The American Headache Society claims that up to 78 percent of Americans suffer from tension headaches, 12 percent from migraines and 1 percent from cluster headaches. Headache pain around, behind or within either eye is suggestive of a cluster headache. Other causes might indicate medical emergencies. Several factors contribute to pain that is felt in the left side and eye.
Cluster headaches are rare vascular-type headaches that are distinct from tension or migraine headaches. According to the American Headache Society, cluster headache sufferers are mainly men with onset between the ages of 20 to 30 years of age. Cluster headaches are characterized by: severe, stabbing pain that is around left or right eye or the temple; headache attacks that last from 15 minutes to three hours and occur once every other day to up to eight times daily; headaches associated with tearing, runny nose, congestion, sweating and/or droopy eyelid on the same side of the head as the pain. Causes of cluster headaches are thought to be related to hypothalamus dysfunction, abnormal hormone and neurotransmitter levels, and perhaps dietary and environmental triggers, as cited by MayoClinic.com.
Sinus Infection Headaches
Sinus infections can cause headaches in or around either the right or left eye and produce symptoms similar to cluster headaches. According to the University of Maryland Medical Center, sinus headaches can be distinguished by pressure-like pain in a specific area of the face or behind the eyes; pain made worse with sudden head movements like bending forward; pain worse in the morning because of collecting and draining mucus; postnasal drip with sore throat; yellow or green discharge from the nose and malaise with mild to moderate fever.
The most likely disease condition that is capable of creating pain in and around the left eye is glaucoma of the left eye. According to the National Eye Institute, glaucoma is a build up of pressure within the eye that can damage the optic nerve and destroy peripheral vision, create eye pain and eventually lead to blindness. African Americans older than the age of 40 have the greatest risk of developing glaucoma.
Infections and Tumors
Infections, abscesses and tumors of the brain or eye socket are rare, but all can generate pain in and around the left eye. The brain tissue does not generate pain directly, but infections, abscesses, encephalitis and cancerous processes can cause intense pain by destroying nerves, blood vessels and other related tissues in or near the eyes.
Brain aneurysms occur when damaged blood vessels leak blood or completely burst, which causes a bleeding, or hemorrhagic stroke. The majority of hemorrhagic strokes happen between the brain tissue and the sensitive arachnoid tissues, and are called subarachnoid hemorrhages. MedlinePlus notes that subarachnoid hemorrhages often create sudden, excruciating headaches near the back of the head, but can cause pain and symptoms in and around the left eye.
Head trauma can cause hemorrhages within the skull and around the eye which produce pain, but a more direct cause of headaches around the left eye is trauma to that region. Rugby and other contact sports frequently lead to head trauma, and sometimes skull or orbital bone fractures. A left orbital bone fracture would produce sudden, severe pain and inflammation around the left eye.