What are characteristic glaucomatous visual field defects?

Characteristic Glaucomatous Visual Field Defects

Glaucomatous visual field defects follow specific patterns including arcuate scotomas, nasal steps, paracentral scotomas, and generalized depression, with defects respecting the horizontal midline and corresponding to retinal nerve fiber layer damage. 1

Primary Patterns of Visual Field Loss

The four major characteristic patterns of glaucomatous visual field defects are: 2

• Arcuate scotoma: The most common pattern, following the arcuate nerve fiber bundle distribution, typically extending from the blind spot in an arc-shaped pattern toward the nasal horizontal meridian 2
• Nasal step: A step-like defect along the horizontal midline, representing differential damage between superior and inferior nerve fiber bundles 2
• Paracentral scotoma: Isolated defects in clusters of test sites near fixation, often appearing early in the disease 1
• Generalized depression: Diffuse reduction in sensitivity across the visual field, typically seen in more advanced disease 2

Key Diagnostic Features

Visual field defects in glaucoma demonstrate several distinguishing characteristics:

• Horizontal midline respect: Visual field loss across the horizontal midline in one hemifield exceeds loss in the opposite hemifield, particularly in early to moderate cases 1
• Correspondence with structural damage: Visual field defects must be consistent with retinal nerve fiber layer (RNFL) damage patterns 1
• Reliability and reproducibility: New glaucomatous defects require confirmation on repeat testing before establishing progression 1

Central Visual Field Involvement

Central visual field defects occur more frequently in early glaucoma than previously recognized, warranting specific attention:

• In early glaucoma, 28% of defects involve the central 5 degrees of fixation, increasing to 59% in moderate and 88% in severe disease 3
• The 10-2 visual field test detects central defects in 16% of eyes with normal 24-2 testing, suggesting standard 24-2 testing may miss early macular damage 4
• Both hemifields are commonly affected even in early disease (49% of early cases), contrary to the traditional teaching of unilateral hemifield involvement 3
• Automated 10-2 central visual field testing can discern central defects missed by wider field perimetry 1

Progression Patterns

As glaucoma severity increases, visual field defects demonstrate predictable evolution:

• Connection to blind spot: Only 27% of early defects connect to the physiological blind spot, but this increases to 64% in moderate and 95% in severe disease 3
• Bilateral hemifield involvement: Increases from 49% in early disease to 80% in both moderate and severe stages 3
• Superior field predominance: Superior visual field defects tend to be deeper and closer to fixation than inferior defects 4

Testing Strategy and Confirmation

The American Academy of Ophthalmology guidelines specify the following approach:

• Standard automated perimetry (SAP) with white-on-white stimuli remains the gold standard for visual field evaluation 1
• Testing strategies should be tailored using 24-degree, 30-degree, and 10-degree programs based on disease severity 1
• Goldmann visual fields (manual kinetic/static threshold testing) serve as an acceptable alternative when automated perimetry is unreliable or unavailable 1
• Confirmation testing is essential before changing treatment when new defects appear or results are unreliable 1

Alternative Testing Modalities

While SAP remains the standard, supplementary tests may detect earlier damage:

• Frequency doubling technology measures contrast sensitivity and demonstrates high sensitivity/specificity for detecting defects predictive of later SAP loss 1
• Short-wavelength automated perimetry (SWAP) isolates short-wavelength sensitive cells but has not demonstrated clear advantages over SAP in clinical trials 1
• These selective functional tests may help diagnose early visual loss in glaucoma suspects when SAP is normal 1

Critical Pitfalls to Avoid

• Do not rely solely on 24-2 or 30-2 testing in early glaucoma, as central 10-degree defects may be missed; consider adding 10-2 testing when macular involvement is suspected 1, 4
• Do not diagnose progression on a single abnormal test; always confirm with repeat testing using the same strategy 1
• Do not assume unilateral hemifield involvement in early disease, as bilateral involvement occurs in nearly half of early cases 3
• Exclude non-glaucomatous causes before attributing visual field defects to glaucoma, including optic disc drusen, optic nerve pits, and retinal or neurological pathology 1