Retinopathy of prematurity in extremely low birth weight infants.

OBJECTIVE

To review the survival rate, the incidence and severity of retinopathy of prematurity (ROP), and the rate of blindness caused by ROP in extremely low birth weight (ELBW, birth weight 500 to 999 g) infants born between January 1, 1977, and December 31, 1992, and to determine whether increasing survival rates of ELBW infants are accompanied by an increase in the rates of severe ROP or blindness.

DESIGN

Prospective cohort study of ELBW infants. Survival rates and visual outcomes were contrasted between children born in successive 8-year periods (1977 through 1984 and 1985 through 1992, inclusive).

SETTING

The premature nurseries at the Royal Women's Hospital, Melbourne, a level-3 perinatal center.

PATIENTS

Of 1001 inborn ELBW infants over the 16-year period, 457 (45.7%) survived their initial hospitalization: of the survivors, 434 (95.0%) were examined by the ophthalmologist, starting at 2 weeks of age if possible, then 2-weekly unit discharge. Children were reassessed after discharge at ages ranging from 1 to 10 years.

RESULTS

Survival rates to hospital discharge rose significantly over time, from 34.5% (145/420) in 1977 through 1984, to 53.7% (312/581) in 1985 through 1992 (odds ratio [OR] 2.2, 95% confidence interval [CI] 1.7 to 2.8). Of the 434 surviving ELBW infants seen by the ophthalmologist, ROP was detected in 48.2% (68/141) in 1977 through 1984, which dropped significantly to 35.8% (105/293) in 1985 through 1992 (OR 0.6, 95% CI 0.4 to 0.9). Severe ROP (bilateral stages 3 to 5) was detected in 25.5% (36/141) in 1977 through 1984, and 17.7% (52/293) in 1985 through 1992, but the reduction was not quite statistically significant (OR 0.6, 95% CI 0.4 to 1.0). Bilateral blindness (visual acuity in each eye less than 6/60) caused by ROP occurred in only 4 (0.88%) survivors overall, 2 in each era.

CONCLUSION

The increase in the survival rate of ELBW infants is not always accompanied by an increase in the rate of severe ROP or blindness, at least for ELBW infants born in some large level-3 centers.