All infant screened bP<0.01, vs No ROP

    Table 2ROP screening findings 2003 to 2005 in UMMC

    YearscreeningStage 1,2Stage 3No ROPTotal20031653455200497526820053154765Total2827133188

    Pearson Chiª²square value =14.422, df = 4, P= 0.001

    Table 3Number and percentage of ROP cases from 2003 to 2005n(%)

    YearnROPTreatedBirth

    <751gROP in birth weight

    < 751g20035521 (38.2)6 (10.9)55 (100)20046816 (23.5)6 (8.8)74 (57.1)20056518 (38.0)15 (23.1)97 (77.8)Total 18855 (29.3)27 (14.4)2116 (76.2)

    separated into different birth weight groups, it shown that those whose birth weight was below 751 grams needed 2.4 times (8.41/3.48) more examinations compared to infants who weighed between 751 to 1250 grams. In infants whose birth weight were below 751 grams, 58.33% (7/12) required more than 1 session, while in infants whose birth weight were between 751 to 1251 grams, 28.6% (4/14) needed more than one session of treatment.

    DISCUSSION

    ROP was the main diagnosis in visual impairment in 46% children born prematurely in Finland between 1972 through 1989 [6]. In another study of visuallyª²impaired children in Brazil, 11.8% were due to ROP[7]. In a study on blind schools in Malaysia by Reddy et al, 20.8% of 358 children¬ðs visual impairment was due to impairment in the retina [8]. Thus, the screening of ROP in premature infants must be carried out properly as the majority of cases with this condition respond favorably to treatment when it is detected early. Many staff are involved in the proper management of this condition, beginning with the referral of these patients at the appropriate time by the paediatrician, the regular examinations to be carried out for each infant by ophthalmologists, and when a patient requires treatment, an entire team of doctors and nursing staff need to be coordinated to attend to the patient during treatment sessions.

    The incidence of ROP in this study of 29.3% (55/188) lies between some figures reported in studies in this region, i.e. 45.8% (103/225) in Vietnam [9], 47.27% in India [14], 29.2%(165/564) in Singapore [10], 10.8% in Beijing [15] and 25.4% (15/59) for Oman [11]. It must be clarified that the screening criteria for each of these studies were different from our study e.g. In the Beijing study, all infants below 2001 grams and below 35 weeks were screened, while that in Vietnam included infants who were 2000 grams and 36 weeks gestation. In an earlier study of 100 infants between 1994 to 1996 from the same hospital, the incidence was 15%[12], however the mean birth weight of the babies with ROP were 993 grams compared to 883.5 grams in this study. Furthermore, the criteria for selection of patients for ROP screening may have differed as well. The mean birth weight of our study patients who developed Stage 3 ROP in which Threshold disease is included was 833.5 grams which is quite similar to that of CRYOª²ROP study which was reported as 831 grams.

    There was a gradual increase in the number of infants admitted for management in SCN from 2003 to 2005, whose birth weight was 750 grams and less (Figure 1). There was also a rise in the number of patients <751 grams who survived and eventually be screened for ROP (Figure 3). The reason for this rise is not obvious from this study but may be due to an increase in the resources in the hospital to manage smaller infants or perhaps an increase in the number of live births from premature deliveries. This probably resulted in an increase in the number of cases with Stage 3 ROP (Table 3).

    It was reported in the landmark CRYPª²ROP study that the incidence of ROP for infants below 751grams was close to 90% as compared to 66 % for those who weighed more than 1250 grams [3,13]. The incidence in our study for infants below 751 grams was 76.2% overall for all the 3 years and further breakdown by years showed incidence of 100% in 2003, 57.1% in 2004 and 77.8% in 2005 (Table 3). As perinatal care improves, there will be a rise in the number of small infants who require ROP screening and it is expected that there will be a rise in the detection of more severe ROP cases as was shown in this study where 83.3% of cases in 2005 had Stage 3 ROP compared to 2003 with 23.8% cases who had Stage 3 ROP.

    The percentage of cases requiring treatment over total number of cases screened from the SCN ward during this study period was 14.4%. This is comparable to other regional studies e.g. 10.9% (6/55) in the Oman study [11] and 10.7% (24/225) in Vietnam [9]. However, in the Beijing study [14], 33.3% (23/69) had required treatment. In the series reported on patients in the same hospital a decade earlier, Chye et al had reported only 4% (4/100) cases required treatment. This could be a reflection of the difference in population of cases screened. The mean birth weight was 993 grams while that of the present study was 883.5 grams. When comparing between the three years from 2003 to 2005, it shown that in 2005 there was more than twoª²fold increase in the number of cases requiring treatment (Table 3). The conventional indication for treatment for this condition since the CRYOª²ROP study has always been the progression to Threshold disease which includes children with Stage 3 ROP but since 2004 some Stage 2 cases were also included for treatment as well to incorporate the revised indications recommended by the ETROP studies [4]. That may partly explain the sudden rise in number of treated cases in 2005 (Figure 4). Another explanation is the increase in the number of Stage 3 cases seen over the 3 years which is attributed to the increase in the number of smaller (birth weight <751 grams) who were admitted to the SCN (Figure 1) as well as the improved survival of this group (Figure 3).

    As the number of infants who require ROP screening and treatment increases, the workload and staff number would need to be increased. Our study had shown that as birth weight decreased, the number of examinations required increased (Figure 4). Those with birth weight below 751 grams needed 2.4 times more examinations compared to infants who weighed between 751 to 1250 grams.

    Lastly, a comment on the screening criteria is warranted. The main guidelines for screening are adapted from either the British or American guidelines [18, 19]. The British recommendation is that all infants with birth weight <1500 grams and ¡Ü32 weeks gestation should begin screening examinations at 6ª²7 weeks of age. However, the American guidelines advocated earlier screening from 4ª²6 weeks of age. The first screening for ROP at UMMC is at 4 weeks chronological age. But many studies have also emerged where modifications are made of the screening criteria based on current local population needs. Ho et al [16] found that all Threshold cases occurred in infants below 1100 grams birth weight and less than 28 weeks gestation in their population in Glasgow while Larrson et al [17] in Uppsala reported that Stage 3 or worse were not seen in any patients >32 weeks gestation. Mathew et al had also concluded that ophthalmic examination may be safely and efficiently concentrated in babies with birth weight <1251 grams and gestational age below 30 weeks [20]. Lee et al in a study of 14 neonatal units in Canada found that screening only infants having a birth weight of 1200g or less was the most costª²effective strategy for routine ROP screening [21]. Thus, it is important to stress that each unit must formulate their own referral criteria based on their neonatal unit populations. The Ministry of Health of Malaysia had also published a clinical practice guideline in late 2005 [9] (i.e. after the period of this study) which recommends screening at 4 to 6 weeks after birth for infants with either of the following: a)birth weight less than 1500 grams or; b) gestational age less than 32 weeks or; c) infants with an unstable clinical course who are at high risk (as determined by the neonatologist or paediatrician ).

    As ROP screening and the subsequent management involves manpower and much time, the cost factor has to be taken into consideration too, especially as smaller babies are surviving with improved perinatal care. Clearly, more data needs to be collected from various hospitals in the country that performs ROP screening examinations to compare the incidence of ROP as well as to plan for the future needs as more hospitals in the country are equipped to manage smaller premature infants.

    CONCLUSION

    There were a rising number of severe ROP cases detected over the study period from 2003 to 2005 at this tertiaryª²care hospital which was related to an increase in the proportion of smaller and more premature infants.

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