 |
|
Brief Reports Indian Pediatrics 2002; 39:267-270 |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
Retinopathy of Prematurity |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
Shobha Sharma Chaya Kelgeri B.S. Avasthi
Retinopathy of prematurity (ROP) is a complex disease process. It ranges from mild transient changes with regression to severe progressive vasoproliferation, scarring, detachment leading to blindness. It can often be treated successfully, if it is diagnosed in time. It’s prevention requires identification of risk factors associated with ROP. The present communication provides the natural history of ROP in babies £1250 g and identifies associated risk factors Subjects and Methods This prospective study enrolled babies with birth weight £1250g and £32 weeks born between July 1998 and June 1999 who were available for follow up for at least 90 days after birth. There were 64 babies £32 weeks and £1250 g admitted during this period; 20 expired and 9 babies were lost to follow up before 90 days of age. Thus 35 babies were available for the study. The ophthalmic examinations began at 4 weeks of age and subsequent examinations were repeated according to the schedule appropriate to the original findings. The screening was done by indirect ophthal-moscopy after dilating the pupils with 0.8% Tropicamide and 5% phenylephrine, 2 instillations done 10 min apart, using a neonatal speculum. The retinal changes were categorized at each examination, on a standard format devised according to the International Classification of Retinopathy of Prematurity(1). Statistical Analysis Data was analyzed using SPSS\PC + (V6) and EPISTAT Statistical packages. The univariate statistical analysis like the Chi-square with Yate ‘s correction, Fisher Exact Probability test, Odds Ratio and Students Unpaired ‘t’ test were applied to the data wherever appropriate. Results Thirty-five babies underwent periodic ophthalmic evaluation, of which 27 [77.1%, 95% CI = 68,85.5] developed some stage of ROP. The prevalence of ROP was indepen-dent of the sex of the neonate (male = 75%, female = 81.8% p >0.05). The median age of onset for diffferent stages of ROP was 35 weeks post conception for stage I, 35.5 weeks for stage II, 36 weeks for stage III and 40 weeks for stage IV and more. The risk factors for ROP that were evaluated are depicted in Table 1. Birth weight and gestational ages were significantly lower in babies who deve-loped ROP compared to those who did not. Of the twenty seven babies with ROP in our study 17.1% had Stage I, 25.7% Stage II, 5.7 Stage III and 25.8% Stage IV and above disease. Fifteen of these babies developed threshold ROP and required treatment, of which two underwent cryotherapy, eight laser photocoagulation and five surgery. The first two babies developing threshold ROP were subjected to cryotherapy but subsequently rest of the babies were given laser photo-coagulation because of its feasibility. Five babies progressed to severe stage of ROP requiring surgery inspite of earlier treatment with either cryotherapy (2 babies) or laser photo coagulation (3 babies).
Table I__Risk Factors for ROP
Discussion Retinopathy of prematurity is a disease that occurs in premature babies and affects the blood vessels of the developing retina. The incidence of ROP has been on the rise because of the improved survival of VLBW babies. The prevalence of ROP in the present study (71.1%) was higher as compared to the other studies, who have reported ROP between 18-47%(2-5). This discrepancy could be because, unlike our study where gestational age and birth weight were restricted to £32 weeks and £1250 g, other studies have included babies up to 2000g(2-4). This may also explain our results of finding a comparatively lesser percentage of Stage 1, as mild grades of ROP are seen with higher gestational age and birth weight. The Cryo-ROP study too has the same criteria as ours and their incidence was comparable to our study(1). However, reports of the incidence of ROP from the fifties and sixties are difficult to compare with the present era due to variations in patient selection, the lack of a standard classification system and lack of appreciation of mild form of ROP which became possible with the availability of indirect ophthalmoscope in 1970’s. In the 1980’s several large studies provided information on the incidence of ROP and reaffirmed that the incidence was inversely related to gestational age and birth weight(5,6). It is also to be pointed out that ours being a referral center, 90% of babies referred to us were critical babies with only 10% of them having had a smooth transition from intravenous fluids to nasogastric feeds and then oral feeds. Though postnatal age was taken as the criteria for screening, it is evident that the median age of onset of ROP was between 35-40 weeks post conception which was compar-able to 37-42 weeks and 34.4-42 weeks (5th-95th percentile) of the other studies(4). The timing of retinal vascular events co-related more closely with post conceptional age, implicating the maturity at birth as the governing factor for the timing of these vascular events than the postnatal environ-mental influences. Thus babies with lower gestational age took longer to develop disease than their more mature counterparts. The ophthalmic examinations are themselves not without problems and hence very tiny babies can wait longer for their first ophthalmic examination(6). Flynn, on multivariate risk analysis techniques concluded that birth weight was the strongest and most consistent predictor of acute ROP(5). Campbell et al. found that 83% of babies with ROP weighed less than 1500 g and the incidence of ROP among survivors with birth weights of less than 1000 g (28%) was approximately three times that of survivors with birth weights between 1001 g - 1500 g (10.1%). In our study all of the babies £750 g developed some stage of ROP as compared to 44.1% in babies weighing between 1001-1250 g. The current understanding of the patho-genesis of ROP is that the developing retinal vasculature is vulnerable to combination of factors though high inspired oxygen has been traditionally conceived as the main culprit. Trying to decrease oxygen may compromise baby’s health and hence each neonate must be treated with the optimum amount of oxygen to sustain life and maintain neurologic functions. With availability of oxygen monitoring devices excessive use of oxygen can be curtailed. Shohat et al. examined 32 possible risk factors in 34 infants with ROP and found apnea with bag and mask ventilation, pro-longed parenteral nutrition, number of blood transfusions and episodes of hypoxemia, hypoxia and hypocarbia to be significantly associated with ROP(8). Hammer et al. in their prospective study of 328 high risk neonates found ventilator hours, xanthine administration, birth weight and maternal bleeding as significant. Darlow et al. found gestational age, principal hospital caring for the infant and indomethacin administration as significant factors on multiple logistics regression analysis(10). Until the conditions that are necessary for the healthy maturation of human babies are better understood, the prevention of blinding ROP hinges on preventing prematurity. Also research work needs to be extended into all fields of pathogenesis, screening and inter-vention options of ROP. Acknowledgement We acknowledge the contribution of Dr. Himanshu Mehta, Dr. Ajay Dudhani, Dr. Anand Kumta for ophthalmic evaluations of the babies and Mr. Arekar for the statistical analysis of our results. Contributors: SS coordinated the study, drafted the paper and will be the guarantor of this paper. CK collected the data and helped in analyzing the data. BSA helped in drafting the paper. Funding: None. Competing interests: None stated.
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| References | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
