The article on the 3½-year outcome of patients enrolled in the Cryotherapy for Retinopathy of Prematurity (CRYO-ROP) study published in the March 1993 issue of the Archives1 displays information in Figure 2 that may be subject to misinterpretation. This figure shows no visual acuity difference between treated and control eyes in the subgroup that had threshold ROP in zone I, thus raising a question regarding the value of treating those eyes. It is important to understand that it is impossible to make such a determination from the results of the CRYO-ROP study, both because of the very small number of eyes with zone I ROP studied (n=16) and because the study was not designed to answer questions regarding zone I ROP. To make this determination, a study would need to be designed to study an adequate number of eyes with ROP in zone I.
The CRYO-ROP study was not
Palmer EA, Hardy RJ. Zone I Retinopathy of Prematurity. Arch Ophthalmol. 1994;112(2):156. doi:10.1001/archopht.1994.01090140030008