Sickle Cell Retinopathy
Sickle cell disease:
Normal HbA = 2 alpha-globin + 2 beta-globin + central haem molecule.
Point mutation at the 6th position of chromosome 11 –> replacement of glutamic acid by a valine in beta-globin of Hb –> HbS.
Both genes are sickle cell variant = SS disease.
When one gene has HbC variant = SC disease (less severe form).
When one gene is normal –> no disease = SC trait (carrier).
Associated with beta-thalassemia gene.
Afro-American / Hispanic – 0.15% sickle cell disease overall.
Black Americans – 8% SC trait.
Orbital – orbital bone infarction ; orbital haematoma (need Abx + steroid Rx or orbital decompression) ; lacrimal gland swelling.
Anterior segment – Paton’s conjunctival sign (corkscrew saccular dilation of conjunctival vessels) ; radial iris neovascularisation (–> NVG) ; hyphaema (EMERGENCY – risk CRAO even with mild IOP rise – need AC washout or paracentesis)
Non-proliferative sickle retinopathy:
1) Salmon-patch haemorrhages (result of sudden giving way of occluded vessel)
2) Black sunburst (localised choroidal ischaemic damage of RPE –> localised CNVM or subretinal tracking of retinal haemorrhage)
3) Peripheral retinal whitening with strong vitreoretinal adhesion – like white without pressure (common).
4) Macular iscahmeia – enlarged FAZ.
5) Rarely – macular hole, ERM, foveoschisis, CNVM
Proliferative sickle retinopathy:
Staging by Goldberg (1971):
Stage I – peripheral vascular occlusion with silver wiring of arterioles at temporal retina.
Stage II – AV anastomosis – non-leaking
Stage III – sea fan neovascularisation (commonly superotemporal)
Stage IV – Vitreous haemorrhage
Stage V – Tractional retinal detachment
Commonly SC disease patient & HbS-beta thalassaemia.
Investigations: Ultrawide field angiography ; OCT macula
Non-proliferative cases: observe 3-6 months.
Proliferative cases: observe (1/3 regress with autoinfarction)
Proliferative cases with bilateral disease, rapid Stage III onwards progression: targeted laser treatment of ischaemic areas.
Vitreous haemorrhage without RD: Observe.
Vitreous haemorrhage with RD: PPV + endolaser +/- preop anti-VEGF.
Scleral buckle – use with caution due to risk of anterior segment ischaemia.