الفهرس 
Normal development of retinal vasculature Normal Development of Retinal VasculatureOnly 14 pages are availabe for public view
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Abstract
Retinopathy of Prematurity (ROP) is a proliferative disease occurs in the incompletely vascularized retina of premature babies. It is an important cause of blindness in children in both developed and developing countries. ROP is described by severity (5 stages), location by zone (I-III), extent by clock hours or sector quadrant and by the presence of pre-plus and plus disease.
The developing retinal vasculature of premature infants is extremely vulnerable, and perturbation of the normal developmental processes can result in retinopathy of prematurity. Vasculogenesis provides a mechanism for rapid formation of a rudimentary vascular plexus in the regions previously invaded by vascular precursor cells and that this plexus is then expanded by angiogenesis to satisfy the increasing metabolic needs of the developing retina. The mechanism of retinal vascularization is thus similar to that of vascularization of the brain during development
Hypoxia stimulates VEGF production which induces neovascularization at the border between vascularized and non-vascularized retina, with in the worse case is ending in retinal detachment. Although VEGF and oxygen play an important role in the development of retinal blood vessels, it is clear that other biochemical mediators also are involved in the pathogenesis.
Babies at risk of ROP require ophthalmic screening to identify whom requiring treatment and this together with the meticulous neonatal management can reduce the risk of vision loss due to the disease. Because of the sequential nature of ROP progression and the proven benefits of timely treatment in reducing the risk of visual loss, effective care now requires that at-risk infants receive carefully timed retinal examinations by an ophthalmologist who is experienced in the examination of preterm infants for ROP and that all pediatricians who care for these at-risk preterm infants be aware of this timing.
Retinal cryotherapy and laser photocoagulation have both proven to be successful methods of treating active ROP. They are used to ablate the avascular retina anterior to the fibrovascular ridge. Cryotherapy was the mode of treatment in the absence of portable laser machines.
Despite appropriate laser treatment, however, progression to tractional retinal detachment was seen in 10% to 15% of cases of threshold ROP and in up to 50%in a subset of infants with particularly aggressive ROP. The concept of a more severe form of ROP, aggressive, posterior ROP (AP-ROP), was introduced in the revised ROP classification and is frequently associated with congestion of iris vessels, prominence of tunica vasculosa lentis, poor pupillary dilation, and vitreous haze, all of which can compromise the integrity of the examination and completeness of laser treatment. The incidence of persistent neovascularization and possibility of unfavorable outcome, especially among cases of AP-ROP, has spurred the quest for alternative treatments. Pharmacologic inhibition of VEGF in ROP has both biological plausibility and empiric clinical success in various retinal vascular proliferative diseases.
Usage of Anti VEGF agents in treatment of ROP is a good choice After exhaustion of laser treatment, As single injection before 40 wk (PMA) before increase in TGF B (which associated with increased risk of fibrous proliferation) and Can be considered in certain races like Hispanics which have more aggressive ROP and this important to study demographics of ROP and If we don’t have laser available.
After that there is a need to do additional animal studies to determine the correct drug and dose that allow best efficacy with fewest recurrences and to test the rate of growth and time to completion of the normal peripheral retinal vasculature, as well as the percentage of recurrence of neovascularization with different doses of pegaptanib, ranibizumab, bevacizumab, to determine the optimal efficacy with the fewest recurrences