primary%20open-angle%20glaucoma
PRIMARY OPEN-ANGLE GLAUCOMA
Primary open-angle glaucoma (POAG) is a chronic, progressive, 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.

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 may result in a falsely low intraocular pressure (IOP)
  • Ocular trauma (eg contusion)

Physical 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

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

Imaging

Biomicroscopy

  • Assess the anterior chamber depth and angle, look for corneal defects, iris pathology or inflammation using slit-lamp biomicroscope to help determine if there is presence of a secondary cause of intraocular pressure (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 and Retinal Nerve Fiber Layer

  • Changes in these structures often precede visual field loss in glaucoma patients
    • Look for changes such as optic disc hemorrhages, peripapillary choroidal atrophy
  • Performed using magnified stereoscopic visualization, digital photography and stereophotographic techniques with red-free illumination

Other Tests

  • Central corneal thickness (CCT) measurement (pachymetry) helps to determine level of risk for ocular damage
  • Visual field test (eg automated static threshold perimetry, short-wavelength automated perimetry or SWAP, frequency doubling technology or FDT)
  • Computer-based quantitative imaging of the optic nerve head and retinal nerve fiber layer 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 optic nerve head
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