Introduction
Retinopathy of prematurity (ROP) is a disorder seen in preterm which was described by Terry in 1942.1 So Retinopathy of Prematurity is also known as Terry’s syndrome.
Terry coined term reterolental fibroplasia because of his impression that it was the pathology that involve embryonic hyaloid proliferation of retina. The term ROP was given by Heath in 1951.2 His studies and research offered thorough details of the disease.
ROP is a potentially preventable cause of irreversible total blindness in premature infants. As the survival of preterm babies increased due to improved perinatal healthcare, ROP has been the favourite research project worldwide. The preterm with less than 2.0kg birth weight classified as low birth weight babies are at the greatest risk of developing ROP.
High ROP rates are associated with comorbidities of preterm birth3 which has major social consequences like blindness especially in middle income countries and south-east Asia. 4 It has implications throughout life of the child and family.
ROP is a multifactorial disease5, 6 with associated risk factors like birth weight gestational age, oxygen supplementation, prolonged mechanical ventilation, anaemia, Intraventricular haemorrhage, necrotizing enterocolitis, sepsis.7 These risk factors which leads to progression of ROP needs to be evaluated. The knowledge of these risk factors will help the ophthalmologists and paediatricians to perform enhanced clinical examination, screening and diagnosis of ROP.
Materials and Methods
It is a retrospective analysis. This analysis was done at tertiary care hospital in Ophthalmology department for duration of 2.5 years. All Patients were dilated with combination drops of Tropicamide 0.8%w/v and Phenylephrine hydrochloride 5%w/v. All the preterm babies(less than 34 weeks) and low birth weight babies of less than 2 kg weight8 were examined after 4 weeks postpartum and babies with less than and equal to 28 weeks were examined at 2 weeks postpartum using 20 D lens with indirect ophthalmoscopy by Vitreoretinal Surgeon. Paediatric speculum was used to spread eyelids and Wire Vectis was used as a depressor. Patients were examined for retinal development till up to oraserrata and followed up till complete development of retina. Data were analysed by Chi-square test. ROP was classified by following International classification of ROP and screening guidelines of Government of India.9
International Classification of Rop (ICROP)9
Zone I: (inner zone): It is limited from optic disc to double the disc fovea distance diameter in all directions.
Extent: Clock hour numbers have been assigned for the extent of the disease.
The extent of the disease is further described as contiguous or non-contiguous ROP clock hours.9
Staging the disease (As defined by the International Classification of ROP)9 ICROP Staging
Stage 1: Thin demarcation line that separates avascular retina to vascularized retina
Stage 2: Ridge that arises from demarcation line
Stage 3: Fibro vascular Proliferation from ridge to the vitreous
Stage 4: Retinal detachment which may be foveal or extra-foveal
Stage 5: Total retinal detachment
Inclusion criteria
Screening of the newborn was done as per the criteria of set by government of India.
All the premature babies which are less than or equal to 34 weeks.
All Low birth weight babies (less than 2 0 kg irrespective of gestational age.
Babies with GA 34-36 weeks and given oxygen therapy with other risk factors.10
Results
Table 1
Magnitude of ROP
| ROP | Frequency(No. of Babies) | Percentage |
| NO | 199 | 67.9% |
| YES | 94 | 32.1% |
| Total | 293 | 100.0% |
Table 1 describe the magnitude of ROP. Out of 293 patients screened for ROP, 94 babies (32%) were found to have ROP of different zones and stages.
Table 2
Distribution of birth weight
| Birth Weight | Frequency | Percent |
| Very low(<1 kg)* | 93 | 31.7 |
| Low (1 to 2.5 kg) | 135 | 46.1 |
| Normal (>2.5 kg) | 65 | 22.2 |
| Total | 293 | 100.0 |
Table 2 shows birth weight distribution of our study. We found out that total 31.7% of 293 babies which accounts for 93 babies were very low birth weight.46% of total babies were low birth weight which accounts for 135 babies. 22% babies were having normal birth weight which accounts for 65 babies.
Table 3
Birth weight association with ROP
| ROP | Birth Weight | Total | ||
| Very low | Low | Normal | ||
| No | 41(20.6%) | 95(47.7%) | 63(31.7%) | 199 |
| Yes | 52(55.3%) | 40(42.6%) | 2(2.1%) | 94 |
| 93 | 135 | 65 | 293 | |
Table 3 shows association between birth weight and ROP.
Table 4
Relation of ROP and gestational age
| ROP | GA(Gestational Age) | Total | |
| PRE term(<34 weeks) | FULL term(>34 weeks) | ||
| No | 77(38.7%) | 122(61.3%) | 199 |
| Yes | 80(85.1%) | 14(14.3%) | 94 |
| 157 | 136 | 293 | |
Table 5
Comparison of Variables
We have observed that statistically significant P value (P less than 0.0001) was found out in low birth weight babies.
Babies having low birth weight have more chances of Retinopathy of Prematurity than normal birth weight babies. This result was statistically significant. (P value was less than 0.0001).
In our study 55% of very low birth weight babies, were having ROP which accounts for 52 out of 93 babies. 29% of low birth weight babies were having ROP (40 out of 135). Only 0.03% of normal birth weight babies were having ROP (2 out of 65).
Among 94 ROP babies 52 were very low birth weight (55%), 40 were low birth weight (42%) and 2 were normal birth weight (2%).
Table 4 shows association between GA and ROP. ROP was found in 80 Out of 157 pre term babies (50%). Only 14 babies out of 136 full term babies had ROP. Out of 94 ROP babies, 80(85%) were pre term babies. 14 out of 94 ROP babies were full term. These findings were statistically significant (P less than 0.0001).
A logistic regression was performed to ascertain the effect of birth weight and gestational age on the likelihood that patients (born babies) have ROP. The logistic model was statistically significant, the model explained 28.6% (Nagelkerke R2) of the variance in ROP and correctly classified 72% of cases. Pre term babies are 4.605 times more likely to exhibit ROP than full term. Normal weight babies are associated with reduced likelihood of exhibiting ROP, whereas very low weight and low weight babies have 7.411 and 2.098 time respectively more chance to develop ROP in as compared to normal weight babies.
Statistical analysis
Descriptive Analysis was used to represent data as percentage, whereas chi-square test was applied to know the association between ROP &GA and ROP& BW at 95% level of Significance. Logistic Regression was applied to examine and describe the relation between a binary response variable (ROP – yes Vs no) and set of predictor variables (i.e. GA and BW)
Discussion
ROP is a pathological process that occurs in immature retina if left undetected can lead to tractional retinal detachment and thereby results in total blindness with increasing burden of blindness as well as economic burden too. To prevent these consequences it is high time requirement to screen the preterm and high risk babies at appropriate time and treat them as and when require till they reach to irreversible stage. In an order to achieve this goal screening guidelines were made and followed, records were kept to assess the prevalence outcome and associated risk factors.
In this study 94 out of 293 babies had ROP of any stage. This study prevalence was 32%. In contrast, the study which was done by Abdel H. A. A. Hakeem11 in England had 19% ROP prevalence. The study done by
Dr. K. Rajendran in Tamil Nadu had prevalence of 19%. Prevalence of Both the studies were lower than our study. The study done by Dr. Anamika Dwivedi8 in Madhya Pradesh had similar Prevalence of ROP which is 30%. Study done by Mukta Sharma10 mentioned 30% of prevalence in developing countries which is similar to our study.
The Study done by Lad EMin the United States12 had 0.17% ROP. We can conclude from all these study results that Prevalence of ROP is much higher in developing countries than developed countries.
The study done by Shah VA13 in Singapore had 29.2% ROP prevalence as compared to our study which has 32%. In the study done by Gupta VP14 in New Delhi ROP was found in 33.3% which is similar to our study. CRYO-ROP15 study, reported ROP of any stage in 65.8% which is quite higher than our study.
The retrospective study done by Vinekar et al.16 138 patients with BWs more than 1250 gm referred for ROP examination, reported 45% of ROP.
The study done by Charan et al.17 reported in 1995 an overall incidence of 47% ROP in their babies with BWs of 1.7 kg or less. The study done by Dhaliwal et al.18 Out of 1413 infants with birth weight less than 1500 g and/or GA of
26-31 weeks, infants with a birth weight below the tenth percentile for GA were more likely to develop any stage of retinopathy of prematurity.
All these studies shows birth weight and pre term are the most important risk factors for developing ROP which result is similar to result.
Conclusion
Retinopathy of Prematurity most commonly seen in low birth weight babies.
High rate of premature birth and increasing advancement of healthcare without proper standards resulted in third epidemic. There is urgent need of screening guidelines of ROP for developing countries like India.
Acknowledgement
It is my privilege to express my deepest gratitude towards those who helped me during my learning and also in completing this study. Special thanks to Dr. Shobhna Mange Viteroretinal Surgeon, Dr. Swati Patel Biostatistician, Dept. of Community Medicine, SMIMER, Dr. Ashwin Vachhani, Professor and Head, Gynaecology and obstetrics department, SMIMER hospital.
