Recent clinical research has shown that the degree of myopia is significantly less following laser therapy when compared with cryotherapy for severe retinopathy of prematurity (ROP).1² This important finding is confirmed by Laws et al in this issue of the BJO (p12). While the associations of prematurity, ROP, and myopia are well known, they are not precisely defined and mechanisms are even less well understood—an ideal opportunity for us to delve briefly into the evidence.

Myopia is probably the normal refractive state in infants before full term^3 4 with the eye becoming more hypermetropic in early infancy. Compared with the eye of the full term baby the features of this myopia are shorter axial length, flatter anterior chamber, and more spherical lens.4 The term myopia of prematurity is not applied to this physiological and temporary type of myopia.

Over three decades ago Fledelius studied a cohort of preterm babies and observed a disproportionate number of myopes; he found that this refractive state persisted even to 18 years of age.5 This type of myopia, myopia of prematurity (MOP), has an early onset and compared with full term and juvenile onset myopes the MOP eye exhibits a relatively highly curved cornea, shallow anterior chamber, and thick lens. Axial lengths are shorter than expected for the dioptric value.6 The hallmark of MOP is …