A wearable display system comprising: an infrared light source (248a, 248b) configured to illuminate an eye (100a, 100b) of a user; an image capture device (252a, 252b) configured to capture an eye image of the eye; non-transitory memory configured to store the eye image; and a hardware processor in communication with the non-transitory memory, the hardware processor programmed to: receive the eye image from the non-transitory memory; characterized in that the hardware processor is further programmed to: estimate an eye shape from the eye image using cascaded shape regression, the eye shape comprising a pupil shape, an iris shape, or an eyelid shape, wherein, to estimate the eye shape from the eye image using cascaded shape regression, the hardware processor is programmed to iterate a regression function for determining a shape increment over a plurality of stages, the regression function comprising a shape-indexed extraction function, and wherein, to iterate the regression function, the hardware processor is programmed to evaluate Δ S t = f t Φ t I S t − 1, for a shape increment ΔSt at stage t of the iteration, where f t is the regression function at stage t, Φ t is the shape-indexed extraction function at stage t, I is the eye image, and S t -1 is the eye shape at stage t -1 of the iteration. an infrared light source (248a, 248b) configured to illuminate an eye (100a, 100b) of a user; an image capture device (252a, 252b) configured to capture an eye image of the eye; non-transitory memory configured to store the eye image; and a hardware processor in communication with the non-transitory memory, the hardware processor programmed to: receive the eye image from the non-transitory memory; characterized in that the hardware processor is further programmed to: estimate an eye shape from the eye image using cascaded shape regression, the eye shape comprising a pupil shape, an iris shape, or an eyelid shape, wherein, to estimate the eye shape from the eye image using cascaded shape regression, the hardware processor is programmed to iterate a regression function for determining a shape increment over a plurality of stages, the regression function comprising a shape-indexed extraction function, and wherein, to iterate the regression function, the hardware processor is programmed to evaluate Δ S t = f t Φ t I S t − 1, for a shape increment ΔSt at stage t of the iteration, where f t is the regression function at stage t, Φ t is the shape-indexed extraction function at stage t, I is the eye image, and S t -1 is the eye shape at stage t -1 of the iteration. estimate an eye shape from the eye image using cascaded shape regression, the eye shape comprising a pupil shape, an iris shape, or an eyelid shape, wherein, to estimate the eye shape from the eye image using cascaded shape regression, the hardware processor is programmed to iterate a regression function for determining a shape increment over a plurality of stages, the regression function comprising a shape-indexed extraction function, and wherein, to iterate the regression function, the hardware processor is programmed to evaluate Δ S t = f t Φ t I S t − 1, for a shape increment ΔSt at stage t of the iteration, where f t is the regression function at stage t, Φ t is the shape-indexed extraction function at stage t, I is the eye image, and S t -1 is the eye shape at stage t -1 of the iteration.