Abstract
Purpose :
Optimal lighting is an essential component of low vision rehabilitation. The LuxIQ assessment tool provides a new opportunity for systematic evaluation of lighting needs; however, to date, this tool has not been evaluated for its ability to provide consistent and repeatable data. The goal of this study was to compare test and re-test data for luminance and color temperature preferences under controlled ambient lighting conditions as well as clinically realistic illumination conditions.
Methods :
Luminance intensity (Lux) and color temperature (Kelvin) preferences were assessed using the LuxIQ in 15 men and 15 women (ages 7 to 96) with low vision (VA 20/25 to 20/2400) and 19 normally sighted participants (ages 21 to 57). The low vision data were collected under uncontrolled conditions, e.g., in the clients’ homes, whereas the control data were obtained at 625 Lux ambient illumination. Participants were asked to adjust the intensity to the level they would find most comfortable while reading, whereby color temperature was fixed at a level of 6500 K. They then had to adjust the color temperature to their preferred level as well. Finally, they had to re-verify the intensity level. The entire procedure was repeated 30 minutes later.
Results :
Using Bland-Altman plots, the 95% limits of agreement (LoA) of inter-test difference scores were calculated. For luminance intensity, the LoAs were -1305 to 1122 Lux and -1572 to 1251 Lux, for normally sighted and low vision patients, respectively. For colour temperature, the LoAs were -640 to 504 Kelvin and -1097 to 1238 Kelvin, for normally sighted and low vision patients, respectively. The mean difference scores ranged from -160 to 70.
Conclusions :
The range of differences between repeated measurements of luminance intensity was between 2500 and 3000 Lux, depending on the administration conditions and the clientele. For color temperature, this range was smaller for normally sighted individuals (572 Kelvin) than that for persons with low vision (1167 Kelvin). These data hint at the importance of controlling ambient illumination during administration of the LuxIQ. The next steps are to evaluate which size of measurement difference is clinically relevant to the functional abilities of low vision patients.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.