Currently, the diagnosis of DED consists of symptoms (i.e., OSDI questionnaire) and positive results of homeostasis tests (i.e., NIBUT), and subjective symptoms are an essential part of a DED diagnosis.
44 As a potential DED screening tool,
26,31,32,45 the recommended methodology and screening parameters for FVA testing have yet to be established, and few studies have described the direct relationship between FVA results and tear film assessment parameters. In this study, the OSDI total score and subscale scores were moderately correlated with the VMR54 and VMR55 (
Table 4), which were considered the most representative of all CFCVA-related parameters (including the parameters at four contrast levels) for quantifying ocular symptoms. The significant correlations of VMR and mean CFCVA at the fourth and fifth minutes with OSDI scores suggest that CFCVA-related parameters of the last two minutes of the ST can provide adequate information regarding dry eye symptoms and can therefore be used to confirm the ocular discomfort and visual disturbance in patients with DED. ROC curve analysis was used to investigate the discrimination performance of the CFCVA-related parameters in differentiating DED from normal controls. VMR54 and VMR55 were the two parameters that demonstrated the best performance among the CFCVA-related parameters for the detection of DED, achieving AUCs of 0.903 and 0.867 with sensitivities of 0.950 and 0.900 and specificities of 0.733 and 0.800, respectively. Furthermore, the combination of VMR and mean CFCVA (VMR54, VMR55, and mean CFCVA55) was considered valid as it increased the discriminatory capacity of CFCVA-related parameters with the highest AUC value of 0.923 (
Table 5,
Fig. 9), where the sensitivity and specificity were 0.900 and 0.867, respectively. In the study by Kaido et al.,
26 the FVA parameters needed to be combined with a dry eye questionnaire to achieve a clinically acceptable level of screening for DED, and the single parameter (VMR) measured with the currently established FVA system in 60 seconds showed relatively low diagnostic capabilities with an AUC of 0.553. In the present study, a single parameter (VMR51) with comparable setups (a 60-second duration under natural blinking conditions) exhibited superior diagnostic capabilities compared to the study by Kadio et al., with an AUC of 0.757. The discrepancy in results could be attributed to the different study populations recruited, known as potential sampling bias, and the different testing methodologies used (specifically, the introduction of reaction time in the CFCVA measurement system) between the studies. As shown in
Table 4, the diagnostic capabilities of VMR values were further improved by extending the continuous measuring time in the ST, but there was no improvement in the discriminative ability of the different VMR values with decreasing contrast. This suggested that extending the continuous measuring time was more effective in detecting vision-related functional abnormalities in patients with DED than simply decreasing the optotype contrast level.