Normal Tension Glaucoma: Who Needs Neuroimaging?



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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

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

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:


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