Asthenopia is a series of indefinite syndromes that cause eye fatigue, eye pain, headache, etc., against a background of organic or functional abnormalities of the eyes or body. Unlike simple “tired eyes,” it refers to a severe condition where symptoms do not recover even with adequate rest. ICD-10 code is H53.1.
Prevalence Trends:
A systematic review and meta-analysis by Song et al. of 63 studies involving 60,589 individuals reported an overall prevalence of asthenopia of 51% (95% CI: 50–52%) 1). It is 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).
Classification:
Asthenopia is classified by cause as follows:
It is also common in children, and complaints may be observed even in children without refractive errors or visual impairment.
“Tired eyes” refers to a temporary 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 factors such as refractive errors, ocular misalignment, and systemic diseases.
The subjective symptoms of asthenopia are diverse and include both ocular and systemic symptoms.
The frequency of symptoms according to a meta-analysis is as follows1).
Blurring, defocusing, and dryness are also frequently reported. In severe cases, blepharospasm may occur. Reflex symptoms such as nausea, facial muscle twitching, and migraine may also appear.
The main findings confirmed by ophthalmic examination are as follows.
Asthenopia is a multifactorial disease, caused by a combination of ophthalmic, systemic, and environmental factors.
Ophthalmic factors:
Systemic factors:
Environmental factors:
Risk factors and protective factors from meta-analysis (OR values):
The main OR values are shown below 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 |
| Improper 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 quality sleep | 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 |
The OR for air conditioner use is based on small-scale studies, so caution is needed in interpretation.
Cases have been reported where hyperopic shift and asthenopic symptoms appeared after COVID-19 infection, suggesting a decreased ability of the ciliary muscle to maintain accommodation 2).
It has been shown that each additional hour of screen time increases the risk of eye strain by an OR of 1.15 1). On the other hand, taking regular breaks reduces the risk to an OR of 0.21. Combining screen time limits with regular breaks is important.
The most important aspect in diagnosing eye strain is a detailed medical history. Carefully check VDT usage time, work environment, timing of subjective symptoms, and eyeglass prescription history.
Essential eye examinations:
It has been pointed out that tear film instability can be a major cause of visual fatigue 3), and evaluation of meibomian gland dysfunction is also important.
Diseases to be excluded:
It is necessary to exclude diseases that present with symptoms similar to asthenopia, such as angle-closure glaucoma, uveitis, and optic neuritis. For VDT workers, VDT examinations based on the Ministry of Health, Labour and Welfare guidelines can also be helpful.
Treatment of asthenopia is based on a multifaceted approach depending on the cause.
Refractive Correction
Appropriate spectacle prescription: The most important treatment for asthenopia. Correct hyperopia, astigmatism, and anisometropia accurately.
Contact lens prescription: Effective in reducing aniseikonia when anisometropia is large.
Cycloplegic agents: If accommodative spasm is confirmed, cycloplegic eye drops (e.g., atropine) are used temporarily.
Ocular Alignment Correction
Prism glasses: Prism glasses are effective for heterophoria of about 10 prism diopters (Δ). Vertical deviation should be actively treated even if the angle is small because the fusion range is narrow.
Vision training: Training for convergence insufficiency and binocular vision dysfunction.
Surgery: Indicated for large-angle deviation or cases resistant to medication and training. Botulinum toxin injection is also a treatment option for strabismus.
Environmental adjustments
Screen time limits: Practice the 20-20-20 rule (every 20 minutes, look at something 20 feet away for 20 seconds).
Dry eye treatment: Use of lubricating eye drops and periocular thermotherapy can improve accommodative function and near vision.
Work environment improvement: Appropriate lighting, monitor position, and anti-glare filters.
Meta-analysis results show that regular breaks are a strong protective factor against eye strain, with an OR of 0.21 1). Knowledge about computer use is also an effective protective factor (OR 0.20), and practicing the 20-20-20 rule is a scientifically based preventive measure.
The pathogenesis of eye strain varies depending on the cause, and multiple mechanisms often combine.
Accommodative mechanisms:
Convergence and binocular vision mechanisms:
In convergence insufficiency with accommodative dysfunction, both accommodative convergence and fusional convergence are insufficient, causing diplopia and eye strain at near.
Tear film mechanisms:
Instability of the tear film has been pointed out as one of the main causes of visual fatigue 3). When the tear film is disrupted due to decreased blink rate or increased evaporation, increased scattered light and increased load on visual information processing occur.
Nutritional and metabolic mechanisms:
DHA (docosahexaenoic acid) accounts for about 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).
Mechanisms after COVID-19:
It has been reported that after COVID-19 infection, decreased parasympathetic innervation occurs, leading to reduced ciliary muscle tone, causing a hyperopic shift and symptoms of eye strain 2).
Thakur et al. (2023) reported three cases of eye strain symptoms after COVID-19 recovery 2). A 31-year-old woman, a 25-year-old man, and a 22-year-old man all showed a hyperopic shift, and symptoms improved with appropriate spectacle correction. It suggests a decreased ability of the ciliary muscle to maintain accommodation.
Cases of hyperopic shift and eye strain symptoms after COVID-19 infection have been reported, and it is thought to involve a decreased ability of the ciliary muscle to maintain accommodation 2). Symptoms may improve with appropriate refractive correction.
There is no internationally agreed diagnostic definition for asthenopia, making comparisons between studies difficult. A meta-analysis by Song et al. (2026) proposes the following unified diagnostic criteria 1).
Standardization of this definition is expected to improve the quality of future epidemiological and interventional studies.
Supplementation with omega-3 polyunsaturated fatty acids (PUFAs) has been suggested to reduce oxidative stress on the ocular surface and improve visual fatigue through stabilization of the tear film 4). However, clinical evidence is still insufficient, and future interventional studies are awaited.
Development of methods to objectively assess tear film stability is progressing 3). If this technology is applied clinically, it may enable objective diagnosis and monitoring of dry eye-related asthenopia.
