June 2022
Volume 63, Issue 7
Open Access
ARVO Annual Meeting Abstract  |   June 2022
Birefringence of the retinal nerve fiber layer is reduced in early glaucoma eyes analyzed by polarization-sensitive OCT
Author Affiliations & Notes
  • Stefan Steiner
    Medizinische Universitat Wien, Wien, Wien, Austria
  • Florian Schwarzhans
    Medizinische Universitat Wien, Wien, Wien, Austria
  • Sylvia Desissaire
    Medizinische Universitat Wien, Wien, Wien, Austria
  • Hemma Resch
    Medizinische Universitat Wien, Wien, Wien, Austria
  • Georg Fischer
    Medizinische Universitat Wien, Wien, Wien, Austria
  • Michael Pircher
    Medizinische Universitat Wien, Wien, Wien, Austria
  • Christoph K Hitzenberger
    Medizinische Universitat Wien, Wien, Wien, Austria
  • Clemens Vass
    Medizinische Universitat Wien, Wien, Wien, Austria
  • Footnotes
    Commercial Relationships   Stefan Steiner None; Florian Schwarzhans None; Sylvia Desissaire None; Hemma Resch None; Georg Fischer None; Michael Pircher None; Christoph Hitzenberger None; Clemens Vass None
  • Footnotes
    Support  none
Investigative Ophthalmology & Visual Science June 2022, Vol.63, 4259. doi:
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      Stefan Steiner, Florian Schwarzhans, Sylvia Desissaire, Hemma Resch, Georg Fischer, Michael Pircher, Christoph K Hitzenberger, Clemens Vass; Birefringence of the retinal nerve fiber layer is reduced in early glaucoma eyes analyzed by polarization-sensitive OCT. Invest. Ophthalmol. Vis. Sci. 2022;63(7):4259.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : To study the circumpapillary birefringence (BIR) of the retinal nerve fiber layer (NFL) in healthy and early glaucoma eyes using polarization-sensitive optical coherence tomography (PS-OCT). The NFL is birefringent, which is caused by intracellular parallel microtubules within the NFL. The number of these microtubules is thought to be reduced as an early sign of glaucoma damage.

Methods : This is a prospective cross-sectional study where we compared circular PS-OCT B-scans in 49 early glaucoma (age: 64 ± 10 years) vs. 49 age-matched healthy eyes (age: 61 ± 9 years). The circular scans (diameter: 3.5 mm) were extracted from volume scans and centered on the optic disc (OD). The BIR value at each virtual A-scan position was the quotient of the retardation (RET) measured at the IS/OS junction divided by the NFL-thickness (NFLT). Early glaucoma was defined by glaucomatous appearance of the OD and repeated pathologic visual field tests with a mean deviation (MD) better than -6 dB. Main outcome parameters were BIR, NFLT, and RET.

Results : Glaucoma eyes showed statistically significantly reduced NFLT (69±13 µm vs. 99±12 µm, p<0.001), RET (6.5 ±1.6° vs. 10.5 ±1.9°, p<0.001) and BIR (0.108 ±0.008°/µm vs. 0.112 ±0.009°/µm, p=0.0033) compared to healthy eyes. Figure 1 shows plots in temporal (T), superior (S), nasal (N), inferior (I) order for NFLT (A), RET (B) and BIR (C). Surprisingly the BIR showed no double-hump pattern as usually observed for NFLT and RET, instead it appeared to have a single dip at the temporal region. This was confirmed in averaged maps shown in Figure 2, whereas: column A-D-G= healthy eyes, B-E-H= glaucoma eyes with superior visual field (VF) impairment (n=27), C-F-I= glaucoma eyes with inferior VF impairment (n=19) and row A-B-C= NFLT, D-E-F= RET, G-H-I=BIR. Glaucoma eyes with both visual field hemispheres affected (n=3) were excluded from the averaged maps.

Conclusions : We report a reduced BIR of the NFL in early perimetric glaucoma, which may be interpreted as a sign of a loss of intracellular microtubules and might contribute to a better understanding of early glaucoma development. Early reduction of BIR in glaucoma models has been shown before in non-human primates. Nevertheless, to establish whether BIR is altered in preperimetric human glaucoma prior to the reduction of NFLT, prospective longitudinal studies are needed.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

 

 

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