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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 22  |  Issue : 1  |  Page : 56-62

Incidence and risk factors of retinopathy of prematurity in a tertiary neonatal intensive care unit: Assiut University Hospital, Upper Egypt


1 Department of Pediatrics, Faculty of Medicine, Assiut University, Assiut, Egypt
2 Department of Medical Physiology, Faculty of Medicine, Assiut University, Assiut, Egypt
3 Department of Ophthalmology, Faculty of Medicine, Assiut University, Assiut, Egypt

Date of Submission26-Sep-2020
Date of Decision28-Nov-2020
Date of Acceptance21-Dec-2020
Date of Web Publication24-Mar-2021

Correspondence Address:
MD., PhD Enas A Hamed
Department of Medical Physiology, Faculty of Medicine, Assiut University, Assiut, PO Box 71516, Egypt. Postal/Zip Code: 71516
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/DJO.DJO_72_20

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  Abstract 

Purpose This prospective study aimed to identify the incidence of retinopathy of prematurity (ROP) in premature infants in a neonatal ICU in a tertiary care hospital and to evaluate the risk factors predisposing to it.
Patients and methods All preterm babies admitted to the neonatal ICU, during the study period, with gestational age (GA) less than 37 weeks and low birth weight (LBW) of less than or equal to 2.00 kg, were included in this study. Examination and follow-up of patients were done by binocular indirect ophthalmoscopy using a 28 D lens with a speculum and scleral depressor to examine the retinal periphery after efficient pupillary dilatation.
Results Of 216 screened neonates, 66 (30.6%) developed ROP. Of these, 27 (40.9%) had stage 1, 35 (53.0%) had stage 2, and four (6.1%) had stage 3 ROP. The incidence was high in the GA group less than 28 (86.7%) weeks and in LBW neonates (100.0%). ROP was associated with LBW (1280±435 g, P<0.001), GA (30.4±1.9 weeks, P=0.005), sepsis (P=0.006), anemia (P=0.007), blood transfusion (P=0.018), bronchopulmonary dysplasia (P=0.001), and O2 therapy (P=0.006) as well as its duration (P<0.0001) by multiple logistic regression analysis.
Conclusion ROP incidence in our tertiary care hospital was 30.6%. The main risk factors for ROP development were low GA, LBW, anemia, blood transfusion, sepsis, bronchopulmonary dysplasia, and O2 therapy and its duration. Prevention of prematurity, control of infection, reduction of blood sampling to prevent occurrence of anemia with subsequent blood transfusion, and judicious use of O2 therapy may be promising factors that may decrease the incidence and severity of ROP.

Keywords: incidence, prematurity, retinopathy of prematurity, risk factors


How to cite this article:
Abdel-Aziz SM, Hamed EA, Abdel-Radi M, Shalaby AM. Incidence and risk factors of retinopathy of prematurity in a tertiary neonatal intensive care unit: Assiut University Hospital, Upper Egypt. Delta J Ophthalmol 2021;22:56-62

How to cite this URL:
Abdel-Aziz SM, Hamed EA, Abdel-Radi M, Shalaby AM. Incidence and risk factors of retinopathy of prematurity in a tertiary neonatal intensive care unit: Assiut University Hospital, Upper Egypt. Delta J Ophthalmol [serial online] 2021 [cited 2022 Aug 18];22:56-62. Available from: http://www.djo.eg.net/text.asp?2021/22/1/56/311896


  Introduction Top


Retinopathy of prematurity (ROP) is a cluster distinguished by formation of abnormal retinal blood vessels owing to incomplete vascularization of the retinal tissue caused by hyperoxia causing vascular endothelial growth factor (VEGF) downregulation and endothelial cell death. This process upregulates VEGF, which results in neovascularization [1]. ROP is emerging as a significant cause of impaired vision and blindness during childhood in developing countries [2].

Nowadays, improvement in services of neonates in developing countries and increased survival of premature and low-birth-weight (LBW) infants had been followed by an increase in ROP incidence. Therefore, studying the epidemiology of ROP is imperative, to decrease the occurrence of visual defects and blindness induced by ROP [3].

There are many factors that affect the occurrence of ROP such as gestational age (GA), BW, race, sex, and neonatal care standards. Screening systems should be modified regionally to compensate for these variations [4],[5]. Many studies noted several risk factors associated with this disease, some of which may cause severe ROP such as BW, GA, supplementary oxygen (O2), excessive mechanical ventilation, Apgar score, pulmonary disorders, anemia, intraventricular hemorrhage (IVH), necrotizing enterocolitis (NEC), and septicemia [6],[7],[8]. Identifying the risk factors that accelerate the progression of ROP and knowledge of its etiology can help ophthalmologists and neonatologists screen carefully, make an accurate diagnosis, and reduce the disease complications [9].

This study aimed to detect the incidence of ROP in premature neonates and the various neonatal and maternal risk factors that predispose to ROP development.


  Patients and methods Top


This prospective observational research was conducted at the Neonatal Intensive Care Unit (NICU) of the Pediatrics Hospital, in cooperation with the Department of Ophthalmology, Assiut University, Assiut, Egypt, during the period from November 2018 to October 2019. The protocol of the study was approved by the Local Ethical Committee and was carried out according to the Declaration of Helsinki. The patients’ parents/guardians signed a written informed consent to participate in the study and for publication of data before their babies were enrolled in the study. Parents were counseled regarding the schedule of follow-up, the course of the disease, and the treatment modalities.

All neonates were recruited in the NICU during the study period who were (a) preterm infants with GA less than 37.00 weeks and (b) BW less than or equal to 2.00 kg. Neonates with fatal congenital anomalies, congenital eye defects such as glaucoma, cataract and corneal opacities, and babies who died before 28 days postnatally or did not come for follow-up were excluded from the study.

The baseline characteristics of the screened babies besides neonatal and maternal risk factors for ROP development were collected. Neonatal risk factors for ROP included sex, delivery mode, GA, BW, respiratory distress syndrome (RDS), neonatal hyperbilirubinemia, neonatal sepsis, NEC, apnea, anemia, blood transfusion, surfactant use, O2 therapy, IVH, and bronchopulmonary dysplasia (BPD). Maternal risk factors such as maternal diabetes mellitus, pregnancy-induced hypertension, prenatal steroid use, maternal premature rupture of membrane, and antepartum hemorrhage were also collected.

Eye examinations for all infants who met the inclusion criteria were done by the same trained ophthalmologist (M.A.R.). The initial screening was made at the fourth week following birth or at 31–33 weeks of postconceptional age, whichever was later. After the initial examination, the retina was examined weekly or every 2 weeks according to the severity of ROP, till complete retinal vascularization or until ROP had been resolved.

The pupils were dilated using topical phenylephrine 2.5% eyedrops (Neo-Synephrine; Ursapharm, Saarbrüken, Germany) and tropicamide 1% eyedrops (Mydriacyl, Alcon Lab, Fort Worth, Texas, USA) that were instilled every 15 min for four times, 1 h before eye examination. Examination and follow-up of patients were done by binocular indirect ophthalmoscopy using a 28 D lens with a speculum and scleral depressor to examine the retinal periphery. ROP was classified by severity (stages 1–5) and location on retina (zones I—III), based on the International Committee for ROP Classification. Stages 1 and 2 mean deferred retinal blood vessel development that was seen as a boundary line at the intersection of vascularized and avascular retina. In stage 3 ROP, neovascularization or extraretinal fibrovascular proliferation happened. Stages 4 and 5 comprised severe ROP, with total or partial retinal detachment. Vessel developments were depicted over the three zones (I, II, and III), with the inner zone I centered upon the optic disc and included a circular zone with a radius of double the distance between presumed optic nerve and fovea. Zone II is the area that encircled zone I till the ora serrata in the nasal retinal area, whereas zone III includes the temporal crescent in between zone II and the ora serrata [10].

Statistical analysis

Data were analyzed by the Statistical Package for Social Sciences (SPSS), version 23 (IBM SPSS; IBM Corp., Armonk, New York, USA). Shapiro–Wilk test was used to evaluate normal data distribution. Values were presented as mean±SD and number and % as appropriate. During univariate analysis, the categorical data were analyzed by χ2 test and Fisher’s exact test, and parametric data were tested with the unpaired Student t test. Multivariate logistic regression analysis was made with the data, which were found significant by univariate analysis. P values less than 0.05 were considered statistically significant.


  Results Top


A total number of 216 neonates who met the inclusion criteria of the study were screened for ROP. Of them, 66 (30.6%) cases developed ROP of any stage. By analyzing the demographic features for the studied neonates, males were 110 (51.0%) and females were 106 (49.0%). Babies delivered by cesarean section were 138 (63.9%) and those delivered by spontaneous vaginal delivery were 78 (36.1%). The mean birth weight was 1540±352 g; five (2.3%) were less than 1000 g, 155 (71.8%) were 1000–1500 g, and 56 (25.9%) were more than 1500–less than 2000 g. The mean GA of the screened babies was 33.2±2.5 weeks; 15 (6%) were less than 28 weeks, 153 (70.8%) were 28–32 weeks, and 48 (22.2%) were more than 32–less than 37 weeks ([Table 1]).
Table 1 Demographic features of the studied neonates (N=216)

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Of all cases, 186 (86.1%) developed apnea; 170 (78.7%) presented with RDS; 170 (78.7%) received O2 therapy, with duration of less than 7 days (47=27.6%) and more than 7 days (123=72.4%); 163 (75.5%) received blood transfusions; 140 (64.8%) developed anemia; 86 (39.8%) received intensive phototherapy; 68 (31.5%) developed IVH; 65 (30.1%) developed sepsis; 45 (20.8%) received surfactant; 30 (13.9%) developed NEC; and seven (3.2%) developed BPD ([Table 2]).
Table 2 Neonatal risk factors for development of retinopathy of prematurity

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The average GA among those who were diagnosed with ROP was 30.4±1.9 weeks compared with 32.1±2.3 weeks in the non-ROP group (P<0.002). The average BW was 1280±435 g among infants with ROP compared with 1460±420 g in infants without ROP (P=0.001). The neonatal and maternal risk factors for ROP were studied and analyzed by univariate analysis. Regarding the neonatal risk factors, there was a statistically significant association between the presence of ROP and BW (P<0.001), GA (P=0.002), sepsis (P=0.003), anemia (P=0.021), blood transfusion (P=0.030), BPD (P=0.004) and O2 therapy (P=0.001), and its duration (P<0.0001). On the contrary, there were insignificant associations between the occurrence of ROP and sex (P=0.856), mode of delivery (P=0.672), RDS (P=0.925), surfactant use (P=0.892), IVH (P=0.653), NEC (P=0.523), hyperbilirubinemia (P=0.432), and apnea (P=0.125) ([Table 2]).

None of the maternal risk factors like maternal diabetes mellitus, pregnancy-induced hypertension, prenatal steroid use, maternal premature rupture of membrane, and antepartum hemorrhage was related with ROP development (P>0.05) ([Table 3]).
Table 3 Maternal risk factors for development of retinopathy of prematurity

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On multiple logistic regression analysis, BW, GA, O2 treatment and its duration, sepsis, anemia, blood transfusions and BPD remained as significant variables ([Table 4]).
Table 4 Multiple logistic regression analysis for risk factors related to retinopathy of prematurity

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Among ROP cases (66/216 cases), 27 (40.9%) of the babies had stage 1, 35 (53%) of them had stage 2, and four (6.1%) of them had stage 3 ROP. None of the infants developed stage 4 or 5 ([Table 5]).
Table 5 Stages of retinopathy of prematurity among the screened neonates

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In respect to the frequency of ROP according to different GA groups, among 15 infants who fell in the GA group less than 28 weeks, 13 (86.7%) developed ROP. Of the 153 infants in the 28–32 weeks group, 44 (28.8%) developed ROP, and of the 48 infants in the more than 32–less than 37-week group, nine (18.8%) developed ROP. So as the GA decreased, the incidence of ROP increased. Regarding the frequency of ROP according to BW groups, the incidence of retinopathy was five (100.00%) of the five neonates weighing less than 1000 g, 56 (36.1%) of the 155 neonates weighing between 1001 and 1500 g, and five (8.9%) of the 56 infants weighing between 1500 and 2000 g ([Table 6]).
Table 6 Frequency of retinopathy of prematurity according to different gestational age and birth weight groups

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  Discussion Top


ROP incidence depends on several items such as geographical area, race, survival rate of neonates, and quality of NICUs. In the present study, the incidence of ROP was 30.6% (66/216). The incidence of ROP varies from one country to another and also from one institute to another in the same country, owing to the differences in economic status, genetics, practice setting, screening programs, and perinatal care level at different institutions. On revising the Egyptian studies regarding ROP incidence, Hakeem et al. [11] reported that 33 (19.2%) infants out of the studied 172 infants developed ROP in a prospective study that was carried out in the NICU of Al-Minia University Hospital from January 2009 to December 2010. Hadi and Hamdy [12] reported that of the screened 152 infants, 52 (34.4%) developed ROP of any stage in a study conducted from January 2010 to January 2012 in three private hospitals at Alexandria, Egypt. Bedda et al. [13] found 73 (33.74%) infants suffering from ROP out of 223 preterm infants screened at El-Shatby University Hospital, Alexandria University in a study conducted from June 2012 to November 2013. Nassar [14] reported an incidence of ROP of 36.5% among 52 screened premature infants admitted to the NICU at Maternity and Pediatrics University Hospital, Al-Minia, Egypt between January 2010 and March 2011. Bassiouny et al. [15] reported, out of the 402 screened preterm babies, 237 (59%) cases having ROP in a study conducted at Mansoura City from March 2013 to March 2015. The international studies reported incidence of ROP in preterm babies ranging from 10 to 45.5%. The incidence was 36.1% in Germany [16], 36.4% in Sweden [17], 32.1% in Turkey [18], and 29.2% in Singapore [19], which was comparable to that in developing countries, such as Saudi Arabia (38.6%) [20], Iran (45.0%) [21], India (19.28%) [22], and Brazil (18.2%) [23]. The advanced technology in developed countries and the high survival rate of preterm infants with low GA and very LBW may account for the higher ROP incidence.

In the present study, among the ROP cases, it was found that 27 (40.9%) of the babies had stage 1, 35 (53.0%) of them had stage 2, and four (6.1%) of them had stage 3 ROP. None of the infants had stage 4 or 5. The high percentage of stages 1 and 2 and the absence of stages 4 and 5 indicate that more cases of earlier ROP stags were documented by early screening. These data were in consistence with Bassiouny et al. [15] who reported 42.6% having stage 1 and 45.1% having stage 2 ROP. Similarly, Babaei et al. [24] reported an incidence of 45.5% for both stages 1 and 2. Lower values were reported by Celebi et al. [8], who reported an incidence of 25.9 and 11.06% for stages 1 and 2, respectively, in extremely LBW infants. Meanwhile, others reported the majority of cases as stage 2 than stage 1. This was also found by Rasoulinejad and Montazeri [21] who reported 16.99 and 63.07% for stages 1 and 2, respectively, and Singh et al. [25], who reported 14.28 and 64.28% for stages 1 and 2, respectively.

Many risk factors were found to predispose to ROP development [26]. The current study showed a significant relation between GA and ROP development. This was in agreement with other studies [11],[14],[27],[28]. Vascularization immaturity increases the retinal susceptibility to oxidative stress destruction and to perinatal factors such as hyperoxia and hypoxia, sepsis, and transfusions of blood [28].

In addition, the current study found that LBW was a significant risk factor for ROP. Other studies [27],[28],[29] revealed that LBW was significantly related with ROP and claimed that to the more need for O2 therapy, sepsis, long time ventilation, and blood transfusions in the very LBW infants. However, Hakeem et al. [11] reported that the birth weight was an insignificant risk factor for ROP, but this is probably owing to the small number of patients (three out of 172 cases) with birth weight less than 1000 g involved in that study.

The results of this study revealed a significant relation between sepsis and ROP. This finding was in accordance with other researchers [11],[27],[30],[31]. They attributed this finding to endotoxin effects on retinal blood vessels which lead to inflammation and leakage that lead to endotoxin-induced retinitis with enhanced active leukocyte adhesion to vascular endothelium [25]. Weintraub et al. [32] reported that sepsis increased the risk for ROP development by 12 folds as it increased the O2 need and interfered with O2 tension that leads to retinal ischemia and ROP. On the contrary, this was in disagreement with others who contributed ROP to both nonoxygen and oxygen regulating factors such as VEGF and insulin-like growth factor 1 [33],[34].

The results of the current study revealed a significant association between ROP and O2 therapy. These results were consistent with previous studies [11],[27],[35]. The fluctuation in O2 exposure leads to hypoxia (2–3 episodes) and hyperoxia (>3 episodes), that was established to be associated with ROP [25]. There was a significant association between high O2 pressure, retinopathy, and O2 therapy duration [23]. However, Palmer et al. [36] found that O2 treatment was an insignificant risk factor for ROP. They recorded that ROP occurred in preterm infants who were not administered O2 treatment. The present study revealed that prolonged O2 treatment time was associated with ROP, which is in concordance with some studies that reported that O2 therapy duration more than 7 days was a significant risk factor for ROP [19],[29],[37]. On the contrary, Hakeem et al. [11] reported insignificant association between O2 therapy and ROP development.

In the present study, there was a significant association between BPD and ROP occurrence. This agrees with previous studies [27],[38] who reported a significant relation between BPD and ROP occurrence. In this research, blood transfusion was an ROP risk factor, which is in consistence with other studies [11],[28],[30],[35],[39]. This can be explained by that adult red blood cells were plenty in adult hemoglobin and 2, 3 diphosphoglycerate that combined with oxygen less tightly, thus releasing more oxygen to the tissues of the retina. However, Hirano et al. [40] reported that it was controversial, and overload of iron rather than blood transfusion frequency leads to ROP.

This study showed insignificant association between sex, delivery mode, RDS, IVH, and phototherapy and ROP occurrence. In agreement with these findings, other studies [11],[41] found insignificant relationship between delivery mode and ROP occurrence. Chaudhari et al. [33] detected an insignificant effect of phototherapy on ROP. In contrast, other studied found some of these factors to be associated with ROP. Darlow et al. [42] reported that male sex was a significant risk factor. Bassiouny et al. [15] reported cesarean section delivery as a risk for ROP occurrence. Dalai et al. [2] and Akkawi et al. [39] reported RDS and apnea as risk factors for ROP occurrence and explained this by systemic hypoxia that leads to hypoxia of the retina and more O2 therapy need. In addition, other researchers [31],[41] found a significant association between ROP occurrence and IVH. Khorshidifar et al. [31] and Kazemi Rad et al. [43] reported significant association between surfactant use and occurrence of ROP.

The results of this study showed insignificant relation between maternal risk factors and development of ROP, in contrast with Dalai et al. [2], who reported a significant relation between maternal diabetes mellitus and occurrence of ROP.


  Conclusion Top


The present study documented the problem of ROP in a tertiary care neonatal unit. Low GA, BW, anemia, blood transfusion, sepsis, BPD, and O2 therapy and its duration were risk factors for ROP development in preterm infants. It is recommended that prevention of prematurity, control of infection, reduction of blood sampling to prevent occurrence of anemia and subsequent blood transfusion, and judicious use of O2 therapy are promising factors that may decrease the incidence and severity of ROP. In addition, timely screening according to the guidelines, recognition, and early treatment of ROP are crucial to prevent the adverse outcome and possible blindness with long-term visual morbidity in these infants.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]



 

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