Retinopathy of prematurity (ROP) is a potentially blinding disease caused by abnormal development of retinal blood vessels in premature infants. The retina is the innermost layer of the eye that receives light and turns it into visual messages that are sent to the brain. When a baby is born prematurely, their eyes are also underdeveloped. As a result, the retinal blood vessels can grow abnormally. Most ROP cases resolve on their own, however; in severe cases, this can cause the retina to pull away or completely detach from the wall of the eye and possibly cause blindness.
Out of all the infants born in the U.S. each year, about 14,000 are affected by ROP. Birth weight and gestational age are the most important risk factors for its development. Babies </=1250 grams and </= 31 weeks gestation are at highest risk.
Other factors associated with ROP include anemia, poor weight gain, blood transfusion, respiratory distress, breathing difficulties and the overall health of the infant. Current research suggests that ROP is a complex disease with multifactorial causes including genetic and environmental factors.
Let’s start from the beginning...
The eye starts to develop at about 16 weeks, when the blood vessels of the retina begin to form at the optic nerve in the back of the eye. The preterm infant’s retina is partially vascularized at about 22 weeks. Ongoing retinal vascular development occurs by angiogenesis (the extension of existing blood vessels by proliferation and migration of endothelial cells). The blood vessels grow gradually toward the edges of the developing retina, supplying oxygen and nutrients. During the last trimester, the eye develops rapidly. When a baby is born full-term, the retinal blood vessel growth is mostly complete (the retina of an infant is not fully vascularized until about 40 weeks). However, if a baby is born prematurely before these blood vessels have reached the edges of the retina, normal vessel growth may stop. The edges of the retina—the periphery—may not get enough oxygen and nutrients.
ROP and Supplemental Oxygen:
Supplemental oxygen used to treat respiratory distress syndrome of prematurity has long been associated with ROP. When ROP was first discovered, the technology to monitor/regulate oxygen did not exist. Throughout the years, technological and medical advances have made it possible to regulate oxygen and detect early forms of ROP.
Oxygen stresses, such as uncontrolled supplemental oxygen and major oxygen fluctuations can delay vascular development. In ROP, delayed retinal vascularization increases the area of avascular retina and increases retinal hypoxia due to a lack of blood vessels and blood flow.
HOW IS ROP DIAGNOSED?
Pediatric ophthalmologists diagnose ROP by performing routine bedside eye examinations. They examine the eyes after the RN dilates the pupils with Cyclomydril drops. Tetracaine is administered by the MD as a topical local anesthetic to numb the eyes and prevent pain during the procedure.
ROP is described by its location in the eye (the zone), by the severity of the disease (the stage) and by the appearance of the retinal vessels (plus disease).
Stage 0 — normal eye.
Stage 1 — a demarcation line that separates normal from premature retina.
Stage 2 — a ridge which has height and width.
Stage 3 — growth of fragile new abnormal blood vessels.
Stage 4 — partially detached retina.
Stage 5 — completely detached retina and the end stage of the disease.
As ROP progresses the blood vessels may engorge and become tortuous (plus disease).
WHO REQUIRES TREATMENT?
When ROP reaches a certain level of severity, the potential for retinal detachment (and blindness) becomes great enough to warrant consideration of laser treatment.
Once it is determined that treatment is necessary, there are typically two options:
The first method is laser ablation which is applied to the immature portion of the retina. This is the oldest and most common method of treatment.
The second method involves an injection of medication into the eye. These medications may be used as an alternative to, or in addition to, laser treatment. This is a newer treatment and while results have been encouraging, further research is being done to help determine long term side effects and rate of ROP recurrence.
Eyes with retinal detachment caused by ROP generally have a poor visual prognosis. Retinal detachment can be treated with vitrectomy and/or scleral buckling procedure. Despite optimal treatment, some eyes with ROP progress to permanent and severe vision loss.