Retinopathy of prematurity

Branch 1: Classification

Examiner: Describe this infant's ROP. Expected response: This is Type 1 ROP. Zone I is the most posterior zone, and Zone I stage 3 disease with plus disease meets Type 1 criteria, which is the treatment threshold established by the ETROP trial [1]. The classification is recorded for each eye by zone, stage, extent in clock-hours, and the presence of plus disease per ICROP-3 [3].

Branch 2: Treatment decision

Examiner: How urgently must you act, and what are the options? Expected response: Type 1 ROP must be treated within 72 hours because untreated disease can progress rapidly to irreversible retinal detachment [1]. The options are laser photocoagulation of the avascular retina and intravitreal anti-VEGF therapy. For Zone I disease, anti-VEGF is often preferred because laser would destroy a large area of posterior retina and BEAT-ROP showed bevacizumab was superior to laser for Zone I stage 3 disease with plus [2].

Branch 3: Anti-VEGF versus laser

Examiner: What are the trade-offs of intravitreal bevacizumab? Expected response: Bevacizumab spares the peripheral retina and causes less myopia than laser, and in BEAT-ROP the dose was 0.625 mg intravitreally [2]. The trade-offs are the need for aseptic intraocular injection, the theoretical systemic effects of suppressing vascular endothelial growth factor in a developing infant, and the risk of late reactivation that demands prolonged surveillance beyond the usual screening window [2].

Branch 4: Pathophysiology

Examiner: Why does this disease happen at all? Expected response: ROP follows a two-phase model. In Phase 1, the relative hyperoxia of extrauterine life and loss of placental insulin-like growth factor 1 suppress vascular endothelial growth factor and IGF-1, causing arrest and regression of developing capillaries and enlarging the avascular retina [3]. In Phase 2, that avascular retina becomes hypoxic and releases a vascular endothelial growth factor surge that, with recovering IGF-1, drives the abnormal neovascularisation we are now treating [3].

Branch 5: Screening and prevention

Examiner: How should this infant have been identified, and what might have reduced the risk? Expected response: The infant met screening criteria by gestational age of 30 weeks or less and birth weight of 1500 g or less, with the first examination at 31 weeks postmenstrual age or 4 weeks of age, whichever was later [4]. Prevention centres on avoiding oxygen swings with a saturation target of 91 to 95 percent and optimising growth, anaemia, and sepsis control [4].