To determine that slower weight premature twins have more risk to develop severe retinopathy of prematurity (ROP) than the higher weight twins. We know that the lower weight twins had less optimal intra-uterine environments than their higher weight twins. We screened 94 consecutive premature twins for ROP. We compared the lower weight twins (n = 47) against their higher weight twins (n = 47). The risk of severe ROP (ROP stage 3 or greater) was significantly higher in the lower weight twin group (p < 0.006). In the same way, in the lower weight twin group the non-perfused area of the temporal retinal artery was higher than that of the other group (an average of 1.2 diameters of the optic nerve head), in the 4-6 postnatal weeks (p < 0.004). The lower weight twin group have an increased risk of severe ROP associated with bacteremia (p = 0.045), or a weight gain less than 7 g per day in the 4-6 postnatal weeks (p = 0.013) or a supplementary postnatal oxygen >4 days (p = 0.007) compared to the higher weight twin group. We confirm Dr. Lee's work that less optimal prenatal factors, in preterm twins, increase the risk of severe ROP.