Sickle Cell Retinopathy

Although systemic disease is most severe in HbSS, ocular disease is most severe in HbSC (a different mutant Hb) and HbThal

• HbSS is the most common (8.5% of North American population of African descent)
• HbThal is much less common (0.03%)

Mutant haemoglobin instead of normal haemoglobin A: leads to sickling in conditions of hypoxia causing blood vessel obstruction and further ischaemia/sickling

Clinical features

• Visual loss is mostly due to proliferative disease and vitreous haemorrhage

• Proliferative retinopathy

  • Stage 1: peripheral arteriolar occlusions
  • Stage 2: AV anastomoses
  • Stage 3: neovascular proliferation (sea-fans)
  • Stage 4: vitreous haemorrhage
  • Stage 5: retinal detachment

• Non-proliferative retinopathy: tortuosity, CWS, microaneurysms, peripheral non-perfusion, equatorial salmon-patches (fresh intraretinal bleeds), angioid streaks

• External/anterior segment:

  • Periorbital swelling from orbital bone infarction/haematoma
  • Comma-shaped conjunctival capillaries
  • Sectoral iris atrophy
  • Hyphaema: increased risk of retinal artery occlusions if raised IOP and of optic nerve compromise
    • Surgery if IOP >25 for 24 hours

Management

• No treatment for small peripheral lesions as most resolve spontaneously (via autoinfarction of new vessels)

  • Treatment may be reserved for those with bilateral disease, extensive proliferative disease, rapid neovascular growth or only eye

• Scatter laser photocoagulation if rapid growth of sea-fans

• anti-VEGF

• Vitrectomy for persistent vitreous haemorrhage or tractional RD

• AC paracentesis for raised IOP in hyphaema