Retinopathy of Prematurity

Retinopathy of Prematurity (ROP) is an eye disorder that can affect premature babies who are born before 31 weeks of gestation and weigh about 1250g or less. It causes abnormal blood vessels to grow in the retina which can result in blindness.

ROP usually develops in both eyes.

Causes of ROP

ROP happens when abnormal blood vessels grow and spread in the retina. The abnormal blood vessels can leak since they are fragile and scar the retina, pulling it out of position resulting in retinal detachment. Retinal detachment is the main cause of visual impairment and blindness in ROP.

The development of ROP may be due to several complex factors. The eye starts developing at around the 16^th week of pregnancy which is when the blood vessels of the retina start to form at the optic nerve in the back of the eye. The blood vessels gradually grow spreading towards the edge of the developing retina supplying it with nutrients and oxygen. In the last 12 weeks of pregnancy, the eye develops rapidly. The retina finishes growing a month or a few weeks after birth. But in premature babies, the normal vessel growth may stop before the blood vessels reach the edge of the retina. This results in the edges of the retina not getting enough nutrients and oxygen.

Stages of ROP

There are five stages of ROP with stage I being mild and stage V being severe.

• Stage I: This consists of mild abnormal blood vessel growth and most children who develop stage I ROP improve without any treatment and develop normal vision.
• Stage II: This consists of moderately abnormal blood vessel growth which resolves on its own and the children eventually develop normal vision.
• Stage III: In this stage there is severely abnormal blood vessel growth. Instead of the abnormal blood vessels following the normal growth pattern along the surface of the retina, they grow towards the center of the eye. A number of infants who develop stage III ROP tend to improve without treatment and eventually develop normal vision. However, when stage III ROP has reached a certain degree and a ‘plus disease’ develops, treatment is required. A plus disease is when the blood vessels of the retina become enlarged and twisted thereby worsening the ROP. Treatment at this point concentrates on preventing retinal detachment.
• Stage IV: This involves a partially detached retina. The bleeding, abnormal vessels cause a scar which pulls the retina away from the wall of the eye.
• Stage V: This is the complete detachment of the retina and the end stage of the disease. If not treated it can cause severe visual impairment and even blindness.

Treatment for ROP

Some forms of ROP are mild and usually correct themselves. The most effective treatments for advanced ROP are Laser surgery and cryotherapy.

Laser therapy burns away the periphery of the retina with the abnormal blood vessels.

Cryotherapy involves freezing the touch spots on the surface of the eye which overlie the periphery of the retina.

Both of these treatments destroy the peripheral areas of the retina, reversing or slowing the abnormal growth of the blood vessels. Unfortunately, they also destroy some side vision. Laser therapy and cryotherapy are performed so as to save the most important part of sight, which is the sharp, central vision that is needed for straight ahead activities such as reading, driving etc.

Treatment options for the most advanced cases of ROP are:

• Scleral Buckling: This involves placing a flexible band made of silicone around the circumference of the eye. It goes around the sclera or the white of the eye causing it to buckle or tighten. It prevents the vitreous gel from pulling on the scar tissue thus allowing the retina to flatten back on to the wall of the eye. However, the band needs to be removed months or years later to avoid the child from becoming nearsighted.
• Vitrectomy: This surgery involves replacing the clear gel in the center of the eye (vitreous gel) with a saline solution. This allows for the easier removal of the scar tissue and eases the tugging on the retina.

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