Retinopathy of prematurity (ROP) is a widely known retinal vascular disorder in preterm infants and a leading cause of visual disability or blindness in children. Advances in antenatal care have resulted in an increase in the survival rate of infants with extremely low birth weight (BW). Approximately 90% of infants who develop ROP do so by a postmenstrual age of 46.3 weeks. In certain patients with or without treatment, the retina may fail to fully vascularize or may develop vascular abnormalities, thus demonstrating persistent avascular retina (PAR) or anomalous vessel findings at the periphery. Because of the advent of technologies such as ultrawide-field fluorescein angiography (UWFFA) persistent vascular abnormalities can be detected more readily and investigated.

The natural history of peripheral nonperfusion and vascular abnormalities, which persist beyond the acute phase of ROP, remains poorly understood. Although patients with a history of type I ROP (treatment requiring ROP) are more likely to exhibit abnormal foveal development and poor vision, a discrepancy still exists between the structural and functional findings of vascular abnormalities in the long term. For instance, circumferential atypical vessels are detected in patients with spontaneously regressed ROP and favorable vision. Additionally, persistent retinal vascular abnormalities may not necessarily predict adverse functional outcomes. The significance of such vessel anomalies and whether they persist or not remain uncertain. The physiologic avascular retina of children of age < 13 years usually extends ≤ 1.5 DD temporally or ≤ 1.0 DD nasally from the ora serrata. Therefore, the PAR (peripheral avascular retina) is defined as the nonperfusion area with measurements ≥ 2.0 DD, which is 3 standard deviations more than the normal value. Infants with persistent avascular retina have unknown long-term structural and functional risks, and theoretically could develop disease requiring treatment, including retinal breaks or tractional bands. Prolonged retinal traction by remnant shunt or extra-retinal fibrovascular proliferation between a stable prenatally vascularized retina in the posterior pole and an unstable postnatally vascularized retina may lead to the development of retinal holes characteristically located in the fragile, anterior undifferentiated avascular retina. Treatment options may vary from observation to retinal laser photocoagulation.

Inclusion Criteria:

• Patients with persistent peripheral avascular retina attending follow up till the age of 18 months in the core study whether;
• regressed ROP: children with regressed ROP who had not received any treatment.
• IVI treatment ROP: children with a history of threshold ROP treated with IVI of anti-VEGF agents.

Exclusion Criteria:

• Eyes with previous laser therapy.
• Eyes with any other pathology, other than ROP.
• Eyes with stage 4 or 5 ROP.
• Patients with hypersensitivity to iodinated contrast media, liver and renal insufficiency, history of asthma.
• Patients who will show hypersensitivity reaction to fluorescein angiography will be excluded from the thesis.
• Patients unfit for general anesthesia.