June 2023
Volume 64, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2023
In-vivo Real-Time Feedback-Controlled Dosimetry of Microsecond Laser Retinal Microsurgery using Optical Coherence Tomography
Author Affiliations & Notes
  • Madeline Evers Olufsen
    Optolab, Institute of Human Centered Engineering, Bern University of AppliedSciences, Biel, Bern, Switzerland
    Biomedical Phototonics Group, Institute of Applied Physics, University of Bern, Bern, Switzerland
  • Christian Burri
    Optolab, Institute of Human Centered Engineering, Bern University of AppliedSciences, Biel, Bern, Switzerland
    Biomedical Phototonics Group, Institute of Applied Physics, University of Bern, Bern, Switzerland
  • Simon Salzmann
    Optolab, Institute of Human Centered Engineering, Bern University of AppliedSciences, Biel, Bern, Switzerland
    Biomedical Phototonics Group, Institute of Applied Physics, University of Bern, Bern, Switzerland
  • Boris Povazay
    Optolab, Institute of Human Centered Engineering, Bern University of AppliedSciences, Biel, Bern, Switzerland
    Biomedical Phototonics Group, Institute of Applied Physics, University of Bern, Bern, Switzerland
  • Christoph Meier
    Optolab, Institute of Human Centered Engineering, Bern University of AppliedSciences, Biel, Bern, Switzerland
    Biomedical Phototonics Group, Institute of Applied Physics, University of Bern, Bern, Switzerland
  • Martin Frenz
    Optolab, Institute of Human Centered Engineering, Bern University of AppliedSciences, Biel, Bern, Switzerland
    Biomedical Phototonics Group, Institute of Applied Physics, University of Bern, Bern, Switzerland
  • Jens F Kiilgaard
    Dept. of Ophthalmology, Rigshospitalet, Kobenhavn, Denmark
  • Footnotes
    Commercial Relationships   Madeline Evers Olufsen None; Christian Burri Heidelberg Engineering, Meridian Medical, Code F (Financial Support), Heidelberg Engineering, Meridian Medical, Code R (Recipient); Simon Salzmann Heidelberg Engineering, Meridian Medical, Code R (Recipient); Boris Povazay None; Christoph Meier None; Martin Frenz None; Jens Kiilgaard None
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science June 2023, Vol.64, 1801. doi:
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      Madeline Evers Olufsen, Christian Burri, Simon Salzmann, Boris Povazay, Christoph Meier, Martin Frenz, Jens F Kiilgaard; In-vivo Real-Time Feedback-Controlled Dosimetry of Microsecond Laser Retinal Microsurgery using Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2023;64(8):1801.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

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.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

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