This is an application to become one of the cooperating study centers in the Cryotherapy for Retinopathy of Prematurity Study. The CYRO-ROP Study consists of essentially two research components: (1) A clinical trial of the safety and efficacy of cryotherapy in reducing blindness in eyes with severe, high, risk, ROP; and (2) a study of the natural history (in accord with the international classification of ROP) of retinopathy of prematurity in very low birth weight infants (less than 1,250 grams). In this proposal, we document the ability of our group of ophthalmologists and neonatologists to enroll, each year 132 very low birth weight infants who have survived at least 28 days in the natural history study. We anticipate that eight to ten of these infants will also develop retinopathy of prematurity severe enough to become eligible for enrollment to the clinical trial, and an additional three to five patients will be referred to our study for enrollment to that trial.