Eye surgery: precision and prevention with femtosecond lasers
Eye surgery: precision and prevention with femtosecond lasers
Interview with Prof. Frederik Raiskup, Director of the Cornea and Refractive Surgery Unit, Department of Ophthalmology, Carl Gustav Carus University Hospital in Dresden
Precision work is absolutely essential in eye surgery since the surgical site is very minute and sensitive. This is why eye surgeons have been using lasers for years. Femtosecond lasers are especially well suited to serve this purpose because they are able to cut tissue with great precision and little energy, which prevents unwanted side effects of surgery.
In this interview with MEDICA-tradefair.com, Prof. Frederik Raiskup talks about the "FEMTO LDV Z8" femtosecond laser made by the Ziemer Company, explains where it is being used and what its advantages are compared to other surgical techniques.
Prof. Raiskup, you have been using the "FEMTO LDV Z8" femtosecond laser since March 2017. What makes this acquisition so special?
Prof. Frederik Raiskup: Until now, in ophthalmology, femtosecond lasers have only been used for corneal incisions in the field of refractive surgery. The year 2000 approximately marks the effective beginning of the era of these types of lasers. Since 2008, we are also able to use this technology in cataract surgery. What makes the "Z8" so unique is that it features integrated optical coherence tomography (OCT) and that we are able to use it for both cataract and corneal surgery.
For what indications do you use this laser?
Raiskup: There is its application in refractive eye surgery on the one hand: by using OCT imaging, we are able to accurately see the patient’s lens and its layers during surgery. Based on these images, we plan and make the incisions required for the extraction of the lens when it is cloudy.
And then there is its application in corneal and refractive surgery to treat vision disorders and its primary use to perform lamellar grafts. In this case, individual layers of the cornea that are cloudy or thinned out are transplanted for example. These layers are between 200 and 400 microns in thickness, which requires very precise incisions.
This laser expands our spectrum of corneal surgery even further as it pertains to the correction of curvatures of the cornea. Patients with an extreme, irregular cornea, so-called corneal ectasia such as keratoconus need a hard contact lens to improve their vision. The femtosecond laser can now also be used in the case of patients who are unable to tolerate these lenses – typically young persons who work full-time. With the laser's help, we are able to implant special corneal rings that compensate for the curvature of the cornea. In these cases, patients can subsequently wear soft contact lenses and possible even glasses.
Next to its broad range of applications, what are the advantages of this type of laser compared to other surgical techniques?
Raiskup: There is its mobility and compact size of 1.0 meters by 0.6 meters and a weight of 250 kilograms. The previous femtosecond laser models are very large, static devices, ranging in size between 3.0 meters by 2.7 meters all the way up to 3.4 meters by 3.7 meters and weighing between 600 and 800 kilograms, preventing them from being moved between operating rooms. The "Z8" laser can be shut down after use, moved and started up again within a few minutes. The actual device is also not as delicate as some other laser types that can only operate in air-conditioned rooms and at a certain humidity level.
What's more, unlike other types of femtosecond lasers, which operate in the microjoule range, this laser uses lower energy in the nanojoule range. This enables finer and more accurate incisions, while the lower pulse energy is gentler on all intraocular structures.
As a surgeon, how do you rate the application of this device?
Raiskup: The femtosecond laser technology makes the incisions with all applications more exact and results in fewer side effects than is the case with other methods. Since we have started to use the system in March, we have not had any problems or intraoperative complications of any procedures we have performed. I am also very pleased with the precision of cuts and the repetition rate between patients.
Having said that, I think it is still too early to say whether this device is truly head and shoulders above other techniques and procedures used with in patient population.
What are the ultimate benefits for patients?
Raiskup: Prevention is the keyword in this instance. For example, we are able to perform gentler surgery with less risk in patients with Fuchs endothelial corneal dystrophy. This form of dystrophy causes the loss of endothelial cells that are in charge of draining the corneal stroma and ensure that the cornea keeps clear. Once they no longer function properly, the cornea becomes edematous and cloudy in appearance, which is an indication for transplant. However, sometimes there is a corneal equilibrium: even though the cells are pathologically altered, they still keep the cornea clear. Intraocular surgery, for example on the lens of the eye, and especially the use of ultrasound in cataract surgery might disturb this balance. As a result, the cornea might be swollen and cloudy after surgery. This is why this kind of corneal dystrophy is also an indication for refractive lens surgery with the femtosecond laser: it allows us to gently open the anterior lens capsule, divide the lens and subsequently use lower ultrasound energy. This minimizes the risk of corneal decompensation and thus also reduces the need to have a possible corneal transplant.
Another example is patients with corneal scarring: here we do not need to perform perforating keratoplasty and are able to conduct a lamellar procedure. The follow-up care for perforating keratoplasty is also crucial and for some patients extensive: this is why we do not advise keratoplasty for patients who are unable to handle post-operative treatment on their own – for example, administering eye drops. For these patients, lamellar surgery, which is much easier and more precise than a manual procedure, as well as the postoperative care on the part of the patient, is simpler and thus more likely to be successful.