Algorithms for optoacoustically controlled selective retina therapy (SRT)

Abstract

Objectives Selective Retina Therapy (SRT) uses microbubble formation (MBF) to target retinal pigment epithelium (RPE) cells selectively while sparing the neural retina and the choroid. Intra- and inter-individual variations of RPE pigmentation makes frequent radiant exposure adaption necessary. Since selective RPE cell disintegration is ophthalmoscopically non-visible, MBF detection techniques are useful to control adequate radiant exposures. It was the purpose of this study to evaluate optoacoustically based MBF detection algorithms. Methods Fifteen patients suffering from central serous chorioretinopathy and diabetic macula edema were treated with a SRT laser using a wavelength of 527 nm, a pulse duration of 1.7 µs and a pulse energy ramp (15 pulses, 100 Hz repetition rate). An ultrasonic transducer for MBF detection was embedded in a contact lens. RPE damage was verified with fluorescence angiography. Results An algorithm to detect MBF as an indicator for RPE cell damage was evaluated. Overall, 4646 irradiations were used for algorithm optimization and testing. The tested algorithms were superior to a baseline model. A sensitivity/specificity pair of 0.96/1 was achieved. The few false algorithmic decisions were caused by unevaluable signals. Conclusions The algorithm can be used for guidance or automatization of microbubble related treatments like SRT or selective laser trabeculoplasty (SLT).

Long-Term Multimodal Imaging Analysis of Selective Retina Therapy Laser Lesions

“…The titration was used to ensure sufficient energy levels for RPE damage. FA was performed directly after treatment with SRT [5,10].…”

“…SRT uses pulse durations below 5 µs, which results in selective RPE cell disruption by intracellular microbubble formation and does not affect the neuroretina or choroid. The microvaporization-induced local RPE defects are closed by the proliferation and migration of neighboring pigment epithelial cells [5]. It is postulated that these remodeling processes contribute to the restructuring of the blood-retinal barrier, the improvement of metabolic functions of the RPE and therefore act as a rejuvenating therapy for the RPE [6].…”

“…SRT has shown therapeutic success in central serous chorioretinopathy and diabetic macular edema [8,[10][11][12]. No side effects or complications of this procedure have been reported so far [5,6,12,13]. One problem in the clinical application of SRT is that neither the optimal irradiation parameters nor the standard treatment strategies regarding the application geometry of laser foci, the number of spots and repetitive treatment regimens have been reported and so far are only based on common therapeutic regimes of conventional laser coagulation treatment [8].…”

Real-time OCT feedback-controlled RPE photodisruption in ex vivo porcine eyes using 8 microsecond laser pulses

“…Thereby, the starting energy is set as 20% of the end energy. Other groups limited the ramp's range even more by setting the start energy as 50% of the end energy, resulting in a much smaller working range [62]. We therefore expect an even better performance for our RFD if this methodology would also be applied.…”

Ultrafast measurement of laser-induced shock waves

“…The rapidly growing use of lasers in medicine requires characterization of many different phenomena that occur in tissue and aqueous environments, often following the formation of micro- and nanobubbles which are generated intentionally or unintentionally during therapeutic and diagnostic procedures. The formation of a laser-induced bubble is accompanied by a shock wave creation [1] , for example during laser surgery and eye therapies, such as capsulotomy, refractive surgery (vision correction), vitreolysis, selective retina therapy [2] or during the formation of laser-induced plasmonic vapor nanobubbles in various fields, from biophotonics and medicine [3] , such as cancer therapy [4] and photoacoustic imaging, to surface cleaning, study of cavitation erosion [5] and emerging and expanding solar energy harvesting technology [6] . Nanoplasmonics promises the use of nanoscale vapor bubbles for diagnostic and therapeutic purposes on sub-cellular and even molecular structures with extremely high precision [7] .…”