Differential Diagnosis for Enlargement of Blind Spot with Shimmering and Dark Patches

Single Most Likely Diagnosis

• Macular Degeneration: This condition often presents with visual disturbances such as shimmering or wavy lines around the blind spot, and the appearance of dark patches, especially when blinking. The enlargement of the blind spot can be a symptom of the progression of macular degeneration, affecting central vision.

Other Likely Diagnoses

• Migraine with Aura: Migraines can cause visual auras, including shimmering lights, zigzag patterns, and blind spots. The symptoms described could be part of a migraine aura, especially if they are transient and accompanied by headache.
• Retinal Detachment: Early signs of retinal detachment can include flashes of light and an increase in floaters, which might be perceived as dark patches around the fixation point. The enlargement of the blind spot could indicate a progressing detachment.
• Optic Neuritis: Inflammation of the optic nerve can cause a range of visual symptoms, including blind spots, pain with eye movement, and disturbances in vision such as shimmering or flashing lights.

Do Not Miss Diagnoses

• Central Serous Chorioretinopathy (CSC): Although less common, CSC can cause sudden distortion and blind spots in central vision, often with a serous detachment of the retina. It's crucial to diagnose and treat to prevent permanent vision loss.
• Retinal Vein Occlusion: This condition can lead to sudden vision loss and might present with similar symptoms, including blind spots and visual disturbances. Prompt diagnosis is essential to prevent further complications.
• Giant Cell Arteritis: This condition can cause sudden, painless vision loss, especially in older adults. While it might not directly cause the described symptoms, it's a critical diagnosis not to miss due to its potential for severe and irreversible vision loss.

Rare Diagnoses

• Leber's Hereditary Optic Neuropathy (LHON): A rare inherited disease that causes central vision loss, often with a sudden onset. It might present with visual disturbances similar to those described.
• Acute Zonal Occult Outer Retinopathy (AZOOR): A rare condition that affects the outer retina, leading to visual field defects and potentially symptoms like those described, including enlargement of the blind spot and visual disturbances.