Examples of eye-imaging apparatus using diffractive optical elements are provided. For example, an optical device comprises a substrate having a proximal surface and a distal surface, a first coupling optical element disposed on one of the proximal and distal surfaces of the substrate, and a second coupling optical element disposed on one of the proximal and distal surfaces of the substrate and offset from the first coupling optical element. The first coupling optical element can be configured to deflect light at an angle to totally internally reflect (TIR) the light between the proximal and distal surfaces and toward the second coupling optical element, and the second coupling optical element can be configured to deflect at an angle out of the substrate. The eye-imaging apparatus can be used in a head-mounted display such as an augmented or virtual reality display.