1, the occurrence of ROP is divided into 3 zones: zone 1 is centered on the optic disc, and the distance from the center of the optic disc to the central macular concavity is drawn as a circle with a radius of 2 times; zone 2 is centered on the optic disc, and the radius from the center of the optic disc to the nasal serrated edge is drawn as a circle; the remaining part outside zone 2 is zone 3. The more backward the early lesion is, the greater the risk of progression. 2, the severity of the lesion is divided into 5 stages: stage 1 occurs at approximately 34 weeks of corrected fetal age, and a demarcation line appears between the vascular and nonvascular areas in the temporal periphery of the fundus retina; stage 2 occurs at an average of 35 weeks (32-40 weeks), and the fundus demarcation line is elevated with ridge-like changes; stage 3 occurs at an average of 36 weeks (32-43 weeks), and retinal vascular dilatation and proliferation occurs on the ridge of the fundus demarcation line, accompanied by In stage 4, tractional retinal detachment occurs due to fibrovascular proliferation, starting at the periphery and gradually progressing to the posterior pole; this stage is divided into A and B according to the presence or absence of macular detachment, A without macular detachment and B with macular detachment. 5, total retinal detachment occurs (approximately 10 weeks after birth). “Plus” disease refers to dilated and tortuous retinal blood vessels in the posterior pole, and a “+” is written next to the stage of the lesion when “Plus” disease exists, e.g., stage 3 +. “Pre-threshold ROP” indicates that the lesion will progress rapidly, requiring a shorter review interval and close observation of the condition, including: any lesion in zone 1, stage 2 + in zone 2, stage 3, stage 3 +. Threshold lesions include: stage 3 + of zone 1 and 2 adjacent lesions up to 5 clock points consecutively, or up to 8 clock points cumulatively, which are lesions that must be treated. 3. Advanced lesions with shallow or absent anterior chamber can be secondary to glaucoma and corneal degeneration.