Infant and child vision research: present status and future directions.

At the turn of the last century William James speculated that the sensory world of an infant would be a “blooming, buzzing confusion. ” In fact, relatively little was known about visual development in infants and young children until the 1950s and 1960s, just before Velma embarked on her scientific career. With the advent of new techniques to assess systematically the vision of non-verbal, seemingly uncooperative subjects, a great deal has now been learned about vision in the first months and years after birth. Although specific information was being gathered from infants and young children, neuroscientists were demonstrating that visual experience could alter the neural circuitry of the developing brain. These insights had implications for the management and treatment of amblyopia. The demonstration of a sensitive period of cortical plasticity was good news in that it held promise for success in the treatment of experience-dependent conditions, but it was also bad news in that it demonstrated that the window of opportunity for aggressive treatment is early in childhood and relatively short. Velma’s work and career exemplify the integration of two key themes in understanding the development of vision in infants and children. The first has been to ask fundamental questions about the development of visual abilities in infants and how these skills integrate with other aspects of their motor and cognitive development. The second has been to ask how clinicians might be able to detect, diagnose, treat, and potentially prevent permanent visual abnormality during the first postnatal years. These two approaches were apparent in a major review published in the early 1990s. Chapters written by a group of scientists and clinicians, including Velma, were compiled and edited by Kurt Simons into the highly cited and referenced book, “Early Visual Development, Normal and Abnormal. ” This current feature issue of OVS, 16 years on, has provided an excellent opportunity to reflect on these themes in the context of additional knowledge. The contributions to this issue illustrate the number of paths that have been taken in the past two decades. The development of the optics of the eye has attracted significant attention for three clinically important reasons. First, retinal image quality defines the information being presented to the developing neural visual system and we need to ensure that this information is appropriate for normal development during infancy and early childhood. Thus, we need to understand normal refractive development and the interaction between the developing optical and neural visual systems, in the context of amblyopia in particular. Second, numerous studies have demonstrated the potential for visual experience to influence the growth of the eye. We need to understand the process of emmetropization, and determine whether it can be encouraged through appropriate refractive correction. Finally, the realization that the incidence and prevalence of myopia is increasing dramatically around the world has revealed an urgent need for understanding the pathological underpinnings of this condition. We have been able to make real progress in our understanding of refractive development with the relatively recent development of autorefractors and photorefractors, as well as more robust approaches to quantifying refractive error. However, significant elements of these core questions still remain. The clinical assessment of the status of the visual system has also attracted attention, from both vision screening and full examination perspectives. There are still significant challenges in obtaining reliable data from “wriggly” children in a screening setting, and we are still some way from reaching a consensus about how best to provide the pediatric population with vision screenings. In addition to the impact of the sensitive period, these assessments also need to occur at a young age before children enter school with its additional visual demands. The recognition that early treatment is frequently beneficial for the developing visual system still drives us to refine techniques for reliably diagnosing, assessing, and monitoring visual status in the general clinical community. Still, we have basic work to do to develop a clear understanding of the mechanisms and natural history of a number of important and relatively common clinical conditions. Large-scale population based studies using efficient techniques are still required to determine the risk factors for these conditions and their natural history. There have also been a number of interesting demonstrations in the past 20 years that visual experience impacts developing neural circuitry at higher stages of processing, and therefore that tools are required to look at the more perceptual and cognitive aspects of function. In this context, there have been a series of studies looking at typical development of these functions and the impact of lower level immaturities on them, and also of complex and difficult clinical conditions. An area in which Velma has shown particular strength is the transfer of new knowledge to clinical care. The most significant contribution has likely been her work in two large clinical trials in retinopathy of prematurity (ROP), the Cryotherapy for ROP Study, and the Early Treatment for ROP Trial. By introducing quantitative assessment of grating visual acuity in infants and young children as a major outcome measure in these two studies, an earlier determination of potential functional benefit could be made rather than waiting until the child was able to provide more “standard” measures of acuity. Such outcome measures allowed 1040-5488/09/8606-0559/0 VOL. 86, NO. 6, PP. 559–560 OPTOMETRY AND VISION SCIENCE Copyright © 2009 American Academy of Optometry