About Retinopathy of Prematurity (ROP)
The internal surface of the back of the eye is lined by a tissue, called the retina. This tissue is equivalent to the film in a camera and is responsible for the initial formation of the visual image. This is then transmitted to the brain. In order to function, the retina requires a blood supply. The normal development of this blood supply for the retina starts at 16 weeks into a pregnancy and is completed by 36 weeks.
If an infant is born prematurely, with the retinal blood vessel development incomplete, problems occur.
Abnormal blood vessels may develop which can subsequently lead to bleeding and scar tissue formation. This may then stretch the retina pulling it out of position. Visual loss may result.
Inheritance and ROP
There does not appear to be any hereditary basis for this condition, ie it is association with premature birth and not specific families.
Causes of ROP
The lack of oxygen in areas of retina which have not developed blood vessels, results in the release of chemicals that promote the growth of new blood vessels. These blood vessels often grow in an irregular manner, for reasons that are not completely understood. The presence of large amounts of oxygen (often needed for the baby's survival) is thought to be possibly toxic to the developing blood vessels. As premature babies have underdeveloped lungs they usually require additional oxygen therapy. There are other undetermined factors also contributing.
Risk factors
The main risk factor is a premature birth. The condition is most common in infants with a birth weight of less than 1250 grams and a gestational age of less than 28 weeks.
Effects of ROP
The milder forms of ROP may resolve spontaneously just as the more severe forms may lead to irretrievable blindness, despite treatment. Unless the ROP resolves, it exerts its effect mainly through the formation of scar tissue which then pulls the retina out of place. This may result only in a minor displacement of the area of the central vision or in a total retinal detachment. In the former case, the corrected visual acuity may be good, whereas in the latter case, even the ability to perceive light may be lost.
Treatment for ROP
Currently, treatment relies on the destruction of the areas of the retina that are without blood vessels.
This becomes necessary only if the disease has reached a certain, well defined stage, as the milder forms often regress spontaneously. By destroying the retina, the stimulus for the growth of the abnormal blood vessels is removed. The destruction is achieved by cryotherapy (literally freezing the retina, using a small pulse) or photocoagulation with laser energy. Rarely, surgery is undertaken in an attempt to remove the scar tissue. To prevent ROP, Paediatricians attempt to minimise the amount of supplemental oxygen the infant is receiving.
Extent of ROP
This is very dependent on the birth weight and gestational age of the infant, as this has a direct influence on the extent of the disease. The disease does not present itself until the time that the normal blood vessel growth would approach completion, ie at 32 weeks of the adjusted gestational age. Five per cent of premature infants will have some scarring changes associated with ROP and 1.2 per cent will be blinded by it. Other late complications may develop (such as cataract and glaucoma).
What next
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Useful contacts
RNIB is not aware of any support group for this condition, however the following may help:
LOOK is an organisation that seeks to identify sight related support groups and put parents in contact. They have regional representatives and their national office can be contacted.
LOOK UK
Queen Alexandras College
Court Oak Rd
Harbourne
Birmingham
B17 9TG
Tel: 0121 428 5038
Partially Sighted Society
7 - 9 Bennetthorpe
Doncaster
South Yorkshire
DN2 6AA
Tel: 0844 477 4966
Fax: 0844 477 4969
Are able to advise on low vision services, lighting and aids.
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