real time optical coherence tomography laser dosimetry ... · selective retina therapy financial...
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Quellgasse 21 | 2501 Biel/Bienneoptolab.ti.bfh.ch | [email protected]
▶ SNF Project Number: 323523_163306/1▶ Institute for Human Centered Engineering▶ optoLab
Real Time Optical Coherence Tomography Laser Dosimetry Control during Selective Retina Therapy
Fig 1. OCT B-Scan passing through the fovea centralis and showing thesensory retina with the retinal pigment epithelium (RPE). The SRT laser spot(green) is targeting the RPE and the collinear OCT laser (red) records aMscan. [Ganglion Cell Layer (GCL), Choroidal Stroma (CS), Internal LimitingMembrane (ILM), External Limiting Membrane (ELM), Bruch’s Membrane(BM)]
Although the eye is a small part of the body, diseases or disabilitiesof the eye have severe consequences on activities of everyday life.Among the retinal diseases, age-related macular degeneration anddiabetic retinopathy are especially problematic and frequent.Treatment of these diseases may be done using selective retinatherapy (SRT) by employing short laser pulses to selectively damagethe retinal pigment epithelium (RPE).
Because only an inner layer of the retina is damaged SRT lacks directoptical feedback using conventional ophthalmoscopic methods. Thelaser pulse duration and power must be re-determined at eachpatient. If the lesion becomes visible, the dose was too high.
Ch. Burri1, D. Kaufmann1, V. Koch1, J. Justiz1, P. Arnold1, Ch. Meier1, B. Považay1
1Bern University of Applied Sciences, HuCE optoLab
Introduction
Selective Retina Therapy
Financial Support, Sponsors & Project Partner
Fig 5. Principle scheme of the combination of the Heidelberg EngineeringHRA+OCT Spectralis system and SRT laser system.
In this SNF project HuCE optoLab of University of Applied ScienceBern is responsible for the engineering, development and integrationof the optical components such as the OCT measurement systemand the SRT laser into new delivery optics hardware.
Research Plan
Fig 2. Fundus photography (a) and fluorescein angiography (b) after SRT.The bright points at (b) marks the SRT laser spots. The test lesions withdifferent energy levels between the vessels showing first gray shadows asevidence of photocoagulation. The treatment spots are not identifiable inthe fundus image.
Problem
SRT selectively targets the RPE without affecting the neural retina,the photoreceptors and the choroid. Therefore tissue damageremains limited to the RPE.
Solution Approach
A B
Fig 3. The OCT Mscan (a) depicts SRT-induced RPE damage in OCT imaging
(a) (b)
▶ Recording the tissue during the laser treatment depth-resolved with collinear OCT Mscans
▶ Image processing to follow the treatment effects in real time
▶ RPE damage leads to detectable dynamic optical effects in OCT Mscans
▶ Effects are linked to thermal expansion, thermal vibration and changes in tissue scattering
(a)
(a) (b) (c)
(d) (e)
(i) (ii)
(iii)
Fig 4. Current state of development and application: (a) Basic setup (b) Optomechanical upgrade to combine SRT with OCT (c) Test treatment on porcineeye (d) Immediately after treatment, eyes were cut open posterior to thelens in the coronal plane and region of interest (RPE) was cut free to a blockof approximately 2:5 cm2 with the thickness of the sclera. A LIVE/DEAD KitL3224 was used to mark living and dead cells, and staining is performed (e)Evaluation took place under a Zeiss fluorescence microscope showing (i)living RPE cells (ii) SRT laser lesion and (iii) single dead cell (red nucleus)