Differences in Contrast Reproduction between Electronic Devices for Visual Assessment: Clinical Implications

Abstract

The easy access to electronic devices for users has resulted in the development of a vast range of programs and applications for visual evaluation and diagnosis that can be downloaded to any device. Some of them are based on tasks and stimuli that depend on luminance. The aim of the present study was to evaluate differences in luminance reproduction between electronic devices and their implications for contrast reproduction. A total of 20 Galaxy Tab A devices with 8-bit graphics processing units were evaluated. Characterization of every screen was performed obtaining the response curve for the achromatic stimulus. Mean, maximum and minimum luminance, standard deviation and coefficient of variation were obtained to assess differences between devices. Variation of luminance with increasing digital level was observed in all devices following a gamma distribution. Comparison between devices for mean results showed that some of them differed by as much as 45 cd/m2. The coefficient of variation varied from ~5 to 9%. Mean percentage of differences in luminance between devices reached 30%. In conclusion, differences in luminance reproduction between devices were present, even considering devices from the same manufacturing batch. It cannot be assumed that the characterization of one device can be extrapolated to other devices. Every device used for research purposes should be individually characterized to ensure the correct reproduction. For clinical purposes, limitations should be considered by visual specialists.

Validation of Digital Applications for Evaluation of Visual Parameters: A Narrative Review

“…For example, a gamma curve does not reproduce saturation at high power-on levels, as can happen on LCD and TFT screens. In contrast, the use of 3DLUT tables, which also approximates luminance values by interpolation can increase the reliability of the approximation [ 7 , 8 ].…”

“…Therefore, it is worth asking to what extent is the use of applications available in digital stores correct with respect to evaluating visual function. Furthermore, in another recent study by our research group, the differences in luminance reproduction between 20 tablets (Samsung Galaxy Tab A, SM-T519, 2019 version), as well as their implications for contrast reproduction were evaluated, having as a result differences between the devices even if they are from the same manufacturing batch [ 8 ]. Although our study is based on applications for smartphones and tablets, it must be disregarded that validation tests are also being carried out on virtual reality devices, as reported by the study by Wroblewski et al [ 9 ] that conducted a validation of the VirtualEye system (with its respective characterization of screens: luminance measurement).…”

“…If the screen of the device has not been previously characterized, how can you be ensuring that the comparison with the gold standard is reliable? At the very least, they cannot be considered to provide the same level of scientific evidence [ 8 , 10 , 11 ].…”

Randomised placebo-controlled clinical trial evaluating the impact of a new visual rehabilitation program on neuroadaptation in patients implanted with trifocal intraocular lenses

“…Twenty tablets were acquired and used for the training, and consequently, only twenty subjects could be simultaneously recruited for the trial. All screens were colorimetrically characterised using the Gain-offset-gamma method [ 21 ]. Subjects were trained in the use of the software, encouraging them to keep the viewing distance constant at 40 cm.…”