- 1.
What is retinopathy of prematurity?
Retinopathy of prematurity (ROP) is a vasoproliferative retinal disease that affects infants born prematurely. It has two phases. In the acute phase, normal vascular development goes awry with the development of abnormal vessels that proliferate, occasionally with associated fibrous proliferation. In the chronic or late proliferation phase, retinal detachment, macular ectopia, and severe visual loss may occur. More than 90% of cases of acute ROP go on to spontaneous regression.
- 2.
Who is at risk for retinopathy of prematurity?
Infants weighing less than 1500 grams at birth and those born at a gestational age of 32 weeks or less are at risk for developing ROP. The disease is more likely to affect the smallest and most premature of infants. The incidence of acute ROP in infants weighing less than 1 kg at birth is three times greater than that of infants weighing between 1 and 1.5 kg. Infants born at 23 to 27 weeks of gestation have a particularly high chance of developing ROP.
- 3.
Who should be screened for retinopathy of prematurity?
Guidelines published by the American Academy of Pediatrics, Section on Ophthalmology; the American Association of Pediatric Ophthalmology and Strabismus; and the American Academy of Ophthalmology recommend that all infants weighing less than 1500 grams at birth or those with a gestational age of 28 weeks or less should be examined. Selected infants with a birth weight between 1500 and 2000 grams with an unstable clinical course should also be examined.
- 4.
Which infants are at highest risk for retinopathy of prematurity?
Infants at particularly high risk are those who weigh less than 1000 grams at birth and those born at less than 27 weeks’ gestation. The first exam should take place 4 to 6 weeks after birth or between 31 and 33 weeks of postconceptional or postmenstrual age.
- 5.
When should follow-up exams be done when screening for retinopathy of prematurity?
The frequency of follow-up examinations is based on the retinal status at the time of the first exam. Exams should be done every 1 to 2 weeks, either until there is complete retinal vascularization or until two successive 2-week examinations show stage 2 ROP in zone III (more on staging is discussed later in this chapter). Infants should then be examined every 4 to 6 weeks until the retina is fully vascularized. If there is prethreshold disease (see further discussion), examinations should be done every week until threshold disease occurs (at which point treatment should be offered) or until the disease regresses.
- 1.
All infants weighing less than 1500 grams at birth
- 2.
All infants with a gestational age of 28 weeks
- 3.
Infants with a birth weight between 1500 and 2000 grams with an unstable clinical course
- 4.
Any infant that the neonatologist considers at risk because of an unstable clinical course
- 6.
How is retinopathy of prematurity classified?
The International Classification of Retinopathy of Prematurity (ICROP) is the system used for describing the findings in ROP. ICROP defines the location of disease in the retina and the extent of involvement of the developing vasculature. It also specifies the stage of involvement with levels of severity ranging from 1 (least affected) to 5 (severe disease).
- 7.
What are the zones of retinopathy of prematurity?
For the purpose of defining location, the retina is divided into three zones, with the optic nerve as the center because vascularization starts from the optic nerve and progresses peripherally ( Fig. 44-1 ). Zone I consists of a circle, the radius of which subtends an angle of 30 degrees and extends from the disc to twice the distance from the disc to the center of the macula (twice the disc-to-fovea distance in all directions from the optic disc). Zone II extends from the edge of zone I peripherally to a point tangential to the nasal ora serrata and around to an area near the temporal anatomic equator. Zone III is the residual temporal crescent of retina anterior to zone II.
Figure 44-1
The zones of retinopathy of prematurity are shown schematically.
- 8.
Describe the stages of retinopathy of prematurity.
Staging pertains to the degree of abnormal vascular response observed. Staging of the eye as a whole receives the stage of the most severe manifestation present.
Stage 1 is a demarcation line. It is a thin but definite structure that separates avascular retina anteriorly from the vascularized retina posteriorly. Abnormal branching of vessels can be seen leading up to the line. It is flat and white and is in the plane of the retina.
Stage 2 is a ridge. The line of stage 1 has height and width and occupies a volume extending out of the plane of the retina. The ridge may be pink or white. Vessels may leave the plane of the retina to enter it. Small tufts of new vessels may be seen on the surface of the retina posterior to the ridge. These vessels do not constitute fibrovascular growth.
Stage 3 is the ridge of stage 2 with extraretinal fibrovascular proliferation ( Fig. 44-2 ). Stage 4 ROP is a subtotal retinal detachment. Retinal detachments in ROP are concave, tractional retinal detachments. Stage 4A ROP is a subtotal retinal detachment that does not involve the central macula. Typically, it is present in the temporal region of zones II and III. Stage 4B ROP is a subtotal retinal detachment that involves the central macula.
Figure 44-2
Stage 3 retinopathy of prematurity.
Last, stage 5 ROP is a total retinal detachment. These retinal detachments are funnel-shaped but may have an open or closed configuration in their anterior and posterior areas.
- 9.
What is plus disease?
Plus disease is indicative of progressive vascular incompetence and is a strong risk factor for the development of more severe ROP. Anteriorly, plus disease is iris vascular engorgement and pupillary rigidity. Posteriorly, plus disease appears as retinal venous dilation and arterial tortuosity in the posterior pole. It is graded as mild, moderate, or severe ( Fig. 44-3 ). When plus disease is present in the posterior pole, a plus sign (i.e., +) is added to the number stage of the disease, i.e., stage 3+. Before the appearance of plus disease, increasing dilation and tortuosity of the posterior vessels signify increased activity of ROP. Pre-plus disease is present when there are vascular abnormalities of the posterior pole that are insufficient for the diagnosis of plus disease, but that demonstrate more venous dilation and arterial tortuosity than normal.
