[1] Haukeland Hosp, Dept Neurol, N-5021 Bergen, Norway
[2] Haukeland Hosp, Dept Paediat, N-5021 Bergen, Norway
[3] Haukeland Hosp, Dept Pathol, N-5021 Bergen, Norway
[4] Univ Glasgow, Western Infirm, Dept Pathol, Glasgow G11 6NT, Lanark, Scotland
[5] Haukeland Hosp, Dept Ophthalmol, N-5021 Bergen, Norway
[6] Ullevaal Univ Hosp, Dept Ophthalmol, N-0407 Oslo, Norway
[7] Newcastle Hosp NHS Trust, No Genet Serv, Newcastle Upon Tyne, Tyne & Wear, England