Retinopathy of Prematurity

Sasha Mansukhani
Retinopathy Of Prematurity - Introduction
Retinopathy of Prematurity (ROP) is a retinal vascular disease affecting premature newborns of low birth weight. The smaller and younger the neonate, the greater is the risk for this potentially blinding disease. Apart from prematurity and low birth weight, excessive oxygen use and various neonatal illnesses are risk factors.
Twenty-two percent of the burden of childhood blindness can be attributed to retinal disease, of which ROP is an important cause(1). Atleast 50,000 children worldwide are estimated to be blind due to retinopathy of prematurity and the number is ever increasing (2).
While progress in neonatology has seen an increase in survival rates of extremely low birth weight babies (ELBW)(3) , there has been a corresponding rise in the incidence of Retinopathy of prematurity(4).

Indian studies have shown that in low birth weight babies, the incidence of ROP varies from 38-51.9%(5,6,7) .

India is now considered at high risk for retinopathy of prematurity, as it is a country whose neonatal care services have improved with better survival rates, while at the same time the existing screening protocols and level of care for ROP is not adequate. Thus has emerged what is considered to be the ‘Third Epidemic of ROP’ of which India, along with several middle-income nations, is a part(8).

The pediatrician and the neonatologist are the first line of defense against this epidemic. While the preterm newborn is at risk of the disease, it must be emphasized that the baby does not have the disease at birth. ROP develops typically by 3-4 weeks of life, yielding a golden window period for detection and treatment. Thus the timely referral of the ‘at risk’ babies to the ophthalmologist for screening is crucial in the final visual outcome.

Recognizing the urgency, the Ministry of Health and Welfare, India has included Retinopathy of prematurity in the screening guidelines of newborns in the ‘Rashtriya BAL Swasthya Karyakram’ (an initiative launched in 2013)(9). ‘The India Newborn Action Plan’ launched in September 2014 by the Health Minister of India, once more emphasizes ROP screening in the ‘Care of the small and sick newborn’ section of the plan(10).

ROP is a fairly new disease, and was first described by Terry in the 1940s(11).

1942: Terry identified the disease & coined the term ‘Retrolental Fibroplasia’(11).
1951: Campbell suggested that the toxic effects of oxygen in the neonates caused the disease(12).
1952: Heath coined the term Retinopathy of Prematurity, which became the more accepted nomenclature(12).
1953: Studies proved that high concentrations of oxygen were causative(12).

Development of retinal vasculature(13)
Retina is avascular till 14 weeks of intrauterine life. At around the 4th month of gestation the vascular complexes grow from the optic disc outwards towards the periphery, in the form of an expanding vascular apron. The vasculature reaches the nasal ora serrata at 8 months of gestation; however the temporal retina is not completely vascularised till 1 month after delivery

Theories of Pathogenesis
1. Classical Theory (Ashton Patz)(14) : Oxygen is implicated as the major causative factor. Hyperoxia occurs due to high concentrations of oxygen given to the baby. This causes a retinal arteriolar spasm which later on becomes permanent closure. When the neonate returns to room air, there is endothelial proliferation adjacent to the closed vessels leading to neovascularisation and retinal traction.
2. Spindle cell or Gap Junction theory (Kretzer)(15) : The avascular retina of the premature neonate contains spindle cells. These cells are attacked by the toxic oxygen metabolites limiting their migration and canalization. Gap junctions are formed between adjacent spindle cells, through which abnormal vessels erupt.
3. Current Theory or Growth Factor theory(16) : Vascular Endothelial Growth Factor (VEGF) plays an important role in the vascularisation of the normal retina. In conditions of increased oxygen saturation, VEGF is inhibited, thus resulting in avascular retina. This hypoxic retina shows a rebound increase in VEGF leading to uncontrolled neovascularisation.

Risk Factors
The risk factors for ROP are listed below(17,18) :-
• Prematurity and low birth weight
• High oxygen levels
• Septicemia
• Acidosis
• Hyperglycemia
• Multiple gestation
• Anemia
• Respiratory distress syndrome
• Apnoeic spells
• Intraventricular hemorrhage

Retinopathy of Prematurity Retinopathy of Prematurity 11/05/2014
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