08/3 Computer assisted retinal laser photocoagulation

		Structural overview of a computer assisted retinal laser photocoagulation system: (a) treatment plan (b) control system (c) target and treatment laser (d) mirror system to derive the laser beam (e) video camera acquiring a live video stream (f) patient eye.

Laser photocoagulation of the retina (applying laser energy to the retina to seal leaking blood vessels) has become an established and important treatment modality for diabetic retinopathy, age-related maculopathy (deterioration of the macula), neovascular complications after vascular occlusion, and a variety of other eye diseases. Some of these diseases have an enormous social and economic impact. Current setups to deliver laser photocoagulation typically consist of a slit lamp equipped with a laser unit, where the laser beam is aimed manually by the ophthalmologist.

Computer assistance offers the potential for improvements for such a setup with respect to accuracy, individualised spot patterns, execution time, safety, and therefore treatment efficacy. The general goal of this project is to build up an integrated computer assisted retinal laser photocoagulation system.

The objectives of this project are:

• to implement a system that allows for patient individualised planning of photocoagulation treatment based on previously acquired medical images of different modalities
  
• to develop and validate a computer navigation system that allows for the precise reproduction of the established treatment plan
  
• to assess the attainable system accuracy of the complete planning and navigation system
  
• to perform animal and clinical feasibility studies to validate the proposed methods, with a special emphasis on pan-retinal photocoagulation.
  

Experimental Design and Methods

Intra-modal and multi-modal registration for different image modalities such as fundus photographs or fluorescein angiograms has to be implemented. A semiautomatic treatment planning system based on preoperatively acquired and registered images has to be developed. This application has to allow for accurate and safe planning of the surgical procedure involving planning parameters like beam size and energy or the beam spot distribution.

To acquire digital fundus images for navigation while delivering photocoagulation, the slit-lamp has to be equipped with a high resolution video image acquisition unit. To ensure intraoperatively the correct relation between the treatment plan and the real-time video stream, real-time image registration has to be implemented. An active, computer controlled laser beam deviation system using Galvano-scanner technique has to be developed and validated to perform the treatment according to the established treatment plan. Clinical evaluation aims at proving the feasibility of the proposed system and at demonstrating that new approaches can complement existing techniques. Methods how to evaluate and compare different specified coagulation modalities have to be outlined.

Expected Value

The possibility to plan retinal photocoagulation treatment on previously acquired image data, to reproduce the treatment plan fast and accurately while delivering photocoagulation, and to store the image data and the delivered treatment including all parameters in a comprehensive database will contribute to the evaluation and comparison of different existing and new photocoagulation treatment modalities. If computer assisted retinal photocoagulation proves to reduce the incidence of approved study end points such as severe visual loss, significant life quality improvement and lowering of socio-economic costs can be expected.