ophthalmology
Medical specialty dealing with the eyes and their diseases.
彼は眼科学を専攻して、眼科医になった。
He majored in ophthalmology and became an ophthalmologist.
Compound of 眼 (gan, 'eye'), 科 (ka, 'department' or 'field'), and 学 (gaku, 'study'). A straightforward Sino-Japanese term for the medical study of the eye.