Guidance of magnetic intraocular microrobots by active defocused tracking

Current laparoscopic techniques for intraocular surgery require that the vitreous humor is removed and at least three cannulas are inserted through the sidewalls of the eye. This paper investigates an alternate intraocular surgical technique based on the use of wireless microrobots guided by external magnetic fields. Issues investigated include the effects of magnetic and viscous drag forces faced by magnetic microrobots in the vitreous humor and the 3D visual servoing of these microrobots using a single microscope view. A new active defocused tracking method is proposed for visually servoing the microrobot along the optical axis of the microscope. This method uses a purposely defocused view of the microrobot to unambiguously resolve depth while servoing. Experimental results demonstrating the method with a microrobot visually servoed in 3D at 60 Hz using a single microscope view are presented.