Asthenopia (due to accommodative or refractive error)

Key points of this disease

• Asthenopia is a set of indefinite symptoms that cause ocular and systemic symptoms just by looking at objects, and is a severe condition that does not improve even with rest (ICD-10 H53.1).
• Causes are broadly classified into four types: accommodative, optical, muscular, and neurological. The most common background is accommodative load due to refractive errors or presbyopia.
• With the spread of digital devices, the overall prevalence has rapidly increased to 51%, and about 90% among digital device users. It has further increased in school-age children and college students during the COVID-19 pandemic.
• Computer vision syndrome (CVS) and digital eye strain (DES) are representative subtypes. Technostress eye (IT eye), mainly characterized by decreased blink rate, is also clinically important.
• Symptoms range from ocular symptoms (blurring, fatigue, dryness, eye pain) to systemic symptoms (headache, neck and shoulder stiffness), and are distinguished from simple tired eyes.
• Diagnosis requires evaluation of refraction, eye position, accommodative function, and tear film, as well as assessment of VDT work environment and lifestyle habits.
• Treatment is based on optimization of refractive correction, the 20-20-20 rule, dry eye treatment, and adjustment of the work environment, combined with symptomatic therapy according to the cause.

1. What is asthenopia?

Forest plot showing prevalence of asthenopia by group (digital device users, students, general adults, etc.)

Song F, Liu Y, Zhao Z, et al. Clinical manifestations, prevalence, and risk factors of asthenopia: a systematic review and meta-analysis. J Glob Health. 2026;16:04053. Figure 2. PMCID: PMC12879263. License: CC BY.

Forest plot showing prevalence of asthenopia and 95% confidence intervals by group type (computer users, digital device users, students, general adults, etc.) and questionnaire used (CVS-Q, CISS, CVSS17, etc.), including comparison between COVID-19 and non-COVID-19 periods. Corresponds to prevalence trends (overall 51%, digital users 90%, increase due to COVID-19) discussed in the section “What is asthenopia?”

Asthenopia refers to a set of nonspecific symptoms including eye fatigue, pain, blurred vision, headache, nausea, and sometimes vomiting that occur simply from looking at objects. Unlike simple “tired eyes,” it is a severe condition that does not improve with rest and is caused by organic or functional abnormalities of the eyes or the whole body. ICD-10 code is H53.1.

In the modern era where digital devices are essential, subtypes called computer vision syndrome (CVS) and digital eye strain (DES) are rapidly increasing. The TFOS (Tear Film & Ocular Surface Society) defines DES as “the development or exacerbation of recurrent ocular symptoms and signs specifically related to viewing digital device screens” ⁵⁾. CVS refers to a variety of symptoms ranging from ocular symptoms (tired eyes, blurred vision, dry eye) to musculoskeletal symptoms (neck and shoulder pain) and neurological symptoms (headache) ⁷⁾. “Technostress eye syndrome (IT eye syndrome)” that occurs during VDT work is a characteristic condition mainly involving dry eye due to decreased blinking and autonomic nervous system disorders.

Prevalence trends:

A systematic review and meta-analysis of 63 studies and 60,589 individuals by Song et al. reported an overall prevalence of asthenopia of 51% (95% CI: 50–52%) ¹⁾. It was high among digital device users (90%) and computer workers (77%), and during the COVID-19 pandemic, it increased from 45% to 64% in school-age children and from 36% to 57% in university students ¹⁾. The global prevalence of digital eye strain is approximately 66% (95% CI: 59–74%), reaching 74% (95% CI: 66–81%) during COVID-19 ¹⁷⁾.

Classification of causes:

The causes of asthenopia can be broadly classified into four types: accommodative, optical, muscular, and neurogenic.

Classification	Main causes
Accommodative	Accommodative load due to refractive error or presbyopia, accommodative spasm, accommodative weakness
Optical	Inappropriate spectacle correction (undercorrection, overcorrection, poor anisometropia correction)
Muscular	Ocular misalignment (strabismus, heterophoria), convergence insufficiency
Neurogenic	Systemic diseases, psychological factors, autonomic nervous system disorders due to VDT work

Q Is "tired eyes" the same as asthenopia?

A

“Tired eyes” refers to a transient condition that resolves with rest. Asthenopia is a severe condition that does not improve with rest and is distinguished as an indefinite syndrome based on underlying conditions such as refractive errors, ocular misalignment, and systemic diseases.

2. Main symptoms and clinical findings

Subjective symptoms of asthenopia include a variety of complaints involving both ocular and systemic symptoms.

Symptom frequency from meta-analysis¹⁾:

In a meta-analysis of 63 studies involving 60,589 participants by Song et al. (2026), the following symptoms were reported.

Symptom	Category	Notes
Blurred vision or difficulty focusing	Ocular	One of the most frequent complaints
Eye fatigue or heaviness	Ocular	Common among all digital device users
Dry eye sensation	Ocular (dry eye)	Mainly due to decreased blink rate
Eye pain/discomfort	Ocular	Persistent dull pain
Headache (frontal)	Systemic	Related to accommodative and convergence effort
Neck and shoulder stiffness	Systemic (musculoskeletal)	Triggered by improper posture and working distance
Diplopia	Ocular	When accompanied by convergence insufficiency
Photophobia	Ocular	Related to ocular surface disorders

Blurred vision, haziness, dryness, and a heavy sensation in the eyes are also frequently reported. In severe cases, blepharospasm may occur. True treatment of asthenopia involves identifying the cause and preventing its onset; it is important to distinguish it from simple eye strain.

Four-category classification of digital eye strain (DES)⁸⁾:

Asthenopia

Eye fatigue/heaviness: Worsens with prolonged near work

Blurred vision: Can occur both at distance and near

Eye pain/discomfort: Perceived as persistent dull pain

Diplopia (rare): Appears when accompanied by convergence insufficiency

Dry eye-related symptoms

Dryness: Mainly due to decreased blink rate

Foreign body sensation/burning: Caused by tear film breakup

Tearing: Due to reflex lacrimation

Photophobia: Appears with ocular surface disorders

Exacerbation of Pre-existing Eye Disease

Manifestation of Uncorrected Refractive Error: Mild astigmatism or presbyopia amplifies symptoms

Headache: Especially common in the frontal region

Difficulty Focusing: Particularly noticeable in presbyopia

Musculoskeletal Symptoms

Neck and Shoulder Pain: Caused by poor posture

Lower Back Pain: Related to improper screen positioning

Wrist and Finger Pain: Occurs with prolonged keyboard use

Characteristic Findings of Technostress Eye Syndrome:

During VDT work, blinking frequency clearly decreases, and combined with office dryness, leads to functional dry eye. After work, compensatory increase in blinking is observed. The near response (accommodation, miosis, convergence) is normally triggered simultaneously during near vision, but after VDT work, this coordination breaks down, causing inconsistency in the simultaneous triggering of the three elements.

Q How can I tell if it's eye strain?

A

If repeated eye dryness, fatigue, blurred vision, and headache occur after prolonged use of digital devices and improve when use is stopped, digital eye strain is likely. It can be assessed using standardized questionnaires such as the CVS-Q (Computer Vision Syndrome Questionnaire, score ≥6 indicates DES). If symptoms persist, it is important to see an ophthalmologist to check for refractive errors, accommodative disorders, and dry eye.

3. Causes and Risk Factors

Eye strain is a multifactorial condition, resulting from a combination of ophthalmic, systemic, and environmental factors.

Ophthalmic Factors:

• Refractive errors (hyperopia, astigmatism, anisometropia, improper spectacle correction): Hyperopia, latent hyperopia, and astigmatism impair accommodation, leading to many complaints during prolonged near work.
• Ocular misalignment (strabismus, heterophoria): Even small-angle latent strabismus can cause eye strain, headache, and shoulder stiffness.
• Accommodative disorders (presbyopia, accommodative spasm, accommodative weakness): The initial complaint of presbyopia (from late 30s) is mostly eye strain.
• Convergence and divergence disorders: Convergence insufficiency with accommodative dysfunction causes diplopia and eye strain during near vision.
• Dry eye: Irritative symptoms due to ocular surface disorders are a main cause of eye strain.
• Glaucoma and ocular hypertension: Associated with optic disc findings and visual field abnormalities.

Systemic factors:

• Circulatory disorders (hypotension, anemia): Often present with eye fatigue.
• Endocrine abnormalities (thyroid dysfunction): Important factor in eye strain.
• Gastrointestinal diseases (gastroptosis, liver disorders): Eye strain appears as a nonspecific complaint.
• Pregnancy, menstrual abnormalities, menopause: Periods prone to nonspecific complaints.
• Barré-Liéou syndrome (sequelae of cervical spine injury): Accompanied by autonomic dysfunction, showing objective abnormalities in pupil and accommodation systems.
• Medications (psychotropic drugs, antihistamines): Many drugs reduce accommodative function; medication history should always be checked.

Environmental factors:

• VDT work (technostress eye syndrome, IT eye syndrome): High incidence of accommodative dysfunction, ocular misalignment, and tear secretion abnormalities.
• Sick building syndrome: chemical irritants in poorly ventilated buildings (e.g., formaldehyde)
• Lighting (glare, luminance contrast, screen position)
• Air conditioning (dryness, direct airflow): air conditioner use has OR 23.02, the greatest risk factor
• Work environment (poor posture, screen distance, prolonged VDT work)

Risk and protective factors from meta-analysis (OR values) ¹⁾:

Factor	OR (95% CI)	Classification
Air conditioner use	23.02 (4.94–107.18)	Risk
Pre-existing eye disease	2.59 (1.43–4.69)	Risk
Poor sitting posture	2.02 (1.51–2.70)	Risk
Hyperopia	1.56 (1.10–2.30)	Risk
Myopia	1.51 (1.27–1.81)	Risk
Screen time (per 1-hour increase)	1.15 (1.09–1.21)	Risk
Regular breaks	0.21 (0.09–0.51)	Protective
Good sleep quality	0.24 (0.20–0.30)	Protective
Computer use knowledge	0.20 (0.13–0.30)	Protective
Anti-glare filter	0.34 (0.19–0.64)	Protective

Specific risk factors for digital eye strain include short viewing distance (OR 4.24), poor ergonomics (OR 3.87), and lack of breaks (OR 2.24)¹⁵⁾. When the screen is positioned above eye level, the exposed ocular surface area increases, worsening dry eye symptoms⁵⁾. In a meta-analysis of computer workers, VDT usage time, work environment, and spectacle correction status were identified as major determinants of prevalence¹⁴⁾.

Cases of hyperopic shift and asthenopic symptoms after COVID-19 infection have been reported, suggesting a decline in the ciliary muscle’s ability to maintain accommodation²⁾.

Q How strong is the relationship between screen time and eye strain?

A

Each additional hour of screen time increases the risk of eye strain by OR 1.15 (95% CI: 1.09–1.21)¹⁾. Conversely, taking regular breaks reduces the risk to OR 0.21. Combining screen time limits with regular breaks is important.

4. Diagnosis and Examination Methods

The most important aspect of diagnosing eye strain is a detailed history. Carefully inquire about VDT usage time, work environment, timing of symptom onset, spectacle prescription history, and use of medications such as psychotropic drugs or antihistamines.

Essential ophthalmic examinations:

Examination	Purpose	Key points
Distance and near visual acuity test	Confirmation of refractive error	Measure all at 5m, near (30cm), and intermediate distance (50cm)
Refraction test	Confirmation of appropriate correction	Autorefractor + subjective refraction. Cyclopentolate eye drops if needed
Accommodation function test	Evaluation of accommodative amplitude and status	Near point measurement, repeated measurement, accommodation function analyzer (HFC analysis)
Eye position test	Evaluation of strabismus and phoria	Alternate cover test, prism cover test
Stereopsis test	Evaluation of binocular vision function	TNO, Titmus
Dry eye test	Evaluation of ocular surface damage	TBUT, Schirmer test, fluorescein staining
Slit-lamp microscopy	Exclusion of anterior segment diseases	Includes evaluation of meibomian gland dysfunction
Fundus examination	Exclusion of glaucoma and fundus diseases	Assessment of optic disc findings and visual field abnormalities

It has been pointed out that tear film instability can be a major cause of visual fatigue³⁾, and evaluation of meibomian gland dysfunction is also important.

Assessment using questionnaires:

Standardized questionnaires include the following⁸⁾¹²⁾.

Questionnaire	Number of items	Diagnostic criteria
CVS-Q (Computer Vision Syndrome Questionnaire)	16 symptoms	Score ≥6 indicates DES
CVSS17 (Computer Vision Symptom Scale)	17 items	Based on Rasch model
DESQ (Digital Eye Strain Questionnaire)	Multiple items	Covers all digital devices

Objective tests (for research/specialized facilities)⁵⁾:

• Critical flicker fusion frequency (CFF): quantification of visual fatigue
• Blink analysis (blink rate, proportion of incomplete blinks): aid in DES diagnosis
• Pupillary response and accommodative microfluctuation analysis (Fk-map): assessment of accommodative spasm/tension
• Eye movement recording and fixation disparity measurement: assessment of convergence insufficiency

Diseases to be excluded:

It is necessary to exclude diseases that present symptoms similar to asthenopia, such as angle-closure glaucoma, uveitis, and optic neuritis. Pay particular attention to the following points.

• Glaucoma / ocular hypertension: Key differentiating points are optic disc findings and visual field findings.
• Dry eye (including MGD): Tear film instability can be a major cause of asthenopia.
• Systemic diseases (thyroid, hematologic, neurologic): Do not overlook organic diseases.
• Drug-induced: Accommodation disorders caused by psychotropic drugs, antihistamines, anticholinergics, etc.

5. Standard Treatment

Treatment of asthenopia is fundamentally based on a multifaceted approach according to the cause. The most important aspect is to identify and eliminate the cause; symptomatic treatment alone leads to recurrence. Treatment is performed in the following order of priority:

1. Resolution of ophthalmic causes (refractive correction, orthoptic treatment, dry eye treatment)
2. Improvement of environment and behavior (optimization of VDT work environment, rest habits)
3. Pharmacotherapy (eye drops, nutritional intervention)
4. Treatment of systemic diseases and drug-induced causes (management of primary disease, medication adjustment)

Refractive correction and orthoptic correction

Proper spectacle prescription: The most important means of treating asthenopia. Accurately correct hyperopia, astigmatism, and anisometropia. Both undercorrection and overcorrection can cause asthenopia.

Contact lens prescription: For large anisometropia, contact lenses are more effective than spectacles in reducing aniseikonia.

Prism spectacles: Prism spectacles are effective for heterophoria of about 10 prism diopters (Δ). For vertical deviation, even small angles have a narrow fusion range, so active treatment should be considered.

Vision training: Training for convergence insufficiency and binocular vision dysfunction. Surgery is indicated for large-angle ocular misalignment.

VDT Environment Improvement and Behavioral Changes

Regular breaks: Take a 10-15 minute break every hour and try to look at distant objects.

20-20-20 rule: Every 20 minutes, look at something 20 feet (about 6 m) away for 20 seconds ¹³⁾.

Monitor distance and position: Keep the distance between eyes and computer at 40-70 cm. Position the screen so that your gaze is slightly downward.

Lighting and environment: Avoid direct sunlight and ensure sufficient indoor lighting. Avoid direct airflow from air conditioning or heating, and ensure proper ventilation. Humidity control is also important.

Medication and Nutritional Therapy

Artificial tears: Soft Santear ophthalmic solution, 2-3 drops per dose, 5-6 times daily

Moisturizing eye drops: Hyalein ophthalmic solution (0.1%), 1 drop per dose, 5-6 times daily + Mucosta ophthalmic solution UD (2%) or Diquas ophthalmic solution (3%), 1 drop per dose, 5-6 times daily

Treatment for accommodative spasm: Mydrin M ophthalmic solution (0.4%), once daily at bedtime (to relieve ciliary muscle hypertonicity)

Eye drops for asthenopia: Sancoba ophthalmic solution (0.02%), 3-5 times daily

Omega-3 fatty acid supplementation: The only oral nutritional intervention with high-quality evidence shown in a systematic review by TFOS ⁶⁾

Blinking exercise: Repeat a set of closing eyes for 2 seconds twice, then forcefully closing eyelids for 2 seconds ¹¹⁾. Effective as conscious blinking practice during VDT work.

Precautions in Treatment

True treatment of asthenopia involves identifying the cause and preventing its onset. Simply prescribing eye drops does not provide a fundamental solution. Treatment of ophthalmic abnormalities (refractive errors, ocular misalignment, dry eye) is the highest priority, and the possibility of systemic diseases or drug-induced causes should always be considered. The efficacy of eye drops and medications for asthenopia is unstable and often ineffective without identifying the cause.

About Blue Light Blocking Lenses

Current randomized controlled trials have not provided evidence that blue light blocking lenses significantly reduce symptoms of eye strain ⁵⁾. The main causes of eye strain are abnormal blinking, accommodative fatigue, and environmental factors, not the wavelength characteristics of light. Priority should be given to the 20-20-20 rule, proper refractive correction, and optimization of the work environment.

Q Are blue light blocking glasses effective for eye strain?

A

Current randomized controlled trials have not confirmed evidence that blue light blocking lenses significantly reduce symptoms of eye strain ⁵⁾. The main causes of eye strain are accommodative fatigue, abnormal blinking, and environmental factors, not the wavelength characteristics of light. For prevention, it is recommended to prioritize the 20-20-20 rule, proper refractive correction, and optimization of the work environment.

6. Pathophysiology and Detailed Mechanisms

The mechanisms of eye strain vary depending on the cause, and multiple mechanisms often combine.

Mechanisms due to refractive error and improper correction:

Squinting in an uncorrected state or improper refractive correction can lead to accommodative spasm or accommodative insufficiency, or conversely, accommodative paralysis. These accommodative abnormalities are major causes of eye strain and can progress into a negative spiral.

Accommodative mechanisms (technostress eye syndrome):

The mechanism of accommodative spasm due to VDT work and prolonged smartphone use is as follows. Continuous near work causes sustained contraction and tension of the ciliary muscle, making relaxation difficult (accommodative spasm). If it becomes more severe, accommodative spasm leads to pseudomyopia-like distance vision impairment. Accommodative function analysis (Fk-map) shows a pattern of accommodative spasm to spasm with high HFC values for near targets. In this state, eye strain tends to become chronic. Improvement can be achieved by instilling a cycloplegic agent (Mydrin M) before bedtime to relax the ciliary muscle.

Convergence and binocular vision mechanisms:

In convergence insufficiency with accommodative insufficiency, both accommodative convergence and fusional convergence are insufficient, causing diplopia and eye strain during near vision. Prolonged near use of digital devices requires sustained accommodative effort, leading to decreased accommodative amplitude, recession of the near point of convergence, and increased accommodative lag ⁹⁾¹⁰⁾.

Mechanisms of abnormal blinking and ocular surface disorders:

During digital device use, the blink rate decreases and incomplete blinks increase ⁵⁾⁸⁾. The normal blink rate is 15-20 times per minute, but it significantly decreases during screen viewing. Decreased blink rate promotes tear evaporation, increases tear osmolarity, and induces ocular surface dryness and inflammation. Tear film instability is one of the main causes of visual fatigue ³⁾.

Nutritional and metabolic mechanisms:

DHA (docosahexaenoic acid) accounts for approximately 50% of the phospholipids in retinal photoreceptors, and supplementation with omega-3 polyunsaturated fatty acids (PUFAs) has been suggested to be effective in reducing oxidative stress in the retina and ocular surface ⁴⁾.

Mechanism after COVID-19:

It has been reported that after COVID-19 infection, decreased parasympathetic innervation leads to reduced ciliary muscle tone, causing a hyperopic shift in refraction and symptoms of asthenopia ²⁾. In three cases (a 31-year-old woman, a 25-year-old man, and a 22-year-old man), hyperopic shifts were observed, and symptoms improved with appropriate spectacle correction. This mechanism is thought to result from damage to the autonomic and parasympathetic nervous systems as a neurological sequela of COVID-19, and attention should be paid to changes in refractive status in the ophthalmological evaluation of long COVID patients.

Asthenopia and tear film stability:

Tear film instability is one of the main causes of visual fatigue ³⁾. Without a normal tear film, the optically uniform ocular surface cannot be maintained, leading to fluctuations and blurring of vision. Decreased blink rate during digital device use is a major mechanism causing this tear film instability. Evaporative dry eye due to meibomian gland dysfunction (MGD) is an important comorbidity that worsens asthenopia, and active evaluation and treatment are necessary.

Q Is COVID-19 infection associated with asthenopia?

A

Cases have been reported in which hyperopic shift and symptoms of asthenopia appeared after COVID-19 infection, and it is thought that decreased ability of the ciliary muscle to maintain accommodation is involved ²⁾. Symptoms may improve with appropriate refractive correction.

7. Latest research and future perspectives

About this section

The following content includes items that are currently in the research stage or under clinical trials. Some items are not standard treatments available at general hospitals. This is reference information for professionals regarding future medical developments.

Proposal for a unified diagnostic definition:

There is no internationally agreed diagnostic definition for asthenopia, making comparison between studies difficult. A meta-analysis by Song et al. (2026) proposes the following unified diagnostic criteria ¹⁾.

Proposed definition: “A syndrome primarily caused by visual tasks, presenting with one or more symptoms related to the eyes or vision (such as eye fatigue, blurring, pain, etc.), which are partially or completely relieved by rest.” If this definition is standardized, it is expected to improve the quality of future epidemiological and interventional studies.

Future directions for treatment and management:

Current treatment for asthenopia is mainly symptomatic, but evolution in the following directions is expected:

• AI-based personalized management: Real-time monitoring of blink rate, screen time, and posture using wearable devices, with individualized feedback
• Precise evaluation of tear components: Improved diagnostic accuracy through eye-drop-based measurement of inflammatory markers (IL-6, IL-8, ICAM-1, etc.) in tears
• Assessment in VR environments: Development of standardized binocular vision evaluation protocols using VR headsets
• Advances in pharmacotherapy: Ocular surface protection and visual fatigue reduction through mucin-stimulating eye drops and anti-inflammatory eye drops
• Digital health interventions: Evaluation of the effectiveness of screen-use behavior modification apps and regular break reminder systems

Global trends in prevalence¹³⁾¹⁷⁾:

Population	Prevalence
World (normal, DES)	66% (95% CI: 59–74%)
During COVID-19 (DES)	74% (95% CI: 66–81%)
Non-students (during COVID)	82%
Students (during COVID)	70%
All ages and overall asthenopia	51% (95% CI: 50–52%)
Digital device users	90%
Computer workers	77%

Impact on children:

DES is also called a “shadow pandemic” in children ¹⁶⁾. The average screen time doubled from 1.9 hours to 3.9 hours before and after the COVID-19 pandemic, and the prevalence of DES in children reached 50.2%. Age 14 or older, male sex, and device use for more than 5 hours per day were identified as risk factors.

Potential of omega-3 fatty acid supplements:

Supplementation with omega-3 PUFAs may reduce oxidative stress on the ocular surface and improve visual fatigue through stabilization of the tear film ⁴⁾. In a systematic review by TFOS, oral omega-3 fatty acid supplementation is positioned as the management method with the highest level of evidence ⁶⁾.

Objective evaluation techniques for tear film stability:

Methods for objectively evaluating tear film stability are being developed ³⁾. If this technology is applied clinically, it will enable objective diagnosis and monitoring of dry eye-related asthenopia. If non-invasive tear film evaluation (NIBUT: Non-Invasive Break-Up Time) during digital device use becomes widespread, it may be possible to track changes in the ocular surface before and after screen time in real time.

Impact of VR head-mounted displays:

VR (virtual reality) head-mounted displays impose a near-distance visual load different from conventional screens, raising concerns about effects on accommodation and vergence function. Development of DES monitoring and prevention systems using AI and wearable devices is also progressing.

Asthenopia and medical economics:

Asthenopia is closely associated with decreased productivity and increased healthcare costs worldwide. With the normalization of remote work after the COVID-19 pandemic, the economic significance of workplace measures against eye strain (ergonomic improvements, regular breaks, periodic eye exams) is being reassessed. Considering that each additional hour of screen time increases the risk by OR 1.15, investment in workplace environment improvements is likely to lead to long-term healthcare cost reductions ¹⁾.

Prevention programs for asthenopia:

The following measures are recommended for preventing eye strain in workplaces and schools:

1. Regular eye exams: Early detection and treatment of refractive errors, strabismus, and dry eye
2. Ergonomic assessment: Monitor height, distance, room lighting, chair height, etc.
3. Institutionalization of the 20-20-20 rule: Structuring regular breaks, such as with the Pomodoro Technique
4. Screen time management tools: Recording usage time and setting limits
5. Use of anti-glare filters: Effective as a protective factor with OR 0.34 ¹⁾

8. References

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2. Thakur M, Panicker T, Satgunam P. Refractive error changes and associated asthenopia observed after COVID-19 infection: Case reports from two continents. Indian J Ophthalmol. 2023;71:2592-2594.

3. Watanabe M, Hirota M, Takigawa R, et al. Objective evaluation of relationship between tear film stability and visual fatigue [Response to Letter]. Clin Optom. 2025;17:281-282.

4. Duan H, Song W, Zhao J, Yan W. Polyunsaturated fatty acids (PUFAs): sources, digestion, absorption, application and their potential adjunctive effects on visual fatigue. Nutrients. 2023;15:2633.

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6. Downie LE, Craig JP, Wolffsohn JS, et al. TFOS Lifestyle: Impact of the digital environment on the ocular surface – Management and treatment. Ocul Surf. 2023;30:253-285.

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12. Mylona I, Glynatsis MN, Floros GD, Kandarakis S. Spotlight on Digital Eye Strain. Clin Optom. 2023;15:29-36.

13. León-Figueroa DA, Barboza JJ, Siddiq A, et al. Prevalence of computer vision syndrome during the COVID-19 pandemic: a systematic review and meta-analysis. BMC Public Health. 2024;24:640.

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15. Lem DW, Gierhart DL, Davey PG. Can Nutrition Play a Role in Ameliorating Digital Eye Strain? Nutrients. 2022;14(19):4005.

16. Bhattacharya S, Heidler P, Saleem SM, Marzo RR. Let There Be Light-Digital Eye Strain (DES) in Children as a Shadow Pandemic in the Era of COVID-19: A Mini Review. Front Public Health. 2022;10:945082.

17. Anbesu EW, Lema DW. Prevalence of computer vision syndrome: a systematic review and meta-analysis. Sci Rep. 2023;13:1801.