A method for determining a point-of-gaze POG of a user in three dimensions, the method comprising: presenting a three-dimensional scene to the user; illuminating the eyes of the user by using one or more on-axis light sources and a plurality of off-axis light sources; capturing image data which includes images of both eyes of the user using a single image capturing device, the single image capturing device capturing the image data from a single field of view having a single corresponding optical axis; estimating a first line-of-sight LOS vector in a three-dimensional coordinate system for a first of the user's eyes based on the image data captured by the single image capturing device; estimating a second LOS vector in the three-dimensional coordinate system for a second of the user's eyes based on the image data captured by the single image capturing device; wherein estimating the first and second LOS vectors comprises, for each eye: detecting a plurality of glints within the image data, each glint comprising a reflection from the eye; establishing a correspondence between each of the glints and a corresponding light source; using at least two of the plurality of glints and the correspondence between the at least two glints and their corresponding light sources to estimate a center of the cornea of the eye in the three-dimensional coordinate system; determining the three-dimensional POG of the user in the scene in the three-dimensional coordinate system using the first and second LOS vectors as estimated based on the image data captured by the single image capturing device. presenting a three-dimensional scene to the user; illuminating the eyes of the user by using one or more on-axis light sources and a plurality of off-axis light sources; capturing image data which includes images of both eyes of the user using a single image capturing device, the single image capturing device capturing the image data from a single field of view having a single corresponding optical axis; estimating a first line-of-sight LOS vector in a three-dimensional coordinate system for a first of the user's eyes based on the image data captured by the single image capturing device; estimating a second LOS vector in the three-dimensional coordinate system for a second of the user's eyes based on the image data captured by the single image capturing device; wherein estimating the first and second LOS vectors comprises, for each eye: detecting a plurality of glints within the image data, each glint comprising a reflection from the eye; establishing a correspondence between each of the glints and a corresponding light source; using at least two of the plurality of glints and the correspondence between the at least two glints and their corresponding light sources to estimate a center of the cornea of the eye in the three-dimensional coordinate system; determining the three-dimensional POG of the user in the scene in the three-dimensional coordinate system using the first and second LOS vectors as estimated based on the image data captured by the single image capturing device. detecting a plurality of glints within the image data, each glint comprising a reflection from the eye; establishing a correspondence between each of the glints and a corresponding light source; using at least two of the plurality of glints and the correspondence between the at least two glints and their corresponding light sources to estimate a center of the cornea of the eye in the three-dimensional coordinate system; determining the three-dimensional POG of the user in the scene in the three-dimensional coordinate system using the first and second LOS vectors as estimated based on the image data captured by the single image capturing device.