[1] Linkoping Univ, Div Pediat, Linkoping, Sweden
[2] Linkoping Univ, Crown Princess Victoria Childrens Hosp, Linkoping, Sweden
[3] Sahlgrens Acad, Inst Neurosci & Physiol, Stat Konsultgrp, Dept Ophthalmol, Gothenburg, Sweden
[4] Reg Vastra Gotaland, Ctr Registers Rep, Dept Mol & Clin Med, Linkoping, Sweden
[5] Univ Gothenburg, Dept Mol & Clin Med, Gothenburg, Sweden
[6] Univ Gothenburg, Sahlgrenska Acad, Dept Hlth Metr, Gothenburg, Sweden