Retinopathy of Prematurity

The immature retinas of preterm neonates are susceptible to insults that disrupt neurovascular growth, leading to retinopathy of prematurity. Suppression of growth factors due to hyperoxia and loss of the maternal–fetal interaction result in an arrest of retinal vascularisation (phase 1). Subsequently, the increasingly metabolically active, yet poorly vascularised, retina becomes hypoxic, stimulating growth factor-induced vasoproliferation (phase 2), which can cause retinal detachment. In very premature infants, controlled oxygen administration reduces but does not eliminate retinopathy of prematurity. Identifi cation and control of factors that contribute to development of retinopathy of prematurity is essential to prevent progression to severe sight-threatening disease and to limit comorbidities with which the disease shares modifi able risk factors. Strategies to prevent retinopathy of prematurity will depend on optimisation of oxygen saturation, nutrition, and normalisation of concentrations of essential factors such as insulinlike growth factor 1 and ω-3 polyunsaturated fatty acids, as well as curbing of the effects of infection and inflammation to promote normal growth and limit suppression of neurovascular development.

Classification and screening

Classification of the stages of retinopathy of prematurity is necessary for the standardisation of treatment practices, and so that interventions can be assessed at a defi ned stage when progression to blindness is likely. Recommendations are summarised in the International Classification of Retinopathy of Prematurity, first published in 1985 and revised in 2005. The retina is divided into three zones and the extent or severity of disease in these zones is classified as stages. Stages 1 and 2 are mild and likely to regress spontaneously. In stage 3, extraretinal neovascularisation can become severe enough to cause total retinal detachment (stage 5), which leads to blindness. The presence of increased dilation and tortuosity of posterior vessels (so-called plus disease) is an ominous sign of progressive disease. The investigators of the Early Treatment for Retinopathy Of Prematurity (ETROP) study reclassified retinopathy of prematurity into type 2 (to be followed up) and type 1 (requires treatment). Type 1 now includes a more virulent form of retinopathy in extremely low-birthweight babies (aggressive posterior retinopathy of prematurity), which involves very central neovascularisation with plus disease.

Screening recommendations:

Unfortunately, there is no hard data on the incidence of ROP in India. Of 3.5 million premature births in India, approximately one in six (about 600,000) children are born at <32 weeks gestational age (GA).[10],[11] Estimating that about 40% of these receive neonatal care and 80% of them survive, about 200,000 children are at risk of developing ROP in India every year. If about 10% of them develop treatable ROP, the number of newborns needing ROP management is at least 20,000 every year.[11] In addition, children with GA 32–36 weeks who receive suboptimal postnatal care and have comorbidities may also be at the risk of developing ROP.

The dynamic and time-bound development of ROP and effectiveness of treatment at an appropriate stage make it amenable for systematic screening. Screening guidelines, however, vary from region to region. The 2019 American Academy of Pediatrics (AAP) guidelines recommend screening of all infants with a BW ≤1500 g or a GA ≤30 weeks and selected infants with a BW between 1500 and 2000 g or GA >30 weeks who are believed to be at risk for ROP (infants with hypotension requiring inotropic support, infants who received oxygen supplementation for more than a few days, or infants who received oxygen without saturation monitoring).United Kingdom guidelines developed by the Royal College of Ophthalmologists (RCO) and Royal College of Pediatrics and Child Health stipulate that babies <32 weeks GA or <1501 g birthweight should be screened for ROP It is known that ROP can develop in bigger and more mature babies in India, which may be attributed to the variable and often suboptimal quality of neonatal care.Indian studies have shown that children with BW of 2000 g can develop ROP. ROP screening in India begins between 3-4 weeks after birth for infants weighing between 1200-2000 gms at birth, or 2-3 weeks for infants <1200 grams at birth.

TREATMENT

Transpupillary laser treatment to ablate nonvascularised retina has effectively replaced cryotherapy, because of better visual outcomes and fewer adverse.

Treatment of Retinoapthy of prematurity can also include other modalities. Some reports suggest that with early retinal Detachment (stage 4), lens-sparing vitrectomy might help to preserve vision.

Long Term Implications

Severe retinopathy of prematurity often leads to long-term visual loss,with blindness in the most severe cases. Without treatment, most non-proliferative retinopathy of prematurity regresses, but even non-proliferative disease is associated with visual deficits, since preterm birth itself has lasting effects on the developing visual system.

Retinopathy of prematurity is also associated with other eye problems. Infants treated with transpupillary laser for severe retinopathy of prematurity have an increased risk of myopia (up to 70% of such infants are affected). Preterm birth is a risk factor for hyperopia and astigmatism. 80% of children with a history of severe etinopathy of prematurity develop strabismus during he first 6 years of life.