Unifying Concepts

Classification of Retinopathy of Prematurity (RP)

Retinopathy of prematurity is a vision-threatening disease associated with abnormal retinal vascular development that occurs only in premature infants.

Criteria for screening

  • United States: infants with a gestational age of ?30 weeks or birth weight of <1500 g and selected infants with a gestational age of >30 weeks and an unstable clinical course
  • United Kingdom: infants with a gestational age of </=31 weeks or birth weight of </=1500 g
  • Canada: infants with a gestational age of </=30 weeks, 6 days, or birth weight of </=1250 g

Timing of screening and examinations

  • First examination at chronologic age of 4–6 weeks or postgestational age of 31 weeks
  • Repeated examinations recommended by examining ophthalmologist on the basis of retinal findings and suggested schedule

Type of examination

  • Dilated binocular indirect ophthalmoscopy
  • Ongoing studies of validation and reliability of retinal imaging as a potential telemedicine alternative for screening by indirect ophthalmoscopy

Classification of retinopathy of prematurity determined in examinations
Zone (area of retinal vascularization)

I: vascularization within a circle centered on the optic nerve, the radius of which is twice the distance from the optic nerve to the macula
II: vascularization extending beyond zone I, within a circle the radius of which is the distance from the optic nerve to the nasal ora serrata
III: vascularization extending beyond zones I and II

Stage (disease severity)

1: line
2: ridge (with volume)
3: intravitreal angiogenesis
4: partial retinal detachment
5: total retinal detachment
Plus disease: dilatation and tortuosity of retinal vessels

Application of laser to peripheral avascular retina for type 1 retinopathy of prematurity

Zone I: stage 3, or stage 1 or 2 with plus disease
Zone II: stage 2 or 3 with plus disease

Under consideration, anti-VEGF agents for stage 3 and plus disease in zone I; additional study needed to determine dose, safety, and type of anti-VEGF therapy*

Visual rehabilitation
Correction often needed for associated refractive errors (ametropia and anisometropia); ongoing screening and treatment recommended for commonly associated amblyopia or strabismus; protective eyewear and low-vision aids may be indicated
* VEGF denotes vascular endothelial growth factor.



  1. Hartnett ME, Penn JS. Mechanisms and Management of Retinopathy of Prematurity. N Engl J Med 2012;367(26):2515-2526 [Medline]
  2. Quiram PA, Capone A Jr. Current understanding and management of retinopathy of prematurity. Curr Opin Ophthalmol. 2007 May;18(3):228-34. [Medline]


Created Dic 27, 2012.

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