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Paediatrics

Retinopathy of Prematurity

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Preventable cause of childhood visual disability

Risk factors

  • Premature <32 weeks
  • Birth weight <1500g
  • Supplementary oxygen
  • Placental abruption
  • Twins
  • Intraventricular haemorrhage
  • Necrotizing enterocolitis
  • Blood transfusion

Pathogenesis

  • Normal complete vascularisation occurs by 40 weeks
  • Biphasic theory: high ambient oxygen is toxic to capillaries and on return to room air there is relative ischaemia
  • Spindle cell theory: sheet of spindle cells secrete angiogenic factors

Stages

  1. Demarcation line separating vascular from avascular zones
  2. Ridge, may be pinkish with neovascular tufts
  3. Ridge with extraretinal fibrovascular proliferation
  4. Subtotal RD
  5. Total RD

Signs of plus disease

  • Increased venous dilation
  • Arteriolar tortuosity
  • Iris vascular engorgement
  • Poor pupillary dilation
  • Vitreous haze

Pre-plus:

  • More venous and arteriolar dilation and tortuosity than normal but insufficient to be plus

Locations

  • Zone 1: circle around disc with radius twice the distance from disc to fovea
  • Zone 2: circle extending from zone 1 to ora nasally and to equator temporally
  • Zone 3: remaining temporal crescent

Hot Topic

When to treat

  • Threshold disease: defined by CRYO-ROP study which established peripheral retinal ablation as standard of therapy

    • Stage 3 ROP with plus disease in zones 1 or 2 and of 5 continuous or 8 non-continuous clock-hours

  • Pre-threshold: the ETROP study suggested benefit in treating pre-threshold

    • Zone 1: any stage ROP with plus disease

    • Zone 1: stage 3 regardless of plus disease or not

    • Zone 2: stage 2 or 3 with plus disease

Treatment timing

  • Aggressive posterior (APROP) disease (aka Rush disease) should be treated within 48 hours

    • Severe and rapidly progressive form with Stage 3 ROP in zone 1 or posterior zone 2

  • Non-aggressive disease should be treated within 48-72 hours

  • The first post-treatment examination should occur 5-7 days afterwards with weekly review to assess for disease regression (and re-treatment at 10-14 days if there is no improvement)

Transpupillary diode laser: first line

  • Should be applied to the entire avascular retina
  • Aim for near-confluent burns
  • Argon laser or cryotherapy may be used if diode laser unavailable

Intravitreal anti-VEGF:

  • Increasingly used for posterior ROP

Hot Topic

College screening criteria

  • Should be screened

    • All babies less than 32 weeks gestation
    • All babies less than 1501g birthweight

  • Must be screened

    • Babies under 31 weeks gestation
    • Babies under 1251g birthweight

  • And they should be screened prior to discharge from hospital

College screening protocol

  • Born <27 weeks gestation: screen at 30-31 weeks gestation

  • Born 27-32 weeks gestation: screen at 4-5 weeks postnatal

  • Born >32 weeks (but <1501g): screen at 4-5 weeks postnatal

  • Weekly screening

    • Any plus or pre-plus disease (see above for definitions)
    • Vessels in zone I or posterior zone II
    • Stage 3 disease

  • Fortnightly screening

    • All other circumstances

Discontinuing screening

  • When no longer at risk of sight-threatening ROP

  • If no ROP: when vascularisation extends in zone III (typically after 36 weeks gestational age)

  • If ROP: when at least 2 signs of regression

    • No increase in severity
    • Resolution
    • Ridge changes from salmon pink to white
    • Vessels transgress through demarcation line
    • Scarring of active lesions

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