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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.

  • Autosomal recessive.

  • 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.


Ophthalmic manifestations:

  1. Orbital – orbital bone infarction ; orbital haematoma (need Abx + steroid Rx or orbital decompression) ; lacrimal gland swelling.

  2. 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)

  3. Retinal changes


Retinal changes:

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


Management:

  • 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.

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