To observe interference stripes produced by tear fluid, a low magnification light source 10 is turned on to illuminate the outermost layer of a tear film on the cornea Ec of a subject's eye. Light reflected from the cornea Ec forms an image on a CCD 16, and an interference stripes pattern 18a created by the lipid film on the cornea is displayed on a monitor 18. To measure the amount of tear fluid, light-emitting elements 20a, 20b of a high-magnification light source are turned on to irradiate a tear fluid meniscus Em that has accumulated on the lower eyelid portion of the anterior ocular segment. Light reflected on the surface of the meniscus Em forms an image on the CCD 16, and images 18b, 18c of the light-emitting elements 20a, 20b are displayed on the monitor 18 as clear images separated by an interval D. The amount of tear fluid can be quantitatively measured by measuring the interval D. A single such structure allows interference stripes created by the tear film of the anterior ocular segment to be observed and the amount of tear fluid to be measured.