Digital Eye Strain is a multifactorial disease which encompass a large group of ocular and vision-related symptoms that can be attributed to prolonged and extended use of smartphones, tablets, e-readers, and computers ^[1][2][1,2]. In recent years, these electronic devices have become nearly ubiquitous in modern society and have given way to an ever-increasing global dependence upon their application across personal, educational, and occupational settings. While computers and smartphones may serve to enhance our daily lives and activities, the American Optometric Association found that as few as two hours of uninterrupted screen time exposure is sufficient for the onset of both ocular discomfort and vision-related problems to develop [2]. Long-term implications associated with digital eye strain have yet to be elucidated, however, a large body of evidence has already demonstrated an array of harmful physiological effects associated with greater time spent using digital display devices ^{[3][4][5][6][7]}[3,4,5,6,7]. In lieu of this, one can safely predict the current global COVID-19 pandemic will further exacerbate the prevalence of digital eye strain into epidemic proportions affecting nearly all age groups.

In this digital era of increasing screen time habits, or time spent looking at these devices and omnipresent exposure, the incidence of screen-induced ocular health issues and visual discomfort will continue to present major public health issues ^[4][5][6][4,5,6]. Some reports estimate the overall prevalence may impact up to 90% of individuals in some populations making this an endemic problem that will require our utmost attention ^{[6][8][9][10][11]}[6,8,9,10,11]. Recently, the Vision Council found that >80% of adults in the United States far exceeded the two hour minimum of daily use associated with greater risk for the onset of digital eye strain symptoms ^[2][12][2,12]. In fact, working-age adults are estimated to spend an average of seven hours daily using computers just for their profession [2], of which, roughly 60% reported experiencing symptoms of screen-induced visual stress [12]. As one would expect, similar habits are seen among children and adolescents wherein >70% regularly exceed two hours of daily exposure ^[12][13][14][12,13,14] and are more often using two or more devices simultaneously ^{[15][16][17][18][19]}[15,16,17,18,19]. In consequence, multi-tasking with more than one electronic device often leads to further risk of developing symptoms and greater incidence of visual fatigue ^[6][12][20][6,12,20]. Moreover, several reports also show that both adults and adolescents routinely use smartphones and hand-held devices roughly one hour before going to sleep and immediately upon awakening in the morning ^{[15][16][18][21][22]}[15,16,18,21,22].

While it is important to note, the physiological implications are not uniform across all electronic devices with digital display technology; for example, it appears there are distinguishable patterns between symptom profiles associated with the overuse of computers versus smartphones ^{[3][16][22][23]}[3,16,22,23]. Hence, this may explain, at least in part, the high prevalence of digital eye strain amongst several types of individuals, including computer users ^[24][25][24,25], visual display terminal or “teleworkers” ^{[3][26][27][28]}[3,26,27,28], technicians [29], university students and young adults ^{[15][30][31][32][33][34][35][36]}[15,30,31,32,33,34,35,36], as well as children and adolescents ^{[17][19][25][37][38][39][40][41][42][43]}[17,19,25,37,38,39,40,41,42,43]. Nonetheless, there is considerable evidence that substantiate the positive relationship between total amount of time spent using digital devices and overall risk of developing symptoms associated with digital eye strain ^{[6][7][20][31][44][45]}[6,7,20,31,44,45].

Traditionally, the effects of digital eye strain have been referred to interchangeably as computer vision syndrome (CVS) ^{[1][2][32][46][47]}[1,2,32,46,47], as well as digital asthenopia ^[29][48][29,48], and vision display terminal (VDT) syndrome ^[3][24][3,24]. Commonly reported symptoms include eyestrain, eye soreness, headaches, blurred vision, diplopia, and dry eyes ^{[4][5][6][8][46][49][50]}[4,5,6,8,46,49,50]. These ocular effects can be categorized according to: (1) external symptoms commonly associated with dry eye disease regarding changes in ocular surface homeostasis ^{[2][15][49][51][52][53][54]}[2,15,49,51,52,53,54]; and (2) internal effects relating to aesthenopic symptoms and visual function impairment ^{[6][8][24][55][56]}[6,8,24,55,56]. Although helpful, these distinctions are not mutually exclusive measures of disease etiology due to the subjective nature of visual sensory processing and high degree of variability among patient-reported symptoms. In consequence, the diagnostic parameters used to characterize digital eye strain often vary among available reports.

While the pathophysiology extends beyond the scope of the present review, it is important to briefly discuss the various contributing factors as they relate to the ability of nutrition in ameliorating symptoms associated with digital eye strain ^{[6][44][49][57]}[6,44,49,57]. A number of excellent reviews which have discussed several putative mechanisms in more detail along with the spectrum of physiological effects can be found elsewhere ^{[4][5][6][8][46][54][58][59]}[4,5,6,8,46,54,58,59].

Dry eye is among the most common ocular complaint reported by individuals with digital eye strain ^{[9][51][52][60][61][62]}[9,51,52,60,61,62]. Symptoms often range from irritation, burning, and stinging, as well as epiphora and foreign body sensations ^[63][64][63,64]. It has been well-documented that greater screen time behaviors represent a major component in developing symptoms of dry eye, often associated with lacrimal gland dysfunction and signs of evaporative dry eye disease ^{[3][27][44][58][60][61][62][65][66][67][68]}[3,27,44,58,60,61,62,65,66,67,68]. In particular, computer usage significantly influence various dynamics of blinking patterns (such as frequency, amplitude, and complete vs. incomplete) thereby further increasing the rate of evaporation and exacerbating tear film instability ^{[18][23][54][58][68][69][70][71][72][73][74][75]}[18,23,54,58,68,69,70,71,72,73,74,75]. The combination of sub-optimal tear production and excessive evaporation can lead to tear hyperosmolarity with subsequent inflammation of the epithelial surface ^{[76][77][78][79][80]}[76,77,78,79,80].

Dry eye-related symptoms of digital eye strain may also be attributed to meibomian gland dysfunction (MGD) ^{[81][82][83][84][85][86][87][88][89]}[81,82,83,84,85,86,87,88,89]. Normal sebum production from these glands serves as an important role in preserving ocular surface homeostasis by regulating evaporation of the tear film. Furthermore normal secretion and movement of meibomian glands depends on adequate blink dynamics, in fact, some reports indicate that dysfunction of meibomian glands may be responsible for triggering initial inflammatory response mechanisms in consequence of abnormal sebum production ^[82][84][85][82,84,85]. Furthermore, greater time spent using electronic devices have been shown to positively correlate with diagnostic parameters for MGD including meibum quality score, lipid margin abnormalities, and meibography gland drop out ^{[88][89][90][91]}[88,89,90,91].

Moreover, it appears that a cascade of pro-inflammatory mechanisms which perturb homeostasis of the ocular surface are implicated in the onset of dry eye symptoms and ocular discomfort associated with digital eye strain. Among patients with dry eye disease, conjunctival and tear fluid samples provide indications of a pro-inflammatory condition marked by increased concentrations of late lipid peroxidation markers concomitant with reductions in endogenous antioxidant enzymes ^[92][93][92,93]. Early pathophysiology likely involves a vicious cycle between pro-oxidative and pro-inflammatory mechanisms which further contribute to worsening dysfunction of the ocular surface ^{[49][59][66][67][81][93][94][95][96][97][98][99][100]}[49,59,66,67,81,93,94,95,96,97,98,99,100].

One school of thought suggests prolonged exposure to digital displays may serve an important role in exacerbating the extent of oxidative damage to various structures of the eye ^{[59][88][89][101]}[59,88,89,101]. Peak spectral emission (visible blue light, 400–490 nm) from light-emitting diodes commonly used in digital display technology have been implicated with causing photo-oxidative damage to the outer retina, that is photoreceptors and retinal pigment epithelial cells ^[102][103][102,103]. It is known that short-wavelength (blue) light is of high energy and capable of proliferating reactive oxygen species (ROS) formation in a time-dependent manner ^[101][102][101,102]. Additionally, oxidative damage and apoptosis brought on by blue light irradiation within ocular surface tissues have been implicated with clinical manifestations of dry eye disease ^{[59][88][89][104]}[59,88,89,104].

With increasing screen time behavior, digital asthenopia (i.e., eye strain or fatigue) remains the most common visual complaint alongside blurred and double vision paired with headaches and ocular soreness ^{[11][24][42][48][55][105][106][107][108]}[11,24,42,48,55,105,106,107,108]. Difficulty focusing between working distances can be attributed to accommodative and vergence-related stress in consequence of uncorrected refractive error or continuous fixation at close-viewing distances ^{[6][8][24][55][56]}[6,8,24,55,56]. In comparison to reading printed text, using hand-held devices such as smartphones and tablets, impose a greater burden on ocular muscles leading to greater recession in near point of convergence and reductions in accommodative function ^{[109][110][111][112]}[109,110,111,112]. In many cases, aesthenopic symptoms seem to emerge over time when the cognitive demands for a visual task overwhelm the individual’s ability to perform them comfortably ^{[1][2][31][34][113][114][115][116]}[1,2,31,34,113,114,115,116]. For instance, the visual demands of uninterrupted computer work can manifest as headaches and ocular discomfort due to glare and increased squinting.

Often presenting as secondary perturbations that may arise in conjunction with vision-related symptoms, clinical manifestations of digital eye strain are not exclusive to theour visual system tissue. For instance, office workers commonly report experiencing myofascial pain and discomfort in the neck, shoulders, and upper back regions ^{[3][5][46][117]}[3,5,46,117]. Indications of musculoskeletal symptoms appear strongly associated with the postural demands of computer work, in addition to poor ergonomic practices and extended periods of physical inactivity ^{[3][6][46][49][50][118][119]}[3,6,46,49,50,118,119].

On the other hand, greater use of hand-held electronic devices have also been associated with the preponderance of psychological disorders ^{[43][120][121][122][123][124][125][126]}[43,120,121,122,123,124,125,126] and disruption in circadian rhythms ^{[21][22][46][117][127][128][129]}[21,22,46,117,127,128,129]. It is well-documented that excessive screen time behaviors before bedtime may significantly alter the sleep-wake cycle which can lead to significant disturbances in sleeping patterns. Particularly among adolescents and younger adults, reports of digital eye strain are often associated with sleeping disorders such as insomnia and excessive daytime sleepiness ^{[21][22][121][122][127][130][131]}[21,22,121,122,127,130,131]. Consequentially, chronic patterns of sleep loss and circadian misalignment ascribed with an evening chronotype are also linked to greater psychosocial stress paired with increased systemic markers of stress-related hormones ^{[132][133][134][135]}[132,133,134,135]. Regular behaviors of excessive screen time activities among students are also strongly associated with greater risk of developing signs of anxiety and depression ^{[120][123][124][126]}[120,123,124,126]. One school of thought suggests dry-eye related symptoms may help to explain, at least in part, some similarities observed between sleeping disorders and changes in mental health condition associated with overuse of hand-held devices in younger populations ^{[68][123][136][137][138][139]}[68,123,136,137,138,139].

Moreover, chronic exposure to psychological stressors have been linked with triggering a pro-oxidative state throughout the body, and it appears that ameliorating systemic oxidative stress may considerably reduce measures of psychological stress as well [140]. Given the relationship between proper dietary behaviors and overall well-being, it is no surprise that regular consumption of nutraceuticals and foods rich in antioxidants (i.e., fresh fruits, leafy green vegetables, and fish) may offer protection against elements of biopsychosocial deterioration ^{[141][142][143][144][145]}[141,142,143,144,145].

Nutraceuticals are dietary supplements that have greater amounts of nutrients that are naturally present in nature and consumed by individuals as routine part of diet. The nutraceuticals are pharmaceutical-grade supplements that have the potential of modulating disease pathways or disease state. Thus, further reinforcing the potential therapeutic application for nutrition to ameliorate the purported systemic oxidative condition associated with digital eye strain. However, they can only be marketed to support the structure or function of the body and the label of the nutraceuticals or dietary supplements includes disclosure that they are not intended to diagnose, treat, cure, or prevent diseases and they are not evaluated by the Food and Drug Administration (FDA) in the US.

Given that a core etiopathogenic mechanism of dry eye-related symptoms involve a chronic pro-inflammatory state, research has been focused on investigating adjunctive nutraceutical strategies aimed at targeting this component of ocular surface dysfunction. Due to their inherent anti-inflammatory properties and immunomodulatory potential, considerable research has been focused on the role of omega-3 polyunsaturated fatty acids (PUFAs) ^{[146][147][148][149][150][151][152]}[146,147,148,149,150,151,152]. By increasing dietary consumption of omega-3 fatty acids compared to omega-6 fatty acids, clinical reports have demonstrated some ability to regulate the body’s inflammatory state by attenuating pro-inflammatory mediators ^[146][148][146,148]. Omega-3 PUFAs also serve an important role in the prevention of chronic systemic conditions such as cardiovascular disease ^{[152][153][154][155]}[152,153,154,155], in addition to exerting protective ocular effects against cataracts ^{[156][157][158]}[156,157,158] and age-related macular degeneration (AMD) ^{[159][160][161][162]}[159,160,161,162].

For the management of ocular surface symptoms in digital eye strain, the capacity for omega-3 fatty acids to offer clinical benefits against the underlying mechanisms of dry eye disease is supported by robust scientific evidence ^{[76][146][147][148][150][152][163][164][165][166][167][168][169]}[76,146,147,148,150,152,163,164,165,166,167,168,169]. In randomized clinical trials, short-term dietary supplementation with omega-3 PUFAs demonstrated enhanced therapeutic benefits in patients with mild-to-moderate dry eye disease (Table 1) ^{[170][171][172][173][174][175][176][177]}[170,171,172,173,174,175,176,177]. A systematic review and meta-analysis found that patients receiving omega-3 PUFAs saw significantly better improvements in tear evaporation, tear osmolarity, and severity of dry eye symptoms compared with placebo [151]. Odds ratio (OR) for improvements in tear break-up time (TBUT) were significantly greater among those in the active treatment groups (OR: 8.72; 95% CI: 4.73–16.09; p < 0.001) [151]. Multivariate analyses performed by separate meta-analyses seem to mirror these findings, wherein short-term supplementation was also associated with increased tear production and secretion from lacrimal glands (Schirmer’s test scores; p < 0.001) ^[167][168][167,168]. Based on the available evidence from clinical trials in patients with dry eye disease, one can postulate that nutraceutical strategies involving omega-3 fatty acids would likely alleviate similar signs of ocular dysfunction brought on by prolonged digital device use. This would particularly be important for individuals that have sub-optimal tear film dynamics and predisposed to dry eye disease and involved in significant activities with digital devices.

To date, short-term omega-3 fatty acid supplementation has demonstrated promising results to offer a similar degree of clinical benefit for symptomatic patients with digital eye strain (Table 1) [171]. Prospective studies involving younger adults with computer vision syndrome (≥3 h/day computer use) demonstrated significant improvements in objective measures of inherent tear film stability and subjective dry eye symptoms in as few as 45 days of supplementation ^[171][178][171,178]. Marked improvements in Nelson grading scores upon impression cytology seem to mirror these findings, providing further evidence of the nutraceutical benefits of omega-3 fatty acids to promote healing of the conjunctival epithelium ^{[169][171][178]}[169,171,178]. Given that hyperosmotic stress plays an important role in causing damage to the ocular surface, these observations wherein short-term supplementation produced a profound normalization in tear tonicity represent clinically meaningful effects to improve the severity of dry eye ^[179][180][179,180]. Similarly, these improvements in tear film stability may also be attributed to the nutraceutical effect of omega-3 fatty acids on ameliorating signs of MGD ^{[81][82][83][84][85][87]}[81,82,83,84,85,87]. Given the importance of sebum production in maintaining proper stability of the tear film layer, the potential for these micronutrients to improve meibum composition scores and meibomian gland secretions should not be overlooked ^{[174][175][177]}[174,175,177]. It should be noted that greater aqueous tear production was also observed following three months of supplementation in patients with computer vision syndrome [171], consistent with reports in dry eye disease ^{[151][167][168]}[151,167,168].

For treatment of digital eye strain, the growing number of preliminary reports offer promising clinical evidence substantiating the capacity for omega-3 fatty acids to ameliorate signs of ocular surface dysfunction and dry eye-related symptoms. However, it is important to acknowledge a recent systematic review and meta-analysis by Singh et al. [181] that concluded that there is low-certainty evidence of benefits of omega-3 supplementation on reduction of dry eye symptoms in individuals that are symptomatic computer users.