Optical coherence tomography controlled selective retina therapy with a novel microsecond laser

Abstract

Selective retina therapy (SRT) is a short pulse (µs-regime) alternative to conventional laser photocoagulation (LPC) for treatment of retinal diseases. LPC leads to collateral damage of retinal layers adjacent to the retinal pigment epithelium (RPE), including healthy, non-regenerative photoreceptors due to the high thermal load, whereas in SRT, RPE cells are destroyed by microbubbles without damaging the neuronal retina. A novel experimental SRT laser operating at 532 nm wavelength can deliver 2 -20 μs pulse sequences. Its tight integration into an upgraded diagnostic SPECTRALIS system combines beam control for treatment planning with real-time optical coherence tomography (OCT) overexposure protection of the photoreceptors. This "Spectralis Centaurus" system, was built and preliminary tested on porcine ex-vivo samples, reaching an unprecedented accuracy with unique planning and follow-up capabilities for upcoming clinical cellular level micro-surgery. The combination of OCT with SRT selectively limits cell death to the RPE by precisely controlling energy deposition while optically monitoring tissue response.

Investigations on Retinal Pigment Epithelial Damage at Laser Irradiation in the Lower Microsecond Time Regime

“… 24 , 25 Further m-mode Optical Coherence Tomography (OCT) was also employed for MBF detection by fringe washout. 26 , 27 …”

“…24,25 Further m-mode Optical Coherence Tomography (OCT) was also employed for MBF detection by fringe washout. 26,27 Very recently, new compact laser sources with high continuous wave power >15 W and variable pulse duration from 2 μs to 50 μs were investigated for retinal therapies. 28 With these new high-power laser sources, for the first time, subvisible effects with repetitive micropulses, 3,[29][30][31] pure thermal tissue damage as in LPC, and MBF-related thermomechanical effects as in SRT might be accessed with just one laser system, only by adjusting the pulse duration and pulse repetition rate appropriately.…”

Selective Retina Therapy

“…The SPECTRALIS Centaurus system integrates hard-, firm-and software to deliver OCT controlled, automatically tissue-adapted power and exposure-limited pulses with the high lateral and axial accuracy provided by the confocal eye tracker [96]. The 532 nm treatment laser is collinearly coupled into the light path of the 870 nm broadband OCT spectrometer via a dichroic beam splitter after adjusting the spot diameter.…”

“…Fig. 11.11 Configuration of the SPECTRALIS Centaurus system [96]. The 532 nm treatment laser is integrated into the specially modified optics of the adapted OCT system (left portion in front of the galvanometric scanner pair) and allows interaction with the multiwavelength laser tracking and exposure system…”

“…12 Overview of the SRT-OCT setup and the measurement protocol[96]. (a) The SRT upgrade module has become an integral part of the SPECTRALIS platform and is (b) inserted into the compact measurement head.…”