Measurement of retinal nerve fiber layer thickness in eyes with optic disc swelling by using scanning laser polarimetry and optical coherence tomography

Abstract

Background: The retinal nerve fiber layer thickness (RNFLT) in patients with optic disc swelling of different etiologies was compared using scanning laser polarimetry (SLP) and spectral-domain optical coherence tomography (OCT).

Methods: Forty-seven patients with optic disc swelling participated in the cross-sectional study. Both GDx SLP (enhanced corneal compensation) and Spectralis spectral-domain OCT measurements of RNFLT were made in 19 eyes with papilledema (PE), ten eyes with optic neuritis (ON), and 18 eyes with nonarteritic anterior ischemic optic neuropathy (NAION) at the neuro-ophthalmology clinic at Kyoto University Hospital. Differences in SLP (SLP-RNFLT) and OCT (OCT-RNFLT) measurements among different etiologies were investigated.

Results: No statistical differences in average OCT-RNFLT among PE, ON, and NAION patients were noted. Average SLP-RNFLT in NAION patients was smaller than in PE (P<0.01) or ON (P=0.02) patients. When RNFLT in each retinal quadrant was compared, no difference among etiologies was noted on OCT, but on SLP, the superior quadrant was thinner in NAION than in PE (P<0.001) or ON (P=0.001) patients. Compared with age-adjusted normative data of SLP-RNFLT, average SLP-RNFLT in PE (P<0.01) and ON (P<0.01) patients was greater. Superior SLP-RNFLT in NAION patients was smaller (P=0.026). The ratio of average SLP-RNFLT to average OCT-RNFLT was smaller in NAION than in PE (P=0.001) patients.

Conclusion: In the setting of RNFL thickening, despite increased light retardance in PE and ON eyes, SLP revealed that NAION eyes have less retardance, possibly associated with ischemic axonal loss.

Keywords: optic disc swelling; optical coherence tomography; scanning laser polarimetry.

Figure 1

Scatter plot of average retinal nerve fiber layer thickness (RNFLT) measurements obtained by Spectralis SD-OCT and SLP with GDx ECC in eyes with papilledema (PE, ♦) and nonarteritic anterior ischemic optic neuropathy (NAION, □). Notes: The best-fit lines for eyes with PE (—) and eyes with NAION (—) are shown. Data for eyes with optic neuritis is not shown because the correlation between OCT and SLP measurements of RNFLT was not significant. Spectralis SD-OCT, Heidelberg Engineering Inc, Heidelberg, Germany; GDx ECC, Carl Zeiss Meditec AG, Jena, Germany. Abbreviations: OCT, optical coherence tomography; SD-OCT, spectral-domain optical coherence tomography; SLP, scanning laser polarimetry.

Figure 2

Representative case of optic neuritis. Notes: A fundus photograph (A) shows optic disc swelling in the left eye. Spectralis SD-OCT (B and C) and SLP with GDx ECC (D and E) reports demonstrate RNFL thickening. Goldmann perimetry (F) shows a central scotoma. Spectralis SD-OCT, Heidelberg Engineering Inc, Heidelberg, Germany; GDx ECC, Carl Zeiss Meditec AG, Jena, Germany. Abbreviations: I, inferior; N, nasal; RNFL, retinal nerve fiber layer thickness; S, superior; SD-OCT, spectral-domain optical coherence tomography; T, temporal; SLP, scanning laser polarimetry.

Figure 3

Representative case of nonarteritic anterior ischemic optic neuropathy. Notes: Fundus photograph (A) shows optic disc swelling with disc hemorrhage in the right eye. Spectralis SD-OCT images (B and C) show RNFL thickening in the superior quadrant, while SLP with GDx ECC imaging (D and E) shows slight RNFL thinning in the superior quadrant. Visual field testing (F) shows an inferior altitudinal field defect. Spectralis SD-OCT, Heidelberg Engineering Inc, Heidelberg, Germany; GDx ECC, Carl Zeiss Meditec AG, Jena, Germany. Abbreviations: I, inferior; N, nasal; RNFL, retinal nerve fiber layer; S, superior; SD-OCT, spectral-domain optical coherence tomography; T, temporal; SLP, scanning laser polarimetry.