Primary%20open-angle%20glaucoma Diagnosis

• 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

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

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

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