Normal Tension Glaucoma: Who Needs Neuroimaging?

Normal Tension Glaucoma: Who Needs Neuroimaging?

• Julie Falardeau, MD, FRCSC
• Casey Eye Institute
• Devers Eye Institute
• Portland, Oregon

Background

• Normal tension glaucoma (NTG) is characterized by:
• Cupping of the optic nerve head
• Visual field loss
• Intraocular pressure (IOP)  21 mmHg
• No obvious or apparent cause for these changes

Nonglaucomatous optic disc cupping

• Following an ischemic optic neuropathy (anterior or posterior - AION or PION)
• Temporal arteritis
• Quigley and Anderson found that 50% of patient with arteritic -AION developed cupping, compared to 10% after non-arteritic-AION
• Severe hypotensive/hypovolemic event
• Demyelinating optic neuritis

• Quigley et Anderson. Cupping of the optic disc in ischemic optic neuropathy. Trans Am Acad Ophthalmol Otol. 1977;83:755-762

Nonglaucomatous optic disc cupping

• Hereditary optic neuropathy
• Leber’s hereditary optic neuropathy
• Autosomal dominant optic atrophy
• Temporal disc excavation and pallor
• Traumatic optic neuropathy
• Infectious
• Syphilis
• Toxic
• Methanol

Nonglaucomatous optic disc cupping

• Compressive lesion
• Meningioma
• Aneurysm
• Dolichoectasia of the internal carotid artery
• Suprasellar mass

Glaucomatous VS Nonglaucomatous cupping

• Distinguishing glaucomatous from non-glaucomatous disc cupping is often difficult
• A detailed history is crucial
• Presence of neurological symptoms
• Chronicity and pattern of visual loss
• History of head trauma
• History of shock or severe low blood pressure

Glaucomatous VS Nonglaucomatous cupping

• Systematic approach recommended
• Demographic characteristics
• Visual acuity
• Optic disc characteristics
• Visual field findings

Demographic characteristics

• A family history of glaucoma among first degree relatives is highly specific (96%) for glaucomatous cupping
• Age under 50 years is 93% specific for nonglaucomatous cupping

• Greenfield et al. The cupped disc: Who needs neuroimaging? Ophthalmology. 1998;105:1866-1874

Visual Acuity

• Patients with nonglaucomatous cupping have significantly lower levels of visual acuity than patients with glaucoma
• Trobe et al found all 20 patients with compressive optic neuropathy had loss of central vision
• Greenfield et al found visual acuity < 20/40 to be 77% specific for nonglaucomatous cupping
• Hupp et al described sparing of central acuity in 3 of 6 eyes with compressive lesions

Optic disc characteristics

• Glaucomatous cupping:
• Vertical elongation
• Cupping more than pallor
• Greater frequency of peripapillary atrophy
• Disc hemorrhage
• Highly specific
• Nonglaucomatous cupping:
• Pallor of the neuroretinal rim
• Highly specific sign but relatively insensitive
• The absence of disc pallor does not exclude compressive lesions

Optic nerve appearance

• Baring of the circumlinear vessels and temporal saucerization
• Common in glaucoma
• Can also be seen in compressive optic neuropathy

• Kupersmith and Krohn. Cupping of the optic disc with compressive lesions of the anterior visual pathway. Ann Ophthalmol 1984;16:948-53

Visual field findings

• Glaucoma
• Nerve-fiber-layer (arcuate) defects, bordering horizontal midline
• Arcuate scotoma
• Nasal step
• Compressive lesion
• Central scotoma
• Temporal hemianopia
• Incongruous hemianopia respecting the vertical meridian
• Glaucomatous types of VF defects can occur

Humphrey perimetry in patients with suprasellar mass

• Ahmed et al. Neuroradiologic screening in normal-pressure glaucoma:
• study results and literature review. J Glaucoma. 2002 Aug;11(4):279-86

NTG and Neuroimaging

• Some physicians routinely obtain neuroimaging studies in patients with NTG
• Cost-to-benefit ratio of performing such studies is unknown

NTG and Neuroimaging

• Ahmed et al found that routine neuroimaging of NTG patients was cost-effective
• 6.5% of 62 consecutive patients with NTG had clinically significant intracranial lesions associated with optic neuropathy and visual field loss typical of glaucoma

• Ahmed et al. Neuroradiologic screening in normal-pressure glaucoma: study results and literature review. J Glaucoma. 2002 Aug;11(4):279-86

NTG and Neuroimaging

• Steward and Reid reported compressive lesions in 2 of 53 patients (3.8%) referred for evaluation of NTG
• In the series by Greenfield et al, none of the patients diagnosed with glaucoma had neuroradiological evidence of compressive lesion

NTG and Neuroimaging

• In Bianchi-Marzoli at al’s series of 29 patients with cupping from unilateral compressive lesion, only one had cupping and field loss as an isolated manifestation of their optic neuropathy
• All others had:
• Reduced acuity
• Decreased color vision
• RAPD

• Bianchi-Marzoli et al. Quantitative analysis of optic disc cupping in compressive optic neuropathy. Ophthalmology 1995;102:436-440.

NTG: Who needs neuroimaging?

• Presence of headache or other neurological symptoms
• Symptoms of decreased vision, fluctuating vision, or visual field loss
• Atypical visual field for glaucoma
• Visual field defect respecting the vertical meridian
• Junctional scotoma
• Central or cecocentral scotoma

NTG: Who needs neuroimaging?

• Atypical rate of progression of VF loss
• Monocular or binocular
• Pallor > cupping
• Asymmetric cupping
• Especially if progressive changes while IOP remains symmetric and well controlled

NTG: Who needs neuroimaging?

• Most likely NTG if:
• Vertical elongation of the cupping
• Presence of notch
• Presence of splinter hemorrhage
• Family history of glaucoma