- During development, retinal vessels grow from the optic disc towards the ora serrata (the peripheral retina).
- Blood vessels reach the nasal ora serrata at 36 weeks and the temporal ora serrata at 40 weeks.
- ROP is the result of arrest of vessel growth and rarely occurs before 32 weeks.
- Arrest of normal vascular development:
- Hyperoxia, often iatrogenic as treatment of neonatal respiratory distress syndrome.
- Arrest of normal growth factor production in the retina.
- Lack of retinal vascular development. o Hypoxia ensues:
- As the developing retina becomes more metabolically active, hypoxia ensues.
- This stimulates the growth of abnormal blood vessels, leading to retinal detachment.
- Other risk factors include birth weight < 1500g, extreme prematurity (<28 weeks), and neonatal hyperglycaemia.
Clinical: Exam may show
- White demarcation separating vascular and avascular areas
- Partial or complete retinal detachment, with or without foveal involvement.
- Abnormal tortuous retinal vessels may be visualised.
Screening and Investigations
- High risk children, born at less than 32 weeks or weighing < 1500g, should be screened for the development of ROP by an ophthalmologist.
- There are specific guidelines for how often children should be screened and at how many weeks after birth depending on the severity of disease and the degree of prematurity.
- Careful control of oxygenation in prematurity is essential in the prevention of ROP.
- Anti-VEGF agents can help to prevent the development of abnormal blood vessels.
- Transpupillary diode laser can be used to ablate the abnormal blood vessels and reduce the risk of retinal detachment.
- The non-vascularised retina can be sacrificed with ablative laser to prevent progression.
- In severe cases, blindness is often inevitable, particularly if retinal detachment occurs.
- Some vision may be preserved in milder cases, particularly if abnormal vessel growth does not occur or is arrested early.
References and Further Reading
- Retinopathy of Prematurity, Hellstrom et al., The Lancet, 2013; 382, 9902: 1445-1457.