The influence of retinopathy of prematurity on ocular growth

Retinopathy of prematurity (ROP) stage 3 eyes that require treatment have a greater tendency to myopia compared with eyes with mild ROP. As the mechanisms controlling this myopia are as yet ill understood, we undertook this study to investigate what effect the initial stage of ROP and modality of treatment had on ocular growth.

Eighty-five children were assessed. All children were refracted and underwent 'through-the-lid' biometry using the Zeiss Humphrey biometer 820. The printout obtained was then recorded on video so that the scan could be captured on computer for formal calibration and measurement by a masked observer. Differences in the distribution of variables between the stages of ROP were analysed by one-way analysis of variance, non-parametric Kruskal-Wallis one-way analysis of variance or Mann-Whitney U-test as appropriate.

A difference between the stages of ROP was apparent only for posterior segment length (PSL) (R: p = 0.03; L: p = 0.05) and a borderline difference for anterior chamber depth (ACD) (R: p = 0.06; L: p = 0.06). However, if stage 3 was divided into categories of treated and untreated, axial length (AL) achieved borderline significance (R: p = 0.07; L: p = 0.05) but with no difference between laser-treated and the other stages for AL. Lens thickness (LT) also appears to be influenced by type of treatment (R: p = 0.06; L: p = 0.13). Myopia was associated with stage 3 (R + L: p = 0.0001) and if stage 3 was subdivided the significance was maintained only for the laser- and cryotherapy-treated eyes.

Laser-treated eyes were less myopic than those treated with cryotherapy. AL does not explain all the myopia found in stage 3 treated eyes. The study confirms the tendency towards anterior segment arrest in stage 3 ROP.