Butzon 2002.

Methods	Quasi‐randomised cross‐over study
Participants	26 symptomatic computer users aged 37 or older, who wore eyeglasses at the computer and had an eye examination in past year (20/20 vision at distance and near) and who worked at computer for at least four hours per day. Age range (37 to 57) Male/Female: 7/23 Mean time spent at a VDT per day: at least 4 hours (type of computer not described) Refractive error: not described Country: USA
Interventions	Eyeglasses vs. non‐optical intervention: computer glasses (progressive (n = 15 Technica by American Optical; n = 8 Access by SOLA), bifocal (n = 1) or trifocal (n = 1, Datlite CRT) glasses) vs. ergonomic self assessment tool (ESAT) with habitual refraction; 3 weeks duration of each intervention period.
Outcomes	Frequency and severity of 14 symptoms at baseline and after each intervention period (3 and 6 weeks)
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Intervention and comparison in a "planned alternating order".
Allocation concealment (selection bias)	Unclear risk	Intervention and comparison in a "planned alternating order"; no attempt at concealment reported.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	No attempt at blinding reported.
Blinding of outcome assessment (detection bias) Primary outcomes	Unclear risk	No attempt at blinding reported.
Blinding of outcome assessment (detection bias) Secondary outcomes	Unclear risk	No attempt at blinding reported.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	26 of 30 participants completed the study and answered all questionnaires. Three persons missing from computer glasses‒ESAT sequence, and one from the ESAT‒computer glasses sequence; no further information on participants not completing the study.
Selective reporting (reporting bias)	Unclear risk	No study protocol. All outcomes mentioned in the Methods section are reported.
Other bias	High risk	No wash‐out period between interventions, and baseline imbalance: the computer glasses‒ESAT sequence had a symptom score of 34.5 and the ESAT‒computer glasses had a score of 43.1.