What is the appropriate management for a patient with bilateral outer visual field loss?

Management of Bilateral Outer Visual Field Loss

A patient presenting with bilateral outer (peripheral) visual field loss requires urgent evaluation for glaucoma, with immediate measurement of intraocular pressure, gonioscopy, optic nerve assessment, and formal automated perimetry to establish diagnosis and prevent irreversible vision loss. 1

Initial Diagnostic Evaluation

Essential Testing Components

• Intraocular pressure (IOP) measurement using Goldmann applanation tonometry to identify elevated pressure as a primary risk factor for glaucomatous damage 1

• Gonioscopy to confirm open anterior chamber angles and rule out secondary causes of glaucoma 1

• Optic nerve head (ONH) examination looking specifically for:

  • Diffuse or focal narrowing/notching of the optic disc rim, especially at inferior or superior poles 1
  • Progressive narrowing of neuroretinal rim with increased cupping 1
  • Disc hemorrhages, which indicate active glaucomatous damage 1
  • Asymmetry between the two eyes consistent with neural tissue loss 1
  • Parapapillary atrophy 1

• Central corneal thickness (CCT) measurement as thin CCT is an independent risk factor for developing and progressing primary open-angle glaucoma 1

Visual Field Testing Strategy

Automated static threshold perimetry (SAP) with white-on-white stimuli is the gold standard for documenting peripheral visual field loss. 1

• Begin with 24-2 or 30-2 testing strategies to evaluate the central 24-30 degrees of vision 1
• Add 10-2 central testing if there is concern for macular involvement, as the 24-2 test samples the central 10 degrees at only four locations and can miss significant central damage 1, 2
• Repeat unreliable or new defect findings before changing treatment, as confirmation is essential 1
• Use the same testing strategy for all follow-up examinations to accurately track progression 1

Imaging Documentation

Obtain baseline optic nerve imaging to complement visual field testing and enable detection of structural progression. 1

• Stereoscopic optic disc photographs provide complementary information to computerized imaging 1
• Optical coherence tomography (OCT) of the retinal nerve fiber layer (RNFL) and macular ganglion cell layer detects structural damage that may precede or confirm visual field loss 2

Differential Diagnosis Considerations

While bilateral peripheral visual field loss is highly suggestive of glaucoma, consider:

• Primary open-angle glaucoma (POAG) - most common cause, may occur with or without elevated IOP (nearly 40% of POAG patients have normal IOP measurements) 1
• Neurological causes - bilateral homonymous hemianopsias from posterior cerebral pathology, though these typically respect the vertical midline 3
• Retinal disease - advanced retinitis pigmentosa or other peripheral retinal degenerations 3

Risk Stratification for Treatment Decision

Not all patients with peripheral visual field loss require immediate treatment, but those with high-risk features should be started on IOP-lowering therapy. 1

High-Risk Features Warranting Treatment:

• IOP ≥26 mmHg with CCT ≤555 μm (36% risk of progression) 1
• Confirmed progressive optic nerve or visual field deterioration on repeat testing 1
• Additional risk factors: older age, family history of glaucoma, African-derived race or Latino/Hispanic ethnicity, disc hemorrhage, large cup-to-disc ratio, diabetes, myopia 1

Lower-Risk Features Allowing Observation:

• IOP <24 mmHg with CCT >588 μm (2% risk of progression) 1
• Stable optic nerve appearance on serial examinations 1
• No additional risk factors 1

Treatment Approach When Indicated

The initial treatment goal is to reduce IOP by 20-30% below baseline, with adjustments based on disease severity and progression. 1

• Medical therapy with topical IOP-lowering medications as first-line treatment 1
• Laser trabeculoplasty can be considered as primary therapy 1
• Target pressure should be individualized based on severity of damage, rate of progression, life expectancy, and risk factors 1

Follow-Up Strategy

Long-term monitoring is essential regardless of whether treatment is initiated, as glaucoma is a chronic progressive disease. 1

• More frequent testing initially (every 3-6 months) to establish baseline and identify rapid progressors 4
• Less frequent testing (annually) once stability is established 4, 5
• Approximately 28% of treated glaucoma patients will show progression over 6 years of follow-up 5

Critical Pitfalls to Avoid

• Do not rely solely on 24-2 visual fields - up to 52.5% of eyes with confirmed macular damage on both 10-2 testing and OCT are missed by 24-2 testing alone 2
• Do not assume normal IOP excludes glaucoma - nearly 40% of POAG patients have normal IOP measurements 1
• Do not make treatment changes based on a single visual field - always confirm new defects with repeat testing before escalating therapy 1
• Do not use CCT correction factors for individual IOP measurements - while thin CCT is a risk factor, there is no generally accepted correction formula 1