Retinopathy of Prematurity

A potentially blinding disorder of retinal vascular development affecting premature infants, resulting from disruption of the normal, orderly process of retinal vascularisation that would otherwise continue in utero through to term gestation.

Representing a significant, though substantially preventable and treatable, cause of childhood visual impairment, with structured, proactive screening of at-risk premature infants essential given the direct, critical relationship between timely detection and treatment and preservation of vision. Risk correlates closely with the degree of prematurity and the specific pattern and intensity of postnatal oxygen exposure.

Pathophysiology

• Normal retinal vascularisation proceeds from the optic disc toward the peripheral retina throughout the third trimester.
• Infants born prematurely are therefore delivered with an incompletely vascularised peripheral retina. The extent of this is directly related to the degree of prematurity at birth.
• After premature birth, the relatively hyperoxic extrauterine environment, particularly where supplemental oxygen therapy is required, suppresses normal vascular endothelial growth factor-driven vessel growth. This is the initial phase of vascular growth arrest.
• A relative hypoxic phase follows as the retina continues to mature and its metabolic demand increases without a correspondingly adequate vascular supply. This triggers excessive, disorganised, and pathological neovascularisation at the border between vascularised and non-vascularised retina.
• This abnormal neovascularisation, if progressive and untreated, can lead to fibrovascular proliferation, retinal traction, and, in the most severe cases, retinal detachment and permanent visual loss. This is the critical, sight-threatening endpoint that proactive screening and timely treatment aim to prevent.

• The condition is asymptomatic in its earlier, potentially treatable stages, with no specific clinical sign apparent to caregivers. Disease can only be reliably identified through structured, proactive screening rather than symptomatic presentation. This underscores the essential importance of full, systematic screening programmes for at-risk infants.
• More advanced, untreated disease may eventually present with leukocoria, strabismus, or nystagmus, reflecting significant, established visual impairment. Presentation at this stage represents a failure of the screening process rather than the intended point of clinical detection.
• Disease severity is formally classified by three features. This structured classification directly informs screening frequency and treatment decisions.
  • Zone: the location of the disease relative to the optic disc, with more posterior zones carrying greater risk.
  • Stage: the severity of the vascular abnormality present, from mild demarcation line through to retinal detachment.
  • The presence or absence of "plus disease": significant vascular dilation and tortuosity of the posterior retinal vessels, indicating more active, aggressive disease.
• Infants born at lower gestational age and birth weight, together with those requiring more prolonged or intensive supplemental oxygen therapy, or experiencing significant neonatal illness more broadly, carry the highest risk of developing clinically significant disease.

• Structured, scheduled screening ophthalmological examination, performed by an appropriately experienced practitioner using indirect ophthalmoscopy, represents the essential diagnostic approach.
• It is offered to infants meeting established gestational age and birth weight screening criteria (according to specific national or regional protocol). The first examination is timed according to a structured schedule relative to both gestational age at birth and chronological age since birth.
• Serial follow-up examinations are performed at intervals determined by the findings of the initial and subsequent assessments. The specific interval is shortened for more advanced or rapidly progressive disease.
• Follow-up continues until the retina has completed normal vascularisation or the disease has regressed to a point where further progression risk is judged to be minimal.
• Full, accurate documentation of disease zone, stage, and the presence or absence of plus disease at each assessment supports consistent, structured monitoring and directly informs the decision regarding treatment threshold.

• Laser photocoagulation, applied to the peripheral, non-vascularised retina, represents the standard, established treatment for disease reaching a defined treatment threshold, aiming to halt the abnormal neovascular stimulus and thereby prevent progression to retinal detachment.
• Intravitreal anti-vascular endothelial growth factor injection represents an increasingly used treatment option, particularly relevant for more posterior, zone one disease. It offers certain advantages over laser treatment for this specific pattern of disease.
• It requires careful, structured, and typically more prolonged follow-up, given the specific, recognised pattern of potential late reactivation with this treatment approach.
• Surgical intervention, including vitrectomy, is reserved for the most advanced disease with established retinal detachment. It offers the potential for some degree of visual preservation, though with substantially more limited overall visual outcome compared with disease treated at an earlier, pre-detachment stage.
• Full, long-term ophthalmological follow-up extends beyond resolution of the acute disease process. There is a recognised, increased longer-term risk of refractive error, strabismus, amblyopia, and, in some cases, retinal detachment occurring later in childhood or even adulthood in individuals with a history of this condition.
• This underscores the importance of sustained, structured surveillance well beyond the initial neonatal screening and treatment period.
• Careful, judicious use of supplemental oxygen therapy in premature infants, targeting appropriate, evidence-based oxygen saturation ranges rather than excessive oxygenation, represents an important, complementary preventive strategy. It works alongside structured screening to minimise the overall burden of this condition.