Blurred vision in one eye can be caused by a variety of factors that include eye strain, infections, eye allergies and sleepiness, according to All About Vision. Blurry vision or darkness in one eye can also indicate severe medical or vision issues, such as stroke or retinal detachment.
The Cleveland Clinic explains that blurred vision can also signify the onset of a migraine headache. In addition to blurriness, black spots and wavy lines may also appear in the field of vision. Visual distortions associated with migraine headaches are referred to as auras. Migraines can be triggered by several factors that include stress, hormonal fluctuations, chemical sensitivity and hunger.