Headaches and Tension-Type Headache (TTH)
Headaches affect 52% of the global population, including 14% with migraines and 26% with tension-type headaches (TTH) [5]. Among adolescents, 69.4% experience headaches [6], with a small percentage suffering from frequent or chronic episodes.

TTH, previously called pressure headache, is common and characterized by non-pulsating, moderate, bilateral pain in the head, scalp, or neck. Episodic TTH occurs less than 15 days per month, while chronic TTH lasts over 15 days monthly or 180 days yearly. TTH affects 46% globally, peaking in adults aged 40-49 and more common in females than males [5,4], and more in higher educated individuals [8].

Triggers for TTH include psychological stress, prolonged screen use, improper posture, and forward head posture. Stress activates the hypothalamic-pituitary-adrenal axis, releasing cortisol, while prolonged visual focus and poor posture increase pericranial muscle tension, contributing to TTH episodes [9,10].

The pathophysiology of TTH is not fully understood, but some trigger points have been identified as possible pathogenesis of TTH. One of the prominent signs of TTH is increased tenderness in the pericranial muscles in both the episodic and chronic stages. Prolonged muscle strain can release chemical mediators for pain and also lead to muscle ischemia. Muscle strain at the suboccipital and upper neck area can pull the dura mater, which can be painful and produce TTH signs [12]. Central sensitization is another role in the pathogenesis of TTH. It can be seen in psychological stress or sleep-deprived states, which leads to increased sympathetic function causing headache by involuntary contraction of cephalic muscles, decreased pain inhibitory activity, hypersensitivity to nociceptive stimuli, and other unclear mechanisms. The nociceptive pathway releases orexin, which inhibits pain, but in psychological stress or sleep-deprived states, orexin is reduced, and pain is increased, leading to headaches [13,14].

Migraine is a neurological disorder characterized by a pulsating quality, moderate to severe unilateral headache intensity that is aggravated by physical activity, usually accompanied by photophobia and nausea. Migraine has its classification, which includes migraine without aura—attacks lasting 4 to 72 hours, migraine with aura—recurrent reversible headaches lasting minutes with preceding disturbances followed by headache and migraine symptoms, and chronic migraine—occurs for greater than 15 days in a month for more than 3 months. Migraine without aura is the most prevalent type of migraine, accounting for 75% of all migraines [15]. Photophobia is the most common symptom of migraine. Individuals with migraine have been shown to exhibit photosensitivity, which is believed to be related to abnormal trigeminal nerve activity and its relationship to the thalamus and visual cortex. It affects about 80% of migraine patients, making daylight conditions unbearable [16]. Visual triggers like bright light, flashing lights, and High-contrast patterns can cause migraine attacks, which occur due to increased stimulation of the cerebral cortex where visual processing occurs [17]. It is believed that trigeminal activation induces several vasodilating molecules during an acute attack of migraine, causing vasodilation of dural and pial vessels. Some of the molecules extend beyond the vasoactive effect, like calcitonin gene-related peptide, substance P, neurokinin A, and pituitary adenylate Cyclase-activating peptide, as they possess the ability to modulate nociceptive neuronal activity in certain areas of the trigeminovascular system [1].

A cervicogenic headache is a headache related to reduced range of neck movement. It presents as a unilateral headache that starts at the neck. For a headache to be classified as cervicogenic, it must originate from the neck and be perceived in the head or face. There must be evidence that the pain is attributed to the neck, and the pain must resolve after three months of successful treatment of the underlying factor [19].

High levels of screen time exposure have been shown to be associated with a high risk of headaches. In young adults, migraine is the commonly associated type of headache following prolonged screen exposure [20,21]. The widespread use of screens among young people has become a defining feature of the modern digital age. Rapid technological advancements have introduced various devices, such as smartphones, tablets, laptops, and televisions, into daily life. Moreover, the COVID-19 pandemic significantly amplified screen usage for both educational and recreational purposes [22].

Eye strain symptoms are more common when reading from a computer screen compared to a printed page, even when distance, font size, contrast, and lighting are identical. This heightened occurrence of eye strain associated with prolonged screen use is referred to as "computer vision syndrome" or "digital eye strain," though the biological mechanisms behind it remain unclear [23]. Digital Eye Strain (DES), also referred to as Computer Vision Syndrome or visual fatigue, describes a collection of ocular and visual symptoms resulting from prolonged use of digital devices, sharing many of the same features. Common manifestations include dry eyes, itching, a sensation of a foreign body, watering, blurred vision, and headaches. Non-ocular symptoms may involve a stiff neck, general fatigue, headaches, and backaches [24]. According to the American Optometric Association (AOA), DES arises from extended use of devices such as desktops, laptops, mobile phones, tablets, e-readers, and similar electronic devices [27].  The AOA further states that continuous digital device usage for two hours can be sufficient to trigger DES [27,28].

DES is multifactorial in origin, with contributing factors including reduced contrast of letters against digital screen backgrounds, screen glare and reflections, improper viewing distance and angles, inadequate lighting, poor posture during device use, and infrequent blinking [25]. The symptoms of DES can be categorized based on underlying mechanisms. Ocular surface-related symptoms result from reduced blinking and tear film instability, presenting as eye irritation, burning sensation, dryness, eye strain, headaches, tired eyes, sensitivity to bright light, and overall eye discomfort [29,30]. Accommodation or vergence-related symptoms are linked to anomalies in the accommodation or binocular visual system due to excessive visual effort, leading to blurred vision at near or far distances after device use, difficulty refocusing between distances, and diplopia (double vision) [29-31]. Extraocular symptoms are primarily musculoskeletal issues caused by improper screen positioning, such as headaches, neck pain, shoulder pain, and back pain [32]. Effective management of DES involves implementing proper ergonomics and healthy screen habits. Reducing daily screen time, maintaining adequate blinking to prevent dry eyes, optimizing lighting and minimizing glare, taking regular screen breaks, using the 20-20-20 rule (every 20 minutes, look at an object 20 feet away for 20 seconds), and ensuring proper screen distance and positioning can help minimize strain [28]. Effective management of DES involves implementing proper ergonomics and healthy screen habits. Reducing daily screen time, maintaining adequate blinking to prevent dry eyes, optimizing lighting and minimizing glare, taking regular screen breaks, using the 20-20-20 rule (every 20 minutes, look at an object 20 feet away for 20 seconds), and ensuring proper screen distance and positioning can help minimize strain [28].

Prolonged Near-Focus Activities and their Neurological Impact Oculomotor response
Near-focus activities such as viewing a near target necessitate proper accommodative and vergence responses to ensure the object of focus appears both clear and single³³. Blurred vision, whether at or near or when shifting focus to the distance after extended computer use, is a common symptom of Computer Vision Syndrome (CVS). This may arise from an inaccurate accommodative response (AR) during the task or an inability to fully relax the AR after prolonged near-vision activity [33]. Interestingly, several recent studies have reported a correlation between ciliary muscle contraction and the occurrence of musculoskeletal symptoms [34,35]. The ciliary muscles adjust the lens to focus on near objects. Prolonged near-focus causes continuous activation of these muscles, leading to accommodative fatigue, which may present as blurred vision and difficulty focusing. Several researchers have measured vergence parameters before and after computer usage. For instance, Watten et al [36]  measured positive and negative relative vergence (vergence ranges) at near both at the start and end of an 8-hour workday. They found significant decreases in both parameters, suggesting that prolonged computer use impairs the ability to converge and diverge effectively. In contrast, Nyman et al [37] reported no significant changes in positive or negative relative vergence at the near following 5 hours of VDT work. Additionally, they found no significant alterations in distance and near heterophoria or the near point of convergence (NPC) after the work period. Similarly, Yeow and Taylor [38] observed no significant changes in NPC after short-term VDT use, which included up to 2.35 hours of continuous use or an average of 4 hours of intermittent use in a typical working environment.

These studies suggest that prolonged computer use may impair the ability to converge and diverge effectively. Over time, these demands may strain the visual system, reducing its ability to adapt to varying focal distances.

Posture has been recognized as a contributing factor to headaches, with the most commonly observed postural issue being excessive forward head posture (FHP). A more pronounced FHP is often associated with cervicogenic headaches and post-concussion headaches. Additionally, it has been reported in cases of migraine, episodic tension-type headaches (ETTH), and chronic tension-type headaches (CTTH) [39].

Tension in neck muscles in relation to poor posture during screen time can stimulate nociceptors (pain receptors), sending signals to the trigeminal nucleus caudalis in the brainstem, leading to referred pain in the head, a characteristic of tension-type headache [40]. According to Bendtsen [41], a primary issue in chronic tension-type headache is believed to be central sensitization within the spinal dorsal horn and trigeminal nucleus, which results from prolonged nociceptive input originating from the myofascial tissues around the head.

Many teenagers report occasionally doing homework while engaging with other media, including watching television (51%), using social networking platforms (50%), texting (60%), and listening to music (76%) [42]. Research indicates that multitasking can disrupt learning and that frequent media multitasking is linked to cognitive differences, even during tasks requiring single-task focus. These findings suggest that the increasing prevalence of media multitasking (MMT) could influence everyday cognitive functioning.

A research study revealed that multitasking results in a significant decrease in task accuracy, an increase in reaction times, and a notable rise in cognitive load. Furthermore, task interruptions were found to significantly elevate reaction times and cognitive load while decreasing task accuracy during monotasking. However, this reduction in accuracy was not statistically significant during multitasking. The study also demonstrated that moderate to high resilience levels significantly mitigate the increased cognitive load associated with task interruptions in multitasking situations [43].

Blue Light Exposure and Headaches
The circadian rhythm is described by the National Cancer Institute as the natural cycle of physical, mental, and behavioral changes that the body goes through in a 24-hour cycle [44]. Although there are idiosyncratic variations in circadian rhythms, the average length is 24 and one-quarter hours [45].  In 1981, Harvard Medical School's Dr. Charles Czeisler demonstrated that daylight helps to sync an individual's circadian rhythm with their surroundings [45]. This interplay between the circadian rhythm and the environment is regulated by the hormone melatonin, which is produced in the pineal gland from tryptophan. Darkness leads to the release of norepinephrine onto pinealocytes, resulting in melatonin secretion and an increased sleep drive [45]. Conversely, light of any kind can suppress melatonin secretion. However, light of the blue wavelength (400–450 nanometers) has more energy per photon of light than other colors in the visible spectrum and suppresses melatonin secretion more powerfully [46]. It follows then that blue light has the greatest potential to disrupt the circadian rhythm. It is important to note, however, that even when light is perceived as white or another color, blue light may still be present [46].

According to the Mayo Clinic, adults should get 7 hours or more of sleep per night. The same article emphatically states that the quality of your sleep is just as important as the quantity. That is, if sleep is frequently interrupted, the quality is reduced, even in spite of having an adequate amount [47]. Primary headaches have been linked to a higher incidence of sleep issues, including insomnia, short sleep duration, and poor sleep quality [48]. Recent studies suggest that sleep deprivation is associated with increased brain hyperexcitability, which increases the susceptibility of the brain to a migraine attack [48]. The past decade has seen more studies highlighting the effects of blue light on the retina and the human body as a whole [49]. Some of these studies have highlighted the fact that exposure to blue light causes reactive oxygen species (ROS) overproduction, retinal apoptosis, and damage to mitochondria, which are present in high numbers, particularly in photoreceptors and in the intraocular portion of ganglion cell axons [50]. Further, researchers have shown that in cortical cultures, exposure to blue light resulted in a greater than 200% increase in the expression of neuronal activity-regulated genes. This increase in gene expression was not noted in response to exposure to red or green light [51]. From these research investigations, it is clear that blue light not only stimulates and damages the retina through reactive oxygen species but also causes hyperexcitability, with both mechanisms playing a role in decreased sleep quality. A migraine is a primary headache characterized by recurrent episodes of unilateral, localized pain that are frequently accompanied by nausea, vomiting, and sensitivity to stimuli like light and sound [52]. Shorter wavelengths of light (blue, indigo, and violet) are known to trigger migraines more than other wavelengths [53]. These shorter light wavelengths are thought to activate certain cells in the retina known as intrinsically photosensitive retinal ganglion cells (ipRGCs). It has been hypothesized that light sensitivity's pain pathway involves ipRGC activation [54].  One research article has shown that because of the indirect pathway between the optic nerve and the trigeminal nerve (especially in the case of the ipRGCs and subcortical structures like the basal ganglia, the thalamus, and the hypothalamus), the idea of a retinal basis for photophobia has been appealing. Although migraine is not the focus of these investigations, the route mapping suggests a possible mechanism that links migraine discomfort and photophobia. Some of the effects of photophobia on mood and hunger that are linked to migraine have been explained by this direct subcortical connection. In fact, migraine discomfort in general has been linked to the trigeminal nerve [54].  It is important to note that the same article, however, mentions that although there is evidence of aberrant retinal responses to light in migraine, there is not a consensus over which retinal cells are responsible and if aberrant retinal functioning is the only mechanism underlying photophobia [54].

Digital eye strain, another name for computer vision syndrome, is a collection of vision and eye issues brought on by extended use of computers, tablets, e-readers, and cell phones [55]. The symptoms of digital eye strain (DES) can be broadly categorized as ocular surface-related symptoms, such as headaches, eyestrain, dry eyes, burning or irritating eyes, sensitivity to bright lights, and eye discomfort, as well as symptoms of accommodation, including impaired close or distance vision after using a computer and trouble focusing at different distances. As it relates to prophylaxis and alleviating symptoms related to eye strain, Brown University categorically states that blue light-blocking glasses are safe to wear, but there is no proof that they provide any protection or lessen the symptoms of eye strain [56]. Instead, they recommend adjusting screen brightness levels, reducing glare from the surroundings, among other methods. This implies that while blue light is problematic, there has not been an established link between blue light and eye strain. To an extent, the American Optometric Association corroborates this claim by stating that individuals can reduce computer screen glare by moving the screen, applying a glare reduction filter, or covering the screen with curtains, drapes, or shades. Additionally, maintaining clean, dirt-free displays and getting rid of fingerprints helps reduce glare and enhance clarity. However, the reason cited for this precaution is that over time, blue light from monitors, tablets, and mobile devices, as well as LED and fluorescent lighting, can impair vision (a feature of eye strain) [57].

Interventions and Knowledge Gaps
Advancements in technology have made it almost impossible to completely avoid exposure to blue light. To do so would require isolating oneself from nearly all forms of technology.

However, evidence-based studies have demonstrated effective measures to mitigate the adverse effects of blue light, particularly in reducing headaches and eye strain.

One such intervention is the use of blue light filters. Based on the knowledge that light at 480nm strongly activates retinal ganglion cells, which exacerbate headache-associated light sensitivity, Wilkins and Wilkinson developed the “FL-41” tint in 1991. This filter has proven effective in reducing light sensitivity and, by extension, the frequency of headaches [58-60]. Another important factor is improved ergonomics in the workplace. Research shows that maintaining consistent brightness levels across a workspace reduces eye strain, a known contributor to headaches [61]. Increasing natural lighting, such as through larger windows, and ensuring proper desk and chair alignment—so that screens are at eye level and an appropriate distance from the user—also play a critical role in preventing screen-related headaches [62]. In addition to environmental adjustments, taking regular screen breaks is a simple yet effective strategy. Studies suggest that stepping away from screens before a headache occurs can significantly reduce their frequency [63]. The 20-20-20 rule provides another practical technique to combat eye strain and its associated symptoms. This method involves looking away from the screen every 20 minutes and focusing on an object at least 20 feet away for 20 seconds. A study conducted by Shivam Kumar and Harshita Pandey confirmed the effectiveness of this practice in reducing eye strain, headaches, and double vision caused by chronic blue light exposure [64]. Despite the availability of these interventions, blue light-associated headaches remain common, largely due to a lack of awareness. For instance, in the study by Kumar and Pandey, an astonishing 72% of participants had never heard of the 20-20-20 rule [64]. This knowledge gap highlights the urgent need for education and awareness programs. Workshops and campaigns focusing on practical techniques for mitigating blue light exposure could significantly reduce the prevalence of what has come to be known as “digital age headaches.”