Retinopathy of prematurity (ROP) is a rapidly increasing cause of avoidable childhood blindness worldwide [1]. It is a vision-threatening disease associated with abnormal retinal vascular development at the boundary of vascularized and avascular peripheral retina [2]. In developed countries, the incidence of ROP seems to be declining over the last few decades. In developing countries, however, high fertility rates and increasing resuscitation of premature infants, often with suboptimal standards of care, have resulted in a third epidemic of ROP [3].

Short gestational age and LBW have been identified as the most important risk factors responsible for ROP, the other recognized risk factors being sepsis, intraventricular hemorrhage (IVH), mechanical ventilation, oxygen therapy, blood transfusion, and exposure to light [4]. Majority of ROP cases are mild and resolve spontaneously without treatment. A small proportion progress to more severe ROP, which, if untreated, can progress to retinal detachment and irreversible vision loss [5].

Recently, there has been observed an increase in the number of preterm babies with ROP in India [6]. This may be the result of high birth rate, high rate of preterm births, and survival of LBW children due to the advanced and expanded provision of medical care [7]. Increased numbers of pediatric ophthalmologists and vitreoretinal surgeons in the country has also led to ROP becoming increasingly recognized [6]. This study was, therefore, planned and initiated to assess the current incidence and severity of ROP in preterm infants and to determine the neonatal and maternal risk factors for the same.

Setting: This study was conducted in Chirayu Medical College and Hospital, a tertiary care Institute at Bhopal, as a prospective, observational study involving babies at risk of ROP. CMCH is equipped with NICU having advanced facilities for neonatal care and resuscitation.

Duration and type of study: This was a prospective study conducted to assess the incidence of ROP in premature infants and to determine risk factors for its development. Enrolment was for a period of 18 months, from 1^st February 2018 to 30^th July 2019.

Data analysis: Statistical analysis was performed using a commercially available statistical software package (STATA, version 11.0, Texas, USA). Univariate comparison of risk factors between eyes with and without ROP was done using Chi-square test and Fisher's exact test. Multivariate analysis was performed with binary logistic regression to compare the incidence of ROP as response variable and various risk factors. A p-value < 0.05 was considered to indicate a statistically significant association between a risk factor and the risk of developing ROP.

One hundred and four babies were enrolled for the study, on the basis the inclusion criteria detailed above. There were 60 (57%) males and 44 (43%) females. ROP was seen in 52 eyes of 27 babies giving an incidence of 25.96% with 25 (92.59%) babies having bilateral disease. Aggressive posterior disease seen in 8 (29.62%) babies while classic ROP with stage 2 or worse was seen in 13 babies (48.14%) [Table 1: Incidence of ROP according to stage].

Table 1: Incidence of ROP according to stage.

The mean Birth weight for the cohort was 1468 g (standard deviation [SD]: 300, range: 830–1870 g). Babies in ROP group had a mean BW of 1278 g (SD: 0.27, range: 830 –1726 g) while the mean for babies without ROP was 1452 g (range: 850 –1870 g, SD: 0.24). This difference was statistically significant with P< 0.001. The incidence of ROP was inversely related to BW with babies weighing <1000 g having the highest incidence of 71.78%.

Table-2: Relationship between birth weight and retinopathy of prematurity.

The incidence is increasing with improvement in survival rates of infants delivered at very low gestational ages [10]. The incidence of ROP in this study was 25.96 % which corresponds to that found in previous studies in India (15.6%–47.3%) [11-15]. Major risk factors for ROP are prematurity, Low birth weight, oxygen therapy, RDS, sepsis and blood transfusion [16]. Of these LBW, low GA and oxygen therapy are considered the most important risk factors for ROP with LBW being the greatest predictor of severity [16,17]. The incidence and severity of ROP show an inverse relationship with BW and GA, with few cases diagnosed in babies weighing over 1500 g or babies whose GA is >32 weeks at birth. Few reports indicate risk of ROP in mature babies as well [14,18-22].

Indian babies have been found to have early onset and more rapid progression of the disease than their counterparts from other countries [21]. Twenty one percent of babies with ROP in this present study weighed >1500 g which is much lower than 65% reported by Hungi et al [18]. ROP babies had mean birth weight of 1278 g in this study, which compares favorably with the study by Charan et al [15] but other studies in India have reported it to be higher than this.

Logistic regression analysis did not show low GA to be a significant risk factor in this present study. This compares favorably with study by Chaudhari et al [13] but is in contrast with finding by Murthy et al [12]. A mean GA of 28.91 weeks for ROP babies in this series was obtained, while previous reports showed range from 30.8 to 32 weeks, so this is lower [11,12,14,15,18]. The lower gestational age, lower birth weight, as well as the lower proportion of babies weighing >1500 g with ROP in this series reflect significantly improved in standards of neonatal care.

Treatment for ROP was carried out in 10 (37.03%) babies in this series. This falls towards the lower end of the range of 26%-75% reported in previous studies [11,12,13,18]. This shows that the incidence of severe ROP maybe declining. This may be related to improvements in neonatal care and monitoring of oxygen therapy in the NICUs. It is possible though that this observed decline in severe ROP may not necessarily be applicable to other hospitals in the area. Studies have demonstrated that with changes in neonatal care such as use of pulse oximeters, target based approach for maintenance of oxygen saturation and education of staff, the rates of treatable ROP can be reduced [23-25].