Kerala Journal of Ophthalmology

: 2022  |  Volume : 34  |  Issue : 2  |  Page : 144--148

The incidence of retinopathy of prematurity and the common risk factors associated with it: A retrospective study in a tertiary care center in Central Kerala

Deepa Molathe Gopalan1, Manju Abraham1, VS Dhanya1, Reshmi Ramachandran2, Adeline Liza Roy1,  
1 Department of Ophthalmology, Government Medical College, Ernakulam, Kerala, India
2 Department of Community Medicine, Government Medical College, Ernakulam, Kerala, India

Correspondence Address:
Dr. Deepa Molathe Gopalan
Department of Ophthalmology, Government Medical College, Ernakulam, Kerala


Aim: The aim of this study is to determine the incidence and risk factors for retinopathy of prematurity (ROP) among newborn babies screened at a public sector teaching hospital in Central Kerala. Materials and Methods: A retrospective case record-based study that included all newborns screened at the study center from May 2015 to May 2017. Newborn babies with significant media opacities and missing data were excluded from this study. A detailed ophthalmic assessment was done and association of ROP with maternal and perinatal risk factors was assessed. Results: Thirty-nine (6.9%, 95% confidence interval [CI]: 5.02, 9.23) of the 565 newborns screened at the department had ROP. This included 14 (2.48%) babies with Stage 1, 17 (3.01%) babies with Stage 2, and 8 (1.42%) babies with plus disease. Placenta previa or abruption (odds ratio [OR] 3.72, 95% CI: 1.32, 10.52), Respiratory distress syndrome (OR: 2.05, 95% CI: 1.05, 4.01) and hyaline membrane disease (OR: 4.19, 95% CI: 1.96, 8.99), a birth weight <2500 g (adjusted OR: 5.06, 95% CI: 1.20, 21.32) were associated with ROP. The risk of ROP reduced significantly with every unit increase of birth weight in a linear regression model (coefficient = ‒511.5, R2 = 0.03). Conclusion: The incidence of ROP is lower in this study population compared to reports from other areas of India. The significant associations with birth weight and gestational age are important as global preterm births are increasing and may possibly lead to an epidemic of ROP More ophthalmologists must be trained in the management of ROP and integrated with neonatal intensive care services.

How to cite this article:
Gopalan DM, Abraham M, Dhanya V S, Ramachandran R, Roy AL. The incidence of retinopathy of prematurity and the common risk factors associated with it: A retrospective study in a tertiary care center in Central Kerala.Kerala J Ophthalmol 2022;34:144-148

How to cite this URL:
Gopalan DM, Abraham M, Dhanya V S, Ramachandran R, Roy AL. The incidence of retinopathy of prematurity and the common risk factors associated with it: A retrospective study in a tertiary care center in Central Kerala. Kerala J Ophthalmol [serial online] 2022 [cited 2023 Feb 8 ];34:144-148
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Full Text


Retinopathy of prematurity (ROP) is a sight-threatening developmental disorder of the retinal blood vessels that is more common in premature and low birth weight infants.[1] Early identification and intervention can preserve sight in these infants, but the disease often goes unnoticed in the early weeks of life. Most of the visually impaired survivors are born in middle-income countries of the world.[2],[3],[4] Improvements in neonatal care and resuscitation have led to the survival of more preterm babies in India and ROP is emerging as a significant cause of visual disability in children.[4]

India has the largest number of premature babies and hence high incidence of ROP among developed countries.[4] India accounts for nearly 10% of the worldwide estimate of blindness and visual impairment due to ROP and >3000 infants become visually impaired each year due to lack of screening and treatment for ROP.[4] A previous study from Kerala reported an incidence of 25.4% ROP among babies admitted to neonatal intensive care units (NICUs) and 9.8% needed laser treatment.[5] Several studies including the CRYO ROP study have reported gestational age (GA) and birth weight as strongest risk factors for ROP.[6],[7],[8],[9] Several other risk factors including the use of supplemental oxygen, maternal factors, antenatal and perinatal factors, and postnatal infantile factors have been reported.[10] However, ROP in India, including the severe forms are seen in more mature babies with higher birth weights as well.[11],[12] We designed a retrospective case record-based study to identify the incidence and common risk factors associated with ROP among the newborn babies screened over 2 years in a tertiary care hospital in Central Kerala.

 Materials and Methods

The study protocol was approved by the Institutional Ethics Committee. Case records over a period of 2 years from May 2015 to May 2017 at the study institute were considered for inclusion. Case records of newborn babies screened at the Ophthalmology Department were identified from the registry for ROP screening at the study institute. Newborn babies with a GA ≤34 weeks, birth weight ≤2000 g were referred for ROP screening. In addition, any newborn baby with a GA >34 weeks with the presence of any risk factor for ROP, or if there was a clinical suspicion of ROP were referred by the neonatologist for screening. Newborn babies with significant media opacity such as congenital cataract and glaucoma, or with incomplete childbirth or perinatal details were excluded from the study.

We retrieved information of the various antenatal and postnatal factors from the case records and entered them into a data collection form after anonymizing individual patient information.

Details of maternal factors including age, parity, type of delivery, multiple pregnancies, obstetric complications such as pregnancy-induced hypertension (PIH), gestational diabetes mellitus (GDM), antepartum hemorrhage (abruption placenta/placenta praevia), febrile illness, and premature rupture of membrane (PROM) were collected from the case records. Details of childbirth and postnatal period including GA, birth weight, sex, asphyxia, oxygen supplementation, presence of sepsis, and metabolic derangements such as hyperglycemia. Hypoglycemia, hyperbilirubinemia, hypocalcemia, and ABO/Rh incompatibility were recorded. GA was recorded in case sheet as per protocol (determined by antenatal ultrasound in the first trimester and calendar method) was taken. Birth weight was recorded by electronic weighing scales. Oxygen supplementation was provided based on hospital NICU guidelines and involves low flow divert through nasal prongs and hoods. Details of high supplementation with continuous positive airway pressure and ventilator were noted. Diagnosis of sepsis was recorded by clinical suspicion, diagnostic tests, and microbiological confirmation.

All ophthalmic assessments were done by trained ophthalmologists within 30 days of life.

Anterior segment assessments were done to look for pupillary dilation, lenticular changes, and media clarity followed by posterior pole and peripheral examinations of all clock hours to look for presence, vascularization, and zone and stage of ROP. Posterior segment assessments were done after dilatation using 1% tropicamide and 2.5% phenylephrine eye drops diluted to 50% with preservative-free lubricants and applied 10 min apart starting 1 h before the examination. Indirect ophthalmoscope and a 20D lens were used to assess the fundus after instilling topical anesthesia drops and with the help of a pediatric eye speculum and scleral depressor. The diagnosis and classification of ROP were based on the International Classification of ROP guidelines.[13] All babies were categorized as no ROP, Stage 1 to 5 ROP and plus disease. The worse affected eye was used to categorize the stage and severity of ROP. If both eyes were symmetrically affected, the right eye was chosen to determine stage and severity. Newborn babies with severe ROP were assessed at 3–5-day intervals, those with less than severe ROP at weekly intervals, and those with no ROP at bi-weekly intervals till complete retinal vascularization was noted.

Data were initially entered into an MS Excel spreadsheet and exported to the SPSS software for statistical analysis IBM SPSS Statistics. Continuous variables were expressed as mean standard deviation (SD) and categorical variables were expressed as proportions. The incidence of ROP was described as a proportion. Risk factors associated with ROP were initially explored using a bivariate analysis using a one-way analysis of variance test and Fisher's exact test. Significant associations with ROP are presented as odds ratio (OR) and 95% confidence intervals (CIs) around the point estimate. P < 0.05 was considered as statistically significant.


The study included 565 newborn babies that were screened for ROP at the study institute. [Table 1] presents the maternal details of the newborn babies that were screened. PIH (n = 85, 15.04%) and gestational diabetes mellitus (n = 65, 11.50%) were the most common maternal comorbid conditions [Table 1], abnormal liquor volume was noted in 71 (12.57%) and PROM in 98 (17.35%) mothers. A cesarean section was performed on 332 (58.87%) women.{Table 1}

Twenty-one (3.72%) babies were born ≤28 weeks of gestation, 118 (20.92%) babies were born between 28 and 32 weeks of gestation and 108 (31.95%) babies were born between 32 and 37 gestation weeks. Three hundred and eleven (55.04%) babies were male. The mean (SD) birth weight of the babies screened for ROP was 1,884.71 (737.87) with an interquartile range of 1430–2200 g. Most of the babies (n = 558, 98.76%) were admitted to the NICU. The neonatal details of the 565 babies screened for ROP are presented in [Table 2].{Table 2}

Thirty-nine (6.9%, 95% CI: 5.02, 9.23) of the 565 newborns screened at the department had ROP. This included 14 (2.48%) babies with Stage 1, 17 (3.01%) babies with Stage 2, and 8 (1.42%) babies with plus disease. [Table 3] presents the association of ROP with maternal factors. None of the mothers with GDM had a baby with ROP in this series and placenta previa or abruption was associated with an increased risk for ROP (OR 3.72, 95% CI: 1.32, 10.52). The association of ROP with postnatal and childbirth factors is presented in [Table 4]. Respiratory distress syndrome (OR: 2.05, 95% CI: 1.05, 4.01) and hyaline membrane disease (OR: 4.19, 95% CI: 1.96, 8.99) were associated with ROP. ROP was significantly associated with a birth weight <2500 g (adjusted OR: 5.06, 95% CI: 1.20, 21.32) and the risk of ROP reduced significantly with every unit increase of birth weight in a linear regression model (coefficient = ‒511.5, R2 = 0.03).{Table 3}{Table 4}


Nearly one in 10 newborn babies screened had ROP in this series. ROP was significantly associated with birth weight, abnormal placentation, respiratory distress syndrome, and hyaline membrane disease in this study. Gestational diabetes showed a protective effect for the development of ROP.

An estimated 0.2% of childhood blindness is attributed to ROP with the prevalence ranging from 0.81/1000 to 1.5/1000 in different states.[14],[15] The KIDROP study from Karnataka in 2015 reported an incidence of any-ROP to be 22.4% with an incidence of 3.5% for severe-ROP requiring treatment.[16] The twin cities ROP project reported any-ROP in 25% of 643 babies screened,[17] while an incidence of 21.6%–32, 0.6% was reported from other studies. The incidence of ROP in our study population (6.9%, 95% CI: 5.02, 9.23) is lower than the estimates reported from other parts of India. The incidence is lower than the 25% reported from a previous study from NICUs in Kerala[5] but the lower incidence of ROP in the screened population may reflect the criteria used to refer newborn babies for screening. The incidence of ROP was 14.7% (95% CI 7.84, 20.50%) in the study population with GA <32 weeks and birth weight <1700 g. Nineteen (6.13%) of the newborn babies between 34 and 36 weeks that were screened had ROP. These babies may have been missed if we had used a strict <32 weeks GA criteria. Only 2 (1.12%) newborn babies with a birth weight >2000 g developed ROP. Compliance with the revised screening guidelines for ROP in India may help minimize the number of preterm babies screened for ROP.

Several risk factors are reported for ROP.[7],[8],[9],[10],[11],[12] A previous study from Kerala reported anemia, oxygen administration, hours on ventilation, and blood transfusion as significant risk factors for ROP.[5] However, only birth weight, abnormal placentation, respiratory distress syndrome and hyaline membrane disease, and GA at birth were significant risk factors in our study. ROP was not associated with supplemental oxygen therapy in this study and maybe associated with the pattern of oxygen supplementation. A previous meta-analysis has reported that early low and late high oxygen saturation was associated with a reduced risk for severe ROP among preterm infants with a GA of <or = 32 weeks.[18] Abnormal placentation was a risk factor for ROP in this study population. A previous study has reported on the higher incidence of ROP even in infants with birth weights exceeding the usual screening criteria in childbirths complicated by severe prenatal blood loss requiring blood transfusions and surgery.[19] Population differences in the risk factors for ROP that affect severity and progression of the disease are well recognized.[2],[4],[10]

The documentation and detailed ophthalmic assessments integrated with neonatal assessments at a tertiary care center may be considered as strengths of the study. The retrospective nature of the study maybe a limitation as standardization between observers was not possible. The single-center nature of the study can also be considered a limitation as the results may not be generalizable to a larger population.

The results of this study from a public sector teaching hospital add to the existing knowledge pool available on ROP in India. The difference in risk factors and the lower incidence in the screened population may reflect differences in the study population and screening criteria. The results of the study, however, highlight the need for studies from different areas and health-care settings in Kerala to obtain reliable estimates of the incidence and risk factors for ROP. Global preterm births are increasing worldwide including in India[20] and will lead to an increased number of newborn babies that need ophthalmic screening. Improved understanding of the changing incidence and risk factors can help improve the screening algorithms to identify high-risk babies for more targeted screening. More ophthalmologists must be trained to screen for ROP and eye screening must be integrated with all NICUs. Currently, there may be <200 ophthalmologists in India that have received specialized training in the screening and management of ROP.[11] Appropriate planning of evidence-based services can help Kerala address the potential epidemic of ROP.


Acknowledging the valuable support of Dr. Praveen Nirmalan, Vitreoretinal surgeon and public health in Ophthalmology researcher in reviewing and editing the manuscript and the tremendous moral support in giving shape to this manuscript.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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