Translation and validation of Convergence Insufficiency Symptom Survey (CISS) to Portuguese - psychometric results

Purpose: Translate and adapt the Convergence Insuficiency Symptom Survey (CISS) questionnaire to the Portuguese language and culture and assess the psychometric properties of the translated questionnaire (CISSvp). Methods: The CISS questionnaire was adapted according to the methodology recommended by some authors. The process involved two translations and back-translations performed by independent evaluators, evaluation of these versions, preparation of a synthesis version and its pre-test. The final version (CISSvp) was applied in 70 patients (21.79 ± 2.42 years) students in higher education, and at two different times, by two observers, to assess its reliability. Results: The results showed good internal consistency of the CISSvp (Cronbach's alpha - α=0.893). The test re-test revealed an average of the differences between the first and second evaluation of 0.75 points (SD ± 3.53), which indicates a minimum bias between the two administrations. The interrater reliability assessed by intraclass correlation coefficient ranged from 0.880 to 0.952, revealing that the CISSvp represents an appropriate tool for measuring the visual discomfort associated with near vision tasks with a high level of reproducibility. Conclusions: The CISS Portuguese version, showed good psychometric properties and has been sown to be applicable to the Portuguese population, to quantify the visual discomfort associated with near vision, in higher education students.