Correlation between headaches and the visual system
Because of the close correlation between eyes and headaches, ophthalmologists are often the first doctors to assess patients with headaches or migraine, visual disturbances associated with headaches and eye pain.
In fact, eye pain and visual disturbances are symptoms many times of neurological origin.
Classification of headaches
The International Headache Society classifies headaches into two main categories: primary headaches and secondary headaches.
Primary headaches
Primary headaches include various types of migraine:
- tension headache
- cluster headache
- paroxysmal migraine
- other miscellaneous headaches not associated with a structural lesion.
Secondary headaches
Secondary headaches are, on the other hand, associated with:
- head injuries
- vascular disorders
- other intracranial processes (such as mass lesions, infections, metabolic disorders, drugs, cranial neuralgia)
- other craniofacial disorders.
Migraine with aura and migraine variants with visual afferent symptoms
Besides headaches, visual manifestations are the most common symptoms of migraine and, more often than not, these fall under the so-called "aura".
An aura consists of neurological symptoms that precede, accompany or, rarely, follow a migraine.
The symptoms of aura, which usually affect both eyes, usually develop within 5-20 minutes and last less than an hour.
Visual afferent symptoms
Visual symptoms are classified as positive or negative.1
Positive symptoms
Positive symptoms include:
- the vision of sparkling spots (called scotomas)
- the vision of flashes (phosphenes)
- heat waves
- kaleidoscopic effects
- fragmented vision (as of cracked glass).
All these symptoms persist even when the eyelids are closed.
In addition, migraine is often accompanied by blurred vision. As with other migraine aura symptoms, visual disturbances often develop gradually and may progress from one type to another.
Negative symptoms
Negative symptoms include:
- hemianopsia of the same name: a particular form of hemianopsia that occurs when one loses vision of one half of the visual field. The prefix 'hemi-' refers precisely to this half. One speaks of lateral (vertical) hemianopsia if the loss affects the right or left half of the eye; of altitudinal (horizontal) hemianopsia if the loss affects the upper or lower half.
- concentric narrowing of the visual fieldso-called 'tunnel vision
- cortical blindness: a condition in which the eyes are healthy, but the brain cannot process visual information due to damage to the visual cortex. This condition can lead to vision loss in both eyes due to bilateral involvement of the occipital lobes. Cortical blindness is caused by lesions in the visual cortex, which is responsible for processing electrical impulses from the eyes.
- transient loss of monocular visual acuity.
A special case of negative symptoms is transient monocular visual loss.
Vision loss may be partial (curtain, shadow or tunnel vision) or complete, with sudden or gradual onset and resolution.
It usually lasts four to 45 minutes, although it can last from seconds to hours. There is no need for an accompanying headache.
Retinal migraine
When migraine is associated with headaches and transient monocular visual symptoms that last less than one hour, we speak of retinal migraine.
The latter is a rare condition, generally characterised by negative symptoms such as scotoma or loss of vision.
Frequency and associated factors
Most people with migraine with aura experience an isolated aura in their lives, without headaches.
Many migraineurs report triggers associated with the visual environment, such as bright lights, fluorescent lights, strobe lights, flickering computer screens and busy visual environments, such as grocery shop aisles.
Ephemeral and autonomous manifestations of migraine
During a migraine attack, abnormalities of the eyelids, pupils and ocular motility are occasionally present. For example, benign episodic pupillary mydriasis produces anisocoria (i.e. a different pupil width), which may be associated with blurred vision, head pain, photophobia, conjunctival injection or transient visual obscurations.
Patients with migraine may also experience diplopia (visual disturbance involving double vision of the image) and cranial nerve palsy. The latter, which affects the oculomotor nerve, occurs in oculomotor ophthalmoplegic migraine, which, however, is no longer considered a type of migraine by the International Headache Society because it is often associated with a secondary cause.
Cluster headache and paroxysmal migraine
Other types of migraine may present ophthalmic symptoms: cluster headache, for example, affects the ipsilateral eye. During a migraine attack, ptosis, miosis and anisocoria may occur. Patients may also manifest conjunctival injection, eyelid oedema and lacrimation.
A form of migraine similar to cluster headache is paroxysmal migraine, whose ophthalmic features include ptosis and miosis, lacrimation, conjunctival injection and eyelid oedema. Many patients also present with photophobia.
SUNCT and SUNA
SUNCT (Unilateral short-lasting neuralgiform headache with conjunctival injection and lacrimation) and SUNA (Unilateral short-lasting neuralgiform headache with cranial autonomic symptoms) are rare forms of primary headache in which lacrimation and eyelid oedema occur.
Other causes of headache and periocular pain
Dry eye
Dry eye is a very common disorder, affecting 10% to 15% of adults.
Dry eye syndrome or DED (Dry Eye Disease) is a complex condition in which multiple risk factors such as genetic alterations, age, gender, diet, environmental conditions, lifestyle, working conditions, immune status, hormonal status and medications contribute to changes in the morphology and function of the elements that make up the ocular surface.
Currently, two main types of DED have been identified, a clinical form resulting from the dysfunction of the lacrimal gland and is defined as 'reduced tear production'. and another defined "from evaporation"induced, instead, by a defect in the functioning of the Meibomian glands, the sebaceous glands present on the eyelids and responsible for producing the oily component of tears.
Affected patients commonly manifest a mix of both types of DED, regardless of aetiology.
Indeed, while the poor quality and/or reduced flow of fluid from the Meibomian gland may cause reduced production of the lipid layer of the tear film and, thus, an 'evaporative' dry eye, in parallel, a chronic 'reduced tear production' state may induce an increased presence of proinflammatory cytokines and cause damage to the ductal orifices of the Meibomian gland.
The most frequent symptoms of DED are dryness, burning, irritation and/or foreign body sensation usually accompanied by visual changes and general deterioration of quality of life.
Since the cornea is richly innervated, dryness of the corneal surface can lead to painful sensations.
Dry eye can mimic headaches and drugs used to treat headaches can cause or worsen this condition.
Angle-closure glaucoma
Angle-closure glaucoma is caused by blockage of the drainage of aqueous humour (the fluid contained in the eye) resulting in a rapid increase in intraocular pressure.
Acute angle-closure glaucoma is characterised by pain, blurred vision, rainbow-coloured halos around lights, nausea and vomiting.
Due to these characteristics, subacute angle-closure glaucoma can mimic migraine.
Inflammatory eye diseases
Many other conditions produce orbital inflammatory diseases and the differential diagnosis includes systemic disorders, neoplasms, congenital malformations, infectious diseases and trauma.
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