Abstract: Disclosed is a device for generating a toroidal source of illumination is disclosed. The device comprises a translucent disc with a concentric hole. A planar coil of side emitting optic fiber is disposed on one surface of the disc. The coil is energized with an LED at one end of the coil. The light emitted by the side of the coil is randomly scattered by the disc producing a toroidal source of light at the other surface of the disc. This source is used with instruments for assessing the dryness of the human eye. Further embodiments describe adaptations for measuring tear breakup time and the height of the tear meniscus in the human eye.