RETINOPATHY OF PREMATURITY

Abstract

Continuous improvement in outcomes cannot be accomplished by simply continuing with the techniques and technologies that led to success in the past. The Cryotherapy for Retinopathy of Prematurity (CRYO-ROP) Study is a significant success story, but progress cannot end there. The scientific validity of laser photocoagulation for ROP has become reasonably accepted by using retrospective studies comparing outcomes with cryotherapy data. 1,2,9,10,11,12,15,16,18,19,24,25,29,30,31 Laser treatment causes less pain, less myopia, and minimal arrthymias, and prevents conjunctival damage compared with cryotherapy. 1,2,6,11,12,13,16 Laser therapy was initially performed with an argon laser (514 nm) delivered by using a beamsteering attachment on the operating microscope. This method was generally performed in the operating room. The invention of the laser indirect ophthalmoscope (LIO) delivery system enabled treatment without an operating microscope. 4,14 Diode lasers are approximately 10,000 times more efficient than argon ion lasers, eliminating the need for watercooling, large enclosures, and special electrical power (230 V AC, three phases, 60 A/phase). The diode laser enabled lightweight, portable LIO-based systems to be used in the neonatal intensive care unit. 4 The near-infrared wavelengths of typical diode lasers (˜810 nm) are primarily absorbed in the melanin pigment of the choroid and retinal pigment epithelium rather than in hemoglobin. This absorption spectrum reduces uptake in the tunica vasculosa lentis and secondary thermal anterior subcapsular cataracts. 5,26 Clinical trials are always based on the reasonable notion that a set of physicians, practicing with state-of-the-art techniques, can disagree on the most effective management. The issue may be whether the treatment is effective compared with the natural history of untreated patients or with an alternative treatment. Further, the physicians must agree on a small, finite number of groups for randomization. It is critical to all randomized trials to determine standardized entrance criteria for randomization. The minimum pathology required for treatment in the context of the study is often referred to as the threshold. If most of the investigators are concerned about treatment complications or skeptical about treatment efficacy, the threshold will require relatively advanced pathology. On the contrary, if the known treatment complications are minimal and there is optimism concerning efficacy, the threshold for randomization will allow less advanced disease. It is seldom possible to have a cohort large enough to compare several different degrees of severity as indications for treatment. Unless early verus late treatment is studied, use of the treatment timing recommended by the study is an arbitrary decision. Large-scale, expensive, randomized trials are essential but can have the unintended consequence of limiting further progress because of the perception that departure from the study entrance criteria is not ethical. The major emphasis that medical malpractice attorneys place on ROP amplifies the rigid adherence to guidelines that were intended to be study entrance criteria.