An eye tracking system for a Near-Eye-Display, NED, device, comprising: two or more sensors configured to generate eye tracking data associated with a first circular feature of a first eye of a user and a second circular feature of a second eye of the user, wherein the first circular feature is at least one of a first pupil of the first eye or a first iris of the first eye, and wherein the second circular feature is at least one of a second pupil of the second eye or a second iris of the second eye; one or more processors; and at least one computer storage medium having computer executable instructions stored thereon which are executable by the one or more processors to: receive the eye tracking data from the two or more sensors; determine, based at least on the eye tracking data, ellipse parameters that define: first ellipses that correspond to projections of the first circular feature of the first eye onto a first sensor plane, and second ellipses that correspond to projections of the second circular feature of the second eye onto a second sensor plane; generate, based at least on the ellipse parameters, propagation data that defines: first three-dimensional, 3D, propagations of the first ellipses through a first predetermined point, and second 3D propagations of the second ellipses through a second predetermined point; and determine, based at least on error minimization techniques applied to the propagation data with respect to an ocular rotation model, pupil orientation parameters that define a first center point of the first circular feature and a second center point of the second circular feature. two or more sensors configured to generate eye tracking data associated with a first circular feature of a first eye of a user and a second circular feature of a second eye of the user, wherein the first circular feature is at least one of a first pupil of the first eye or a first iris of the first eye, and wherein the second circular feature is at least one of a second pupil of the second eye or a second iris of the second eye; one or more processors; and at least one computer storage medium having computer executable instructions stored thereon which are executable by the one or more processors to: receive the eye tracking data from the two or more sensors; determine, based at least on the eye tracking data, ellipse parameters that define: first ellipses that correspond to projections of the first circular feature of the first eye onto a first sensor plane, and second ellipses that correspond to projections of the second circular feature of the second eye onto a second sensor plane; generate, based at least on the ellipse parameters, propagation data that defines: first three-dimensional, 3D, propagations of the first ellipses through a first predetermined point, and second 3D propagations of the second ellipses through a second predetermined point; and determine, based at least on error minimization techniques applied to the propagation data with respect to an ocular rotation model, pupil orientation parameters that define a first center point of the first circular feature and a second center point of the second circular feature. receive the eye tracking data from the two or more sensors; determine, based at least on the eye tracking data, ellipse parameters that define: first ellipses that correspond to projections of the first circular feature of the first eye onto a first sensor plane, and second ellipses that correspond to projections of the second circular feature of the second eye onto a second sensor plane; generate, based at least on the ellipse parameters, propagation data that defines: first three-dimensional, 3D, propagations of the first ellipses through a first predetermined point, and second 3D propagations of the second ellipses through a second predetermined point; and determine, based at least on error minimization techniques applied to the propagation data with respect to an ocular rotation model, pupil orientation parameters that define a first center point of the first circular feature and a second center point of the second circular feature.