RETINOPATHY OF PREMATURITY ROP
Category: Child Health
Abstract : Retinopathy of Prematurity (ROP, retrolental fibroplasia, retinal neovascularization) Retinopathy of prematurity (ROP) is a serious vasoproliferative disorder affecting extremely premature infants. ROP often regresses or heals, but it can lead to severe visual impairment or blindness. Significant ROP can lead to lifelong disabilities for the smallest survivors of neonatal intensive care units.
Retinopathy of Prematurity (ROP, retrolental fibroplasia, retinal neovascularization)
Retinopathy of prematurity (ROP) is a serious vasoproliferative disorder affecting extremely premature infants. ROP often regresses or heals, but it can lead to severe visual impairment or blindness. Significant ROP can lead to lifelong disabilities for the smallest survivors of neonatal intensive care units.
ROP remains a serious problem despite striking advances in neonatology.
Pathophysiology:
ROP primarily occurs in extremely low birth weight (ELBW) infants. Most research suggests that a low birth weight, a young gestational age (GA), and the severity of the illness (eg, days the patient receives supplemental oxygen) are associated factors. Recently, other associations have been described. However, the severity of the illness appears to be a major predictor of severe disease. The smallest, sickest, and most immature infants are at the highest risk for serious disease. African American infants appear to have less severe ROP. Retinal vasculature begins to develop around the 16th week of gestation. It grows circumferentially and becomes fully mature at term. Premature birth results in the cessation of normal retinal vascular maturation. Blood vessels constrict and can become obliterated, resulting in delays of normal retinal vascular development. Early on, oxygen and nutrients can be delivered to the retina by means of diffusion from the underlying choroid. The retina continues to grow in thickness and eventually outgrows its vascular supply. Over time, retinal hypoxia occurs and results in an overgrowth of vessels. This process is mediated in part by vascular endothelial growth factor (VEGF). These problems result in ROP.
Frequency:
• In the US: The incidence varies with birth weight, but it is reported to be approximately 50-70% in infants whose weight is less than 1250 g at birth. Hussain et al reviewed the incidence and the need for surgery in neonates with ROP who were born at 22-36 weeks' GA between July 1989 and June 30, 1997. The incidences were 21.3% (202 of 950) for ROP of any stage and 4.6% (44 of 950) for ROP at stage 3 or worse. No ROP was noted in infants born after 32 weeks' GA. No infant born after 28 weeks needed retinal surgery. Despite the increased survival of ELBW infants, they found a considerable reduction in the incidence and severity of ROP compared with reports from an earlier period. However, infants before 28 weeks' GA and those with birth weights less than 1000 g were still likely to need retinal surgical treatment for ROP.
Investigators from the Supplemental Therapeutic Oxygen for Prethreshold Retinopathy of Prematurity (STOP-ROP) multicenter trial concluded that maintaining oxygen saturation in the high 90-percent range did not reduce the severity of the retinopathy when compared with the saturations in the low 90-percent range. However, it did result in more pulmonary adverse events. In a subanalysis of infants who did not have plus disease (ie, tortuosity of vessels) at the time of study entry, the progression to threshold was significantly decreased when compared with the progression in infants with plus disease. Thus, a critical window for oxygen administration may exist.
Mortality/Morbidity:
Long-term outcomes for serious disease include severe visual impairment and blindness. In addition, myopia, amblyopia, and strabismus may occur. Recently, Repka et al described the need for subsequent ophthalmic intervention.
Race: Some reports indicate a decreased incidence of progression to threshold disease in black infants. Most evidence comes from the Cryotherapy for Retinopathy of Prematurity (CRYO-ROP) study. Further evidence that African American race is protective against the development of severe ROP has been reported in studies of candidemia in very low birth weight infants. The exact mechanism for the decreased incidence of progression to surgery in black infants has not been described.
Sex: Although some reports indicate a male predilection, the CRYO-ROP study reveals no differences based on sex.
History:
• Infants at highest risk for ROP are those with the lowest birth weights and youngest GAs. In tiny infants, the PaO2 in room air may be toxic to their retinal vessels.
• Prolonged exposure to supplemental oxygen is also a risk factor.
• The severity of illness (including sepsis), blood transfusions, days receiving mechanical ventilation, a patent ductus arteriosus, and intraventricular hemorrhage are also associated with ROP.
• The effect of blood transfusion on ROP is controversial. The smallest, sickest infants receive more transfusions than their healthy counterparts, and they may have more frequent or severe ROP. However, theoretical risks associated with factors such as volume and iron load may place infants who receive more transfusions at higher risk for ROP.
Physical:
• Screening: An ophthalmologist experienced in evaluating infants for ROP should perform a screening examination.
• International classification
o To standardize examinations, a group of physicians organized an international classification of ROP (ICROP) in 1984 and updated the classification in 1987.
o ROP is characterized by 3 parameters: stage, zone, and plus disease (ie, tortuosity of vessels).
• Examination recommendations
o The American Academy of Pediatrics and the American Academy of Ophthalmology have joint recommendations for infants who should be screened for ROP. These guidelines include a birth weight less than or equal to 1500 g and a GA less than or equal to 28 weeks. In addition, infants with birth weights greater than 1500 g who are believed to be at high risk for ROP should also be examined. An experienced ophthalmologist should perform the examination, which should occur at 4-6 weeks of age or by 31-33 weeks' postconceptional age.
o Screening guidelines have been the focus of recent studies. The issue of cost-effectiveness versus missing cases of ROP is controversial. In addition, Subhani et al recently suggested that infants should be examined by the age of 4-6 weeks, contrary to the standard postconceptional age criteria.
o Follow-up examinations are based on initial examination findings.
Other Tests:
• Ophthalmologic evaluation
o Record the vascular maturity (how far out the vessels have grown), as indicated by zone, stage of disease, and the presence or absence of plus disease.
o The eyes can be divided into 3 zones (1, 2, and 3), and the ROP is quantified on the basis of the number of clock hours during which the disease is present in the retina.
Staging:
• The ICROP describes 5 stages of ROP, as follows:
o Stage 1 is characterized by a line of demarcation. Extra vessels can be seen growing at the leading edge of the retinal vasculature. The line of demarcation separates the vascularized portion of the retina from the anteriorly positioned avascular retina.
o Stage 2 is characterized by a ridge that has extra vessels plus the elevation of tissue, which can be seen on examination.
o Stage 3 refers to extra retinal neovascularization or vessels that are growing into the vitreous toward the examiner.
o Stage 4 refers to partial retinal detachment.
o Stage 5 is total retinal detachment.
• Plus disease refers to the tortuosity of vessels. Rapidly progressing plus disease is sometimes referred to as Rush disease.
• In addition, the zone of disease is designated, as follows:
o Zone 1 is the innermost area of the retina surrounding the macula.
o Zone 2 is the middle third of the retina nasally extending to the edge of the retina
o Zone 3 is the most peripheral area of the retina on the temporal side.
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