
Recent advancements in virtual reality (VR) and augmented reality (AR) technologies have led to the introduction of innovative ophthalmic diagnostic devices. While previous attempts to use head-mounted displays (HMDs) for VR/AR applications in ophthalmology were hindered by limitations such as low resolution, long axial length optics, poor battery performance, and heat generation, recent technological breakthroughs have improved the wearability, performance, and user experience of VR/AR devices. The introduction of thinner and lighter pancake lenses, the development of high-resolution micro–organic light-emitting diode (OLED) displays, and the enhancement of eye-tracking capabilities have all contributed to this progress. Additionally, improvements in application processor performance have eliminated the need for personal computer connections for high-resolution image rendering, enabling standalone operation of many software applications. As a result, various VR/AR devices, such as Pico® (Pico Interactive), Quest® (Meta), Vision Pro® (Apple), and HoloLens® (Microsoft), have gained popularity. These continued advancements in HMD technology are accelerating the widespread adoption of VR/AR devices and expanding the possibilities for their use in various fields. The HoloLens® (Microsoft Corp.), for example, is being used in construction and industrial settings as a guide for assembly procedures, as well as in military applications for identification and guidance [1,2].
In the field of ophthalmology, VR/AR devices offer unique features that can be leveraged for diagnosis, treatment, education, and more. AR is already being applied in operating rooms to enhance specific colors (NGENUITY®; Alcon Laboratories) and assist surgereons with optical coherence tomography imaging (ARTEVO 800®; Zeiss). The availability of these devices enables developers to create diagnostic tools without the need for new hardware, simply by integrating software into existing devices, reducing developmental burdens. A notable example of software integration into existing devices is Virtual Eye® (Virtual Vision), a visual field tester that incorporates an HMD and operates on Pico® via integrated software (Fig. 1).
Building upon both our previous experience in developing and publishing a metamorphopsia diagnostic device using a three-dimensional monitor and recent patent filings [3,4], this review comprehensively examines the principles, components, potential applications in ophthalmology and other fields, current applications, and limitations of VR/AR devices, focusing on HMDs.
VR/AR devices operate either by completely blocking the user's view or overlaying virtual information onto the real world. VR devices track the user's head movements to generate real-time virtual images, while AR devices capture the real world through a camera and combine the resulting views with virtual information.
Broadly, these devices require a camera to capture external images, a display to project images, an optical system to enable the user to view the images, and a controller for operation. Additional components include a microphone for voice recognition, a speaker for audio output, and an eye-tracking system to track eye movements.
During device use, each eye of the user is presented with a slightly different image, creating binocular disparity and enabling stereoscopic vision. This optical separation of the eyes is particularly advantageous for ophthalmic examinations that require separate assessments of each eye.
The optical system of VR/AR devices plays a crucial role in providing users with a clear and wide field of view (Fig. 2). The distance between the user and the virtual image is determined by the focal length of the lens and the distance between the lens and the display. However, relying solely on lenses would result in bulky devices that are uncomfortable to wear. Therefore, various methods have been employed to overcome this challenge.
Conventional Lens: These lenses offer excellent image quality with minimal distortion, providing a clear and natural field of view. However, they are thick and heavy, leading to discomfort and increased device size and weight.
Fresnel Lens: This type of lens employs concentric grooves on the lens surface to refract light, reducing lens thickness while maintaining optical performance [5]. These lenses are thin, lightweight, and cost-effective but can cause ghosting and light-scattering due to diffraction, resulting in lower image quality compared to conventional lenses.
Pancake Lens: A pancake lens folds the light path by reflecting light multiple times, greatly reducing the distance between the lens and the display [6]. These lenses offer exceptional thinness, lightness, and design flexibility, with excellent image quality, minimal distortion, and chromatic aberration. However, they are complex and expensive to manufacture, and brightness may decrease due to multiple reflections.
Pancake lenses have gained popularity in recent VR/AR devices due to their ability to enhance wearability and performance while maintaining excellent image quality. Notably, the Meta Quest 3 (Meta) and other recent VR devices incorporate pancake lenses to deliver a more immersive VR experience.
The display of VR/AR devices is essential for providing users with high-resolution images and enhancing immersion. Various types of displays, such as OLEDs and liquid crystal displays, are used, each with unique characteristics in terms of color reproduction, response time, and power consumption. The development of micro-OLED displays with even higher resolutions and refresh rates is actively underway. The resolution of modern displays has significantly improved compared to those of the past, offering sufficient resolution for use in ophthalmic examination devices.
Modern VR/AR devices include controllers with the following features to enable operation while viewing images.
Motion Tracking: Controllers are equipped with various sensors, such as gyroscopes, accelerometers, and magnetometers, to accurately track the user's hand movements. This allows natural interaction in the virtual environment, such as grabbing or throwing objects.
Buttons and Triggers: Controllers have various buttons and triggers for object selection, menu navigation, and action execution.
Haptic Feedback: Controllers provide tactile feedback through vibration, enhancing the virtual experience; for example, users can feel vibrations when grabbing a virtual object or bumping into a wall.
Touchpad or Joystick: Some controllers include a touchpad or joystick for movement, menu navigation, and viewpoint adjustment in the virtual environment.
These controllers are designed for the mass market and offer superior operability and intuitiveness compared to triggers found in ophthalmic diagnostic devices. This makes them relatively easier to use for elderly individuals and children with potentially lower cognitive abilities.
VR devices are used for ophthalmic surgical training, allowing trainees to experience and practice surgical procedures performed by skilled surgeons in an immersive environment. VR-based training simulators have been developed and used for various surgical fields, including cataract and retinal surgeries (Fig. 3) [7,8].
Traditional surgical training methods, such as wet lab exposure, have the advantage of incorporating actual surgical equipment. However, they are only available at specific training centers and are expensive. Additionally, training uses model eyes and eggs, which results in significant differences from real human eyes.
On the other hand, VR devices are relatively less expensive and have fewer spatial and temporal constraints [9]. They help to establish a highly immersive virtual environment (visual/spatial/tactile) similar to the human eye by providing responses such as vibration through haptics [10]. In addition, surgical training using VR allows practice by reproducing specific surgical situations and enables difficult adjustment and repetitive training [10,11].
VR devices can present images to one eye or different images to each eye, enabling the separation, comparison, and treatment of binocular functions. This capability can be used to assess differences in binocular function by observing the perception of variations between images presented to each eye or to detect early metamorphopsia. Various ophthalmic examination devices, such as visual field testers and metamorphopsia assessment devices, have been developed or are under development [4,12]. VR-based examinations can measure a wider visual field range than traditional methods and provide patients with a more comfortable and immersive experience. Additionally, VR devices allow precise control of visual stimuli and real-time measurement of patient responses, enabling the assessment of visual functions that were previously difficult to evaluate.
Visual Field Test Devices: VR HMDs can be used to perform visual field tests, aiding in the diagnosis of various ophthalmic diseases like glaucoma and retinal diseases [13,14]. Notably, Oculus, a well-known HMD developer, has created software for this purpose, highlighting the competitiveness of VR platforms in this field [15].
Metamorphopsia Assessment Devices: VR HMDs present visual stimuli such as grids or Amsler grids and assess the degree of distortion perceived by the patient to diagnose metamorphopsia. The author has filed a Patent Cooperation Treaty patent in this area and is developing self-examination software [4].
Strabismus and Diplopia Tests: VR devices can present different images to the two eyes and simulate distant objects, potentially replacing tests like the Hess test and Worth four-dot test, which traditionally require large examination spaces [16].
Color Vision Deficiency Test Devices: VR HMDs present visual stimuli of various colors to assess the patient's color-discrimination ability and diagnose color vision deficiencies. Olleyes® (Olleyes) is a VR-based device designed for color vision deficiency testing that can diagnose various types of color vision deficiencies.
Eye Movement Test Devices: VR HMDs use built-in eye-tracking sensors to measure eye-movement trajectories, speed, and accuracy, aiding in the diagnosis of eye-movement disorders. Eye-Sync (SyncThink) is a device that measures and analyzes eye movements using a VR HMD, showcasing the application of eye-tracking sensors [17].
VR devices are also used in the treatment of amblyopia. VR-based amblyopia treatment engages patients through interesting content like games, improving adherence and treatment outcomes [18]. Various visual stimuli and training programs provided in the VR environment can aid in improving visual acuity and developing binocular vision in amblyopia patients.
VR/AR technology is expected to be applied in a wider range of areas within ophthalmology.
Eye-Tracking Technology: The integration of eye-tracking technology in VR/AR devices can help users focus on images and enable examiners to monitor user status in real-time. This can be used for the diagnosis and treatment of eye-movement disorders and visual rehabilitation.
Red–Green–Blue Color Testing: VR/AR devices can present red, green, and blue colors individually to aid in the early detection of color vision deficiencies and glaucoma.
Surgical Education: VR/AR technology can go beyond surgical simulations and provide augmented reality information in real surgical environments, improving surgical accuracy and safety. For example, it can overlay the patient's computed tomography or magnetic resonance imaging images in real-time during surgery or provide information on the position and angle of surgical instruments.
Surgery: Alcon's NGENUITY® and Zeiss's ARTEVO® digital microscopes are already relatively widespread AR devices. However, these devices currently require a relatively large space for operation and can be hindered by obstacles. HMDs can offer a solution to overcome these limitations.
Visual Rehabilitation: VR/AR-based visual rehabilitation programs can help visually impaired patients recover visual function and improve their ability to adapt to daily life. For example, they can be used to provide magnification of specific areas of the visual field for patients with low vision due to macular degeneration or to assist in eccentric viewing training.
Telemedicine: The coronavirus disease 2019 pandemic has accelerated the digital transformation of healthcare, exposing the vulnerability of the traditional healthcare system and prompting many healthcare providers to adopt telehealth solutions [19,20]. Virtual health has revolutionized healthcare delivery using technology to overcome geographic barriers [20,21]. VR technology allows users to feel like they are in a virtual space, potentially enhancing the telehealth experience by boosting user acceptance, engagement, and presence [22,23].
VR/AR technology can enable ophthalmologists to remotely diagnose and consult with patients. Virtual consultations have shown potential as an alternative care model, especially in ophthalmology, and can provide accurate diagnostic services with public acceptance. Notable examples include a case report of successful orbital tumor removal by a general ophthalmologist telementored by a distant specialist and the transfer of expertise from ophthalmologists to general practitioners for corneal foreign body removal in a rural setting using real-time slit lamp image transmission [21]. In particular, the capacity of VR to provide visual images is anticipated to have a significant impact in the field of ophthalmology, where visual function is assessed, monitored, and improved [20,21]. VR/AR devices can facilitate screening tests or self-examinations, increasing the likelihood of early disease detection and improving prognosis.
Early Disease Screening at Home: The potential for VR/AR devices to facilitate early screening of eye diseases at home represents a significant advancement in preventive eye care [24]. These technologies could enable regular, convenient self-assessments, potentially leading to earlier detection of conditions like glaucoma, macular degeneration, or diabetic retinopathy [25-27].
The integration of VR/AR technologies in ophthalmology brings forth several ethical considerations that warrant careful attention. Data privacy is a primary concern as these devices can collect vast amounts of sensitive patient information, including eye-movement patterns, visual acuity data, and potentially even retinal images. Ensuring the security and confidentiality of these data is paramount, necessitating robust encryption methods and strict data-handling protocols [28].
Informed consent becomes more complicated in the context of VR/AR applications. Patients must be thoroughly educated about the nature of these technologies, their potential risks, and the extent of data collection [29]. This is particularly crucial considering the immersive nature of VR experiences, which may be disorienting or anxiety-inducing for some patients, especially the elderly or those with certain neurological conditions [30].
The inability to observe the patient's condition while wearing the HMD remains a significant drawback. While mirroring technology allows the examiner to view the images projected to the patient, unlike in the past, the examiner cannot directly observe the patient's eyes when the HMD is worn. However, integration of eye-tracking technology is a promising development, as it enables the examiner to partially assess the patient's gaze.
Fatigue induced by VR and AR HMDs is a significant consideration in their usage, impacting both users and developers. Prolonged immersion in VR/AR environments can lead to a range of physical discomforts, including eyestrain, headache, and nausea, collectively known as "cybersickness." The weight and fit of HMDs can also contribute to physical fatigue, particularly during extended sessions. Moreover, cognitive fatigue may result from the intensive visual and auditory stimulation characteristics of VR/AR experiences, affecting attention span and mental acuity over time. Addressing these challenges involves advancements in display technology to reduce latency and improve visual fidelity, ergonomic design to enhance comfort during prolonged wear, and innovative software solutions that optimize user interfaces and minimize sensory overload. As VR/AR applications expand across various industries, mitigating fatigue remains crucial to ensuring a comfortable and sustainable user experience that supports long-term adoption and benefit realization.
Furthermore, the implementation of home-based screening raises its own set of challenges. Ensuring the accuracy and reliability of at-home tests is crucial, as is developing clear protocols for follow-up care when abnormalities are detected [31]. There also is need to address the digital divide, ensuring that these technologies are accessible to all demographic groups, including the elderly and those in lower socioeconomic brackets [32,33].
The integration of VR and AR technologies into ophthalmology represents a significant advancement with transformative potential. These technologies, driven by innovations in HMD technology, optics, and sensor capabilities, are reshaping the conduct of ophthalmic diagnostics, treatments, and training.
VR/AR devices have demonstrated utility in enhancing surgical precision, improving diagnostic accuracy, and facilitating patient engagement. They enable surgeons to overlay critical information directly onto their field of view during procedures, enhancing decision-making and reducing intraoperative errors. In diagnostic settings, VR/AR devices offer novel methods for visual field testing, metamorphopsia assessment, and color vision deficiency testing, providing clinicians with more comprehensive tools for early disease detection and management.
The future of VR/AR in ophthalmology holds promise in areas such as visual rehabilitation, telemedicine, and further advancements in surgical education. By leveraging technologies like eye-tracking for real-time assessment and Red–Green–Blue color testing for precise diagnosis, these devices are poised to address current limitations and expand their applications across diverse ophthalmic specialties.
However, there are also drawbacks that need to be overcome. To use HMDs in the field of ophthalmology, their accessibility must be improved for elderly individuals and children with lower cognitive abilities. Caution during use is particularly required as the patient's condition cannot be visually assessed while wearing the HMD. Additionally, overcoming cybersickness remains a necessity. Nevertheless, with advancements in technology, HMDs are becoming lighter, offering wider fields of view, and experiencing reduced latency, leading to improved usability.
In conclusion, VR/AR technology stands at the forefront of innovation in ophthalmology, offering unprecedented opportunities to improve patient outcomes and revolutionize the delivery of eye care. As these technologies continue to evolve, they hold the potential to redefine standards of practice and elevate the quality of care for patients worldwide.
Use of the above images has been officially permitted by Virtual Vision, Pico and Alcon.
The authors declare no conflicts of interest relevant to this article.
Conception; Design (YT Kim), Data acquisition; Analysis; interpretation; writing; review (AY Kim, YT Kim); Final approval of the article (All authors)
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