Imaging thermal expansion and retinal tissue changes during photocoagulation by high speed OCT

Area of Science:

• Ophthalmology
• Biomedical Optics
• Laser Surgery

Background:

• Understanding thermal effects in retinal photocoagulation is crucial for improving ocular laser treatments.
• Current methods for monitoring tissue changes during laser irradiation have limitations in speed and resolution.

Purpose of the Study:

• To investigate the utility of high-speed Doppler Optical Coherence Tomography (OCT) for real-time visualization of thermally induced tissue changes during retinal photocoagulation.
• To correlate OCT-measured tissue motion with temperature increases and macroscopic tissue alterations.

Main Methods:

• High-speed Doppler OCT (860 frames/second) was employed to image tissue dynamics in enucleated porcine eyes during laser irradiation.
• Optoacoustics was used for non-invasive temperature measurements.
• In vivo measurements were performed in rabbits, compensating for global tissue motion.

Main Results:

• Doppler OCT successfully imaged tissue motion and correlated it with temperature increases and macroscopic whitening of the retinal pigment epithelium (RPE).
• Reversible thermal expansion was observed at low laser irradiance, while irreversible tissue changes were detected at higher irradiance.
• Submicrometer resolution measurements of tissue expansion were achieved in vivo.

Conclusions:

• Doppler OCT provides spatially resolved measurements of retinal temperature increases and thermally induced tissue changes.
• This technology enhances the understanding of photocoagulation mechanisms.
• Doppler OCT holds potential for developing new strategies in retinal laser treatments and improving treatment reproducibility.