To compare the shape of the anterior segment of eyes with keratoconus and normal controls using anterior segment optical coherence tomography (AS-OCT).Included in the study were eyes with keratoconus (60 eyes of 40 patients), eyes with suspected keratoconus (10 eyes of 10 patients), and normal controls (21 eyes of 13 persons). Anterior segment imaging was performed in these eyes with AS-OCT, and the distance for angle to angle, anterior chamber depth and distribution of corneal thickness including the increasing ratio from center to periphery were compared.There was no significant difference in the distance of angle to angle among the three groups. The ratio of eyes with anterior chamber depth of more than 3.6 mm in the eyes with keratoconus was significantly higher than in the normal group. Although the corneal thickness from the center to the 3 mm periphery in the keratoconus group and in the keratoconus suspect group was significantly thinner than those in the normal group, there were no significant differences in the corneal thickness at the 4 mm superior or temporal areas among the three groups. Increasing ratio of the corneal thickness from the center to the periphery showed the higher value in the keratoconus group than in the others.AS-OCT enabled us to understand the configuration of the anterior segment of the eye and the distribution of the corneal thickness quantitatively even for the advanced keratoconus cases with corneal scar. AS-OCT may be useful as an aid to contact lens prescription and surgical planning.