Is the severity of refractive error dependent on the quantity and extent of retinal laser ablation for retinopathy of prematurity?

Background/aim: To test the hypothesis severity of acquired refractive error in Retinopathy of Prematurity (ROP) is dependent on the quantity of laser treatment delivered.

Methods: Two groups (treated and untreated infants) were age and weight matched. Data on the number of laser burns and Retcam II retinal images were analysed using computer aided design software to determine the proportion of area treated. Data were collected until the age of 6 years.

Results: The study comprises 43 infants (86 eyes). Twenty-one infants (42 eyes) in the treated group, mean gestational age (GA) was 26.40 (±2.5) weeks versus 27.30 (±1.7) weeks in the matched untreated group (P = 0.650). Birth weight (BW) in the treated group was 812 g (±86) and 804 g (±135) (P = 0.185) in the untreated group. Mean refractive error at 72 months was -2.23 (±4.06) in the treated group and +2.04 (±0.90) in the untreated group (P < 0.005). At 72 months 50% of treated eyes were myopic versus 19% of controls (P = 0.013). Mean laser burns applied were 1855 (±659), mean proportion of retina treated 45% (±10). Myopic eyes had a mean treatment area of 49% (±13) versus 43% (±10) hypermetropia and 42% (±5) emmetropia (P = 0.030). A larger treatment area was associated with a higher degree of myopia and anisometropia at 72 months (P < 0.050). These associations were not found for hypermetropia.

Conclusions: The extent of myopia after retinal laser ablation for ROP is higher if a greater number of laser burns or a larger proportion of the retina is treated.