In-vivo Real-Time Feedback-Controlled Dosimetry of Microsecond Laser Retinal Microsurgery using Optical Coherence Tomography

Evers Olufsen, Madeline; Burri, Christian; Salzmann, Simon Adrian; Povazay, Boris; Meier, Christoph; Frenz, Martin; Kiilgaard, Jens (27 April 2023). In-vivo Real-Time Feedback-Controlled Dosimetry of Microsecond Laser Retinal Microsurgery using Optical Coherence Tomography In: ARVO Annual Meeting 2023. New Orleans. 23.04.2023 - 27.04.2023.

Purpose : In the treatment of various retinal diseases, mild photocoagulation and selective retina therapy (SRT) are in high demand, as they selectively damage the retinal pigment epithelium (RPE) while sparing the neurosensory retina and choroid. However, due to the high inter- and intraindividual variability of RPE and choroidal absorption, as well as optical transmission, laser optical microsurgery requires reliable real-time feedback-controlled dosimetry (RFD) to prevent unwanted overexposure. The aim of this in-vivo experiment was to investigate microsecond laser microsurgery and RFD using optical coherence tomography (OCT). Methods : Four pig eyes were exposed to laser pulses of 4, 8, 12, and 20 μs duration in ramp-mode (pulse energy range: EStart = 50 µJ / EEnd = 130 µJ, max 15 pulses; repetition rate: 100 Hz) using the SPECTRALIS CENTAURUS device (HuCE-optoLab, BFH-TI, CH). The device consists of a modified imaging platform (SPECTRALIS HRA+OCT, Heidelberg Engineering, DE) extended with a prototype laser (Meridian Medical; wavelength: 532 nm; peak power: 30 W) for SRT. For each laser lesion, the increasing ramp’s end energy was individually controlled in real-time using OCT dosimetry (central wavelength: 870 nm; scan rate: 80 kHz) and an algorithm. Retinal changes were assessed with fluorescein angiography (FA), color fundus photography (CFP) and OCT 1 hour post irradiation. Results : A preliminary evaluation of 168 laser lesions shows that RFD using OCT can interrupt the ramp-mode in real-time for each lesion individually, leading to a controlled retinal damage. On average a pulse end energy of 80 µJ was applied, corresponding to an average ramp-mode interruption at pulse 7 of 15. The preconditioned algorithm enabled treatment with a clearly visible breakdown of the blood-retinal barrier (BRB), according to FA, and barely visible treatment lesions, according to CFP. OCT B-scans covering the treated areas provided a first indication of the morphological tissue impact. Conclusions : The SPECTRALIS CENTAURUS device with OCT based laser dosing proved to induce minimal visible damage and BRB breakdown over a wide range of pulse durations. The novel irradiation scheme and algorithm are currently being optimized and tested in multiple subjects to further improve sensitivity to reduce laser irradiation. Future work will address correlation of multimodal imaging and histology.

Item Type:	Conference or Workshop Item (Poster)
Division/Institute:	School of Engineering and Computer Science > Institute for Human Centered Engineering (HUCE) School of Engineering and Computer Science > Institute for Human Centered Engineering (HUCE) > HUCE / Laboratory for Optics School of Engineering and Computer Science
Name:	Evers Olufsen, Madeline; Burri, Christian0000-0003-2690-7527; Salzmann, Simon Adrian0000-0001-5453-8808; Povazay, Boris0000-0001-5571-5116; Meier, Christoph; Frenz, Martin and Kiilgaard, Jens
Subjects:	R Medicine > R Medicine (General) T Technology > T Technology (General)
Language:	English
Submitter:	Christian Burri
Date Deposited:	07 Jul 2023 11:37
Last Modified:	07 Jul 2023 11:37
Related URLs:	Organisation
URI:	https://arbor.bfh.ch/id/eprint/19559