The Empress underwent laser treatment Sunday at the Imperial Household Agency hospital to relieve pressure from within her right eye, agency officials said.

The treatment is aimed at preventing glaucoma, which is marked by increased pressure within the eyeball, resulting in damage to the optic disk and a gradual loss of vision, they said.

The Empress has suffered from eye fatigue since late May and complained of abnormal vision Sept. 23, the officials said.

The operation was conducted by Makoto Araie, professor of ophthalmology at the University of Tokyo, they said.

The Empress may also need to receive treatment in her left eye, the officials said.