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Comparison of the visible effect on the fundus in peripheral laser photocoagulation between conventional pattern lasers and Navilas

Session Details

Session Title: New drug treatment and technology

Session Date/Time: Friday 27/09/2013 | 14:30-16:00

Paper Time: 15:42

Venue: Hall 3 (Level 0)

First Author: I.Kozak SAUDI ARABIA

Co Author(s):    J. Chhablani   A. Mathai   P. Rani   S. Alshahrani     

Abstract Details


Pattern laser photocoagulation treatment like with Pascal system (Topcon Corp., Tokyo, Japan) as well as navigated pattern laser treatments with Navilas (OD-OS GmbH, Berlin, Germany) gain more popularity for the treatment ofproliferative diabetic retinopathy. While conventional slit-lamp based patternlasersprovide only a “slit” image during laser application through microscope optics, the Navilas provides an 80 degree full fieldimage of the retina on a computer screen through an ophthalmoscope optics while applying laser patterns. This study compares the visible effect of the laser photocoagulation spotsapplied with conventional slit lamp pattern laserswith the laser spots applied with the Navilas Laser System.


Two tertiary care academic centers


In total,37 eyes of 24patients were treated with panretinal pattern photocoagulation using contact lens. 23 eyes received Navilas pattern treatment with 30ms pulse duration (1662 +/-409 spots) and 14 eyes received the treatment using conventional pattern laser system Pascal (1014 +/-618 spots) using 30ms pulse duration. For all eyes treated, color images were acquired immediately after the treatmentwith Navilas Laser System, even if treatment occurred on conventional pattern laser. A subset of 20 spots was selected for each patient’s eye treated as close as possible to the oraserrata from the acquired post treatment images. When reviewing the post treatment images on a separate computer, an ellipse was drawn around each visible boundaries of each laser spot with an imaging analysis software(ImageJ, NIH). Major and minor diameter of each spotwas measured in pixel coordinates, convertedinto physical coordinates using Navilas calibration factors to evaluate the effective spot diameter and area and then compared to the adjusted spot diameter by the physician, taking the magnification of the contact lens into account. The ratio between the major and minor diameter (ellipse ratio) was evaluated to determine the circularity of each spot (1 = circular).


All treatments were safe with no adverse events. The ellipse ratio for laser spots after Navilas panretinal photocoagulation treatment pattern was 1.05 and for Pascal 1.11 (p=0.016). While both systems show a higher ellipticity of the laser spots the further they are applied in the periphery (subset analysis), the ellipticity with Navilas is less than typically observed in the conventional pattern laser (ellipse ratio Navilas and Pascal 1.27 and 1.30, respectively (p=0.43), not significant).


Navilas provides asmaller variation in measured spot size and less elliptical photocoagulation burns. This effect can be explained with the Navilas optics allowing a broader focus of all spots of each pattern on the fundus. With the navigated photocoagulator, the physician is required less to tilt the contact lens to reach the periphery, inducing less astigmatism into the optical path for a more circular projection in the laser spot. Furthermore, the usual spot-size errors found at a slit lamp due to operator accommodation and depth of focus are greatly reduced due to machine vision and computer control of imaging and laser delivery. The overall smaller variation and more circular form of the burn with Navilas should result into a more regular scarring with less side effects where such application is required. With Navilas, the actual spot size corresponds more accurately to the desired spot size and therefore may lead to a more systematic treatment. User errors can be avoided for a more standardized treatment.

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