The intraocular pressure (IOP) of glaucoma caused by fluid build-up in the eye can cause a headache. In some instances, migraine headaches are actually cases of glaucoma that have not been treated. The pressure build up in the eye can cause a headache that is felt in and around the eyes and forehead and can sometimes be severe enough as to cause nausea and vomiting.
In a case study published in the Journal of Investigative Ophthalmology & Visual Science, researchers investigated the incidence of headaches in those suffering from glaucoma and discovered that patients suffering from low-tension glaucoma seem more at risk for headache and migraine symptoms.
“Glaucoma | National Headache Foundation.” National Headache Foundation. N.p., n.d. Web. 16 Nov. 2011. http://www.headaches.org/education/Headache_Topic_Sheets/Glaucoma
Phelps, Charles D., and James J. Corbett. “Migraine and Low-Tension Glaucoma.” Investigative Ophthalmology & Visual Science 26.1 (1985): 1105-1108. Print.