Fig.: The winners of the 2013 DOG video award, sponsored by Leica Microsystems. Photo from left to right: Prof. Dr. med. Bertold Seitz, President of the German Ophthalmological Society (DOG), Prof. Dr. Dr. h.c. Franz Grehn (first prize), Dr. med. Raid Darawsha (second prize), Dr. Tim Schulz, who received the third price on behalf of Prof. Dr. med. Burkhard Dick, Andreas Baldauf, Leica Microsystems. Source: DOG, Stefan Zeitz, Berlin.
Glaucoma causes gradual damage to the optic nerve that can lead to blindness. The most common reason for glaucoma is elevated intraocular pressure. This happens when the normal balance of production and drainage of aqueous humor in the eye is disrupted, usually by impaired outflow. The aqueous humor, a clear fluid in the interior and posterior chamber, contains nutrients for the lens and corneal endothelium. It is produced in the ciliary body of the eye and secreted into the posterior chamber. From there it flows through the pupil to the anterior chamber, where it is returned through the so-called iridocorneal angle to the bloodstream.
The goal of any therapy is to lower the patient’s intraocular pressure to stop the optic nerve from being damaged further. As it is not possible to regenerate the optic nerve, however, visual function cannot be improved, so treatment is aimed at preventing further loss of vision. If neither medication therapy with eyedrops nor minimally invasive laser treatment prove successful, there are a number of surgical procedures to be considered. The most common of these is so-called trabeculectomy, which involves opening the sclera to regulate aqueous humor drainage and channel it into the conjunctiva. "The critical point of this method is the opening: it has to oroduce exactly the right amount of outflow to reduce the intraocular pressure needed by the particular patient. However, opening the sclera directly can result in the aqueous humor flowing too quickly, leading to excessively low eye pressure. You also have to consider the issues of wound healing – these too are influenced by the surgical technique."
Simulating the dynamics of the healthy eye
In the healthy eye there is a sophisticated system for regulating aqueous humor drainage: a series of several resistance planes ensures that the aqueous humor drains slowly and continuously. The system is also able to adjust to changing parameters and thereby maintain the ideal outflow dynamics. Franz Grehn modeled his new operation method on the example of nature: "The new technique is based on the idea of simulating two of the resistance planes of the healthy eye," the ophthalmologist explains. Two openings are made in the so-called Schlemm’s canal that runs in a ring pattern between the cornea and the sclera and is responsible for aqueous humor drainage. "Distributing the drainage resistance to two planes slows down the flow rate of the aqueous humor, which is beneficial for wound healing," says Grehn in explanation of the benefits of the new technique, which are also proven in a controlled comparison study. Also, the indirect opening via Schlemm’s canal avoids the necessity to cut the iris (iridectomy), which is regarded as a risk factor for the development of a cataract when applying the traditional trabeculectomy procedure of a direct opening in the sclera.
Operation video as incorruptible document
The video distinguished by the DOG was made as a counterpart to a clinical comparison study, primarily addressing ophthalmologists who are familiar with the procedures of glaucoma surgery. It is therefore not as much a classic educational video as a model demonstration of an innovative surgical procedure. The visual presentation of the operation is commented by Grehn’s explanations. “The video was recorded with the movie function of the surgical microscope we used,” says Grehn. "As the visual field is extremely small in eye surgery, one of the challenges was to keep the operating area exactly in the camera frame – that’s not always the case in everyday surgery. For me as the surgeon, it meant that I had to operate with a video eye, so to speak." Videos are playing an increasingly important role in medicine: the fact that they can be watched any number of times is a key advantage not only in training but also for sharing knowledge with colleagues. Video sequences can make lectures more graphic or be used for discussions among doctors. Franz Grehn particularly appreciates the incorruptibility of the medium: "The video does not miss anything. When I record a surgical procedure, the style of operating is immediately visible. The critical scenes can be analyzed, too. This makes the video an incorruptible document and an ideal addition to traditional forms of presentation."