The Case for Navigated Retinal Laser Therapy

Navilas offers increased accuracy and reduced patient pain when treating DME.

Marcus Kernt, MD

One of the key elements to consider when developing new technology is the optimization of patient care by ensuring accurate treatment, minimizing discomfort and alleviating postoperative effects. Experience has demonstrated that conventional retinal lasers, while valuable clinically, do require surgeons and patients to accept a few trade-offs, most notably in patient comfort and procedure duration. So how do we ensure that photocoagulation procedures for patients suffering from diabetic macular edema and other retinal diseases will not only be safe but a less painful option to patients?

LASER PHOTOCOAGULATION, AN EVOLVING TECHNOLOGY

Laser has played an important role in the treatment of many retinal conditions, such as diabetic retinopathy, vascular occlusions, retinal tears and other ocular diseases. Ever since Gerd Meyer-Schwickerath, MD, introduced retinal photocoagulation therapy using the xenon arc photocoagulator during the 1950s, and Campbell and colleagues' first descriptions of successful retinal laser photocoagulation in 1964, we have seen its evolution take shape.^1,2 Most importantly, we have seen photocoagulation transform into a less painful and more accurate technology in the treatment of retinal diseases.

The Diabetic Retinopathy Study (DRS) in 1971 marked the progression of photocoagulation clinical trials, which involved more than 1,700 patients enrolled across 15 medical centers. This important study consisted of having one eye of each patient randomly assigned to immediate photocoagulation and the other to follow-up without treatment, regardless of the course followed by either eye. The eye chosen for photocoagulation was randomly assigned to either of two treatment techniques: one using an argon laser and the other a xenon arc photocoagulator.³

As a major result of the DRS and other population-based studies, such as the Early Treatment of Diabetic Retinopathy Study, it could be shown that retinal laser photocoagulation was safe and effective as treatment for both diabetic retinopathy and DME, the leading causes for visual impairment in diabetic subjects. The downside was that, at the time, these procedures had to be repeated a number of times, often leading to retinal hemorrhages, burns and patient discomfort.

This initiation of controlled trials and the subsequent many years of research led to what is now a faster and less painful delivery of laser treatment, offering different capabilities and modalities reserved for individualized treatment. Essential diagnostics for the planning of laser treatment, such as fluorescein angiography, were mostly separated from the actual treatment device, until the development of the Navilas navigated laser photocoagulation system (OD-OS Retina Navigation Company, San Francisco). As a result, individual shortcomings during the transfer process and potential loss of accuracy could not be excluded. Proponents of the Navilas system, such as myself, believe that integrating diagnostic information into the surgical device overcomes previous shortcomings in laser surgery protocols, helping retinal physicians to achieve the best outcomes when treating their patients.

ABOUT NAVILAS

Navilas is a fundus-imaging and laser-treatment device that allows real-time, widefield digital fundus imaging, procedure planning, electronic documentation and precise retinal photocoagulation delivery.^4,5 The integrated system features different imaging modes, such as color, infrared and fluorescein angiography, to help assess the pathology and plan an appropriate laser treatment on its high-resolution touch-screen monitor. This computerized planning mode offers surgeons the ability to overlay images when planning for a better assessment.

A significant feature is the aptitude of the laser to track eye movement during laser treatment. The laser pulses can be delivered spot by spot or consecutively, as in common pattern-style lasers. Due to its integrated imaging capabilities, the ability to switch to the color imaging mode during treatment and assess the delivered energy gives the surgeon an opportunity to adjust as needed. After each laser spot has been delivered, immediate feedback is processed, detailing the degree of accuracy in treatment.

The various integrated modalities in the Navilas system give surgeons greater confidence when treating near vital structures and to deliver accurate laser spot placement in every treatment, offering patients a superior level of care.

ACCURACY AND PAIN

In 2010, a prospective study to evaluate clinical outcomes with the Navilas laser photocoagulation system was conducted at the Ludwig-Maximilians University Department of Ophthalmology in Munich. Thirty-six patients with clinically significant macular edema were assessed. Apart from determining clinical outcomes of the Navilas procedure, treatment pain was also evaluated.

The primary goal of this study was to assess the accuracy in placement of the laser application. Treatment intensity was controlled manually during treatment, so the laser spots applied were barely visible directly after treatment was concluded. An evaluation of the number of laser spots and their accuracy was completed after four weeks using optical coherence tomography and color imaging (CI) captured with the Navilas system. After one month, 4137 laser spots were analyzed to determine the accuracy of spot placement.

After analyzing spot placement with the Navilas OCT images, results showed that, in total, 79% of the planned laser spots were visible on CI, of which 96% were within 100 µm of the planned target position. On an intention-to-treat basis for CI, 76% of the laser spots were placed and visible within the 100-µm target. OCT confirmed that the laser effects were limited to the outer retina, and time for focal treatment was a mean <7 (+/−3) minutes. Accuracy of treatment indicated in the study that the Navilas system offers a precise pre-plan treatment.

A secondary aspect of this study consisted of patients being asked to quantify their feeling of pain after treatment by showing the degree on a visual analog scale (VAS; 0 = no pain; 10 = very bad pain). Thirty-six patients treated with the Navilas system were included in the study, as well as a matched control group treated with conventional laser during the same time period at our diabetes clinic.

In all patients, treatment pain was quantified by VAS and the Navilas group was compared to the matched control group receiving conventional laser treatments. Pain on the VAS after Navilas treatment was a mean of 1.6 (SD 1.0), significantly lower (P<.001) than for the control group, with 4.4 (SD 1.8). Tracking pain has been found to be a helpful diagnostic tool when evaluating the patient's feeling of treatment-related pain. By using a VAS, the patient bypasses the cognitive level of the brain, resulting in a truer representation of pain. The study results found that pain was significantly lower in the Navilas group compared to those treated with conventional slit lamp–based laser, due to the shorter procedure time and the ability to avoid areas that should not be targeted, which protects the patient from additional pain or scarring.

Figure 1. Using the Navilas system, the surgeon first identifies areas to treat (blue circles) and areas to block from laser energy (yellow circle).

Figure 2. The treatment plan is automatically stabilized on the living fundus and visible onscreen during treatment.

Figure 3. Postoperative photo showing the correspondence between the treatment plan and the treated tissue.

WHY I PREFER NAVILAS

Focal retinal laser treatment for the long-term stabilization of DME has been proven as highly effective over the past decades and still continues to be the gold standard of care, keeping in mind that a maximum level of safety and accuracy when treating close to the fovea is warranted.

The results of our study indicate that the Navilas system provides both a high degree of safety combined with the advantages of computerized precision and accuracy. This combination potentially provides significant advantages over conventional, manual slit lamp–based lasers. Another important aspect of our data is that the Navilas treatment resulted in significantly less pain compared to standard laser treatment.

One of the most gratifying things about being a physician is the ability to treat your patients with technology that you have clinically assessed and can recommend as a safe and painless procedure. The ingenuity behind an integrated photocoagulation system such as Navilas over the standard laser procedure may enable surgeons to perform more accurate treatments as well as provide a more comfortable experience for both the surgeon and the patient in a shorter amount of time. I have found that the Navilas system not only results in improved patient willingness to undergo laser therapy but also in safer treatment outcomes. RP

REFERENCES

1. Meyer-Schwickerath G. [Light coagulation; a method for treatment and prevention of the retinal detachment]. Albrecht Von Graefes Arch Ophthalmol. 1954;156:2-34.
2. Campbell CJ, Noyori KS, Rittler MC, Innis RE, Koester CJ. The application of fiber laser techniques to retinal surgery. Arch Ophthalmol. 1964;72:850-857.
3. The Diabetic Retinopathy Study Research Group. Photocoagulation treatment of proliferative diabetic retinopathy: A short report of long range results. Diabetic Retinopathy Study (DRS) Report Number 4. In: Waldhausl WK, ed. Diabetes 1979: Proceedings of the 10th Congress of the International Diabetes Federation, Vienna, Austria, September 9-13, 1979. Brussels, Belgium; International Diabetes Foundation; 1979.
4. Kernt M, Cheuteu R, Vounotrypidis E, et al. Focal and panretinal photocoagulation with a navigated laser (NAVILAS). Acta Ophthalmol. 2010 Oct 14. doi: 10.1111/j.1755-3768.2010.02017.x. [Epub ahead of print]
5. Kozak I, Oster SF, Cortes MA, et al. Clinical evaluation and treatment accuracy in diabetic macular edema using navigated laser photocoagulator NAVILAS. Ophthalmology. 2011 Jan 24 [Epub ahead of print]