Benign Paroxysmal Positional Vertigo (BPPV): This condition is characterized by brief, episodic vertigo triggered by specific head movements, which could explain the worsening symptoms when opening eyes. It's a common cause of vertigo in adults and fits the patient's presentation of dizziness and nausea without fever or hemodynamic instability.

Vestibular Migraine: Although typically associated with headaches, vestibular migraines can present with vertigo, nausea, and sensitivity to visual stimuli, which could worsen symptoms when opening eyes. The absence of a headache does not rule out this diagnosis.
Labyrinthitis: An inner ear disorder that can cause vertigo, dizziness, and nausea. It might not always present with hearing loss or tinnitus, making it a consideration in this case.
Inner Ear Infection (Serous Labyrinthitis): Similar to labyrinthitis but often related to a viral upper respiratory infection. It could cause the described symptoms without fever.

Posterior Circulation Stroke: Although less common, a stroke in the posterior circulation can present with vertigo, nausea, and visual disturbances. It's critical to rule out this diagnosis due to its severe implications and the need for urgent treatment.
Multiple Sclerosis: An episode of vertigo and nausea could be part of a clinically isolated syndrome or a relapse in multiple sclerosis, especially if there are other neurological symptoms.
Acoustic Neuroma: A benign tumor on the nerve connecting the inner ear to the brain, which can cause vertigo, nausea, and hearing changes. Early detection is crucial for effective management.

Meniere's Disease: Characterized by episodes of vertigo, hearing loss, tinnitus, and ear fullness. While it's a possibility, the classic presentation includes hearing symptoms, which are not mentioned here.
Mal de Debarquement Syndrome: A rare condition that occurs after a journey by boat, plane, or car, causing a persistent feeling of swaying or imbalance. It's less likely given the lack of recent travel history but could be considered if relevant.
Superior Semicircular Canal Dehiscence: A rare condition where there's an abnormal opening in the bone overlying the superior semicircular canal, leading to vertigo and autophony (hearing internal sounds unusually loudly). It's an unlikely cause but could be considered with specific auditory symptoms.