RESEARCH ARTICLE


Scanning Laser Topography and Scanning Laser Polarimetry: Comparing Both Imaging Methods at Same Distances from the Optic Nerve Head



Stephan Kremmer*, 1, 2, Marcus Keienburg 2, Gerasimos Anastassiou 1, 2, Maurice Schallenberg 2, Klaus-Peter Steuhl 2, J. Michael Selbach 1, 2
1 Eye Hospital, Evangelisches Krankenhaus Gelsenkirchen, Munckelstr. 27, D-45879 Gelsenkirchen, Germany
2 Department of Ophthalmology, University of Duisburg-Essen, Hufelandstr. 55, D-45122 Essen, Germany


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© Kremmer et al.; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at the Eye Hospital, Evangelisches Krankenhaus Gelsenkirchen, Munckelstr. 27, D-45879 Gelsenkirchen, Germany; Tel: 0049 – 209 – 37261; Fax: 0049 – 209 – 378555; E-mail: stephan.kremmer@arcor.de


Abstract

Purpose:

To compare the performance of scanning laser topography (SLT) and scanning laser polarimetry (SLP) on the rim of the optic nerve head and its surrounding area and thereby to evaluate whether these imaging technologies are influenced by other factors beyond the thickness of the retinal nerve fiber layer (RNFL).

Materials and Methodology:

A total of 154 eyes from 5 different groups were examined: young healthy subjects (YNorm), old healthy subjects (ONorm), patients with normal tension glaucoma (NTG), patients with open-angle glaucoma and early glaucomatous damage (OAGE) and patients with open-angle glaucoma and advanced glaucomatous damage (OAGA). SLT and SLP measurements were taken. Four concentric circles were superimposed on each of the images: the first one measuring at the rim of the optic nerve head (1.0 ONHD), the next measuring at 1.25 optic nerve head diameters (ONHD), at 1.5 ONHD and at 1.75 ONHD. The aligned images were analyzed using GDx/NFA software.

Results:

Both methods showed peaks of RNFL thickness in the superior and inferior segments of the ONH. The maximum thickness, registered by the SLT device was at the ONH rim where the SLP device tended to measure the lowest values. SLT measurements at the ONH were influenced by other tissues besides the RNFL like blood vessels and glial tissues. SLT and SLP were most strongly correlated at distances of 1.25 and 1.5 ONHD.

Conclusions:

While both imaging technologies are valuable tools in detecting glaucoma, measurements at the ONH rim should be interpreted critically since both methods might provide misleading results. For the assessment of the retinal nerve fiber layer we would like to recommend for both imaging technologies, SLT and SLP, measurements in 1.25 and 1.5 ONHD distance of the rim of the optic nerve head.

Keywords: Glaucoma, normal tension glaucoma, retinal nerve fiber layer, scanning laser topography, scanning laser polarimetry, same OD diameter distances.