A system for use in a medical procedure, comprising: a head mounted display comprising: a camera (6a, 6b) configured to detect light from a target; a near-eye display (4a, 4b) positioned between a wearer's eyes and the target, the display configured to display an image of the target based on the light detected by the camera, such that the image overlays a wearer's view of the target; and a distance sensor (10a, 10b), configured to determine a distance between the head mounted display and the target throughout a medical procedure; and a processor, configured to: determine a mismatch between the image of the target obtained from the camera and the wearer's view of the target based on the value of the distance measured by the distance sensor, and a position and orientation of the wearer's eyes relative to the head mounted display; wherein the processor is configured to determine the position and orientation of the wearer's eyes relative to the head mounted display through a calibration procedure; or wherein the system comprises an eye tracking sensor to determine the position and orientation of the wearer's eyes relative to the head mounted display; adjust the position of the image on the display such that it is corrected based on the determined mismatch such that the image matches the wearer's view of the target; and repeat the determination of the mismatch and the adjustment of the position of the image throughout the medical procedure to take into account changes in the distance measured by the distance sensor throughout the medical procedure. a head mounted display comprising: a camera (6a, 6b) configured to detect light from a target; a near-eye display (4a, 4b) positioned between a wearer's eyes and the target, the display configured to display an image of the target based on the light detected by the camera, such that the image overlays a wearer's view of the target; and a distance sensor (10a, 10b), configured to determine a distance between the head mounted display and the target throughout a medical procedure; and a camera (6a, 6b) configured to detect light from a target; a near-eye display (4a, 4b) positioned between a wearer's eyes and the target, the display configured to display an image of the target based on the light detected by the camera, such that the image overlays a wearer's view of the target; and a distance sensor (10a, 10b), configured to determine a distance between the head mounted display and the target throughout a medical procedure; and a processor, configured to: determine a mismatch between the image of the target obtained from the camera and the wearer's view of the target based on the value of the distance measured by the distance sensor, and a position and orientation of the wearer's eyes relative to the head mounted display; wherein the processor is configured to determine the position and orientation of the wearer's eyes relative to the head mounted display through a calibration procedure; or wherein the system comprises an eye tracking sensor to determine the position and orientation of the wearer's eyes relative to the head mounted display; adjust the position of the image on the display such that it is corrected based on the determined mismatch such that the image matches the wearer's view of the target; and repeat the determination of the mismatch and the adjustment of the position of the image throughout the medical procedure to take into account changes in the distance measured by the distance sensor throughout the medical procedure. determine a mismatch between the image of the target obtained from the camera and the wearer's view of the target based on the value of the distance measured by the distance sensor, and a position and orientation of the wearer's eyes relative to the head mounted display; wherein the processor is configured to determine the position and orientation of the wearer's eyes relative to the head mounted display through a calibration procedure; or wherein the system comprises an eye tracking sensor to determine the position and orientation of the wearer's eyes relative to the head mounted display; adjust the position of the image on the display such that it is corrected based on the determined mismatch such that the image matches the wearer's view of the target; and repeat the determination of the mismatch and the adjustment of the position of the image throughout the medical procedure to take into account changes in the distance measured by the distance sensor throughout the medical procedure.