Migraine: This condition is common in adolescents and can cause transient visual disturbances (including blurred vision) and balance issues (leading to unsteady gait) due to its neurological effects. Migraines can present with a variety of symptoms, including aura phases that might involve visual disturbances.

Vestibular Neuritis or Labyrinthitis: These inner ear disorders can cause sudden onset of vertigo, leading to unsteady gait, and may also cause transient visual disturbances due to the connection between the vestibular system and vision.
Benign Paroxysmal Positional Vertigo (BPPV): Although more common in older adults, BPPV can occur in teenagers and causes brief but intense episodes of vertigo triggered by specific head movements, potentially leading to unsteady gait and possibly transient blurred vision.
Anxiety or Panic Attacks: These can manifest with a wide range of physical symptoms, including dizziness (which might be perceived as unsteady gait) and visual disturbances due to hyperventilation or other physiological responses to anxiety.

Stroke or Transient Ischemic Attack (TIA): Although rare in adolescents, a stroke or TIA can cause sudden visual disturbances and balance problems. It's crucial to consider and rule out these conditions due to their severe implications and the need for immediate medical intervention.
Multiple Sclerosis: This autoimmune disease can present with a wide range of neurological symptoms, including vision problems and balance issues. Early diagnosis is critical for managing the disease.
Brain Tumor: Any new onset of neurological symptoms, including transient blurred vision and unsteady gait, warrants consideration of a brain tumor, given the potential for serious outcomes if left untreated.

Chiari Malformation: A structural defect in the cerebellum that controls balance, which can cause problems with coordination and balance, and sometimes visual disturbances.
Acute Demyelinating Encephalomyelitis (ADEM): A rare autoimmune disease that can cause a variety of neurological symptoms, including vision problems and ataxia (unsteady gait).
Wilson's Disease: A genetic disorder that leads to copper accumulation in the body, affecting the brain and liver. It can cause neurological symptoms, including balance problems and visual disturbances, but is very rare and typically presents with other systemic signs.