الفهرس 
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Abstract
Retinopathy of prematurity (RaP) is a disease characterized by
retinal neovascularization including the vitreous, possibly leading to retinal
detachment and finally to blindness. It occurs in premature newborns, its
incidence and severity are inversely related to maturity, i.e. gestational age
and birth weight.
Several etiological factors have been incriminated; the immaturity
and O2 are the two main factors. Bright light in the premature nursery has
been implicated in the pathogenesis of Rap. Hypercarbia, steroids,
exchange tranfusion, fundus pigmentationa and sex are more common risk
factors. Vitamin E deficiency has a role in the development of Rap.
The incidence of Rap varies widely ranging from 15% to 65% of
premature. Rap occurred in approximately 7% of infants of birth weight
between IOOO-1500g. It increased to 42% among survivors weighting
between 500 and 750 g. The incidence may reach 72% and 89% of infants
weighting less than 900g.
However, the pathogenesis of Rap was altributed to disturbance in
the balance between O2 supply and metabolic needs of the retinal tissue.
This balance is disturbed by an increase in O2 supply. Hyperoxia disturbs
the spindle cells and gap junction occurs. This lead to release of angio
genic factors with subsequent neovascularization. Hyperoxia leads to
vasoconstriction followed by vasodilation. Vasodilation leads to flattening
of the endothelial cells. This flattening increase the rate of mitosis resulting
ill neovascularization. Also hyperoxia is associated with loss of vascular
endothelial growth factor (VEGF) production which leads to cessation of
normal vessel growth. VEGF not only causes abnormal neovascularization
in ROP, but it is also important for normal vasculogenesis.
The pathological changes are classified into stages:
1- Acute ROP, where a demarcation line is seen clinically that separates
the peripheral avascular retina from the vascular retina.
1- Regression of the disease : can be identified by failure of acute changes
to progress.
3- Cicatricial ROP: where avascular retina changes into a contracting scar.
The disease is classified according to the International classification
of ROP into 5 stages:
Stage I: Demarcation line.
Stage 2: Ridge
Stage 3: Ridge with extraretinal fibrovascular proliferation.
Stage 4: Subtotal retinal detachment
A: Extrafoveal retinal detachment.
B: Retinal dechment including fovea.
Stage 5: Total retinal detachment.
The retina is devided into three zones centered on the optic disc.
The extent of the disease is specified by the hours of the clock involved.
The main factor in the prevention ofROP is to avoid pretenn births.
Vitamin E is used as a prophylactic. It is suggested that vit. E decrease the
incidence, and severity of active ROP. O2 monitoring is used as a
prophylactic factor, it is not known what is the critical concentration of O2.
It was suggested to maintain arterial P02 between 50 and 80 mmHg.
Treatment of threshold ROP prevents severe visual loss in a very
high percentage of cases. Cryotherapy at early stage leads to better
anatomical and fimctional results than given at more advanced stages. The
aim of the treatment is to produce extensive chorioretinal scars to reduce
the fibrovascular proliferation. Cryotherapy may be done at 5-7 weeks
according to the gestational age.
Laser treatment is as effective as cyrotherapy. The advantages of
laser are rapid response to adequate treatment, rapid diagnosis of
inadequate treatment, ease of repeated treatment and application in the
neonate units.
Surgical interventions by means of scleral buckling and vitreous
surgery are used for treatment of retinal detachment. Stage 4 ROP is
treated by scleral buckling. It has success rate of 66% to 7()% for stage 4A
and 67% for stage 4B retinal detachment. Total retinal detachment (Stage
V) is treated with vitreous surgery.
The sequel of the disease include: myopia, strabismus, amblyopia,
glaucoma and phthisis bulbi.