Touch Screen Displays : Vision Care Experiment

Touch Screen Displays

Modern desktop and portable tablet computers are ideal for onsite vision testing. They are relatively easy to operate and their touch screen displays allow great usability.  Spatial resolution is sufficient for testing most routine and unencumbered illnesses that occur in patients over 70 years of age. Perhaps most important is the acceptance of touch screen technology by older patients who appear to be able to easily interact with the new devices comfortably. The attraction of this concept that patients’ visual function may be monitored from distance while they remain at their nursing homes, thus reducing the number of travel time and hospital visits.

Three devices were tested for this study, an iPad Mini 4 (manufactured by Apple Inc.) a Google Nexus 9 (manufactured by Google Inc.) and Galaxy Tab 2 (manufactured by Samsung Electronics).  All three devices use LCD screens but the iPad uses IPS (in plane switching) technology while both the Nexus and the Tab 2 use the PLS (plane line switching) technology. Although they use similar principles, PLS is claimed to be brighter and have wider viewing angles than IPS.

While LCD devices often exhibit an electromagnetic and optic responses many researchers found that majority of LCD manufacturers build correction tables into the video card itself.  This results in LCD responses mirroring the response of a CRT.  CRT screens typically require from 30 to 35 minutes of warm up time before light stabilizes. Our tests showed that all three devices could be used with confidence within a few minutes of turn on from cold. For total light stability a 10-minute warm up period is required for all devices, much quicker than CRT screens. Moreover, as can be seen from testing, the Nexus has the largest range of available contrasts. Tables do have results that are close to all industry standards, particularly the Nexus 10.

For a potential hand held devices such as a tablet PCs with touch screen displays, the effect of reflections and tilting of the screen on displayed light and contrast is important. Our testing confirmed that the combination of reflections from light sources and tilting of the screen with reference to the viewing angle can have clinically significant effects on observed light and contrast.  This means that older patients are better covered by using these devices instead of traditional CRT equipment.

The recent experiments of using an iPad and Android devices for visual testing demonstrate convincingly that such devices are ready for adoption in all major nursing houses and hospitals. It is recommended that proper IT training and relevant IT security procedures are established to ensure proper handling of these devices by older patients.

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