Abstract
The purpose of this study is to analyze the factorial structure of the Convergence Insufficiency Symptom Survey questionnaire with 15 items, in order to identify latent dimensions that can contribute to a more focused implementation. The questionnaire was self-administered in paper by 183 university students, in the age span of 18 to 30. Both Kaiser-Meyer-Olkin measure and Bartlett's sphericity test were performed to ensure the validity of the factorization. In order to analyze the principal components, factors which obtained eigenvalues greater than 1 were chosen. The extraction of factors was performed after computing a Promax rotation and a Kaiser criterion. In each extracted factor, the internal consistency was used to prove its reliability. Bartlett's sphericity test was statistically significant (p <0.001), and the Both Kaiser-Meyer-Olkin test was 0.89, confirming the factorization of this instrument. Exploratory factor analysis followed by a Promax rotation and scree plots graphic, extracted three factors that explained 62.1% of the total variance. The composition of each factor suggests the following meanings: Factor 1 (somatic sensation) includes 8 of 15 items; Factor 2 (impaired vision) includes 3 of 15 items; Factor 3 (cognitive performance) includes 4 of 15 items. Cronbach's alpha coefficient demonstrated good internal consistency (α> 0.75) in three dimensions. The multivariate statistical analysis of the Convergence Insufficiency Symptom Survey revealed a three-factor structure, so new forms of questionnaire analysis can be designed in order to obtain gains in the management of a symptomatic patient, using 3 subscores, one for each factor, instead of a total score. The factorial structure of the questionnaire can be used with a high level of confidence in future investigations, which aim to assess which dimensions are most affected in each type of visual changes and develop more targeted therapeutic performances.
Highlights
Reading and other near activities are visually demanding tasks that can become difficult and uncomfortable with the manifestation of symptoms such as eye fatigue, text movement, blurring, and loss of concentration, even when visual acuity is good and with normal binocular vision [1,2,3,4]
The visual discomfort can be caused by several factors, specially (1) eye problems, such as the presence of uncorrected refractive errors, accommodative or binocular anomalies [8,9] and (2) others situations, like unsuitable working conditions related to lighting and temperature levels, high continuous working time, short working distances, excessive use of electronic devices and mental status [2,3,7,10,11]
The data matrix was considered adequate since Kaiser-Meyer-Olkin index (KMO) was excellent (0.89) and the Bartlett’s Sphericity Test (p
Summary
Reading and other near activities are visually demanding tasks that can become difficult and uncomfortable with the manifestation of symptoms such as eye fatigue, text movement, blurring, and loss of concentration, even when visual acuity is good and with normal binocular vision [1,2,3,4]. Factor structure of the CISS questionnaire population highly predisposed to report visual discomfort associated with performing tasks at near distances [2,3,5]. The presence of these symptoms potentiates a decrease in visual performance and affects school performance [4,6], contributing to a decrease in quality of life [3]. The visual discomfort can be caused by several factors, specially (1) eye problems, such as the presence of uncorrected refractive errors, accommodative or binocular anomalies [8,9] and (2) others situations, like unsuitable working conditions related to lighting and temperature levels, high continuous working time, short working distances, excessive use of electronic devices and mental status [2,3,7,10,11]
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