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  • Morphologic Differences Between NAION and NTG Eyes

    By Lynda Seminara
    Selected By: Prem S. Subramanian, MD, PhD
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    Journal Highlights

    Investigative Ophthalmology & Visual Science
    2020;61(8):21

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    Nonarteritic anterior ischemic optic neuropathy (NAION) can often mimic normal tension glaucoma (NTG) in terms of retinal nerve fiber defects and damage to the visual field (VF). Howev­er, morphologic changes in the lamina cribrosa (LC) of the optic nerve head result from glaucomatous damage and may help to distinguish the two con­ditions. In a study of Korean patients, Kim et al. compared the LC of eyes with NAION to that of eyes with untreated NTG and found that LC depth (LCD) and curvature index (LCCI) were much greater in the NTG eyes.

    The study included 48 NAION eyes, 48 NTG eyes, and 48 healthy eyes matched for age, intraocular pressure, axial length, and optic disc area. NAION eyes had undergone sudden painless loss of visual acuity but had no evidence of glaucoma or other retinal diseases. NTG eyes had glaucomatous optic nerve damage along with visual field loss. Control eyes had no history of ocular symptoms or surgical inter­vention other than simple cataract removal. The LCD and LCCI of each eye were scanned across seven hori­zontal planes of the LC using optical coherence tomography. These values were averaged and then compared for the three groups of eyes.

    Findings of the analyses showed that average LC values were greater for NTG eyes than for NAION or healthy eyes (p < .001), even though intraocular pressure, axial length, retinal nerve fiber layer thickness, and visual field index were similar for the three groups. No meaningful difference was detected be­tween NAION and control eyes. LCCI findings were more pronounced in the areas affected by NTG (p = .010 vs. un­affected areas) yet were consistent in all regions of NAION eyes. LCD did not differ between affected and unaffected areas of NTG or NAION eyes.

    According to the authors, these findings offer further evidence of the pathophysiologic differences between NAION and NTG. They noted that the LCCI parameter seems more useful than LCD for evaluating affected and unaffected areas of NTG eyes, and therefore may be the more valuable biomarker for glaucoma diagnosis.

    The original article can be found here.