Refractive Error: The most common cause of blurry vision in adolescents is a refractive error, such as myopia (nearsightedness), hyperopia (farsightedness), or astigmatism. This is due to the shape of the eye not being perfectly round, causing light to focus incorrectly on the retina.

Dry Eye Syndrome: This condition can cause blurry vision due to insufficient tear production or poor tear quality, leading to irritation and discomfort.
Allergies: Seasonal or environmental allergies can lead to itchy, watery eyes, which may cause temporary blurry vision.
Fatigue or Eye Strain: Prolonged use of digital devices, reading, or other visually demanding activities can cause eye strain, leading to occasional blurry vision.
Migraines: Some individuals may experience visual auras or blurry vision as part of a migraine episode.

Diabetic Retinopathy: Although less common in adolescents, undiagnosed diabetes can lead to retinopathy, causing blurry vision. It's crucial to consider this diagnosis, especially if the patient has other symptoms like polyuria, polydipsia, or weight loss.
Brain Tumors: Rarely, brain tumors, such as optic gliomas, can cause visual disturbances, including blurry vision. This diagnosis is critical to rule out due to its severe implications.
Multiple Sclerosis: This autoimmune disease can cause optic neuritis, leading to blurry vision, among other symptoms. Early diagnosis is essential for effective management.

Keratoconus: A progressive eye disease where the cornea thins and bulges, causing distorted vision.
Uveitis: Inflammation of the uvea, which can lead to blurry vision, eye pain, and sensitivity to light.
Optic Neuritis: Inflammation of the optic nerve, which can cause blurry vision, pain, and loss of color vision.
Papilledema: Swelling of the optic disc due to increased intracranial pressure, which can cause transient blurry vision.