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رگزایی
In one study,43 even relatively mature preterm infants (gestational age at birth of 31·7 weeks [range 28-35 weeks]) lost retinal vessels (phase 1) and progressed to severe zone-1 neovascularisation (phase 2) when exposed to 100% oxygen after birth.
In stage 3, extraretinal neovascularisation can become severe enough to cause total retinal detachment (stage 5), which leads to blindness.
Type 1 now includes a more virulent form of retinopathy in extremely low-birthweight babies (aggressive posterior retinopathy of prematurity), which involves very central neovascularisation with plus disease.116 Screening guidelines vary with the characteristics of the premature population and neonatal intensive care practices in different settings.
Cryotherapy emerged in the 1980s as the method used on the first widely studied intervention-ablation of non-vascularised retina-that reduced structural and functional disease associated with retinopathy of prematurity.131 In the CRYO-ROP study,132 preterm infants were treated at the point of progression of retinopathy of prematurity (a subcategory of stage 3), at which time retinal neovascularisation was equally likely to progress to retinal detachment (high risk for blindness) or to regress.
Prevention by reduction of risk factors that disrupt normal retinal vascularisation is likely to be more effective than late treatment of neovascularisation, not only with respect to vision, but also other comorbidities of premature birth.
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