Retinopathy of prematurity

Short abstract

An old problem comes calling again

That retinopathy of prematurity (ROP) is occurring with increasing frequency in transitional economies is no longer debatable. Recognising this fact, the World Health Organization has identified ROP as a leading cause of vision impairment in children in the developing world.¹ Others have identified ROP as an important, increasingly common, and potentially treatable condition in emerging economies.²,³ No doubt, improvements in neonatal care in various regions of the world are allowing smaller infants to survive. The question is, what constitutes a low birthweight infant in an emerging economy? To answer this question requires information on the demographics of ROP in these regions.

But demographics of ROP in transitional economies are hard to ascertain. Without this knowledge, it will be difficult to identify those infants who should be screened and treated. Reports of the disease occurring in larger than expected birthweight infants, in increasing frequency, in more mature infants, are alarming. These reports are well designed and carefully conducted but they are hampered by the chaos that exists in medical care delivery in the developing world. This must be especially true when premature infants are considered. Nothing should be left to chance in evaluating premature infant disease in the developing world, and no demographic data should be considered entirely reliable unless directly observed.

Consider the following. Many premature infants in transitional economies do not have access to hospital care ever, let alone early in their lives. They are born outside the hospital, often in rural environments. Scales for weighing children are absent or poorly calibrated, and estimates of gestational age may be based on guesswork, the lunar cycle, or nothing at all. Families are often caught by surprise by the premature arrival of their child, and may not know that medical care could improve survival. The healthcare delivery system is fragmented, unless the infant's family has resources to allow hospitalisation. Even so, the family would need to live near an urban centre to gain access to more modern types of treatment. Thus we may not know the number of premature infants in a given region. We know of some infants observed to have the disease, but cannot effectively estimate how many premature infants die or are not evaluated in the first months after birth.

Important obstacles stand in the way of better understanding the epidemiology of ROP in emerging economies. Some obstacles are obvious, such as insufficient medical resources to allow identification of premature infant demographics. Improved organisation of healthcare delivery will allow better characterisation of premature infants. A significant shortage of full time, geographically based specialists in ROP poses an additional obstacle. Visiting experts to the developing world help diagnose and treat ROP, with resulting transfer of skills. On the other hand, it is difficult for a visitor to reliably appreciate the extent of the problem of ROP in these developing regions. Consultants to developing regions are shown or told of cases. Increasingly, we hear that these cases are atypical, at least by western standards. We must assume the worst; that ROP is increasing, and that paradigms for screening and treatment may need modification for emerging economies.

A treatment is available that can substantially reduce the rate of unfavourable outcomes, but surveillance for the disease is required

Some other obstacles to the study of the epidemiology of ROP are not so obvious. Equipment used to treat ROP rusts, is unfamiliar to practitioners, and/or periodically requires servicing. Reliable haemoglobin saturation monitoring is highly problematic. In the United States it may take days to find appropriate personnel to repair broken laser equipment. This sort of support simply does not exist in the developing world. Recognition of ICROP (International Classification of Retinopathy of Prematurity) diagnostic findings requires ongoing review and calibration of doctors. Physical findings and management of ROP and its prevention are debated even in the Western world. Meanwhile, emerging economies are visited by Westerners with varying opinions about ROP classification findings, treatment timing, management of oxygen, management of other medical issues, use of oxygen, antioxidants, light in the nursery, respirators, and so on.

By now, the reader may be feeling less than sanguine about the potential for reducing the prevalence of blindness from ROP in emerging economies. Along comes the enlightened article by Chen and Li published in this issue of the BJO (p 268) to offer more than just a glimmer of hope that ROP can be studied and treated. Although these authors raise the spectre that a new epidemic of ROP may be emerging, they indirectly demonstrate that screening programmes are slowly coming into existence, at least in major metropolitan areas.

Implied in this paper is the fact that ROP surveillance has attained an important status in some regions of China. To be sure, it is very alarming that zone I cases are occurring, but recognition of these cases is the first step in prevention and management. It is also a concern that larger birthweight infants may develop severe ROP. Here, too, understanding the epidemiology of ROP in this part of the world will lead to better diagnosis and treatment.

The Western world has much to learn from research emanating from the developing world. To the extent that the epidemiology in these regions differs from that in the Western world, these differences may serve as a basis for understanding what initiates the disease, and what reduces its incidence. In the United States, the incidence of the disease has not changed much in the past 15 years, despite significant medical advances in the care of preterm infants.⁴ Chen and Li suggest that imprecise use of oxygen could be a factor in the apparently increasing incidence and severity of ROP in China. This is a plausible explanation, and one that might explain how and why ROP should occasionally be so severe in larger and more mature infants. Could oxygenation policy in the United States affect the incidence of the disease?

The fact remains that ROP is recognised with increasing frequency in developing regions of the world. A treatment is available that can substantially reduce the rate of unfavourable outcomes, but surveillance for the disease is required. Chen and Li are to be congratulated for studying the incidence of ROP in their country, and for bringing to our attention the alarming observation that many infants are blinded by ROP in China. Exactly how such surveillance should occur in China and other developing nations will depend on local factors. The first step in reducing blindness from ROP is recognising that the problem exists.