There are a variety of eye problems that can cause headache. In some cases, the headache is caused by the person squinting and overworking the eye muscles in an attempt to better focus their vision. In other cases, problems of internal pressure and swelling within the structures of the eye can ‘refer’ pain into other areas of the head. Difficulties with vision, such as blurring caused by long-sightedness, can be corrected with prescription glasses or contact lenses. Other disorders, such as glaucoma, need to be medically investigated and treated promptly. Once the cause of eyestrain is corrected, the associated headaches should ease.
The structure of the eye
The eye is our organ of vision. An image passes through its many layers and is focused on the back of the eye, called the retina. The retina contains light sensitive cells, called rods and cones. Information on shape, colour and pattern is picked up by the retina and carried to the brain via the optic nerve. The eye focuses images with two structures, the lens and the cornea. The lens is fine focus, while the cornea is fixed focus. The cornea is plumped up by a small chamber containing fluid called aqueous humour, while vitreous humour is the thick, jelly-like fluid that fills the main body of the eyeball and keeps it firm.
The cornea and the lens work together to focus images on the retina at the back of the eye. Sometimes, this delicate interplay fails and the small muscles of the eye are forced to work harder. The result is tired, aching eyes, blurred vision and headache. Most conditions can be corrected with prescription glasses or contact lenses.
The main problems that cause eyestrain and associated headache include:
- Astigmatism - the cornea is not a regular shape, which means that objects look blurry from certain angles. A person with astigmatism tends to squint in order to better focus their vision, which can contribute to headache.
- Hyperopia - or long-sightedness. Instead of focusing the image squarely on the retina at the back of the eye, the image is focused to a point behind the eye.
- Presbyopia - the lens becomes hard and inflexible with age. The symptoms include difficulties in focusing closely, sore eyes, sluggish changes in focus when looking from one distance to another, and headache.
Glaucoma is a build-up of fluid
The eye disease glaucoma can cause severe headache in some cases. Intraocular pressure refers to the amount of pressure inside the eye exerted by the aqueous humour. Glaucoma is characterised by a build-up of aqueous humour, caused by insufficient drainage. The result is damage to the optic nerve. It is not possible to prevent glaucoma from developing, but early detection may help to curb its progression. The two main types of glaucoma include:
- Open angle glaucoma - the slow build-up of intraocular pressure over time; this type usually presents no symptoms.
- Angle closure glaucoma - the sharp increase in intraocular pressure results in severe pain, blurred vision, watering of the eyes, nausea and vomiting. This type of glaucoma attack needs prompt medical intervention.