Tension Headache: This is often the most common cause of headaches and can be associated with blurry vision due to tension in the muscles around the eyes. It's typically characterized by a band-like pressure around the forehead, back of the neck, or both.

Migraine: Migraines can cause severe headaches and are often accompanied by visual disturbances, including blurry vision, and sometimes an aura. The visual symptoms can precede the headache.
Dry Eye Syndrome: This condition can cause blurry vision and may be accompanied by headaches due to the strain on the eyes.
Refractive Errors: Uncorrected or under-corrected vision problems like myopia, hyperopia, or astigmatism can lead to headaches and blurry vision.
Sinusitis: Inflammation of the sinuses can cause headaches and, if the sinuses around the eyes are affected, may lead to blurry vision due to the proximity and potential to cause pressure on the eyes.

Giant Cell Arteritis: Although less common, this condition is critical to diagnose because it can lead to blindness if not treated promptly. It typically affects older adults and can cause headaches and visual disturbances, including blurry vision.
Stroke or Transient Ischemic Attack (TIA): A sudden onset of headache and blurry vision could be indicative of a stroke or TIA, especially if accompanied by other neurological symptoms like weakness or speech difficulties.
Brain Tumor: While rare, a brain tumor could cause increased intracranial pressure, leading to headaches and visual disturbances, including blurry vision.
Idiopathic Intracranial Hypertension (IIH): This condition, also known as pseudotumor cerebri, can cause increased pressure around the brain, leading to headaches and visual symptoms, including blurry vision and double vision.

Multiple Sclerosis: This autoimmune disease can affect the brain and spinal cord, leading to a wide range of symptoms, including vision problems and headaches.
Optic Neuritis: Inflammation of the optic nerve can cause pain and blurry vision, typically in one eye, and can be associated with multiple sclerosis.
Papilledema: Swelling of the optic disc due to increased intracranial pressure can cause blurry vision and is often associated with headaches. It can be a sign of a serious underlying condition.
Temporal Arteritis: Similar to giant cell arteritis, this condition involves inflammation of the arteries in the temple and can cause headaches and visual disturbances.