[Calculated birth date as critical temporal marker for cryocoagulation of retinopathy of prematurity]

The time course of retinopathy of prematurity (ROP) is investigated for all preterm babies who underwent initial ocular therapy (cryocoagulation, encircling band or vitrectomy; 1983-1992; 156 eyes, 82 children; mean gestational age 28.1 weeks; mean birth weight: 864 g). Group I (ROP3+ in 5 adjacent or 8 accumulated clock hours): 63 eyes, 34 babies. The conceptional age at the time of cryo was 37.4 +/- 2.1 weeks. The disease progressed to cryo threshold before the presumed date of birth in 81% of cases. Group 2 (ROP4 and 5): 51 eyes, 27 babies. The gestational age at the time of first observation of ROP4 was 41.7 +/- 3.5 weeks. At least 39% of the detached cases arrived at stage 4 before the presumed date of birth. Group 3 (ROP3+ in less than 5 clock hours): Cryo-application in this grade of ROP is not generally accepted. We treated 42 eyes of 21 babies. Conceptional age at cryo therapy was 39.2 +/- 3.4 weeks.

The time window for efficient ablative cryotherapy of ROP is clearly before the presumed date of birth. Eyes requiring therapy are at high risk for retinal detachment (ROP4) to be already present at 40 weeks conceptional age and later. Exceptions are ROP3+ cases of minor lateral extension.