[1] McMaster Univ, Michael G DeGroote Sch Med, Hamilton, ON, Canada
[2] Univ British Columbia, Fac Med, Vancouver, BC, Canada
[3] Univ Toronto, Fac Arts & Sci, Toronto, ON, Canada
[4] Queens Univ, Queens Sch Med, Kingston, ON, Canada
[5] Univ Toronto, Dept Ophthalmol & Vis Sci, Toronto, ON, Canada
[6] Univ Toronto, Dept Med, Div Neurol, Toronto, ON, Canada
[7] Univ Toronto, Dept Ophthalmol & Visual Sci, Dept Med, Div Neurol, 801 Eglinton Ave,Ste 301, Toronto, ON M5N 1E3, Canada