[1] Yonsei Univ, Gangnam Severance Hosp, Dept Neurosurg, Coll Med, Seoul, South Korea
[2] Yonsei Univ, Severance Hosp, Dept Neurosurg, Coll Med, Seoul, South Korea
[3] Sungkyunkwan Univ, Kangbuk Samsung Hosp, Dept Ophthalmol, Sch Med, Seoul, South Korea
[4] Sungkyunkwan Univ, Kangbuk Samsung Hosp, Dept Neurosurg, Sch Med, 29 Saemunan Ro, Seoul 03181, South Korea