Red Glass Test for Diplopia and Retinal Correspondence

Introduction

• Purpose: Identifying diplopia, its type, suppression, and retinal correspondence (normal & anomalous).
• Concept: Bifoveal fixation allows single vision when fixating on a light.
• Red Glass Mechanism:
  • Red glass placed in front of one eye alters light perception.
  • Fixating eye sees red light; other eye sees white.
  • Fusion Response: Results in pink or washed-out red light.

Test Procedure

• Deviations: Image falls on extrafoveal point, causing diplopia.
• Scenario Setup: Red glass on the fixating eye; patient views distant white light.

Scenarios and Outcomes

Scenario 1: Right Esotropia

• Diplopia: Present
• Type: Uncrossed
• Suppression: No
• Retinal Correspondence: NRC (Normal Retinal Correspondence)
• Conclusion: Right esotropia with NRC and no suppression.

Scenario 2: Right Exotropia

• Diplopia: Present
• Type: Crossed
• Suppression: No
• Retinal Correspondence: NRC
• Conclusion: Right exotropia with NRC and no suppression.

Scenario 3 & 4: Tropia with Suppression

• Diplopia: None
• Type: N/A
• Suppression: Yes (Indicated by seeing only bright red light)
• Retinal Correspondence:
  • Use vertical prism to determine NRC or ARC.
  • NRC: Vertical + horizontal separation.
  • ARC: Pure vertical separation.
• Conclusion: Tropia with suppression, type determined by cover test.

Scenario 5: Esotropia with ARC

• Diplopia: None
• Type: N/A
• Suppression: Absent (Fusion response)
• Retinal Correspondence: ARC (Anomalous Retinal Correspondence)
• Conclusion: Presence of ARC indicated by fusion response in tropia.

Scenario 6: Neutralized Esotropia

• Diplopia: None
• Type: N/A
• Suppression: Absent (Fusion response)
• Retinal Correspondence: NRC
• Conclusion: Right esotropia with NRC and absence of suppression with neutralizing prism.

Scenario 7: Paradoxical Diplopia

• Diplopia: Present
• Type: Crossed
• Suppression: No
• Explanation: Paradoxical diplopia indicates ARC, where pseudofovea interprets orientation differently.
• Clinical Relevance: Prism correction without ARC correction can result in paradoxical diplopia.

Clinical Considerations

• Usefulness: Best used in adults with diplopia but orthophoric on cover testing.
• Children: Testing with red filter can be challenging.