Retinopathy of Prematurity (ROP)
Basics about the Eye Condition that May Affect Some Premature Babies
This article describes the causes, signs, diagnosis and treatment of this eye disease that a small minority of premature babies may develop.
If a baby is born prematurely, there is a small chance that the blood vessels of the retina are incompletely developed. This leads to the development of abnormal blood vessels which can produce bleeding and scar tissue formation. Consequently, the retina stretches – and is pulled out of position. Visual loss may be the result of this.
The retina is the lining tissue to the internal surface of the back of the eye. The tissue is similar in concept to the film in a camera. It produces the initial formation of the visual image created by the eye. This is then transmitted to the brain where the picture is produced.
The retina needs a good blood supply to function. In pregnancy, the normal development of this blood supply for the retina begins at 16 weeks into a pregnancy; it is completed by 36 weeks of pregnancy.
Causes
There is no hereditary reason for this condition. The lack of oxygen in parts of the retina which still have not developed blood vessels means that chemicals are released that cause the growth of new blood vessels. These may grow in an irregular way, for reasons that are not yet fully understood. Researchers believe that large amounts of oxygen (required for the survival of the baby) can be toxic to the growing blood vessels. There may be other factors that are as yet undetermined.
Risk factors
The main risk is premature birth. ROP is most prevalent if babies are born weighing less than 1250 grams with a gestational age of less than 28 weeks.
Consequences of ROP
It is possible that milder forms of this condition resolve themselves spontaneously. More severe forms of ROP may produce irreversible blindness. If ROP does not resolve, the effects of the condition are produced mainly through the formation of scar tissue pulling the retina out of place. This could result in a small displacement of the area of central vision, meaning that the corrected visual acuity may be good. In the case of a complete retinal detachment, even the ablity to see light may be lost.
Treatment
Treatment involves the destruction of areas of the retina that do not have blood vesels. This is only required if the disease has reached a well-defined stage, as the milder forms may resolve without treatment. By destroying the retina, the growth of abnormal blood vessels ceases. Destruction of the retina is carried out with the use of cryotherapy (freezing the retina), or photocoagulation using laser energy. In rare cases, surgery is used, to attempt to remove the scarring.
Sight
The birth weight and gestational age of the baby has an influence on the severity of the disease, should it occur. The condition shows no signs until the time that the normal blood vessel growth would be almost complete (32 weeks of the adjusted gestational age). There are many tests that are performed in newborn babies, and they all exist to check for good health and discover any anomalies.
5 per cent of premature babies have some scarring changes relating to ROP, and 1.2 per cent will be blinded as a result of this condition.
