To report the current incidence and the need for surgery for retinopathy of prematurity (ROP) in neonates (22–36 weeks' gestational age [GA], July 1, 1989 through June 30, 1997).
Retrospective analyses using computerized perinatal database kept on all admissions, a review of patient charts, and eye examination log books.
Level 3 regional referral NICU.
A total of 2528 infants <37 weeks' GA were admitted during this time. Of these infants, 950 met the criteria for eye examination beginning at 4 to 6 weeks of age and repeated every 2 weeks until complete vascularization of the retina or death or discharge.
The incidence of ROP was (202/950) 21.3% for any stage and 4.6% (44/950) for stage 3 ROP or greater. No ROP was noted in infants born at >32 weeks' GA. No infant born at >28 weeks needed retinal surgery. Using birth weight (BW) criteria, stage 3 ROP was not noted in infants with BWs >1500 g; retinal surgery was not needed in infants with BWs >1000 g. A number of perinatal factors were associated with ROP on univariate analysis. However, using multiple logistic regression analyses of these factors, only GA and days on supplemental oxygen therapy were associated significantly with the development of ROP. Despite increased survival of extremely low BW infants, we found a considerable reduction in incidence and severity of ROP compared with reports from an earlier chronological period. However, infants <28 weeks' GA or with BWs <1000 g were still at considerable risk for retinal surgical treatment for ROP.
We conclude that the incidence and severity of ROP have decreased significantly in the present era of surfactant therapy.
Comments
Risk factors for severe ROP: Response to Drs. Termote, Schalij-Delfos and Cats
December 21, 1999.
We would like to thank Drs. Termote, Schalij-Delfos and Cats for sharing their findings on ROP from Utrecht, Netherlands, and for bringing to discussion some possible influences on ROP-incidence figures. The specific questions asked and the responses are as follows:
1. Did you introduce HFOV or other new methods of mechanical ventilation in your unit during the study period and did you investigate the efficacy of these new methods of treatment on the incidence and severity of ROP in your population?
We introduced the use of HFOV in our NICU in 1992 but this modality of ventilation was initially used in the "rescue" mode for infants with severe lung disease or those with air-leaks. We started to use "elective" HFOV and SIMV (synchronized intermittent mandatory ventilation) in late 1995. However, we have not yet analyzed the data regarding the use of these modalities and ROP.
2. Did you also look for significant risk factors for severe ROP in your population?
We had not studied the risk factors specifically for severe ROP (Stage 3 or more) in our original paper. However, in response to your question we re-analyzed our data and the results from univariate analysis of risk factors are shown below. Data represents mean + SD for continuous variables with Student's t-test * for significance; or % for nominal variables analyzed with Chi-square test#.
TABLE
3. Is it feasible that the decrease in severe ROP in your population is also the result of a decrease in severe ROP in RDS patients selectively, which would concur with our observations as mentioned above?
Unfortunately, we did not code for the severity of RDS and therefore are unable to evaluate the relationship between severe ROP and severity of RDS. Thank you for initiating this interchange of knowledge and ideas.
Sincerely,
Naveed Hussain, MBBS, DCH University Of Connecticut Health Center, Farmington, CT
Jonathan Clive, PhD University Of Connecticut Health Center, Farmington, CT
Vineet Bhandari, MD, DM Albert Einstein Medical Center, Philadelphia, PA
Possible influences on ROP-incidence figures.
To the Editor,
We read your article "Current incidence of Retinopathy of Prematurity, 1989-1997" with great interest. In a recent paper, accepted for publication in the Journal of Pediatric Ophthalmology and Strabismus, we reported about the incidence and severity of ROP in our tertiary care unit in Utrecht (The Netherlands), between 1986 and 1995. The study period was divided in two consecutive 5 year periods '86-'90 and '91-'95, to evaluate the effects of new methods of treatment (surfactant replacement therapy (SRT) and high frequency oscillatory ventilation (HFOV)) and general improvements in quality of care during the second period. In our study the overall incidence of ROP in the years 1986-1990 was not significantly different from the incidence of ROP in the years 1991-1995 (89/291 = 30.6% versus 172/466 = 36.9% respectively). As in your study, the incidence of severe ROP (ROP stage 3 or more) was significantly lower in the second period (15.7% versus 6.4%, p=0.015). Using logistic regression, we found that only SRT was associated with a decreased risk for severe ROP, the factors HFOV and general improvements in quality of care had no influence. We also compared the incidence of severe ROP in the two periods, for ROP patients with and without RDS. In patients with RDS the incidence of severe ROP decreased significantly during the second period (20.3% versus 6,4%, p=0,008). For patients not suffering from RDS however, the incidence of severe ROP remained unchanged.
1. Did you introduce HFOV or other new methods of mechanical ventilation in your unit during the study period and did you investigate the effect of these new methods of treatment on the incidence and severity of ROP in your population?
2. Did you also look for significant risk factors for severe ROP in your population?
3, Is it feasable that the decrease in severe ROP in your population is also the result of a decrease in severe ROP in RDS patients selectively, which would concur with our observations as mentioned above?
Sincerely yours,
Jacqueline Termote, Nicoline Schalij-Delfos and Bernard Cats.