Development of a Refractive Error Quality of Life Scale for Thai Adults (The REQ-Thai)
Roongthip Sukhawarn MD, MSc*, Nonglak Wiratchai PhD**, Pyatat Tatsanavivat MD*, Somwung Pitiyanuwat PhD***, Manop Kanato MD****, Sabong Srivannaboon MD*****, Gordon H Guyatt MD, MSc, FACP, FACCP, FRCPC******
Affiliation : * Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand ** Faculty of Education, Chulalongkorn University, Bangkok, Thailand *** The office for National Education Standards and Quality Assessment (Public Organization), Bangkok, Thailand **** Department of Community Medicine, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand ***** Faculty of Medicine, Mahidol University, Siriraj Hospital, Bangkok, Thailand ****** Departments of Clinical Epidemiology and Biostatistics and Medicine, Faculty of Health Sciences, McMaster University, Canada
Objective : To develop a scale for measuring refractive error quality of life (QOL) for Thai adults.
Material and Method: The full survey comprised 424 respondents from 5 medical centers in Bangkok and from 3 medical
centers in Chiangmai, Songkla and KhonKaen provinces. Participants were emmetropes and persons with refractive correction
with visual acuity of 20/30 or better. An item reduction process was employed by combining 3 methods-expert opinion, impact
method and item-total correlation methods. The classical reliability testing and the validity testing including convergent,
discriminative and construct validity was performed.
Results : The developed questionnaire comprised 87 items in 6 dimensions: 1) quality of vision, 2) visual function, 3) social
function, 4) psychological function, 5) symptoms and 6) refractive correction problems. It is the 5-level Likert scale type. The
Cronbach’s Alpha coefficients of its dimensions ranged from 0.756 to 0.979. All validity testing were shown to be valid. The
construct validity was validated by the confirmatory factor analysis. A short version questionnaire comprised 48 items with
good reliability and validity was also developed.
Conclusion : This is the first validated instrument for measuring refractive error quality of life for Thai adults that was
developed with strong research methodology and large sample size.
Keywords : Questionnaire, Scale development, Vision-targeted health-related quality of life, Factor analysis, Refractive error, Refractive correction, Refractive surgery, Reliability, Validity, Thai adults
