Retinopathy of prematurity (ROP) is a disorder of retinal vascular development in premature infants and is a major cause of childhood blindness worldwide. Dhaliwal et al conducted a prospective, population-based study looking at the incidence of ROP in the Lothian region of south-east Scotland from 1990 to 2004 and found the following1:

• (1) Significant increase in survival of infants with birth weight <1500 g and/or gestational age <32 weeks

• (2) Significant reduction in the number of infants treated for ROP

• (3) Reduction in the incidence of any degree of ROP and severe (stage 3 or greater) ROP although both did not reach statistical significance.

Treatment criteria for ROP have changed in Lothian since the publication of the Early Treatment for Retinopathy of Prematurity (ETROP) study.2 Before January 2005, infants with ‘threshold’ or ‘plus’ disease were treated. After January 2005, ‘type 1’ ROP as defined by ETROP, stage 2 or stage 3 ROP in zone 1 or 2, with associated plus disease, or stage 3 ROP in zone 1 without plus disease were treated. These are broader treatment criteria and one would expect more infants to be treated following the change.

We extended the Lothian population-based study using similar methodology1 to include a further 5-year period from 2005 to 2009 and we aimed to investigate the trend in incidence and management of ROP over the past two decades.

We found no change in trend either in the proportion of infants born with birth weight <1500 g and/or gestational age of <32 weeks in the past 20 years. However, contrary to previous findings of Dhaliwal et al,1 there was no longer a significant trend towards increasing number of infants surviving to corrected gestational age of 42 weeks (p=0.65) (table 1).

A total of 559 infants were screened for ROP between 2005 and 2009. According to the data supplied by Information Services Division (ISD)[AU: Please check and the approve the expansion of ISD.] Scotland, 587 babies were eligible for screening (table 1) but we were unable to cross-check our data with ISD Scotland due to data protection legislation.1 The incidence of ROP throughout the study period was stable but we found a new linear trend towards reduction in the number of infants with severe ROP (stage 3 or greater ROP) (p=0.01) (table 1). There was also a continuing trend towards fewer infants undergoing treatment for ROP (p=0.04).

In the subgroup analysis, we observed more infants without ROP and fewer with that of severe ROP with birth weight <750 g (p=0.02, p=0.006) in the past 20 years (tables available on request). More infants of gestational age between 25 and 26 weeks were also found to have no ROP (p=0.05) and fewer infants in the same gestational age were found to have severe ROP (p=0.01) (table 2).

In conclusion, the incidence of ROP proves stable in the past two decades in the Lothian region with reducing number of infants with severe ROPs. The observed trends may be explained by the advances in neonatal care with increasing emphasis on nutrition, oxygen administration and postnatal monitoring.