Retinopathy of prematurity is a condition affecting preterm and low birth weight neonates. It mainly affects infants born before 32 weeks gestation. Abnormal blood vessel development in the retina can lead to scarring, retinal detachment and blindness. Early detection and treatment can prevent vision loss.
Pathophysiology
Retinal blood vessel development starts at around 16 weeks and is complete by 37–40 weeks gestation. The blood vessels grow from the middle of the retina to the outer area. This vessel formation is stimulated by hypoxia, which is normal in the retina during pregnancy. Vascular endothelial growth factor (VEGF) promotes the development of new vessels.
VEGF and blood vessel development are suppressed when the retina is exposed to higher oxygen concentrations in a preterm baby, particularly with supplementary oxygen during medical care.
When the hypoxic environment recurs, the retina responds with overproduction of VEGF, new abnormal vessel development (neovascularisation) and scar tissue formation. The abnormal blood vessels may regress and leave the retina without a blood supply. The scar tissue may cause retinal detachment.
Assessment
The retina is divided into three zones:
- Zone 1 includes the optic nerve and the macula
- Zone 2 is from the edge of zone 1 to the nasal ora serrata, the border between the retina and ciliary body
- Zone 3 is the temporal crescent of the retina beyond zone 2
The retinal areas are described as a clock face (e.g., “there is disease from 3 to 5 o’clock”). The areas of disease are described from stage 1 (slightly abnormal vessel growth) to stage 5 (complete retinal detachment).
“Plus disease” describes additional findings, such as tortuous vessels and hazy vitreous humour.
Screening
Babies born before 32 weeks or under 1.5kg are screened by an ophthalmologist. Screening starts at:
- 30-31 weeks corrected gestational age in neonates born before 27 weeks
- 4-5 weeks of postnatal age in neonates born after 27 weeks
All retinal areas need to be visualised. Screening involves monitoring the retinal vessels as they develop and looking for plus disease. Screening occurs at least every 2 weeks and stops once normal retinal vessels enter zone 3, usually around 36-40 weeks corrected gestational age.
Treatment
Treatment involves systematically targeting areas of the retina to stop new blood vessels from developing.
Transpupillary laser photocoagulation is the first-line treatment for halting neovascularisation.
Other treatment options include:
- Intravitreal VEGF inhibitors (e.g., bevacizumab or ranibizumab)
- Surgery (if retinal detachment occurs)
Last updated May 2025
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