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Threshold ROP
  1. D Clark
  1. Correspondence to: D Clark University Hospital Aintree, Department of Ophthalmology, Walton Hospital, Rice Lane, Liverpool L9 1AE L9 1AE, UK;

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Retinopathy of prematurity (ROP) remains a major cause of visual loss in very premature infants. First described by Terry1 in 1942 the condition reached epidemic proportions before the introduction of controlled oxygen administration. During the 1970s and 1980s a second epidemic occurred as a result of the increased survival of very low birthweight infants (under 1000 g).

While the incidence and severity of ROP have reportedly declined in some centres, there still remains a significant threat to vision in infants born between 23 and 26 weeks gestation.2 The retinopathy progresses more rapidly in this group and may proceed directly from immature vessels without the appearance of the characteristic ridge. The choroidal vessels are readily visible through the pale retinal pigment epithelium leading to the false interpretation that the retinal vasculature is more fully developed3

The increased survival of these infants and their subsequent transfer from regional back to more local neonatal units may mean ophthalmologists with limited experience being requested to examine and interpret the atypical features of retinopathy associated with these babies.

In this issue of the BJO (p 1500), Schulenburg and Tsanaktsidis demonstrate photographically and by fluorescein angiography the morphologically different ROP often seen in infants born less than or equal to 25 weeks gestational age. Applying the conventional threshold for treatment in these cases may lead to a poor outcome, whereas recognition of this different morphology and its speed of progression is fundamental to successful management.

The functional outcome at 10 years of age of threshold cryotherapy treated infants was disappointing. Distance acuity in the range 6/60 to 6/18 occurred in 30.4%, and only 25.2% had a visual acuity 6/12 or better.4 Laser treatment may offer advantages over cryotherapy and has been associated with better functional outcomes.5

Laser certainly makes treating posteriorly located ROP easier and this may have contributed to the improved structural results.6

Should posterior disease be treated earlier?

Recent investigation into the early treatment of high risk prethreshold ROP has shown better functional outcomes at 9 months of age than conventional treatment at threshold.7 Schulenburg and Tsanaktsidis’s paper is timely because early recognition of the serious nature of the high risk signs of this atypical ROP predominantly seen in extremely premature babies of 23–25 weeks gestational age, combined with appropriate early intervention, should improve the visual outlook in these cases.

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