Migraine with Aura: This condition is characterized by visual disturbances, including seeing curtains or zigzag patterns, before the onset of a headache. The visual symptoms are usually transient and can be followed by a headache, making it a common cause of such visual disturbances.

Ocular Migraine: Similar to migraine with aura, ocular migraines can cause visual disturbances like seeing curtains, but they typically do not involve a headache. The symptoms are usually confined to one eye.
Retinal Detachment: This is a serious condition where the retina separates from the back of the eye. It can cause sudden flashes of light and seeing a curtain or shadow descending over the field of vision.
Vitreous Detachment: The vitreous gel in the eye can shrink and pull away from the retina, causing flashes of light and floaters. In some cases, it might be perceived as a curtain over the vision.

Stroke or Transient Ischemic Attack (TIA): Although less common, a stroke or TIA can cause sudden visual disturbances, including seeing a curtain over part of the visual field. Given the potential for severe and permanent damage, it's crucial not to miss this diagnosis.
Temporal Arteritis (Giant Cell Arteritis): This condition involves inflammation of the blood vessels and can lead to sudden loss of vision, which might be described as a curtain falling over the eye. It's a medical emergency requiring prompt treatment.

Charles Bonnet Syndrome: This condition occurs in people with significant vision loss and can cause complex visual hallucinations, including seeing patterns or shapes that might resemble a curtain.
Occipital Lobe Seizures: Seizures originating in the occipital lobe of the brain can cause visual disturbances, including seeing shapes or patterns that could be described as a curtain over the vision.
Multiple Sclerosis: In rare cases, multiple sclerosis can cause visual disturbances due to lesions in the optic nerve or brain, potentially leading to symptoms like seeing a curtain over part of the visual field.