Crowded optic nerve head evaluation with optical coherence tomography in anterior ischemic optic neuropathy

Abstract

PurposeTo characterize the optic nerve head (ONH) structure in patients with non-arteritic anterior ischemic optic neuropathy (NAION) compared to healthy control subjects using spectral domain optical coherence tomography (SD-OCT) via the enhanced depth imaging method.MethodsIn this prospective, cross-sectional, comparative study, we assessed 66 eyes of 33 patients with unilateral NAION and 31 eyes of 31 healthy normal subjects in an academic institution. The peripapillary nerve fiber layer thickness, disc area, and quantitative parameters of the ONH structures, including the Bruch's membrane opening (BMO) area, anterior laminar depth, and prelaminar thickness and depth were compared between the three groups.ResultsLinear mixed model analysis after adjusting for age, sex, and axial length showed that the BMO area was similar in eyes with NAION (1.89±0.33 mm2), their fellow eyes (1.85±0.35 mm2), and control eyes (1.88±0.37 mm2; all P>0.99). Anterior laminar depth was also similar in the three groups. The mean prelaminar tissue thickness of the NAION eyes was 445±176 μm, which was thinner than the prelaminar tissue of their unaffected fellow eyes (mean, 539±227 μm, P=0.004), but both were thicker than the prelaminar tissue of the normal subjects (mean 243±145 μm, P=0.001 and P<0.001, respectively).ConclusionsThe thick prelaminar thickness is associated with unilateral NAION in the affected and unaffected eyes.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1

Optic nerve head parameters. Top: original OCT image. Bottom: Schematic illustration of measurements: internal limiting membrane (ILM), Bruch’s membrane (BM), connection line between two BM terminations (Bruch's membrane opening (BMO); dash red line), lamina cribrosa (LC); anterior laminar depth (ALD); prelaminar depth (PLD); Prelaminar tissue thickness (PLT; yellow line). A full colour version of this figure is available at the Eye journal online.

Figure 2

Upper row: (left) An infrared image of the normal optic nerve used to measure Bruch's membrane opening (BMO) area. Several BMO lines were marked on all optic nerve head raster scans (right). These lines on B-scan were projected onto en face infrared images. Ends of lines connected and BMO area was measured. In this case BMO area is 1.55 mm2. A raster line across the center of optic nerve shows BMO distance (Right; red line), anterior laminar depth (red arrow), and anterior and posterior borders of lamina cribrosa (yellow arrows). Red numbers shows central BMO distances. Middle row: (left) the BMO area is 1.72 mm2 in an optic nerve with a history of non-arteritic anterior ischemic optic neuropathy (NAION) 5 months ago. Prelaminar tissue is thicker than normal eyes (Right). Lower row: The BMO area is 1.80 mm2 in an unaffected optic nerve head of the same patient with NAION with thick prelaminar tissue.