For preventing Retinopathy of Prematurity, concentration of oxygen should be: March 2007

Ans. C: 50-60% Retinopathy of prematurity/ ROP/retrolental fibroplasia /RLF is a disease of the eye that affects prematurely born babies. As such, all preterm babies are at risk for ROP, and very low bih weight is an additional risk factor. Normally, maturation of the retina proceeds in-utero and at term, the mature infant has fully vascularised retina. However, in preterm infants, the retina is often not fully vascularised. ROP occurs when the development of the retinal vasculature is arrested and then proceeds abnormally. The key disease element is fibrovascular proliferation. This is growth of abnormal new vessels that may regress, but frequently progresses. Patients with ROP are at greater risk for strabismus, glaucoma, cataracts and myopia later in life. Retinal vascularization is judged to be complete when vessels extend to the ora serrata. Retinal examination with scleral depression is generally recommended for patients born before 30-32 weeks gestation, with bihweight 1500 grams or less, or at the discretion of the treating neonatologist. The initial examination is usually performed at 4-6 weeks of life, and then repeated every 1-3 weeks until vascularization is complete (or until disease progression mandates treatment). The most difficult aspect of the differential diagnosis may arise from the similarity of two other diseases: Familal Exudative Vitreoretinopathy which is a genetic disorder that also disrupts the retinal vascularization in full-term infants. Persistent Fetal Vascular Syndrome also known as Persistent Hyperplastic Primary Vitreous that can cause a traction retinal detachment difficult to differentiate but typically unilateral. Prophylaxis is most impoant. In the management of premature infants, the Pa02 level from the umbilical aery should be monitored, levels of 50-100 mm Hg being regarded as unlikely to produce constriction of immature retinal vessels. Unsatisfactory guides includes 'pinkiness', oxygen given at less than 40% in the tent and vascular constriction as seen by ophthalmologist. In establishes cases: Peripheral retinal ablation is the mainstay of ROP treatment. The destruction of the avascular retina is performed with a solid state laser photocoagulation device Cryotherapy, a technique in which regional retinal destruction was done using a probe to freeze the desired areas, However, cryotherapy is no longer preferred for routine avascular retinal ablation in premature babies, due to the side effects of inflammation and lid swelling. Scleral buckling and/or vitrectomy surgery may be considered for severe ROP Intravitreal injection of bevacizumab has been repoed as a suppoive measure in aggressive posterior retinopathy of prematurity.