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Florian Schwarzhans, Stephan Holzer, Hemma Resch, Georg Fischer, Michael Pircher, Christoph K Hitzenberger, Clemens Vass; Investigation of various parameters acquired by PS-OCT of healthy subjects, glaucoma suspects and glaucoma patients. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4065.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate Polarization-Sensitive (PS) parameters such as birefringence and retardation as well as the thickness of the retinal nerve fiber layer (RNFL) in healthy subjects (HS), glaucoma suspects (SUS) and early glaucoma patients (GLA).
All subjects underwent a complete ophthalmologic examination including Heidelberg retinal tomograph (HRT), Cirrus optical coherence tomography (OCT) and visual field (VF) test (Humphrey field analyzer). SUS were classified according to suspect appearance of the optic disk (OD) on clinical examination together with a VF test within normal limits. GLA subjects were diagnosed based on pathologic appearance of the OD together with an abnormal VF test with a mean deviation of >-6.0dB.Subjects were scanned with a prototype PS-OCT operating at 840nm with an A-Scan rate of 70kHz, and a field of view of 30°x30° (1024 A-Scans x 250B-Scans) centered at the OD.From the volume scan 3.45mm diameter circumpapillary B-Scans were derived and retinal layer segmentation was performed using a custom built software developed in MATLAB®. Retardation information was detected in the photoreceptor layer and birefringence was calculated by dividing retardation by RNFL-thickness.We used HRT data to group our subjects’ data sector-wise according to the Moorfields regression analysis of HRT. From the 6 sectors we chose the clinically most important sectors temporal superior (TS) and temporal inferior (TI) for detailed analysis.
18 HS, 49 SUS and 14 GLA subjects were successfully scanned. Globally the 3 groups showed the following mean values for RNFL thickness, retardation and birefringence (+/- standard deviation) respectively. HS: 97.3 (8.8), 14.4 (1.7), 0.15 (0.01); SUS: 82.3 (10.6), 12.2 (2.5), 0.15 (0.02); GLA: 71.0 (12.3), 10.4 (2.1), 0.15 (0.02). TS sector showed a trend in decreasing birefringence from 0.17 (HS) to 0.14 (SUS) to 0.12 (GLA) (fig 1). TI sector did not clearly show this trend.
Additional to the reduction of RNFL-thickness and retardation we observed also a reduction of birefringence in early glaucoma. This might support the hypothesis that early in the disease process of glaucoma the RNFL damage may start with disorganisation or loss of intracellular axonal structures (and corresponding loss of birefringence) prior to the actual loss of the axons themselves.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Comparison of the 3 groups considering HRT
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