Eye is part of the sensory system. Therefore eye is part of the brain. Through
eye, the light signal is modify to electric signal before send to the brain.
If the brain can’t perceive the light signal very well, some stress signal
will send out to the eye in order to perceive back a normal light signal. These
include the ability of the eye to converge, to focus, refocus and etc. In this
situation, when the eye cannot cope with it anymore, headache will occur. Anyway,
this is one of the reason that can cause headache, however headache related
to the eye is multifactorial. Any pressure or physical changes through the eye
can also cause headache, such as glaucoma, optic neuritis, papiloedema, etc.
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