الفهرس 
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Abstract
SUM MAR Y
Retinal neovascularization is a serious compli~ation
which occurs in a varity of disease entities such as diabetes
mellitus, retinal vein occlusion, sickle cell disease,
retinopathy of prematurity, Eales’ disease, sarcojdosis
and others. The exact mechanism by which these diseases
can induce retinal neovascularization is unknpwn. It
seems that the retinal ischaemia, localized or generalized,
produced by these disease plays a fundamental role in the
pathogenesis of neovascularization.
In diabetes, retinal ischaemia is produced by the
pathology in the vessels’ wall .1n retinal vein occlusion,
stagnation produces retinal ischaemia. In sickle cell disease,
retinal ischaemia is produced by microemboli or by
viscosity induced thrombosis. In retrolental fi~roplasia,
retinal ishcaemia is produced by arteriolar occlusions due
to oxygen toxicity. In Eales’ disease and sarcoidosis, inflammation
of the vascular walls cause narrowing and may
be occlusion of retinal vessels with resultant retinal ischaemia.
Regardless how retinal ischaemia is produced, it is
speculated that such hypoxic retinal areas elaborate a vasoformative
substance that stimulates the growth of new vessels.
Most of these neovascularization occur in the areas
of retinal ischaemia or at the interface between ischaemic
and perfused areas with the neovascular tufts growing into
the ischaemic zones. This has made some investigators suspect
that the neovascular tissue is growing in response to
a stimulus generated by the hypoxic retinal tissue.
The site of the neovascular tufts either in the retinal
periphery or on the disc,which is considered more serious
as it is more vulnerable to cause vitreous haemorrhage
and retinal detachment than peripheral retinal neovascularization.
Significant progress has been achieved in photocoagulation
therapy techaniques and vitrectomy surgery by which
major benefit in control of retinal neovascularization is
ful£illed • However many cases seem to be away from control
and will not be controllable until we have a firm grasp of
the mechanism of neovascularization.