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EARLY ablation of the avascular retina produces improved visual outcomes in patients with high-risk pre-threshold retinopathy of prematurity, a large multicentre study indicates. The Early Treatment for Retinopathy of Prematurity (ETROP) randomised 317 ROP patients at 26 centres to early intervention in one eye and conventional management in the fellow eye. Another 84 infants with asymmetric disease were randomised to early treatment or conventional management of the affected eye. All infants had high-risk pre-threshold disease. The most common treatment used was laser ablation, but cryotherapy was also performed in some cases. Conventional treatment consisted of observation unless ROP progressed to the threshold level. Masked testers using the Teller acuity card measured grating acuity at six months of age. The researchers evaluated structural outcomes at six and nine months of age. There was no difference in the amount of refractive errors in the two groups at nine months. Similarly, cataract and aphakia not associated with total retinal detachment or vitrectomy occurred in 1.2% of each treatment group. These assessments demonstrated a marked advantage in favour of early intervention. Unfavourable visual acuity outcomes were reduced from 19.5% to 14.5% in the early treatment group. Unfavourable structural outcomes were also reduced, from 16.6% to 9.1%. Both results were statistically significant. "This study represents another important step in our ongoing efforts to decrease preventable blindness in premature babies. We have identified a group of children whose eyes would not have been treated before using the conventional threshold definition, but many of these eyes clearly benefited from earlier treatment. However, not all treatment is successful and we have more to do," said Graham Quinn MD, Children's Hospital of Philadelphia . Researchers have long endeavoured to identify more effective interventions for patients with ROP. Previously a large prospective clinical trial of retinal cryotherapy, CRYO-ROP, concluded that nearly half of patients had no better than 20/200 visual acuity at the age of ten. And among those who had better than 20/200, less than half had 20/40 or better. Subsequent studies showed no benefit from supplemental oxygen therapy or from reduction in light exposure. The CRYO-ROP study established a threshold for ablative treatment when ocular findings indicated a risk of retinal detachment of at least 50%. The current study was designed to determine whether earlier intervention, i.e., where the risk of retinal detachment was less than 50%, might be better, recognising the objection that this might subject some eyes to surgery that would otherwise regress spontaneously. The ETROP protocol utilised a new computerised risk model to identify high-risk infants early in the disease. The program assessed numerous risk factors believed to be associated with higher risk including birth weight, ethnicity, gestational age, and ophthalmic examination findings. The researchers screened all participants with the first 42 days of life. They performed serial examinations to monitor the progression of disease. They followed all infants with retinal vessels ending in zone 1 but no ROP, or with vessels in zone 2. They entered the patient's data into the computer program if at least one eye reached the pre-threshold ROP stage. Subsequent analysis of the data provided additional insight into risk stratification. The data confirmed the value of ablation in eyes with type I ROP, that is, any disease in zone 1. It also supported intervention in eyes with any stage of ROP abnormal dilation and tortuosity of the posterior retinal vasculature. The data also supported intervention in eyes with zone 1 stage 3 ROP; or zone 2 stage 2 or stage 3 ROP with plus disease. The data also gave some indication of when watchful waiting was the preferred option. This included type 2 ROP (zone 1 stage 1 or stage 2) without plus disease; or stage 3 ROP without plus disease. The researchers suggested that such cases be considered for treatment only if they progress to type 1 or threshold ROP. "Before this study, we did not have a precise clinical model to follow to help predict which infants will ultimately develop vision loss from ROP, so we often had to defer treatment until the disease reached the treatment 'threshold,' at which point there was still a 25 percent chance of retinal detachment," explained Michael Repka MD, a paediatric ophthalmologist at the Johns Hopkins Children's Center in Baltimore Maryland. He noted that although there is a slight risk with ROP treatment, the benefits of these treatments are well established. The treatment preserve the most important part of vision - the sharp, central vision needed to read, see faces, or perform detailed tasks that require hand-eye coordination. The researchers caution that there may be potential long-term risks with early treatment. They will continue to follow the infants enrolled in the protocol until the age of six years to determine whether the benefits of early treatment persist into childhood. The ETROP study was funded by the US National Eye Institute and the National Institutes of Health. The results appeared in the December 2003 issue of the Archives of Ophthalmology. |
