Eye Size Recognition to Control AAC Devices for Persons with Amyotrophic Lateral Sclerosis (ALS)

摘要

Objective: Various kinds of control switches for AAC (Augmentative and Alternative Communication) devices have been developed so far. It is, however, difficult for persons with ALS (Amyotrophic Lateral Sclerosis) to use these switches effectively in their advance stages, because of severe physical constraints. Then, blinking that is the typical residual function of the severely physically disabled is not an available one for persons with ALS (PALS) in their advanced stages. On the other hand, some of PALS can open their eyes normally and widely, even in their advanced stages. However, no control switches can be operated by this residual function. In these circumstances, the purpose of this research is to develop a control switch, for AAC devices, that can be operated by PALS residual function to open their eyes normally and widely. Main Content: It is known clinically that some PALS can open their eyes normally and widely even in their advanced stages, as non disabled persons do. Difference of eye size between at open normally and at open widely can be utilized as an effective residual function to control switches. From these facts, it is supposed that comparison of an eye can be utilized to control switches. According to this principle, an Eye Size Recognition System (ESRS) has been experimentally designed by applying face recognition technology commonly used in digital camera. ESRS can measure an eye size, and compare it to a threshold that was measured and set in advance to. ESRS outputs an electrical signal to interface with control switches and PCs. To verify practicality and effectiveness of ESRS, two types of experiments have been pursued. As there are not so much differences in eye's movement such as opening normally and widely between PALS and non disabled persons, these experiments have been carried out by non disabled persons. In the 1st experiment, non disabled 35 persons were asked to open their eyes bigger to activate ESRS. Then, the 2nd experiment has been done one year later to the 1st experiment. In the 2nd experiment, subjects were 12 of 35 persons who were the subjects of the 1 st experiments, and they were asked to use the system again. To have reference data against the 2nd experiment, a person was asked to use ESRS for twelve days during a month to verify continuous operability in daily life. Result and Conclusion: In the 1st experiment, 91% of the subjects could activate ESRS successfully, and the others failed. It is considered from this result that ESRS has a potential for practical use, and it is also considered that the threshold of ESRS should be set according to each person's physical capability. In the 2nd experiment, 91% of the subjects could operate the testing system by using the threshold that have been measured and set one year before. In the additional experiment, the subject could use ESRS without failure for twelve days during a month, Consequently, it is strongly considered that these results indicate basic effectiveness and practicality of ESRS as a control switch for AAC devices. ESRS has been experimentally used by PALS at his home. After further clinical evaluation, ESRS will be commercial available in near future.