An apparatus for providing gaze tracking in a near-eye display comprising: a light source configured to generate light of a first range of wavelengths and light of a second range of wavelengths; a light modulator configured to receive light of the first range of wavelengths from the light source and modify the light of the first range of wavelengths so as to impart an image thereon and generate an image beam (103, 109) therefrom, wherein the light modulator is further configured to receive light of the second range of wavelengths from the light source and modify the light of the second range of wavelengths so as to impart a pattern thereon and generate a probe beam (105, 111) therefrom; one or more light guides comprising: one or more in-coupling diffractive element areas, and one or more out-coupling diffractive element areas; wherein the one or more in-coupling diffractive element areas are configured to receive and in-couple the image beam and the probe beam into the one or more light guides; wherein the one or more out-coupling diffractive element areas are configured to out-couple, from the one or more light guides: the image beam to a user's eye for user viewing, and the probe beam to the user's eye for detection of reflection therefrom; the apparatus further comprising: a detector configured to detect reflections of the probe beam (105, 111); and a controller configured to control the light modulator to modify the pattern of the probe beam (105, 111) dependent upon the detection of the reflected probe beam. a light source configured to generate light of a first range of wavelengths and light of a second range of wavelengths; a light modulator configured to receive light of the first range of wavelengths from the light source and modify the light of the first range of wavelengths so as to impart an image thereon and generate an image beam (103, 109) therefrom, wherein the light modulator is further configured to receive light of the second range of wavelengths from the light source and modify the light of the second range of wavelengths so as to impart a pattern thereon and generate a probe beam (105, 111) therefrom; one or more light guides comprising: one or more in-coupling diffractive element areas, and one or more out-coupling diffractive element areas; one or more in-coupling diffractive element areas, and one or more out-coupling diffractive element areas; wherein the one or more in-coupling diffractive element areas are configured to receive and in-couple the image beam and the probe beam into the one or more light guides; wherein the one or more out-coupling diffractive element areas are configured to out-couple, from the one or more light guides: the image beam to a user's eye for user viewing, and the probe beam to the user's eye for detection of reflection therefrom; the image beam to a user's eye for user viewing, and the probe beam to the user's eye for detection of reflection therefrom; the apparatus further comprising: a detector configured to detect reflections of the probe beam (105, 111); and a controller configured to control the light modulator to modify the pattern of the probe beam (105, 111) dependent upon the detection of the reflected probe beam. a detector configured to detect reflections of the probe beam (105, 111); and a controller configured to control the light modulator to modify the pattern of the probe beam (105, 111) dependent upon the detection of the reflected probe beam.