primary%20open-angle%20glaucoma
PRIMARY OPEN-ANGLE GLAUCOMA
Treatment Guideline Chart
Primary open-angle glaucoma (POAG) is a chronic, progressive, irreversible, usually bilateral disease of the eye with an insidious onset.
It is most often characterized by optic nerve damage, defects in the retinal fiber layer and subsequent visual field loss in the absence of underlying ocular disease or congenital abnormalities.
It is generally asymptomatic until it has caused a significant loss of visual field.
Occasionally, patients with very high intraocular pressure may complain of nonspecific headache, discomfort, intermittent blurring of vision or even halos caused by corneal edema.

Primary%20open-angle%20glaucoma Diagnosis

History

  • Review of history of family, ocular and systemic diseases (eg DM, hypertension, asthma, vascular disorders) are obtained during initial evaluation
  • Current medications (ocular and systemic) being taken and history of adverse reactions to these drugs
  • History of eye surgery
    • Cataract surgery, photorefractive keratectomy, laser-assisted in situ keratomileusis (LASIK), and small-incision lenticule extraction (SMILE) may result in a falsely low IOP due to corneal thinning
  • Ocular trauma (eg contusion)
  • Using questionnaires such as the National Eye Institute - Visual Function Questionnaire-25 (NEI-VFQ-25) and Glau QoL to assess functional status or visual problems

Ophthalmic Examination

Visual Acuity

  • Measure and determine best corrected near and distance visual acuity

Examination of Pupils

  • Examine for reactivity and presence of afferent pupillary defect

Confrontation Visual Field

  • Evaluate visual fields in addition to automated visual field test

Examination of the Fundus

  • Look for cupping, macular degeneration, disc edema, retinovascular occlusion, optic nerve pallor and pits
    • Cupping is the hallowing out of the optic nerve or “disc” and a diameter of >50% of the vertical disc signifies glaucoma

Diagnostic Tests

Biomicroscopy

  • Assess the anterior chamber depth and angle, and look for corneal defects, iris pathology or inflammation using slit-lamp biomicroscope to help determine if there is presence of a secondary cause of IOP elevation

Tonometry

  • Bilateral measurement of IOP using Goldmann applanation tonometry done at varying times of the day or on different days to detect fluctuations
  • It is recommended to measure untreated IOP more than once prior to starting treatment

Gonioscopy

  • Important to exclude secondary causes of IOP (eg peripheral anterior synechiae, angle neovascularization, angle recession, etc) or exclude diagnosis of angle-closure glaucoma

Examination of Optic Nerve Head (ONH) and Retinal Nerve Fiber Layer (RNFL)

  • Changes in these structures often precede visual field loss in glaucoma patients
    • Look for changes such as optic disc hemorrhages, peripapillary choroidal atrophy, optic nerve cup enlargement, narrowing of the neuroretinal rim or thinning of RNFL
  • Performed using magnified stereoscopic visualization, digital photography and stereophotographic techniques with red-free illumination

Other Diagnostic Tests

  • Central corneal thickness (CCT) measurement (pachymetry) helps to determine level of risk for ocular damage
  • Visual field test [eg standard automated perimetry (SAP) or automated static threshold perimetry, short-wavelength automated perimetry (SWAP), frequency doubling technology (FDT)]
  • Computer-based quantitative imaging of the ONH and RNFL using one of the following modalities: Optical Coherence Tomography (OCT), confocal scanning laser ophthalmoscopy [CLSO: Heidelberg Retinal Tomogram (HRT)] and scanning laser polarimetry
    • For early detection of nerve fiber layer thinning, facilitating earlier diagnosis and detection of optic nerve damage
    • Serves as an adjunct to the clinical examination of the ONH

Diagnosis

Clinical Characteristic Diagnostic of POAG 

  • Evidence of optic nerve damage from either or both of the following:
    • Optic disc or RNFL structural abnormalities
      • Diffuse or focal narrowing of the optic disc rim
      • Progressive narrowing of the neuroretinal rim with increase in cupping of the optic disc
      • Diffuse or localized thinning of the parapapillary RNFL
      • Optic disc hemorrhages involving the disc rim, parapapillary RNFL or lamina cribrosa
      • Optic disc neural rim asymmetry of the 2 eyes consistent with loss of neural tissue
      • Beta-zone parapapillary atrophy
      • Thinning of RNFL and/or macula on imaging
    • Reproducible visual field abnormality
      • Visual field damage consistent with RNFL damage
      • Visual field loss across the horizontal midline in 1 hemifield that exceeds loss in opposite hemifield
      • Absence of other known explanation
  • Adult onset
  • Open anterior chamber angles
  • Absence of other known explanations for progressive glaucomatous optic nerve damage (eg uveitis, trauma, pigment dispersion syndrome, pseudoexfoliation syndrome)

Categories of POAG Based on Severity

  • Mild
    • Definite optic disc, RNFL or macular imaging abnormalities consistent with glaucoma and normal visual field as tested with SAP
  • Moderate
    • Definite optic disc, RNFL or macular imaging abnormalities consistent with glaucoma and visual field abnormalities in 1 hemifield that are not within 5 degrees of fixation
  • Severe
    • Definite optic disc, RNFL or macular imaging abnormalities consistent with glaucoma and visual field abnormalities in both hemifield and/or loss within 5 degrees of fixation in at least 1 hemifield as tested with SAP
  • Indeterminate
    • Definite optic disc, RNFL or macular imaging abnormalities consistent with glaucoma, inability of patient to perform visual field testing, uninterpretable/unreliable visual field test results
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