Abstract
Purpose:
Dry eye is common in Asian populations, but there are limited validated language-specific instruments available to assess ocular symptoms. This study aimed to develop and assess the psychometric properties of a Chinese version of the ocular comfort index (OCI).
Methods:
The original 12-item OCI was translated and back-translated by 32 bi-lingual volunteers and a preliminary version of the Chinese OCI was produced for analysis. Subsequently, 165 bi-lingual volunteers completed both the English and the Chinese versions of the OCI. The items scores for preliminary Chinese OCI were compared to the English version using Cronbach α. Rasch analysis (rating scale model with Winsteps software v3.74) was used to assess overall fit of the model, rating responses, item fit and person separation reliability. A subsequent version of the Chinese OCI was produced as indicated by Rasch analysis. Repeatability of the Chinese OCI was evaluated in a sub-group of 20 participants after a 1 week interval by calculating the Coefficient of Repeatability (CoR) and intra-class correlation (ICC) for the total OCI score.
Results:
Cronbach α coefficients for all items were above 0.85. Rasch analysis indicated that two items in the Chinese OCI required deletion or modification, due to misfit to the Rasch model and disordered category thresholds. Removal of these items results in improved measurement precision. The person-separation reliability was 0.89 however the targeting of item difficulty was not optimal (mean person measure:-2.05) The CoR for the Chinese OCI was ±5.84 and the ICC coefficient was 0.96 (95% confidence interval 0.91, 0.98).
Conclusions:
The psychometric properties of the Chinese OCI are robust and comparable to the original English version. However, to confirm the effective targeting of item difficulty to patients’ ability, the Chinese OCI scale needs to be validated in a Chinese dry eye population.
Keywords: 486 cornea: tears/tear film/dry eye •
468 clinical research methodology