Retinopathy of prematurity (retrolental fibroplasia)

Traction on retina which may lead to retinal detachment.

Who?

• All infants whose gestational age is less than 29 weeks should be screened for retinopathy of prematurity (ROP) independent of oxygen exposure.
• Prematurity is the principal predisposing factor for the occurrence of ROP; the risk of ROP varies inversely with gestational age. I
• In infants whose gestational age is less than 29 weeks, the incidence of any ROP is 66%, moderate ROP is 18%, and severe ROP is 6%.
• In the preterm infant, supplemental oxygen therapy is a major risk factor for the occurrence of ROP.
• However, ROP is uncommon in infants whose gestational age is 32 weeks or older or whose birthweight is more than 1,500 g, even when the infants are exposed to supplemental oxygen.
• Incidence 10-70% reported in infants who survive w/ birth wt < 1.5 kg.

Etiology/Pathogenesis:

• related to immaturity of retinal vessels of preterm infants (28-40 weeks gestation: growth of retinal vessels occurs)
• contributing factors: hyperoxia, hypercarbia, intermittent hypoxia, sepsis
• hyperoxia -> vasospasm -> endothelial damage in retinal vessels -> tissue edema/injury -> reactive proliferative neovascularization and fibrous scar tissue can retract retina, which may result in retinal detachment. This sequence may regress at any time before detachment
• ROP is classified according to location and extent of disease, severity of abnormal vascularization, and the presence or absence of dilatation of the posterior retinal vessels (referred to as plus disease).
• The location of the disease is described by zones I to III: circular regions centered around the optic disk, diameter of zone 1 is twice the optic nerve-macular distance.
• Extent of disease: comparing the retina with a clock face marked off by hours 1 to 12.  I.E. vascular involvement from 7 oclock to 12 oclock would mean 5 clock hours involvement
• The severity of abnormal vascularization is described by stages 1 to 3.
  1. stage 1: Demarcation line: a simple border or line seen at the edge of vessels dividing vascular from avascular retina
  2. Ridge: line structure of the previous stage has now acquired a volume and risen above the surface of the retina to become a ridge
  3. Ridge w/ extraretinal fibrovascular proliferation
  4. Subtotal retinal attachment
     1. 4A subtotal retinal detachment not involving the fovea
     2. 4B Subtotal retinal detachment involving the fovea
  5. Total retinal detachment
• Prethreshold ROP is defined as zone I, any stage; zone II, stage 2 with plus disease; or zone II, stage 3. Prethreshold ROP carries a poor prognosis for visual function and warrants weekly monitoring by eye examination for progression.
• Threshold ROP is defined as stage 3 disease extending to five contiguous or eight cumulative hours in zone I or II with plus disease. Threshold ROP is an indication for cryotherapy or laser photocoagulation.
   

Management

• All infants whose gestational age is less than 29 weeks should be screened for retinopathy of prematurity (ROP) independent of oxygen exposure.
• The optimal time for initial retinal examination is between 4 and 6 weeks' chronologic age or 31 and 33 weeks' postmenstrual age, whichever occurs earlier.
• Retinal vascularization typically starts near the optic nerve at approximately 20 weeks' gestational age. Progression of the retinal vessels toward the periphery of the retina occurs steadily thereafter. Abnormalities of retinal vessels become evident at approximately 4 weeks' chronologic age or 31 weeks' postmenstrual age. Earlier eye examinations, therefore, will have a minimal yield.
• The optimal time for final retinal examination in ROP is at 44 weeks' postmenstrual age. Normally, the retina is fully vascularized at that age. Any progression or new occurrence of ROP is extremely unlikely thereafter.

Treatment

• usually resolves spontaneously.
• With active, rapidly progressively disease, cryotherapy or laser therapy to prevent traction.
• Prethreshold ROP carries a poor prognosis for visual function and warrants weekly monitoring by eye examination for progression.
• Threshold ROP is an indication for cryotherapy or laser photocoagulation.

Prognosis:  related to severity of vascularity and subsequent spontaneous regression. Myopia is common. Blindness follows retinal detachment.
 

References:
Fierson WM, Palmer EA, Biglan AW, Flynn JT, Petersen RA, Phelps DL.
Screening examination of premature infants for retinopathy of
prematurity. A joint statement of the American Academy of Pediatrics,
the American Association for Pediatric Ophthalmology and Strabismus,
and the American Academy of Ophthalmology. Pediatrics.
1997;100:273-274
Palmer EA, Flynn JT, Hardy RJ, et al. Incidence and early course of
retinopathy of prematurity. The Cryotherapy for Retinopathy of
Prematurity Cooperative Group. Ophthalmology. 1991;98:168-1640
The Committee for the Classification of Retinopathy of Prematurity.
The international classification of retinopathy of prematurity. Arch
Ophthalmol. 1984;102:1130-1134
Wright K, Anderson ME, Walker E, Lorch V. Should fewer premature
infants be screened for retinopathy of prematurity in the managed care
era? Pediatrics. 1998;102:31-34