Validation of Binocular Vision and Ocular Surface Assessment Tools in Digital Eye Strain Syndrome: The DESIROUS Study

Abstract

Background: To understand if binocular vision disorders are associated with Digital Eye Strain Syndrome (DESS), a study protocol is needed to ensure consistency across observational studies. This study aims to test the feasibility of a protocol to assess DESS, screen time, binocular vision, and dry eye. Methods: DESIROUS is an observational cross-sectional study among Polytechnic students at the Lisbon School of Health Technology, Portugal. The protocol includes three questionnaires (Computer Vision Syndrome Questionnaire [CVS-Q], Convergence Insufficiency Symptom Survey [CISS], and Dry Eye Questionnaire version 5 [DEQ-5]), an assessment of visual acuity and binocular vision (cover test for near and distance, stereopsis, near point convergence (NPC), near point accommodation (NPA), accommodative facility, vergence), and the ocular surface break-up tear (BUT) test. The questionnaires were validated using Cronbach's alpha. Interobserver variability for BUT was assessed using Cohen's Kappa, Intraclass Correlation Coefficient (ICC), and Bland-Altman analysis involving three observers (A, B, and C), compared against an expert as the gold standard. Results: A total of 18 students were included in the validation phase (mean age: 21.50 ± 0.62 years; females: 77.8%). The internal consistency of the CVS-Q (α = 0.773) and the CISS (α = 0.756) was considered good, while the DEQ-5 showed a reasonable internal consistency (α = 0.594). Observer A had the highest agreement with the gold standard (Cohen's Kappa = 0.710 and p < 0.001; ICC = 0.924, p < 0.001). Conclusions: We provide a protocol to assess binocular vision and the ocular surface, with an emphasis on objective measures while integrating other assessment approaches. Further studies are necessary to validate this protocol, potentially incorporating new measures to enhance its validity across different populations.

Keywords: accommodation; binocular vision; convergence; digital eye strain; ocular surface.

Figure 1

DESIROUS flow diagram. Legends: ESTeSL: Lisbon School of Health Technology; CVS-Q: Computer Vision Syndrome Questionnaire; CISS: Convergence Insufficiency Symptom Survey; DEQ-5: Dry Eye Questionnaire version 5; BUT: tear film break-up time.

Figure 2

Cronbach’s alpha for the three questionnaires included in the pilot study.

Figure 3

Bland–Altman scatter plot: (A)—between the expert and Observer A; (B)—between the expert and Observer B and (C)—between the expert and Observer C. Legend: black line (--): mean line; gray line upper (--) = mean difference + 1.96 x SD difference; gray line lower (--) = mean difference—1.96 x SD difference.