L. Windsor, O.D., F.A.A.O.
Laura K. Windsor, O.D., F.A.A.O.
Published in Vision Enhancement Journal
Retinopathy of Prematurity (ROP), originally called retrolental
fibroplasia, was the leading cause of blindness in children in the 1940s
and 1950s. It was first described in the medical literature in 1942 by
Terry. In 1952, Campbell theorized that the condition was caused by the
use of oxygen therapy to treat the immature lungs in premature infants.
Today, we realize that oxygen is not the only factor in developing ROP.
High levels of oxygen have been associated with ROP, but lower levels of
oxygen may lead to more respiratory complications and death in premature
infants. Better oxygen level monitoring has led to better control of the
oxygen given to premature infants. Today, however, there is an increase
in ROP due to the fact that neonatal care advances mean more low weight
premature infants are surviving.
occurs in over 16% of all premature births. In babies weighing less than
1,700 grams at birth, over 50% will develop ROP. In the United States,
over 2,100 children annually experience the complications of ROP. Of those
estimates of 500 to 1,200 cases of new blindness or severe complications
are reported. Studies have found that about 30% of infants with advanced
ROP have 20/200 or less in their better eye.
are a number of risk factors that are associated with ROP. These include:
Infants born under 32 weeks gestation
levels of supplemental oxygen
less than1500 grams (the lower the birth rate, the higher the incidence)
carbon dioxide levels
Bradycardia (low heart rate)
Intraventicular hemorrhage (bleeding into the brain)
Multiple prenatal maternal factors including heavy smoking, diabetes, and
16 weeks to birth, retinal blood vessels grow out from the optic nerve to
reach the peripheral retina. The last twelve weeks of a normal 40 week
gestation are crucial in the development of fetal eyes. In premature
infants, the normal growth of blood vessels stops. It is theorized that
the area without adequate blood supply emits a chemical trigger to
stimulate growth of the abnormal vessels. These vessels lead to a
formation of a ring of scare tissue attached to both the retina and the
vitreous gel that fills the center of our eyes. As the scar contracts, it
may pull on the retinal creating a retinal detachment. Regardless of the
gestation age at birth, ROP seems to occur at about 37 to 40 weeks.
understanding of ROP is changing. Traditionally the view was that high
oxygen exposure was the cause. While it is certainly one of the major
factors, studies now show that it is not just exposure to oxygen or other
toxic agents after birth, but may also relate to actions that occur to the
fetus prior to birth. Both chronic hypoxia (lack of oxygen) and
intrauterine growth retardation may relate to ROP development. As many as
one third of ROP cases may be the result of prenatal conditions. Light
exposure has been suggested as another factor. To date, scientific studies
have not confirmed light as a cause.
risk premature infants are usually monitored by a retinal specialist or
pediatric ophthalmologist during their stay in a neonatal care unit.
Guidelines for screening will vary within different hospitals, but
recommendations may typically include:
Infants born at 23-24 weeks
should be examined within three to four weeks.
Infants born at or beyond
25 to 28 weeks should be examined by the fourth to fifth week.
Infants born after 29 weeks
should be examined prior to discharge from the hospital.
premature children are at a higher risk for other eye and vision
complications. Thus, eye examinations every six months are recommended for
all infants born under 32 weeks or that weigh less than 1500 grams. Twenty
percent of these premature infants without ROP will still develop a
crossing or turning out of the eyes and significant refractive problems
requiring prescription eyeglasses.
Doctors classify ROP by anatomical zones, clock dial like location within the eye and
stages of severity. Zone 1 is the center of the retina while zone 3 is
the far peripheral retina. In 1984, an international classification system
was developed. Stage 0 is the mildest form of ROP while Stage 5 is the
most severe indicating total retinal detachment. Doctors may also use the
terms “popcorn” referring to a scarring that is regressing following
abnormal vessel growth. The term, “hot dog”, may refer to a red hot ridge
of increasing abnormal vessel grow.
Vision Complications of ROP
retina may become stretched and pulled by the contraction of the scars in
the eye. This may physically pull the macula, the most sensitive part of
the retina, causing abnormal vision. It may also cause folds in the retina
and lead to retinal detachment.
retina is the light sensitivity “film-like” portion of the eye. A retinal
detachment occurs when this delicate tissue is dislodged from the internal walls of the eye. Retinal
detachment (RD) is common in patients with ROP. In many cases, it leads to
profound vision loss. Early detection and treatment is crucial. In stage
5, the most severe form of ROP, retinal detachment surgery may not be
attempted due to the poor prognosis versus risk of operating on a
Strabismus is another complication and it is the crossing in or turning
out of an eye. This may occur from the loss of vision in one eye or be
related to the large refractive differences between the eyes. This
difference is called an anisometropia or antimetropia. For example, one
eye may be 1 unit of myopia (nearsightedness) while the other eye is six
units of nearsightedness.
the vision loss or the strabismus, there is a loss of depth perception.
Amblyopia is another condition found in ROP patients. It is a loss of
vision in one eye, because the brain does not use that eye to see.
Ambylopia can occur from either the strabismus or the large difference in
refractive error between the two eyes.
cataract and corneal problems can develop. Severe damage may lead to
Phthisis bulbi, a shrinking of the severely damaged eyes. Glaucoma may
develop either early or as a later in life complication of ROP.
Additionally, ROP patients may have high amounts of nearsightedness
patients who experience significant vision loss, nystagmus, a rapid
fluttering of the eyes, may occur. Nystagmus is common in all patients
whose vision loss occurs at an early age.
Complications Later in Life
10% of all premature infants may develop glaucoma later in life. Sudden
angle closure glaucoma has been found to occur in the 2nd or 3rd
decade of life. Additionally, 20% of those without ROP will still develop
strabismus (the crossing or turning out of the eyes) and significant
refractive problems requiring prescription eyeglasses. Additionally,
approximately 3% of ROP patients will develop retinal detachments later on
in life. Patient’s eyes must be examined regularly throughout their life.
prevent ROP, good prenatal care is essential. This care lessens the risk
of delivering premature infants. Next, careful monitoring of oxygen
therapy and other risk factors are crucial to preventing ROP. In the
hospital, monitoring by a retinal specialist skilled in ROP is essential
in lessening the advancement of ROP.
Cryotherapy or the freezing of the retinal tissue has been used since the
1970s to treat ROP. Today, laser therapy has been shown to be as effective
as cryotherapy, but with less systemic side effects. Both therapies work
by destroying a small part of the retina, thus reducing the need for
oxygen and abnormal blood vessel growth. It may also thin the retina
allowing more oxygen to diffuse into the retina.
detachment of the retina occurs, scleral buckling may be required. It is a
procedure that places a band around the globe of the eye. This brings the
retina back into contact with the inner layers of the eye. A vitrectomy is used to remove scar tissue from within the eye in the more severe cases of ROP. During the vitrectomy, the lens of the eye is usually removed as well.
the difficulty of performing these surgeries on the small eyes of
premature infants, these surgeries are usually performed only by a small
number of ophthalmologists with extensive experience in ROP.
Adult Low Vision Care
vision care is based on the degree of vision loss. It may be as simple as
appropriate eyewear. Bifocals may be helpful from school age on. Also,
the use of magnifiers and closed circuit television systems may be
necessary to help ROP patients. The Jordy II has been helpful in patients
with severe vision loss.
profound vision loss, Braille and other alternate mediums may be
required. Electronic scanning or reading technologies have already opened
many computer possibilities for even the totally blind.
Special Low Vision Concerns in Young Children
an adult low vision patient, a child’s visual system, eye, nerves and
brain, are still developing. Parents need instruction on creating the
best environment for their visually impaired child. Visual stimulation
techniques, proper toys selection, creating proper contrast, alternate
learning methods, parental narration and control of light and glare must
be planned. In addition to other specialists, these children should be
followed by the appropriate low vision professionals. As the child grows,
educational needs must be assessed and the appropriate educational
environment developed for each child.
patients frequently develop high amounts of myopia (nearsightedness) that
require correction with eyeglasses. Bifocals and strong reading eyewear
are often helpful. Contact lenses may be used in cases of severe
anisometropia where the refractive powers of each eye are quite different.
This often occurs if a vitrectomy is performed and the lens of the eye is removed. This is
particularly important in children to avoid the development of amblyopia.
Eye Safety Issues
ROP patients frequently have one better eye, protection of the remaining
functional eye is important. Patients who have only one functional eye
should wear adequate protective eyewear fulltime. When possible,
polycarbonate lenses are preferred due to their high impact resistance.
Additionally, physical education in school and other recreational
activities must be limited to safe, non-traumatic activities due to
increased risks for retinal detachment.
Association for Retinopathy of Prematurity and Related Disorders, provides
an Internet site at
www.ropard.org. They also publish a newsletter on ROP. Their postal
address is ROPARD P.O. Box 250425 Franklin, Michigan 48025.