Focal and panretinal photocoagulation with a navigated laser (NAVILAS®)

Abstract

Editor, L aser photocoagulation is a well evidence-based standard therapy for both proliferative diabetic retinopathy (PDR) and diabetic macular oedema (DME), recently supplemented by e.g. anti-VEGF treatment (Elman et al. 2010). Over the last decades, numerous technical advances have been introduced to laser therapy including subthreshold techniques (Nakamura et al. 2010) and pattern laser generation (Bolz et al. 2010). However, the advantages of computerized precision well known from refractive surgery (‘eye tracking’) have not become widely available despite several technical approaches towards that goal (Naess et al. 2002). Navilas is a novel fundus imaging and laser treatment device (ODOS GmbH, Teltow, Germany) that allows imaging (infrared, colour, fluorescein angiography) and integrated laser treatment of the retina, including pattern laser generation. Besides documentation, safety and patient comfort, the main theoretical advantages lie in retina navigation. The device offers retina navigation by computerized image and target assistance systems, resulting in high precision and reproducibility of theoretically <60–110 lm (Neubauer et al. 2009). It fundamentally differs from other laser devices by applying not a slitlamp, but a scanning slit-based instrument. The instrument takes approximately 25 images per seconds in imaging or treatment mode. For focal laser treatment, the field of view is 50 , and the optical resolution with the instrument used in this study was 1280 · 1024 pixels, for that angle, resulting in approximately 20– 26 pixels ⁄degree. For panretinal laser treatment, a specific widefield lens, resulting in 85 field of view, is used. Because of the slit imaging principle, images of high contrast and sharpness can be obtained (Neubauer et al. 2010). Another difference to slitlampbased laser devices is the touch-screen monitor used for imaging, planning and treating fundus changes (Fig. 1). This allows the retina surgeon to plan laser spots on the screen and then apply automated patterns and single spots as appropriate. A prepositioning mode may be used to automatically advance the targeting aiming beam from targeted retinal position to position after the aiming beam, and the preplanned target can be stabilized on the living fundus. For treatment, the surgeon actuates the laser manually after the target lock has been verified by the surgeon. Exemplarily, we report on two cases of in vivo-navigated laser treatment applying the Navilas device for focal and peripheral laser treatment in diabetic retinopathy. A 52-year-old man suffering from type 2 diabetes for 8 years and mild to moderate nonproliferative diabetic retinopathy (NPDR) on both eyes attended our clinic for routine control. Visual acuity of the right eye had decreased from 20 ⁄ 20 to 25 ⁄ 30 over the last year, the left eye was 20 ⁄ 20. Funduscopy revealed moderate NPDR and retinal thickening originating from the upper vessel arcade extending into the macular region. On fluorescein angiograpy, significant exudation was present in this area. Therefore, focal macular laser photocoagulation for clinically significant macular oedema was performed on the right eye utilizing Navilas. Treatment was preplanned on the software system based on colour fundus imaging (Fig. 2A). Navigated, semi-automatic pattern laser application was conducted without complications (laser settings: spot size: 100 lm, time 100 ms, energy 80–100 mW). One week after treatment, Navilas fundus imaging and spectral-domain optical coherence tomography of the treated areas were conducted, and confirmed laser application to the preplanned area (Fig. 2B and C). A 69-year-old man with a longstanding history of type 2 diabetes and NPDR presented with a decrease of vision of his right eye. Visual acuity had decreased from 20 ⁄30 to 10 ⁄ 100 during the last month; visual acuity on the left eye was 25 ⁄30. Clinical examination revealed PDR with multiple areas of peripheral retinal neovascularisation and a mild vitreous haemorrhage on the right and moderate NPDR on the left eye. Panretinal full scatter photocoagulation (usually applied over 3–4 sessions at our institution) was suggested as a treatment for the right eye. However, the first treatment session using a conventional 532 -nm slitlamp-based laser and a standard contact lens (‘TransEquator’ by Volk, USA) had to be aborted after 50 laser spots. The patient did not agree to continue treatment, as he could not tolerate the contact lens and felt significant pain from retinal laser application. One week later, panretinal pattern photocoagulation using the Navilas laser device was conducted. Because of the optical design of the device, laser treatment can be applied either with or without the use of a contact lens. Although currently not recommended by the manufacturer in selected cases, such as in patients with corneal irritations or blepharospasm, it might be advantageous to not apply Fig. 1. Navilas fundus imaging and laser treatment device applying a slit-based camera and touch-screen monitor for imaging, planning and treating fundus changes.