Comparison of progressive addition lenses for general purpose and for computer vision: an office field study

BCLA CLEAR Presbyopia: Management with contact lenses and spectacles

This paper seeks to outline the history, market situation, clinical management and product performance related to the correction of presbyopia with both contact lenses and spectacles. The history of the development of various optical forms of presbyopic correction are reviewed, and an overview is presented of the current market status of contact lenses and spectacles. Clinical considerations in the fitting and aftercare of presbyopic contact lens and spectacle lens wearers are presented, with general recommendations for best practice. Current options for contact lens correction of presbyopia include soft simultaneous, rigid translating and rigid simultaneous designs, in addition to monovision. Spectacle options include single vision lenses, bifocal lenses and a range of progressive addition lenses. The comparative performance of both contact lens and spectacle lens options is presented. With a significant proportion of the global population now being presbyopic, this overview is particularly timely and is designed to act as a guide for researchers, industry and eyecare practitioners alike.

Trapezius activity during personal computer work with progressive addition lenses for general purpose and for computer work in neophytes

INTRODUCTION

This study analysed the impact of general purpose progressive addition lenses (GP-PALs) and computer progressive addition lenses (PC-PALs) on the activity of the trapezius muscle during computer operation.

METHODS

In this randomised, single-blinded, crossover study, surface electromyography (SEMG) signals were recorded bilaterally from the trapezius muscle during a 30-min computer task performed wearing different presbyopic corrections. The amplitude probability distribution function and its percentiles, gap frequency, muscular rest time and sustained low-level muscle activity periods were analysed in 32 subjects with artificially induced presbyopia. Subjectively perceived differences in vision and postural load between lenses were evaluated using a seven-item questionnaire (non-standardised, visual analogue scale ranged from 1 [bad] to 100 [good]).

RESULTS

Considering the SEMG data, no significant difference in the muscular activity of the trapezius muscle was observed when using GP-PALs or PC-PALs for computer operation. However, PC-PALs showed statistically and clinically significantly higher results for subjectively perceived visual quality (78.4-31.3; p < 0.001), spontaneous tolerance (79.2-31.3; p < 0.001) and field of view (75.9-23.5; p < 0.001) compared with GP-PALs.

CONCLUSIONS

Even though the electromyographic approach did not show a significant differentiation between the lenses, the subjective evaluation was clearly in favour of PC-PALs. Eye care practitioners should always take an occupational history of presbyopes, ask about the workplace situation and consider the use of PC-PALs.

Trial frame for evaluating eye movements

Eye movement research is an established methodology and widely used in fundamental research fields such as psychology or neuroscience. Most research is performed in controlled environments with screen-based eye trackers, but demand for a wearable requirement is on the rise. Yet, a state of the art wearable eye tracking system thus far has not been feasible for subjects with refractive errors; therefore, a trial frame is proposed for researching the eye movement of people with or without refractive errors. Two iris cameras and several infrared radiation LEDs were fixed behind the frame for recording eye images. The images were sent to a host computer using 2.4G wireless, which was also fixed on the frame. The entire electronic system in the trial frame was driven using a battery. Eye position in the images was recognized and segmented by a model that was trained through machine learning. Then the pupil and blinks were detected from the segmented eye area using ellipse fitting and the eye aspect ratio. Experiments showed that the correct rate of pupil and blink detections were 97.24% and 96.14%, respectively.

Analysis of real-world visual ergonomics at the visual display unit

INTRODUCTION

In this interventional study, the ergonomic workplace set-up and the impact of character size on subjectively estimated working productivity and computer vision syndrome (CVS) were evaluated in the field.

METHODS

The number of displays and their size, resolution, surface structure, position in the room and relation to the eye were evaluated for 152 units. CVS was assessed using the CVS-Questionnaire. Habitually used character size for an uppercase E was recorded and compared to the ISO 9241-303:2011, national standards (e.g., ANSI/HFES 100-2007) and national guidelines (e.g., German DGUV Information 215-410). In case of failure to comply with these standards, character size was increased to 22 angular minutes to reach the recommended ranges. Reasons for returning to former or smaller character sizes were recorded, and subjectively perceived changes in productivity were estimated by the participants using a visual analogue scale before and 2 weeks after the intervention using a questionnaire.

RESULTS

The average visual display unit consisted of two non-glare (matt) 24″ widescreen monitors that were located approximately 73 cm (primary) and 76 cm (secondary) from the eyes. The mean (SD) habitually set character size was 14.29 angular minutes (3.53) and therefore both statistically and clinically significantly too small compared with ISO 9241-303:2011 (p < 0.001). Increasing the character size to 22 angular minutes produced a 26% reduction in subjectively rated productivity (p < 0.001). No significant correlation between character size and symptoms of CVS was demonstrated.

CONCLUSIONS

In the workplaces investigated, recommendations for character size were not adhered to. This resulted in a reduction in productivity and was not compatible with some of the work requirements, for example, obtaining a broad overview of a spreadsheet.

Assessment of Visual Quality Improvement as a Result of Spectacle Personalization

Personalized spectacles customized according to an individual's facial anatomy were developed to provide enhanced visual performance and overall comfort when compared to standard spectacles. In this comparative crossover trial, each subject was randomly assigned to wear either personalized spectacles or standard spectacles for two weeks and then tried the second pair for another two weeks. Visual acuity and reading speed were measured, and visual quality and comfort were assessed using specific questionnaires. The correlation of the wearing parameters with the subjects' satisfaction was calculated. According to our results, the subjects wearing personalized glasses reported significantly less experience of swaying and significantly higher overall satisfaction compared to those wearing the control spectacles. At the end of the study, 62% of subjects preferred the personalized spectacles, and visual quality was the primary reason for their spectacle preference followed by wearing comfort. The difference from the ideal cornea-vertex distance was significantly lower when wearing the personalized spectacles compared to the control frames. In addition, the absolute value of the difference from the ideal cornea-vertex distance was significantly correlated with patient satisfaction. These results suggest that personalized spectacles, customized according to an individual's facial anatomy for the ideal wearing parameters, result in both visual and comfort advantages for wearers.

Visual satisfaction with progressive addition lenses prescribed with novel foveal fixation axis measurements

Progressive addition lens (PAL) prescription is usually conducted using the pupillary centre as a reference, which in general does not coincide with the visual axis (kappa distance), and this difference could induce undesired prismatic effects in far and near vision distances and adaptation problems. This study aimed to assess the impact on subjects' visual satisfaction with PALs prescribed based on foveal fixation axis (FFA) measurements. Two different PALs (LifeStyle 3i, Hoya Lens Iberia) were randomly prescribed [one with a customized inset (the difference between the FFA measurements (Ergofocus®, Lentitech, Spain) at far and near distances and the second with a standard inset (2.5 mm)] to be used by 71 healthy presbyopic volunteers in a prospective double-masked crossover clinical study involving one month of use of each PAL. Patients were self-classified into four groups according to their previous experience with PALs: neophyte, PAL users, PAL drop-out, and uncomfortable PAL users. Visual function and overall satisfaction with each PAL were collected and compared. Ninety-seven percent (95% CI 93-100%) of participants successfully adapted to PALs prescribed with FFA without significant differences (P = 0.26) among the study groups (100% neophyte and uncomfortable PAL users (95% CI 100% in both groups), 89% (95% CI 67-100%) PAL users and 94% (95% CI 82-100%) PAL drop-out group). There were no statistically significant differences in visual function (P > 0.05) between customized and standard inset PALs. Customized and standard inset lenses showed similar satisfaction (P > 0.42) that increased significantly (P < 0.01 without any carry-over effect) after 30 days of wear. PALs prescribed with FFA measurements showed high visual satisfaction, suggesting that these measurements are suitable for prescribing PAL adaptation processes. Additional research is necessary to assess differences in PAL users' performance with different prescription methods and lens designs.

Computer vision syndrome-related symptoms in presbyopic computer workers

PURPOSE

To evaluate the prevalence of computer vision syndrome (CVS)-related symptoms in a presbyopic population using the computer as the main work tool, as well as the relationship of CVS with the electronic device use habits and the ergonomic factors.

METHODS

A sample of 198 presbyopic participants (aged 45-65 years) who regularly work with a computer completed a customised questionnaire divided into: general demographics, optical correction commonly used and for work, habits of electronic devices use, ergonomic conditions during the working hours and CVS-related symptoms during work performance. A total of 10 CVS-related symptoms were questioned indicating the severity with which they occurred (0-4) and the median total symptom score (MTSS) was calculated as the sum of the symptoms.

RESULTS

The MTSS in this presbyopic population is 7 ± 5 symptoms. The most common symptoms reported by participants are dry eyes, tired eyes and difficulties in refocusing. MTSS is higher in women (p < 0.05), in laptop computer users (p < 0.05) and in teleworkers compared to office workers (p < 0.05). Regarding ergonomic conditions, MTSS is higher in participants who do not take breaks while working (p < 0.05), who have an inadequately lighting in the workspace (p < 0.05) and in the participants reporting neck (p < 0.01) or back pain (p < 0.001).

CONCLUSION

There is a relationship between CVS-related symptoms, the use of electronic devices and the ergonomic factors, which indicates the importance of adapting workplaces, especially for home-based teleworkers, and following basic visual ergonomics rules.

Intrasession repeatability and agreement of a new method to measure the foveal fixation axis

Purpose

Ophthalmic lens adaptation, particularly with progressive addition lenses, requires accurate measurements of the patient nasopupillary distance (NPD) and interpupillary distance (IPD), which are usually collected using the pupil centre as a reference. However, differences between the pupil centre and visual or foveal axis could induce some subsidiary effects of correcting lenses. This study aimed to assess the intrasession repeatability of a new prototype (Ergofocus®; Lentitech, Barakaldo, Spain) that can measure the foveal fixation axis (FFA) distance and assess the agreement with the NPD measurements collected using a traditional method (frame ruler).

Methods

The FFA at far and near distances was measured three consecutive times in 39 healthy volunteers to determine the intrasession repeatability according to the British Standards Institute and International Organization for Standardization. Additionally, the FFA and NPD (standard frame ruler) were measured in 71 healthy volunteers and compared using Bland-Altman analysis. Two blinded experienced practitioners conducted each FFA and NPD measurement.

Results

The FFA measurements showed acceptable repeatability at far distances (right eye (RE): Sw = 1.16 ± 0.76 mm and coefficient of variation (CV) = 3.92 ± 2.51%; left eye (LE) Sw = 1.11 ± 0.79 mm and CV = 3.76 ± 2.51%) and at near distances (RE: Sw = 0.97 ± 0.85 mm and CV = 3.52 ± 3.02%; LE: Sw = 1.17 ± 0.96 mm and CV = 4.54 ± 3.72%). Additionally, agreement with the NPD showed large differences at far distances (RE: -2.15 ± 2.34, LoA = -6.73 to 2.43 mm (P < 0.001); LE: -0.61 ± 2.62, LoA = -5.75 to 4.53 mm (P = 0.052)) and near distances (RE: -3.08 ± 2.80, LoA -8.57 to 2.42 mm (P < 0.001); LE: -2.97 ± 3.97, LoA: -10.75 to 4.80 mm (P < 0.001)).

Conclusions

FFA measurements showed clinically acceptable repeatability at both far and near distances. Agreement with the NPD measured using a standard frame ruler showed significant differences, suggesting that both measurements are not interchangeable in clinical practice to prescribe and center ophthalmic lenses. Further research is necessary to assess the impact of FFA measurement in ophthalmic lens prescriptions.

New insights in presbyopia: impact of correction strategies

Presbyopia occurs when the physiologically normal age-related reduction in the eyes focusing range reaches a point, when optimally corrected for distance vision, that the clarity of vision at near is insufficient to satisfy an individual’s requirements. Hence, it is more about the impact it has on an individual’s visual ability to function in their environment to maintain their lifestyle than a measured loss of focusing ability. Presbyopia has a significant impact on an individual’s quality of life and emotional state. While a range of amelioration strategies exist, they are often difficult to access in the developing world and prescribing is generally not optimal even in developed countries. This review identified the need for a standardised definition of presbyopia to be adopted. An appropriate battery of tests should be applied in evaluating presbyopic management options and the results of clinical trials should be published (even if unsuccessful) to accelerate the provision of better outcomes for presbyopes.

Surface Electromyography of the Trapezius and Sternocleidomastoid during Computer Work with Presbyopic Corrections

SIGNIFICANCE

During computer work in controlled laboratory conditions, wearing multifocal contact lenses (MFCLs) showed no lower muscle load but increased subjective perception of comfort with equivalent visual quality and comparable tolerance.

PURPOSE

Because musculoskeletal complaints are frequent among computer workers, this study used the muscle electrophysiological activity of shoulder and neck muscles in presbyopic computer workers who received either progressive addition lenses for general purpose (GP-PALs) or MFCLs.

METHODS

For this crossover study, 11 presbyopic computer workers aged 55 ± 4 years (mean ± standard deviation) were equipped with GP-PALs and MFCLs in a randomized order. Surface electromyography signals were recorded bilaterally from shoulder and neck muscles during short-term computer work tasks using an optimally adjusted visual display unit workplace. The amplitude probability distribution function, the number and total duration of EMG gaps, and sustained low-level muscle activity periods of the surface electromyography signals were calculated. Comfort and correction type preferences were assessed. Head inclination was objectively evaluated.

RESULTS

Multifocal contact lenses elicited no significant lower muscle load than GP-PALs. The number of sustained low-level muscle activity periods longer than 60 seconds was similar between visual aids. The total amount of gaps was significantly higher with MFCLs (44 gaps) compared with progressive addition lenses for general purpose (15 gaps) in all analyzed periods for all participants. However, there were no significant differences for the median in the intraindividual comparisons (P = .22, dz = 0.52). Multifocal contact lenses scored statistically significant higher in comfort values with equivalent visual quality and comparable tolerance (P = .003, dz = 1.51).

CONCLUSIONS

Although the study failed to show clear results, wearing MFCLs seems to enhance working comfort compared with GP-PALs subjectively.

Comparison of physiognomy and frame angle parameters using different devices to prescribe progressive addition lenses

Clinical relevance: Accurate measurement of several physiognomy parameters (interpupillary, nasopupillary and fitting height distances) and frame angles (pantoscopic and frame wrap angles) is essential for prescribing progressive addition lenses for presbyopic patients.Background: Few reports have described the repeatability of different devices commonly used to conduct essential measurements for prescribing progressive addition lenses.Methods: Interpupillary, nasopupillary (at far and near distances) and fitting point heights were measured three consecutive times in 21 healthy volunteers with four devices (traditional frame ruler, PD-5 interpupilometer, OptiCenter, and VisiOffice). Pantoscopic and wrap frame angles were also measured three times with Essilor standard pantoscopic ruler, Opticenter and VisiOffice.Results: The frame ruler, PD-5 and Opticenter showed better repeatability for interpupillary and nasopupillary distance (co-efficient of variation close to 1%, within-subject standard deviation or Sw < 0.50 mm) measurements at far and near distances than Visioffice (co-efficient of variation > 2%, Sw > 0.50 mm). Fitting point heights measurements showed worse repeatability with all devices (frame ruler: co-efficient of variation close to 5%, Sw = 0.46 mm; Opticenter co-efficient of variation > 5%, Sw > 0.80 mm; Visioffice co-efficient of variation > 10%, Sw > 1.50 mm). Pantoscopic angle measurements showed very low repeatability with the ruler and Opticenter (co-efficient of variation > 25%, Sw > 1.90 mm). The frame wrap angle showed unacceptable repeatability values with the ruler (co-efficient of variation > 10%, Sw = 0.49º) and Visioffice (co-efficient of variation > 60%, Sw > 2.50º), but acceptable repeatability with Opticenter (co-efficient of variation < 1%, Sw = 0.05º).Conclusions: Interpupillary and nasopupillary distance measurement showed acceptable repeatability with all the assessed methods; however, these measurements alone are no longer sufficient for free-form progressive addition lens prescription, which requires fitting point heights and pantoscopic and frame wrap angle measurement. Such measures display a lack of repeatability that could induce centration errors and could affect vision and/or adaptation of the user.

Computer vision syndrome in presbyopic digital device workers and progressive lens design

PURPOSE

To estimate the prevalence of computer vision syndrome (CVS) in presbyopic digital device workers using two ophthalmic progressive lens designs during the working day, and to analyse the association of CVS with sociodemographic, occupational, digital device exposure and refractive factors.

METHODS

This time series, quasi-experimental design study included 69 presbyopic digital device workers (age range: 46-69 years; mean ± SD = 54.7 ± 5.0). All used desktop computers at their workplace. Progressive addition lenses (PALs) and occupational lenses were used for three months each. CVS was measured with the CVS-Q^© questionnaire before intervention (baseline) and at 1 week, 1 month and 3 months after wearing the lenses. A multivariate logistic regression model was used to identify the factors that were associated with an improved CVS-Q^© score.

RESULTS

37.7% of the subjects were female and 78.3% were ametropes; 65.2% had advanced presbyopia. 56.2% used digital devices at work >6 h day^-1 . The prevalence of CVS at baseline, after wearing PALs for three months and after three months of occupational lens wear was 68.1%, 33.3% and 18.8%, respectively. The mean CVS-Q^© score was lower with occupational lenses than with PALs (p = 0.001). 40.6% of the digital device workers improved their CVS-Q^© score ≥2 points with the occupational lenses. Ametropes were less likely than emmetropes to improve with occupational lenses (OR = 0.27, p = 0.05). 89.8% of the sample workers were satisfied or very satisfied with the occupational lenses and 71% were similarly satisfied with the PALs. 73.9% chose the occupational lenses as their first choice of lens for digital device use, compared with 17.4% for PALs.

CONCLUSIONS

Computer vision syndrome is reduced in presbyopic desktop computer workers wearing occupational lenses compared with PALs, especially in emmetropes.

Optical performance of progressive addition lenses (PALs) with astigmatic prescription

The progressive addition lens (PAL) is a spectacle lens design with progressive refractive power changes across the lens surface to provide sharp vision at different viewing distances for patients with reduced accommodative strength. It has gained in popularity not just for presbyopic patients, but also patients with occupational (office, driving, or digital device) and therapeutic (e.g., myopia control) needs. However, despite the increasing prevalence of astigmatism in adults > 40 years old who rely on PAL correction, no metric is available to reflect the optical variation in PALs with astigmatic prescriptions. Based on recent studies, four novel optical metrics sensitive to variation of refractive power across the lens surface of PALs have been developed. These metrics were used to compare the optical performance of PALs of various prescriptions, designs, and manufacturers. For each lens, the refractive power profile was first measured with a Moire-deflectometry-based instrument.The data was then exported and analyzed using a two-dimensional error map for each of the four metrics. The results revealed significant impacts of astigmatic prescription, providing evidence for the usefulness of these metrics in quantifying the optical performance of PALs for patients with astigmatic prescriptions.

Exploring the benefits and limitations of augmented reality for palletization

Superimposing virtual visual information within the real world is referred to as augmented reality (AR). This technique becomes increasingly popular and due to technical advances can be applied to various purposes ranging from consumer entertainment to industrial use cases. Workplaces equipped with AR assistance-systems promise fast and accurate performance. Within the field of intralogistics, palletization constitutes a field of application which may benefit from guidance by AR. In the present investigation, participants performed a palletization task while they received instructions via three different devices (paper list, tablet, AR glasses). Performance data and subjective ratings were obtained. Participants subjectively preferred to work with the AR device. Number of errors was reduced while at the same time handling times were prolonged when the AR device was used. In all experimental conditions, performance improved in the course of the experiment. Least improvement was observed in the AR condition, which emphasizes that such applications allow decent performance without prior experience. Overall, the present results indicate that the utility of AR applications is limited when task demands are low. Such applications might be more useful in unclear and complex situations. Furthermore, AR possesses high hedonic qualities which may ease the integration of novel work processes.

Prevalence of Computer Vision Syndrome and Its Relationship with Ergonomic and Individual Factors in Presbyopic VDT Workers Using Progressive Addition Lenses

This cross-sectional study estimated computer vision syndrome (CVS) prevalence and analysed its relationship with video display terminal (VDT) exposure, as well as sociodemographic, refractive, environmental, and ergonomic characteristics in 109 presbyopic VDT workers wearing progressive addition lenses (PALs). Usual spectacles were measured with a lens analyser, and subjective refraction was performed by an optometrist. CVS was measured with the CVS-Q©. VDT exposure was collected. Ergonomic evaluations were conducted in a normal working posture looking at the screen. Air temperature and relative humidity were measured (thermohygrometer), and illumination was measured (luxmeter). Descriptive analysis and differences in CVS prevalence, as a function of the explanatory variables, were performed (chi-square test). Multivariate logistic regression was used to identify factors associated with CVS (OR and 95% CI). The mean age was 54.0 ± 4.8 years, and 43.1% were women. The mean hours of VDT use at work was 6.5 ± 1.3 hours/day. The prevalence of CVS was 74.3%. CVS was significantly associated with women (OR 3.40; 95% CI, 1.12–10.33), non-neutral neck posture (OR 3.27; 95% CI, 1.03–10.41) and altered workplace lighting (OR 3.64; 95% CI, 1.22–10.81). Providing training and information to workers regarding the importance of adequate lighting and ergonomic postures during VDT use is advised to decrease CVS and increase workplace quality of life.

Presbyopic Personal Computer Work: A Comparison of Progressive Addition Lenses for General Purpose and Personal Computer Work

SIGNIFICANCE

Computer-specific progressive addition lenses (PC-PALs) are shown to reduce computer vision syndrome (CVS) symptoms, increase visual comfort and tolerance, and improve body posture at the personal computer. They are highly preferred by computer workers. Increasing their use may aid prevention measures within the workplace health management.

PURPOSE

This study investigates whether technical differences between general-purpose progressive addition lenses (GP-PALs) and PC-PALs are subjectively manifest in CVS.

MATERIALS AND METHODS

One hundred ninety presbyopic visual display unit (VDU) workers aged 53 ± 6 years (mean ± SD) were fitted with GP-PALs and PC-PALs in a subject-masked, randomized, crossover study. Subjects tested both corrections at their personal workplace for 2 weeks each, for VDU work only. Comfort and lens type preferences were assessed using a 24-item questionnaire developed for this study.

RESULTS

Computer vision syndrome was perceived approximately seven times more often with GP-PALs compared with PC-PALs. Eighty-four percent of subjects preferred PC-PALs for their VDU work. Computer-specific progressive addition lenses ratings were statistically and clinically significantly better than GP-PALs (5.95 vs. 4.42 of 7 points; 1.53; 95% confidence interval, 1.20 to 1.85). An existing ametropia or prior experience with PALs did not influence the score. Only 14.2% of subjects had received information about specific VDU eyewear from their optician or optometrist, whereas 79% expressed the wish to be informed about these products.

CONCLUSIONS

Computer-specific progressive addition lenses reduce the perception of the CVS and are highly preferred by VDU workers.

Adaptive eyeglasses for presbyopia correction: an original variable-focus technology

We propose an original variable-focus technology specially designed for presbyopia-correcting adaptive eyeglasses. It has been thought through to offer vision comfort without cutting on aesthetics. It relies on a fluid-filled variable-focus lens (presenting 2 liquids and 1 ultra-thin membrane) assisted by a low-power, high-volume microfluidic actuator. It also features a distance-sensing system to provide automatic focusing. We demonstrate the qualities of this novel technology on our first prototype. Our prototype achieves the necessary 3-diopter-high power variation on a 20-millimeter-wide variable zone with low actuation pressures (~200 Pa at most), and the preliminary optical quality analysis shows the spatial resolution is much better than the one specified by classic eye charts. We discuss further improvements in terms of optics, aesthetics and portability. In particular, we point out that this variable technology is compatible with standard base curves, and we highlight an optimal configuration where the power consumption of our opto-fluidic engine is about 25 mW peak.

Optical correction of refractive error for preventing and treating eye symptoms in computer users

BACKGROUND

Computer users frequently complain about problems with seeing and functioning of the eyes. Asthenopia is a term generally used to describe symptoms related to (prolonged) use of the eyes like ocular fatigue, headache, pain or aching around the eyes, and burning and itchiness of the eyelids. The prevalence of asthenopia during or after work on a computer ranges from 46.3% to 68.5%. Uncorrected or under-corrected refractive error can contribute to the development of asthenopia. A refractive error is an error in the focusing of light by the eye and can lead to reduced visual acuity. There are various possibilities for optical correction of refractive errors including eyeglasses, contact lenses and refractive surgery.

OBJECTIVES

To examine the evidence on the effectiveness, safety and applicability of optical correction of refractive error for reducing and preventing eye symptoms in computer users.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL); PubMed; Embase; Web of Science; and OSH update, all to 20 December 2017. Additionally, we searched trial registries and checked references of included studies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-randomised trials of interventions evaluating optical correction for computer workers with refractive error for preventing or treating asthenopia and their effect on health related quality of life.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed study eligibility and risk of bias, and extracted data. Where appropriate, we combined studies in a meta-analysis.

MAIN RESULTS

We included eight studies with 381 participants. Three were parallel group RCTs, three were cross-over RCTs and two were quasi-randomised cross-over trials. All studies evaluated eyeglasses, there were no studies that evaluated contact lenses or surgery. Seven studies evaluated computer glasses with at least one focal area for the distance of the computer screen with or without additional focal areas in presbyopic persons. Six studies compared computer glasses to other types of glasses; and one study compared them to an ergonomic workplace assessment. The eighth study compared optimal correction of refractive error with the actual spectacle correction in use. Two studies evaluated computer glasses in persons with asthenopia but for the others the glasses were offered to all workers regardless of symptoms. The risk of bias was unclear in five, high in two and low in one study. Asthenopia was measured as eyestrain or a summary score of symptoms but there were no studies on health-related quality of life. Adverse events were measured as headache, nausea or dizziness. Median asthenopia scores at baseline were about 30% of the maximum possible score.Progressive computer glasses versus monofocal glassesOne study found no considerable difference in asthenopia between various progressive computer glasses and monofocal computer glasses after one-year follow-up (mean difference (MD) change scores 0.23, 95% confidence interval (CI) -5.0 to 5.4 on a 100 mm VAS scale, low quality evidence). For headache the results were in favour of progressive glasses.Progressive computer glasses with an intermediate focus in the upper part of the glasses versus other glassesIn two studies progressive computer glasses with intermediate focus led to a small decrease in asthenopia symptoms (SMD -0.49, 95% CI -0.75 to -0.23, low-quality evidence) but not in headache score in the short-term compared to general purpose progressive glasses. There were similar small decreases in dizziness. At medium term follow-up, in one study the effect size was not statistically significant (SMD -0.64, 95% CI -1.40 to 0.12). The study did not assess adverse events.Another study found no considerable difference in asthenopia between progressive computer glasses and monofocal computer glasses after one-year follow-up (MD change scores 1.44, 95% CI -6.95 to 9.83 on a 100 mm VAS scale, very low quality evidence). For headache the results were inconsistent.Progressive computer glasses with far-distance focus in the upper part of the glasses versus other glassesOne study found no considerable difference in number of persons with asthenopia between progressive computer glasses with far-distance focus and bifocal computer glasses after four weeks' follow-up (OR 1.00, 95% CI 0.40 to 2.50, very low quality evidence). The number of persons with headache, nausea and dizziness was also not different between groups.Another study found no considerable difference in asthenopia between progressive computer glasses with far-distance focus and monofocal computer glasses after one-year follow-up (MD change scores -1.79, 95% CI -11.60 to 8.02 on a 100 mm VAS scale, very low quality evidence). The effects on headaches were inconsistent.One study found no difference between progressive far-distance focus computer glasses and trifocal glasses in effect on eyestrain severity (MD -0.50, 95% CI -1.07 to 0.07, very low quality evidence) or on eyestrain frequency (MD -0.75, 95% CI -1.61 to 0.11, very low quality evidence).Progressive computer glasses versus ergonomic assessment with habitual (computer) glassesOne study found that computer glasses optimised for individual needs reduced asthenopia sum score more than an ergonomic assessment and habitual (computer) glasses (MD -8.9, 95% CI -16.47 to -1.33, scale 0 to 140, very low quality evidence) but there was no effect on the frequency of eyestrain (OR 1.08, 95% CI 0.38 to 3.11, very low quality evidence).We rated the quality of the evidence as low or very low due to risk of bias in the included studies, inconsistency in the results and imprecision.

AUTHORS' CONCLUSIONS

There is low to very low quality evidence that providing computer users with progressive computer glasses does not lead to a considerable decrease in problems with the eyes or headaches compared to other computer glasses. Progressive computer glasses might be slightly better than progressive glasses for daily use in the short term but not in the intermediate term and there is no data on long-term follow-up. The quality of the evidence is low or very low and therefore we are uncertain about this conclusion. Larger studies with several hundreds of participants are needed with proper randomisation, validated outcome measurement methods, and longer follow-up of at least one year to improve the quality of the evidence.

The impact of different lenses on visual and musculoskeletal complaints in VDU workers with work-related neck complaints: a randomized controlled trial

Objectives

The impact of wearing lenses on visual and musculoskeletal complaints in VDU workers is currently unknown. The goal of this study was 1) to evaluate the impact of wearing VDU lenses on visual fatigue and self-reported neck pain and disability, compared to progressive lenses, and 2) to measure the effect of both lenses on head inclination and pressure pain thresholds during the performance of a VDU task.

Methods

Thirty-five eligible subjects were randomly assigned to wear progressive VDU lenses (VDU group) (n = 18) or progressive lenses (P group) (n = 17). They were enquired about visual complaints (VFQ), self-perceived pain (NRS) and disability (NDI) at baseline (with old lenses), and 1 week, 3 months and 6 months after wearing their new lenses. In addition, Forward Head Angle (FHA) and PPTs were assessed during and after a VDU task before and 6 months after wearing the new lenses. A short questionnaire concerning the satisfaction about the study lenses was completed at the end of the study.

Results

In both groups, visual fatigue and neck pain was decreased at 3 and 6 months follow up, compared to baseline. All PPTs were higher during the second VDU task, independent of the type of lenses. The VDU group reported a significantly higher suitability of the lenses for VDU work.

Conclusion

It can be concluded that there is little difference in effect of the different lenses on visual and musculoskeletal comfort. Lenses should be adjusted to the task-specific needs and habits of the participant.