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Overview
Retinopathy of prematurity or ROP (formerly known
as retrolental fibroplasia) is the abnormal growth
of blood vessels within the retina and vitreous
that occurs in some premature infants.
Abnormal blood vessel growth (neovascularization)
does not deliver nutrients to the retina; rather,
it is associated with significant disease as the
blood vessels are fragile and prone to leak. The
progression to later stages of ROP can lead to the
formation of scar tissue on the retina, vitreous
hemorrhage, and retinal detachment.
Many infants who have early ROP improve
spontaneously. The severity of ROP varies, ranging
from nearly normal vision to total blindness.
Signs of ROP are found in very premature babies
and one in ten progresses to more severe stages.
Typically, the smallest and earliest premature
babies are at the highest risk for developing ROP.
Incidence and Prevalence
More than 80% of premature babies who weigh less
than 1000 grams (2.2 lbs.) develop ROP. The
incidence of ROP is rising because of the medical
profession’s ability to improve survival rates
among the most premature babies.
Risk Factors
The greatest risk factor is prematurity,
particularly at 32 weeks gestation or less. Low
birth weight (1500 grams or lower) also increases
the risk. Other risk factors include the
following:
-
Duration of intubation
-
Intraventricular hemorrhage (bleeding into the
ventricles of the brain)
-
Multiple prenatal maternal factors (e.g.,
diabetes, preeclampsia, heavy smoking,
inadequate oxygen supply to the fetus)
-
Respiratory
distress syndrome
-
Sepsis (i.e., infection in the blood or other
tissues)
-
Vitamin E deficiency
Causes
The human eye develops rapidly between 28 and 40
weeks gestation. The blood supply to the retina
begins to form at about 16 weeks gestation,
starting at the optic nerve. Blood vessels grow
from the optic nerve toward the edges of the retina—a process that
continues until the fetus reaches term.
When a baby is born prematurely, normal blood
vessel development may cease and abnormal growth
may begin. Supplemental oxygen use is likely
associated with development of ROP.
Signs and Symptoms
There are no symptoms of ROP and infants must be
screened by an ophthalmologist.
Screening is recommended for
-
all premature infants (born at less than 35
weeks gestation or who weighed less that 1800
grams) who received supplemental oxygen, and
-
infants born at less than 30 weeks gestation or
who weighed less than 1300 grams, whether or not
they received supplemental oxygen.
Diagnosis
Diagnosis is made by ophthalmologic examination.
The eye exam is usually performed before the baby
is discharged, or at 5 to 7 weeks after birth if
the infant remains hospitalized. After putting
drops in the eyes to dilate the pupils and allow
for better visualization, the doctor views the
retina through the lens of an indirect
ophthalmoscope (see
Basic Eye Exam).
ROP is graded according to its severity. Stage
I indicates that the outer edges of the retina
are not receiving a normal blood supply. A
demarcation line is visible where normal and
abnormal blood vessels meet.
Stage II
indicates that the demarcation line has progressed
to a ridge that develops as the abnormal vessel
growth continues.
Stage III
indicates that the ridge has grown and the vessels
have spread into the vitreous. There may be
scarring and fluid leakage.
Stage IV
indicates progression to partial detachment of the
retina.
Stage V
is complete detachment of the retina.
Treatment
Treatment for ROP depends on the stage and degree
of retinal findings. Generally, Stages I and II
resolve on their own and only require periodic
evaluation. Treatment is initiated when
threshold ROP, stage III with certain
qualifying signs, is seen. This means that the
condition of the eye has degenerated to a point
beyond spontaneous resolution and where vision is
seriously threatened. The goal of treatment is to
help reduce the risk of retinal detachment and
dragging of the macula, which can severely impact
vision.
Laser photocoagulation
is the most common treatment modality. A laser is
directed to a designated spot to destroy abnormal
vessels and seal leaks. The procedure usually is
performed under general anesthesia because these
infants are typically extremely premature and have
multiple medical problems. Laser photocoagulation
is the preferred method of treatment by surgeons,
because there is little postoperative pain and
swelling.
Cryotherapy
can be used to treat threshold ROP but is not the
preferred method. Cryotherapy involves destroying
abnormal tissue by freezing and is often used to
treat Grade III ROP. A probe chilled with nitrous
oxide is placed on the surface of the eye. Because
the tissue of the sclera is thin, the freezing
temperature is easily transmitted to the retina.
Cryotherapy reduces the risk for retinal
detachment from 43% to 21%. It is an effective
therapy for preserving vision in many infants with
ROP, but it does have drawbacks. Narcotic
analgesia may be required after the procedure to
relieve pain. Cryotherapy also causes significant
swelling of the eye and eyelid, which makes
postoperative assessment difficult.
Scleral buckle
may be used in Stages VI and V ROP to prevent
retinal detachment. This procedure is used when
laser or cryotherapy fails to prevent disease
progression. A band made from silicone or other
flexible material is placed around the back of the
eyeball to “buckle” (indent) the sclera. This
brings the eye wall closer to the retina, helps to
reattach it, and relieves the traction that was
pulling on it to cause detachment. Infants often
have the band cut at a later date to accommodate
the growing eye.
Vitrectomy
is performed on Stage V patients, when scleral
buckling is no longer effective. This is a complex
procedure, which involves the use of microscopic
instruments to remove the vitreous from the eye
and replace it with a saline (salt) solution. When
the vitreous is removed, traction on the retina is
relieved.
Scar tissue on the retina is cut or peeled away
once the vitreous is removed, allowing the retina
to reattach. Unfortunately, the lens frequently
has to be removed as well to allow all scar tissue
to be removed. Vitrectomy techniques that preserve
the lens are becoming more common.
Prognosis
Success rates for reattachment of the retina range
from 25% to 50%. However, reattachment does not
guarantee that the infant will have functional
vision. Only about one-quarter of infants whose
retinas reattach are able to see well enough to
recognize patterns or to grab for a toy.
Premature infants with ROP have a high risk for
strabismus and amblyopia.
Infants with regressed ROP are at risk for eye
problems as they grow. These are called late
complications of ROP. In addition to
strabismus and amblyopia, they are also at risk
for
myopia,
glaucoma,
and retinal detachment. ROP complicated by retinal
detachment is the leading cause of blindness in
children in the United States. Approximately 500
cases of ROP-related blindness are reported every
year.
Infants with Stages IV and V ROP may have severe
amblyopia, which makes therapy and visual
rehabilitation difficult. Those with Stage V also
have a 30% risk for developing angle closure glaucoma.
Prevention
The best way to prevent ROP is to avoid premature
birth. Prenatal care and counseling can
help prevent premature births and inform a mother
about factors that influence her baby’s health in
utero.
Other preventative interventions include closely
monitoring oxygen needs in premature babies.
Regular eye exams should be discussed with the
baby’s physician, regardless of the stage of ROP |
