Expert perspectives on the evolution of retina practice, procedures, technologies and instrumentation.
Samir N. Patel, MD; Yoshihiro Yonekawa, MD, FASRS; and James F. Vander, MD
Retinopathy of prematurity (ROP) was originally described as retrolental fibroplasia (RLF) by T.L. Terry, who in 1942 first connected the condition with premature birth. In the report, he describes a, “Grayish-white, opaque membrane behind each crystalline lens.” He was in fact seeing severe bilateral traction retinal detachment. With technological and clinical advances facilitating survival of more premature infants, including liberal oxygen supplementation, ROP became more common, and by 1950, ROP had become the largest cause of childhood blindness in the United States and throughout the technologically developed world.
Early on, visual outcomes were often poor despite attempts with surgical and radiation interventions. In the 1960s, photocoagulation for ROP was pioneered by Nagata et al with xenon lasers, but delivery though vitreous haze proved difficult prior to the advent of the indirect ophthalmoscope laser. In the late 1980s, the International Classification of Retinopathy of Prematurity paved the way for the Multicenter Trial of Cryotherapy for Retinopathy of Prematurity (CRYO-ROP). CRYO-ROP showed the effectiveness of peripheral retinal cryotherapy for infants with threshold ROP. Despite the efficacy of cryotherapy for the treatment of ROP, several drawbacks prompted investigators to pursue other treatment modalities.
First, although cryotherapy may be easily administered to anterior locations, posterior treatment was challenging. For zone I disease, cryotherapy was technically difficult in these eyes because of the posterior location of the ridge and large retinal area requiring treatment. Indeed, in CRYO-ROP, for infants with zone I ROP, the beneficial effect was limited to a reduction in unfavorable anatomic outcomes from 92% to 75%. Furthermore, adjunctive measures were often necessary to facilitate cryotherapy, including conjunctival incisions for posterior application.
Around the same time as CRYO-ROP, a portable binocular laser indirect ophthalmoscope was being introduced for adult patients with retinal pathology.[5,6] This new technology greatly reduced some of the challenges posed by cryopexy for the treatment of ROP. Laser photocoagulation made it much easier to assure complete treatment, reduced physical stress on the infant and reduced post-treatment inflammation among many advantages.
After the initial reports of the CRYO-ROP study group, McNamara et al investigated laser photocoagulation as a means for retinal ablation and as an alternative to cryotherapy (Figure 1). Their initial studies used a fixed, water-cooled argon green laser (Coherent, Palo Alto, CA).[7-11] These early studies demonstrated that compared to cryotherapy, laser photocoagulation yielded better anatomic and functional results including improved visual acuity, and less risk of retinal dragging, axial length elongation, and lens thickening.[7-9, 12]
Further advances including the development of a solid-state diode technology permitted miniaturization of laser instrumentation and led to a portable diode laser with indirect ophthalmoscopy (OcuLight SLx, IRIS Medical, Mountain View, CA) that allowed for treatment of infants in the neonatal intensive care unit. Clinically, use of the indirect diode laser photocoagulation gained popularity as it made treatment easier for both the infant and surgeon with results that were at least as good if not better than those achieved with cryotherapy.
The remarkable shift from cryotherapy to laser as the modality of choice was most evident with the Early Treatment of Retinopathy of Prematurity (ETROP) study that enrolled infants between 2000 and 2002.[16,17] Although the study protocol allowed for treatment with either laser therapy or cryotherapy, laser therapy was preferred with only one eye (1/356) receiving cryotherapy at threshold ROP and all others treated with laser. Longitudinal data continues to support the anatomic and functional success of laser treatment for ROP.
Today, while there have been many advances in ROP management, laser photocoagulation remains one of the primary treatment modalities for ROP.
(Milestone essay published 2022)