Gene therapy for retinopathy of prematurity: the eye is a window to the future

Retinopathy of prematurity: Past, present and future

Retinopathy of prematurity (ROP) is a vasoproliferative disorder of the retina occurring principally in new born preterm infants. It is an avoidable cause of childhood blindness. With the increase in the survival of preterm babies, ROP has become the leading cause of preventable childhood blindness throughout the world. A simple screening test done within a few weeks after birth by an ophthalmologist can avoid this preventable blindness. Although screening guidelines and protocols are strictly followed in the developed nations, it lacks in developing economies like India and China, which have the highest number of preterm deliveries in the world. The burden of this blindness in these countries is set to increase tremendously in the future, if corrective steps are not taken immediately. ROP first emerged in 1940s and 1950s, when it was called retrolental fibroplasia. Several epidemics of this disease were and are still occurring in different regions of the world and since then a lot of research has been done on this disease. However, till date very few comprehensive review articles covering all the aspects of ROP are published. This review highlights the past, present and future strategies in managing this disease. It would help the pediatricians to update their current knowledge on ROP.

Retinopathy of prematurity promising newer modalities of treatment

Retinopathy of prematurity (ROP) is a disorder of neonatal retinal vascularization. The incidence is increasing in developing countries like India in view of the rising numbers of preterm deliveries and improved neonatal care. Traditional modalities of treatment included cryotherapy and laser therapy, which were laborious and required special training. Hence, research is on way to find novel treatment modalities directed at various levels of pathogenesis for this blinding disease. We reviewed the published and unpublished literature on newer methods of ROP management. The pathogenesis of ROP has been studied with respect to the mediators of angiogenesis. Anti vascular endothelial growth factor (Anti-VEGF) therapy has been extensively studied and the studies have demonstrated its promising role early stages of ROP. The role of Insulin like growth factor (IGF), Granulocyte colony stimulating factor (GCSF), and June kinases (JNK) inhibitors are being studied by various researchers across the world. Gene therapy holds promise in the reversal of ROP changes.

Defective trafficking of rhodopsin and its role in retinal degenerations

Retinitis pigmentosa is a retinal degeneration transmitted by varied modes of inheritance and affects approximately 1 in 4000 individuals. The photoreceptors of the outer retina, as well as the retinal pigmented epithelium which supports the outer retina metabolically and structurally, are the retinal regions most affected by the disorder. In several forms of retinitis pigmentosa, the mislocalization of the rod photoreceptor protein rhodopsin is thought to be a contributing factor underlying the pathophysiology seen in patients. The mutations causing this mislocalization often occur in genes coding proteins involved in ciliary formation, vesicular transport, rod outer segment disc formation, and stability, as well as the rhodopsin protein itself. Often, these mutations result in the most early-onset cases of both recessive and dominant retinitis pigmentosa, and the following presents a discussion of the proteins, their degenerative phenotypes, and possible treatments of the disease.

Severe visual impairment and blindness in children in the UK

BACKGROUND

Prevention of visual impairment and blindness in childhood is an international priority. However, many countries do not have contemporary information about incidence and causes, from which the scope and priorities for prevention and treatment can be identified.

METHODS

In the UK, children aged younger than 16 years newly diagnosed with severe visual impairment or blindness (SVI/BL, WHO criteria) during 2000 were identified through national active surveillance schemes in ophthalmology and paediatrics. From these data, we calculated yearly age-group specific incidence and cumulative incidence. Causes were classified by the anatomical site or sites affected and by timing of the insult or insults and causal factors, where known.

FINDINGS

Of 439 newly diagnosed children, 336 (77%) had additional non-ophthalmic disorders or impairments (SVI/BL plus). Total yearly incidence was highest in the first year of life, being 4.0 (95% CI 3.6-4.5) per 10000, with a cumulative incidence by 16 years of age of 5.9 (5.3-6.5) per 10000. 10% (44) of all children died within 1 year of diagnosis of blindness. Prenatal causal factors affected 61% (268) of children, with perinatal or neonatal and childhood factors each affecting 18% (77). Incidence and causes varied with presence of non-ophthalmic impairments or disorders, birthweight, and ethnic origin. At least 75% (331) of children had disorders that were neither potentially preventable nor treatable, with current knowledge.

INTERPRETATION

Severe visual impairment and blindness in childhood in the UK is more common, occurs more frequently in the context of complex non-ophthalmic impairments, and has greater associated mortality, than previously assumed. An increased rate in children of low birthweight and from ethnic minority groups, together with the observed diversity and complexity of the causes, reflect recent secular changes in the population at risk, specific risk factors, and strategies available for treatment.