What conditions are associated with a relative scotoma organized like stars around the fixation point?

Conditions Associated with Star-Like Relative Scotomas Around Fixation Point

Stargardt disease is the most likely condition to present with relative scotomas organized like stars around the fixation point, specifically in the form of a dense ring scotoma pattern. 1, 2

Conditions Causing Star-Like Scotoma Patterns

Primary Causes:

• Stargardt Disease

  • Presents with bilateral central ring scotomas that appear star-like around fixation 1
  • Two common scotoma patterns in Stargardt disease 2:
    1. Dense ring scotoma (50% of cases) - appears as star-like pattern around fixation
    2. Dense central scotoma (50% of cases)
  • Visual acuity is significantly better in patients with ring scotoma compared to central scotoma 2

• Macular Dystrophies

  • Cone dystrophy can also present with ring scotomas around fixation 2
  • These conditions often show stable fixation points when the ring scotoma pattern is present 2

Secondary Causes:

• Age-Related Macular Degeneration (AMD)

  • Geographic atrophy can cause central scotomas with star-like patterns 3
  • 63% of AMD patients with geographic atrophy place the scotoma to the right of fixation, 22% place it above fixation 4

• Acute Idiopathic Blind Spot Enlargement Syndrome (AIBSES)

  • Can present with paracentral scotomas that may appear star-like 5
  • Often misdiagnosed as optic neuritis due to similar presentation 5

Diagnostic Approach

Recommended Testing:

1. Microperimetry

   • Gold standard for detecting scotomas and fixation patterns 6, 5
   • Allows accurate detection of both fixation and scotomas even with unstable fixation 6
   • Can differentiate between ring scotomas and central scotomas 2

2. OCT and OCT-A

   • Standard OCT to rule out macular pathology 5
   • OCT-A can detect perfusion loss that may correspond to scotomas 5

3. Amsler Grid Testing

   • Useful for periodic monitoring of central vision and scotoma changes 5
   • Patients can self-monitor changes in scotoma patterns

Differential Diagnosis:

• Multiple Evanescent White Dot Syndrome 5
• Acute Zonal Occult Outer Retinopathy 5
• Central Serous Chorioretinopathy 5
• Hydroxychloroquine Toxicity (especially in younger patients) 1
• Epiretinal Membrane (can cause shimmering scotomas) 5

Clinical Significance and Management

Functional Impact:

• Ring scotomas generally allow for better visual acuity than central scotomas 2
• Patients with ring scotomas typically maintain stable fixation points 2
• Reading rates are affected by scotoma pattern and size 4:
  • Faster reading with scotoma above fixation
  • Slower reading with scotoma to the left of fixation
  • Size of atrophic area strongly correlates with maximum reading rate

Management Approach:

1. Vision Rehabilitation

   • Essential for patients with central or paracentral scotomas 6, 5
   • Magnification devices to optimize use of remaining vision 6

2. Treatment of Underlying Condition

   • Corticosteroids may reduce scotoma size in some cases 5
   • Surgical intervention may be considered for epiretinal membranes causing shimmering scotomas 5

3. Regular Monitoring

   • Periodic assessment of scotoma patterns and fixation stability 5
   • Monocular Amsler grid testing to detect changes 5

Key Clinical Pearls

• The pattern of scotoma (ring vs. central) significantly impacts visual function and reading ability 2, 4
• Stargardt patients use different fixation strategies compared to AMD patients with similar scotomas 4
• Fixation patterns tend to remain stable over time in patients with ring scotomas 2, 3
• Patients with Stargardt disease often fixate at a considerable distance from the scotoma border, while AMD patients fixate immediately adjacent to the atrophy 4