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Evolution of surgical techniques has made paediatric primary intraocular lens (IOL) implantation more popular.1 As the comfort level of implanting younger children increases, postoperative target refraction accuracy and emmetropisation of refractive error have become important management problems.
The normal neonatal eye is hyperopic, and over the first 18 months of life, axial elongation, lenticular change and corneal flattening move the focussing system towards emmetropia2 3 with axial elongation playing the primary role.4 While being sensitive to genetic factors,5 the globe axial elongation and resultant myopic shift seen in the first 2 years of life is thought to be an active process—emmetropisation—influenced by visual stimulus within a sensitive period. Evidence that emmetropisation is an active light dependent process, with the sensory component most likely in the retinal amacrine cells, comes from a large volume of animal model work.6–8 It is speculated that the effector component is controlled by the ocular matrix metalloproteinases (MMPs) which orchestrate posterior segment remodelling.8 The primary site of this motor arm is unclear and may be located at the posterior pole,9 or the area around the ciliary body.10 11
As with the normally developing eye, the primary effector of the myopic shift seen in pseudophakic children is globe axial elongation.12–14 However, the myopic shift is large,12 15 shows considerable variance12–21 (table 1) and is devoid of consistent correlation with either a child's preoperative axial length or the implanted IOL power.13 15 20 Age is the significant influencing factor, with younger children exhibiting larger and more unpredictable myopic shifts.12 15 18 20
In this month's issue, Sminia et al (see page 547) compare the axial eye length growth of the two fellow eyes within one …
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Funding This work was undertaken at UCL Institute of Child Health/Great Ormond Street Hospital for Children, which received a proportion of funding from the Department of Health/NIHR Biomedical Research Centres funding scheme. LS is funded by Ulverscroft Vision Research Group.
Competing interests None.
Provenance and peer review Commissioned; externally peer reviewed.