A housing includes a pair of housing walls that face each other with an inner space therebetween. Difference in size of conjunctiva sac or interpalpebral length of individuals is absorbed even by an appliance of one size, the eyelids can be opened by fitting the eyelids opening device to the eyelids or the face while burden on the eyeball is reduced and high safety is ensured. A first end of the fiber optic unit is bonded to the photosensor to create a joint between the fiber optic unit and the photosensor.