haemorrhage in the other which was the first allusion to a specific retinopathy. It is interesting to note that the subsequent published case reports of SCR were all related to vitreous haemorrhage. Welch and Goldberg published a landmark case control study of 143 patients to document and categorise all the retinal findings for this condition. This classification is still in practice today. The natural course of the ‘incipient’ stage of SCR was poorly understood. A longitudinal study performed by Galinos et al. was the first time that remodelling of the peripheral retinal vasculature was documented. Although the proliferative stage was better understood, it produced some therapeutic challenges, especially as a number of proliferative cases were known to spontaneously regress or auto-infarct.
Pathophysiology
Sickle cell disease (SCD) is a severe hematological disorder of chronic hemolysis, vascular injury and tissue ischemia impacting multiple organ systems.
Goldberg’s classification:
Grade retinopathy severity based on clinically significant alterations of the retinal vasculature with disease progression
- Stage 1: Peripheral arteriolar occlusion
- Stage 2 :Peripheral arteriovenous anastomoses
- Stage 3: Actual retinal neovascularization occurs, with a shape resembling Gorgonia flabellum (sea fan)
- Stage 4: Vitreous hemorrhage
- Stage 5: Retinal detachment (tractional/rhegmatogenous), due to mechanical traction by the fibrovascular membranes
Non-proliferative sickle cell retinopathy (stages I–II)
Commonly observed in patients with HbSS genotype
- Peripheral retinal vascular closure/anastomoses
- Salmon-patch hemorrhages
- Iridescent spots
- Black sunbursts
Proliferative sickle cell retinopathy (stages III–V)
More frequently manifested in patients with HbSC
- Sea fans (extra-retinal neovascularisations that subsequently become fibrovascular and tend to begin peripherally) (HALLMARK)
Complications
Sight threatening complications:
- Paracentral middle maculopathy
- Central retinal vein occlusion (CRVO)
- Vitreous hemorrhage
- Retinal detachment
Diagnosis
Screening: Fundus examinations
Annual fundus examinations are recommended from 10 years age
- Non-proliferative sickle cell retinopathy (NPSR): Salmon patches, iridescent spots & black sunbursts
- Proliferative sickle cell retinopathy (PSR): Sea fan/parachute configurations
Fluorescein angiography:
Ideal investigation for evaluation of retinal blood flow and detection of neovascularization
Optical coherence tomatohraphy (OCT):
Help reveal areas of macular thinning.
Management
Laser photocoagulation
Mainstay of treatment
Intravitreal anti-VEGF injections
Vitrectomy:
Indicated in nonclearing vitreous hemorrhages and retinal detachment