Estimating cornea radius for use in eye tracking

An eye tracking system comprising processing circuitry configured to:

• perform calibration, the calibration comprising estimating values for a plurality of parameters defining respective optical properties of an eye, said plurality of parameters including an initial value of a radius of a cornea of the eye;
• perform eye tracking for the eye using the values estimated at the calibration, including the initial value of the radius of the cornea:
• estimate an updated value of the radius of the cornea;
• and
• perform eye tracking for the eye using the updated value of the cornea radius and a value estimated at the calibration, prior to the estimation of the updated value of the radius of the cornea, for a parameter other than the cornea radius of the eye.

A non-transitory computer-readable storage medium storing instructions which, when executed by an eye tracking system, cause the eye tracking system to:

• perform calibration, the calibration comprising estimating values for a plurality of parameters defining respective optical properties of an eye, said plurality of parameters including an initial value of a radius of a cornea of the eye;
• perform eye tracking for the eye using the values estimated at the calibration, including the initial value of the radius of the cornea;
• estimate an updated value of the radius of the cornea;
• and
• perform eye tracking for the eye using the updated value of the cornea radius and a value estimated at the calibration, prior to the estimation of the updated value of the radius of the cornea, for a parameter other than the cornea radius of the eye.