Abstract
Purpose: :
Recently, a new approach to conventional photocoagulation, the selective retina therapy (SRT), has been introduced for treatment of diabetic retinopathy, age-related maculopathy and a variety of other eye diseases. The SRT confines the induced laser lesions to the retinal pigment epithelium (RPE) layer, leaving the neural retina unaffected. However, with the dose of energy applied during SRT, the lesions remain ophthalmologically invisible due to the absence of denaturized tissue close to the retinal surface. To guarantee the repeatable and reliable therapy and dosimetry control during treatment necessary for a wider acceptance of the therapy, new imaging techniques need to be evaluated towards their capabilities to visualize the laser lesions during the therapy.
Methods: :
In this manuscript, we evaluate the feasibility of optical coherence tomography (OCT) as a method for therapy monitoring. OCT represents a non-invasive high-resolution imaging modality with a variety of fields of application, predominantly in ophthalmology. A self-designed, high-resolution FD-OCT system was used to image dissected retina samples before and after SRT treatment. The samples were taken from fresh pig eyes with detached anterior segment, placed in a sample cell and irradiated with the SRT laser with varying pulse energies within the range used for treatment. Whenever possible, the samples were stored on ice and covered with PBS to prevent from unwanted cell death.
Results: :
From the irradiated samples, 10 x 10 x 3 mm C-Scan volumes with a lateral resolution of 20 µm and an axial resolution of 2.3 µm in tissue were recorded. The processed scans show the potentially of high-resolution OCT to visualize SRT laser lesions in the RPE layer. The results show a good agreement between OCT scans and microscopic images with clearly visible laser lesions if sufficient energy is applied.
Conclusions: :
We were able to show that OCT is a feasible technique for the detect ion of SRT lesions in the RPE layer. The resolving power of the OCT system proved to be sufficient to reliably detect the induced lesions under laboratory conditions, thus making it a promising approach for SRT therapy monitoring. The incorporation of OCT into the treatment system and automation of therapy monitoring could greatly increase the proliferation of the SRT technique.The authors would like to thank the Dr. Werner Jackstaedt foundation in Wuppertal, Germany, for the generous financial support of this ongoing study.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • laser • retinal pigment epithelium