# Applications of Smart Glasses in Applied Sciences: A Systematic Review
## 4 Discussion  
Systematic reviews were conducted to examine the research trends of smart glasses and analyze them based on the research aim. The answers to the RQs obtained through the analysis are summarized as follows:  
* RQ 1: Research related to smart glasses has been actively conducted since the launch of Google Glass in 2017. This development has been the most researched in the field of healthcare, focusing on areas of clinical and surgical assistance for healthcare professionals or assisting persons with mental or physical disabilities.
* RQ 2: Google Glass products were used the most, followed by Microsoft's HoloLens. Google Glass is an Android-based product, and HoloLens is a Windows-based product. Thus, Android OS is used the most, followed by Windows.
* RQ 3: The purpose of the studies was mostly to determine ways to visually represent information using smart glasses, and transmitting data acquired through smart glasses was the most frequently described. A camera sensor was the most commonly used device.
* RQ 4: Most of the acquired data appeared in the form of AR. The acquired data are mainly processed in the device, and Wi-Fi is the most frequently used data transmission method.  
The advantages of smart glasses are summarized as follows:  
* Cognitive behavior through an optical fluoroscopic display allows the user to better recognize the context of the information when it is received, providing a more immersive experience (compared to mobile devices) [76; 77].
* Users can view digital images from the front without switching their line of sight to their smartphones.
* Visual and head direction sensor technology that can confirm the direction of the user's interest provides information based on the more elaborate head orientation and position, as well as a more immersive and personalized experience.
* Owing to wireless interaction between the device and the user (e.g., voice recognition and air motion), both hands can be used freely without buttons or touchpads.
* There is no need to remember difficult or complicated processes in the field, and it is possible to learn accurately and quickly through virtual videos provided in front of users, improving work efficiency [53].
* Efficiency can be improved through these advantages.  
Although smart glasses are equipped with various functions, such as sensors and batteries, they are still insufficient in terms of weight and design, and more studies need to be commercialized. For smart glasses to be commercialized, it is necessary to discuss the related laws and regulations in terms of price and privacy invasion. Several limitations of smart glasses are summarized as follows:  
* Cameras and GPS-like sensors attached to smart glasses have potential elements of privacy breaches.
* With sensors and batteries to improve functionality, effort is required to achieve a universal smart glass design.
* According to the user environment, it is necessary to consider the appropriate interaction technology (e.g., speech recognition or air motion).
* Smart glasses can be used in reading visual media and articles with long texts, and can technically complement works of fiction, such as novels.
* We must continually develop technologies that can modify existing types of content used in mobile apps and implement dynamic forms of content allowing apps on smartphones to be used successfully when applied in AR [52].
* Next-generation smart glass applications must adopt specific strategies for tailoring content to specific types of smart glasses.