Calibration process for femtosecond laser intraocular lens modification system using video and OCT targeting
The XYZ beam position of an ophthalmic laser system is calibrated by measuring a fluorescent signal induced by the focused laser beam in a thin glass coverslip via multiphoton absorption. A video camera measures the XY position and intensity of the fluorescent signal as the focused laser beam strikes the coverslip. The Z position of the focus is determined by scanning the targeted z position and identifying the Z scanner position of peak fluorescence. An OCT system measures the real space Z location of the coverslip, which is correlated with the Z scanner position. Other laser system parameters are assessed by repeatedly scanning a lower energy laser beam in a piece of IOL material, and observing damage (scattering voids) formation in the IOL material. Based on the rate of damage formation, laser system parameters such as beam quality, numerical aperture, pulse energy, and pulse duration, etc. can be assessed.
1 . A method for calibrating and operating an ophthalmic laser system, comprising:
generating a low energy pulsed laser beam, the low energy laser beam having a pulse energy configured to cause formation of damages in an IOL (intraocular lens) material only after multiple irradiations;
controlling a laser delivery optical subsystem of the ophthalmic laser system to repeatedly scan the low energy laser beam in a piece of the IOL material;
controlling an imaging subsystem of the ophthalmic laser system to measure formation of damages in the piece of IOL material after repeats of laser scans, and to determine a rate of damage formation; and
determining an effective laser intensity of the laser beam based on the rate of damage formation.
2 . The method of claim 1 , further comprising:
determining a laser treatment plan based on the effective laser intensity; and
operating the ophthalmic laser system according to the laser treatment plan to treat a patient's eye, including generating a treatment laser beam and scanning the treatment laser beam in the patient's eye.
3 . The method of claim 1 , wherein the step of controlling the imaging subsystem of the ophthalmic laser system to measure the formation of damages in the piece of IOL material includes controlling a video camera or an OCT (optical coherence tomography) device of the ophthalmic laser system to measure the formation of damages in the piece of IOL material.