Digital eye strain: Prevalence, measurement and amelioration
Digital device usage has increased substantially in recent years across all age groups, so that extensive daily use for both social and professional purposes is now normal. Digital eye strain (DES), also known as computer vision syndrome, encompasses a range of ocular and visual symptoms, and estimates suggest its prevalence may be 50% or more among computer users. Symptoms fall into two main categories: those linked to accommodative or binocular vision stress, and external symptoms linked to dry eye.
Although symptoms are typically transient, they may be frequent and persistent, and have an economic impact when vocational computer users are affected. DES may be identified and measured using one of several available questionnaires, or objective evaluations of parameters such as critical flicker–fusion frequency, blink rate and completeness, accommodative function and pupil characteristics may be used to provide indices of visual fatigue. Correlations between objective and subjective measures are not always apparent.
A range of management approaches exist for DES including correction of refractive error and/or presbyopia, management of dry eye, incorporating regular screen breaks and consideration of vergence and accommodative problems. Recently, several authors have explored the putative role of blue light-filtering spectacle lenses on treating DES, with mixed results. Given the high prevalence of DES and near-universal use of digital devices, it is essential that eye care practitioners are able to provide advice and management options based on quality research evidence.
In 2018 we published a review of the prevalence, measurement and amelioration of digital eye strain: in BMJ Open Ophthalmology. This article is a summary of the original, which can be accessed for further information via the link below.
The use of digital devices has substantially increased over recent years and not just among the young [Office_for_National_Statistics, 2019] (Figure 1). Digital device use for social situations, in education, at work and during daily living tasks has become expected. There are several terms in use for the resulting ocular and visual symptoms such as digital eye strain, visual fatigue and computer vision syndrome.
Figure 1. Recent internet use (within the last 3 months) among UK adults in 2011 and 2019. Data obtained from the Office for National Statistics 
Symptoms generally related to [Sheedy et al., 2003; Portello et al., 2012]:
Eye dryness, linked to reduced blinking and partial blinking when concentrating on a digital screen
- irritated / burning eyes
- dry eyes
- eye discomfort
Stress on eye focus and the maintenance of binocular vision:
- blurred vision at near
- blurred distance vision after computer use
- difficulty refocusing from one distance to another
- pain in the neck and shoulders
Other symptoms could result from both aetiologies:
- eye strain
- tired eyes
- sensitivity to bright lights
- eye discomfort
These symptoms have an overall prevalence of around 50 % [Portello et al., 2012; Guillon and Maissa, 2010; Courtin et al., 2016; Tauste et al., 2016] of people as a result of extended screen use, with any particular symptom occurring in about 30% of people. While symptoms are typically transient, they can be frequent and persistent, disrupting quality of life and having an economic effect in terms of reduced productivity or exclusion from career opportunities. [Daum et al., 2004].
Several subjective questionnaires have been developed to help quantify digital eye strain. These include:
- Hayes questionnaire – 10 item[Hayes et al., 2007]
- Visual Fatigue Scale – 6 item[Benedetto et al., 2013]
- Computer-Vision Symptom Scale – 17 item[Gonzalez-Perez et al., 2014] - Rasch-based
- Computer Vision Syndrome Questionnaire – 32 item [Mar Segui et al., 2015] -including a version for contact lens wearers[Tauste et al., 2016]
The associated fatigue type effects can be objectively assessed through changes in:
Critical flicker–fusion frequency:
Negative changes in CFF following a prolonged computer task have been observed to correspond with certain subjective ocular complaints (such as pain in/around the eyes, eyes feeling heavy, itchy eyes)[Lin et al., 2017] while other studies found no correlation with symptoms,[Maeda et al., 2011; Ide at el., 2015] although this might be linked to task duration.[Chi and Lin, 1998]
Blink rate and completeness:
A dramatic reduction in blink rate with computer use has been observed in numerous studies,[e.g. Patel et al., 1991; Freudenthaler et al., 2003; Tsubota and Nakamori, 1993] and may be relevant to dry eye symptoms that frequently occur with DES. Incomplete blinking occurs more with digital screen use. [Argiles et al., 2015]
Accommodative / vergence function:
There is little if any increase in the lag of accommodation between viewing digital and paper displays [Wick and Morse, 2002; Penisten et al., 2004; Collier and Rosenfield, 2011], nor accommodative microfluctuations [Grey et al., 2000] or accommodative facility[Rosenfield et al., 2010] or an association with digital eye strain, although it may be changes are only evidence with longer viewing times. [Chi and Lin, 1998].
There are no differences in vergence functions between individuals involved in computer work and those not using a computer.[Yeow and Taylor, 1989,1991; Rosenfield et al., 2010; Collier and Rosenfield, 2011].
More demanding tasks, such as faster on-screen presentation [Nishiyama, 1990] and tracking cause greater increases in pupil diameter, although only a weak correlation with subjective complaints has been established.[Chi and Lin, 1998] Gray et al  reported a significant overall increase in pupil size during 20-minute tasks on various displays in some visually-normal subjects whereas Saito et al.,  observed a reduced pupil diameter and increased amplitude of pupillary reflexes following a prolonged VDT task.
However, the association between subjective symptoms and objective characteristics of the visual system are not always apparent.
Management approaches for digital eye strain include:
A full refractive correction of refractive error and any presbyopia
- Provision of spectacles to correct small refractive errors in pre-presbyopic employees should increase productivity by at least 2.5%.[Daum et al., 2004]
- Astigmatism should be fully corrected as even low levels (0.50 to 1.00 D) impacts negatively on subjective visual comfort,[Wiggine et al., 1991,1993] whilst higher levels of uncorrected astigmatism can increase task errors almost 4-fold and reduce productivity of computer workers substantially.[Daum et al., 2004]
- Computer glasses, with progressive lenses designed to optimise vision in the intermediate and near regions, may reduce symptoms in presbyopic computer users to a greater extent than ergonomic intervention.[Butzon et al., 2002; Morgen et al., 2004]
Management of dry eye
- Use of lubricating eye drops or dietary supplementation [Acosta et al., 1999] with omega-3 fatty acids [Bharava et al., 2015] has been shown to reduce symptoms such as tiredness, dryness and difficulty focusing during sustained computer use,[Acosta et al., 1999] although complete resolution of symptoms may not occur. [Guillon et al., 2004]
- Increased blinking has not been found to alter symptoms during a computer task. [Acosta et al., 1999]
Incorporating regular screen breaks
- Some organisations promotes the 20-20-20 rule (a 20 second break every 20 minutes, to view a distant object at 20 feet) to alleviate digital eye strain [AOA Computer Vision Syndrome report, 2017] as frequent short breaks can relax accommodative and vergence responses, attenuating asthenopic symptoms without impairing productivity.[Galinsky et al., 2007; Balci and Daghazadeh, 2003]
Management of accommodative and convergence anomalies:
- There is no strong evidence for this approach.
- Reduced subjective complaints and smaller reductions in critical flicker frequency in young adults when reading from a screen with reduced blue light background compared to the conventional white background of a modern tablet device [Isonon et al., 2013], but the sample size was small.
- Three studies have examined the effect of blue-light reducing spectacles of digital eye strain, with mixed results on symptoms and objective measures of visual fatigue.[Lin et al., 2017; Ide et al., 2015; Cheng et al., 2014]
- Digital eye strain, visual fatigue and computer vision syndrome are the commonly used terms to describe ocular symptoms relating to the use of digital devices.
- The association between subjective symptoms and objective characteristics of the visual system are not always apparent.
- The management of digital eye strain should include a full refractive correction of refractive error and presbyopia, optimised lens designs, management of dry eye, regular screen breaks and, potentially, blue-filtering solutions.