Purpose: To report a series of infants who progressed from mild retinopathy of prematurity (ROP) to severe ROP with retinal detachment without demonstrating detectable threshold disease.
Methods: Between January 1993 and August 1998, seven infants at Oregon Health Sciences University, followed in accordance with the Cryotherapy for Retinopathy of Prematurity Study (CRYO-ROP) protocol, progressed to retinal detachment despite documentation that threshold had not been reached. This outlying subset of patients was analyzed and compared to the cohort in the CRYO-ROP study.
Results: Six of 7 patients were male, 6 (86%) patients had symmetric disease, and all patients were born outside the study hospital. Mean birth-weight was 877 g and mean gestational age was 26 weeks. Mean postconceptual age at the time of retinal detachment was 41 weeks. Because of bilateral detachment in 3 patients, the total number of study eyes is 10. Failure to achieve threshold resulted from insufficient clock hours or insufficient stage in 2 eyes and lack of plus in 8 eyes. Zone I disease was present in 1 eye.
Conclusion: Rarely, despite adhering to ROP examination protocol, the retina may detach without demonstrating antecedent threshold disease. Very low birthweight is a factor that may lead to a less predictable course. This study found a lack of plus disease results in failure to reach threshold more often than the occurrence of insufficient clock hours of stage 3 disease. Further study is needed to determine if selected cases of subthreshold ROP may benefit from ablative therapy.