Detection of Retinal Glial Cell Activation in Glaucoma by Time Domain Optical Coherence Tomography

Abstract

Background: Activated retinal astrocytes and Müller cells (ARAM) have been found in glaucoma patients. This study investigated whether presumed ARAM can be detected by optical coherence tomography (OCT), and assessed their relationship to the retinal nerve fiber layer (RNFL) thickness.

Patients and Methods: Single-center observational study involving 35 age-matched healthy controls and 19 patients with primary open-angle glaucoma (POAG) between 45 − 82 years of age. Presumed ARAM was defined as patchy, discrete glittering but transparent changes of the macula. The retina was documented by red-free photography to assess distribution of ARAM, and compared to the RNFL thickness measured around the fovea by OCT. A linear mixed effects model was used to detect a difference between eyes with ARAM versus eyes without ARAM.

Results: ARAM was not found in healthy subjects. The mean RNFL around the fovea was not significantly thicker in healthy controls (34.01 SD ± 22.24) than in POAG patients with ARAM (30.86 microns SD ± 15.09; p = 0.36) or without ARAM (33.19 microns SD ± 19.87; p = 0.46). Furthermore, the median RNFL thickness was similar to the control group (29 microns) but slightly thinner in POAG patients (each 27 microns with ARAM and without ARAM). In a subgroup analysis of POAG patients with ARAM, the within subject standard deviation of RNFL was significantly lower in areas with ARAM (SD 10.12) than in areas without ARAM (SD 17.30) (p < 0.001).

Conclusions: Although the mean and median RNFL thickness was comparable between the groups, the variability of the RNFL thickness was significantly lower in areas with ARAM than in areas without ARAM suggesting that ARAM may mask RNFL loss in POAG patients.

Zusammenfassung

Hintergrund: Aktivierte retinale Astrozyten und Müller-Zellen (ARAM) wurden bei Glaukompatienten beschrieben. Diese Studie ermittelte, ob ARAM mittels optischer Kohärenztomografie (OCT) erkannt werden können, und untersucht ihr Verhältnis zur retinalen Nervenfaserschicht(RNFS)-Dicke.

Patienten und Methoden: In dieser monozentrischen Beobachtungsstudie wurden 35 gesunde Probanden und 19 Patienten mit primärem Offenwinkelglaukom (POWG) im Alter zwischen 45 – 82 Jahren eingeschlossen. ARAM wurde als fleckige, diskret glänzende, aber transparente Veränderungen der Makula definiert. Die Netzhaut wurde fotografisch dokumentiert, um die Verteilung von ARAM zu untersuchen, und diese mit der RNFS-Dicke um die Fovea, im OCT gemessen, zu vergleichen. Ein lineares, gemischtes Modell wurde zur Erfassung von Unterschieden bei Augen mit und ohne ARAM eingesetzt.

Ergebnisse: ARAM wurde bei gesunden Probanden nicht gefunden. Die mittlere RNFS um die Fovea war nicht signifikant dicker bei gesunden Probanden (34,01 SD ± 22,24) als bei POWG-Patienten mit ARAM (30,86 Mikron SD ± 15,09; p = 0,36) oder ohne ARAM (33,19 Mikron SD ± 19,87; p = 0,46). Zudem war die mediane RNFS vergleichbar dick bei gesunden Probanden (29 Mikron) wie bei POWG-Patienten (je 27 Mikron mit ARAM und ohne ARAM). POWG-Patienten mit ARAM zeigten eine geringere Dickeschwankung an ortsspezifischen Arealen mit ARAM (SD 10,12) als an solchen ohne ARAM (SD 17,30) in einer Untergruppen-Auswertung (p < 0,001).

Schlussfolgerungen: Obwohl die mittlere und mediane RNFS-Dicke zwischen gesunden Probanden und POWG-Patienten vergleichbar waren, zeigte sich eine signifikant geringere Schwankung der RNFS-Dicke in Arealen mit ARAM als an solchen ohne ARAM, welche einen Verlust von RNFS bei POWG-Patienten verbergen könnte.

Key words

astrocytes - glaucoma - glial cells - intraretinal gliosis - Müller cells - retinal nerve fiber layer (RNFL) thickness - optical coherence tomography

Schlüsselwörter

Astrozyten - Glaukom - Gliazellenglial cells - intraretinale Gliose - Müller-Zellen - retinale Nervenfaserschicht(RNFS)-Dicke - optische Kohärenztomografie (OCT)

¹ The first two authors have equally contributed to the study.

Publication History

Received: 15 September 2011

Accepted: 02 October 2011

Publication Date:
11 April 2012 (online)

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