Enhanced Depth Imaging of Central Laminar Thickness in Optic Neuropathy: Comparison with Normal Eyes

Abstract

The purpose of this study was to compare central laminar thickness (LT) among patients with glaucomatous optic neuropathy (GON), patients with non-GON, and normal subjects using enhanced-depth imaging optical coherence tomography (EDI-OCT). Enrolled were 57 patients (n = 64 eyes), including 30 women and 27 men. Three groups were identified: GON (n = 18 eyes), non-GON (n = 16 eyes), and control (n = 30 eyes). The GON group comprised eyes with primary open-angle glaucoma (POAG) (n = 9) and normal-tension glaucoma (NTG) (n = 9). The non-GON group comprised eyes with demyelinating optic neuritis (n = 9), anterior ischemic optic neuropathy (AION) (n = 2), compressive ON (n = 2), Leber hereditary ON (n = 2), and traumatic ON (n = 1). GON and non-GON groups were further divided into mild, moderate, and severe subgroups. Inclusion in the GON group was based on mean deviations (MDs) of visual fields; inclusion in the non-GON group was based on critical flicker frequency (CFF) responses. Intraclass correlation coefficients (ICCs) were used to verify reproducibility of measurements. LTs of GON and non-GON group eyes were thinner than those of control group eyes (p50.01); LTs of GON group eyes were thinner than those of non-GON group eyes (p = 0.01). LTs of severe GON subgroup eyes were thinner than those of moderate and mild GON subgroup eyes (p50.001; p = 0.024, respectively). LTs of severe non-GON subgroup eyes were thinner than those of mild non-GON subgroup eyes (p = 0.002). These results show that EDI-OCT is valuable for documenting structural abnormalities in optic neuropathy (ON).

Differentiating ischemic optic neuropathy from glaucoma using diagnostic tests

“…Thinning of the RNFL is observed in both glaucomatous and chronic AION eyes when compared to healthy control eyes [11, 13, 19, 20, 32‒34]. In early/preperimetric glaucoma, the RNFL thinning is observed in the superotemporal and inferotemporal region while moderate glaucoma also involved the temporal RNFL.…”

“…In both POAG and NAION eyes, two forces that result in sclera and BMO expansion are proposed: one pushing the LC backward and compressing the PT, and another one related to the hoop stress (inner circumferential pressure supported by the peripapillary sclera) [21]. Mechanical stress thus plays an important role in the pathogenesis, but both diseases remain multifactorial [16,34,37]. Other factors include interindividual variability (e.g., the geometry of the eyeball), vascular factors, an abnormally low cerebrospinal fluid pressure in NTG eyes resulting in higher translaminar pressure gradient which could induce posterior LC displacement, a hypercompliant LC in NTG compared to NAION, inflammation, infiltration, toxicity, heredity factors, and a possibly innate deeper LC in NTG eyes compared to healthy and NAION eyes [16,34,37].…”

“…In NAION eyes, most studies found a comparable [16,33,37] or even a shallower [21] LCD compared to healthy controls. The central LC thickness of glaucomatous eyes and AION eyes both show greater thinning compared to the control group, whereby the lowest values could be found in the glaucoma group [33,34]. The LC curvature index (LCCI) is another parameter to analyze the LC morphology and, similarly to the LCD, was significantly greater in the glaucomatous group than in NAION and healthy control eyes [37].…”

Optic Nerve Head Changes in Patients with Optic Neuritis Secondary to Multiple Sclerosis: A Comparison of The Affected and Fellow Healthy Eyes

“…It was reported that the laminar thickness was thinner in glaucomatous eyes than in the controls due to increased intraocular pressure 13 . Also, it was recently suggested that as compared to the eyes of healthy controls, LC thicknesses were lower in the eyes with non-glaucomatous optic neuropathy 17 . Increased intraocular pressure is thought to disrupt LC hemodynamics due to its mechanical effect on microcirculation in LC 14 , 15 , 21 , 22 .…”

“…Besides ocular diseases such as glaucoma, LC has also been investigated in the central nervous system diseases affecting the optic nerve such as Parkinson's disease and MS. It was shown that this important structure which is related with retinal nerve fibers is also affected in patients with these disorders [15][16][17] .…”