Glaucoma is a progressive optic neuropathy with characteristic optic nerve structural damage and visual field loss. Glaucoma is one of the common causes of irreversible blindness worldwide.1 While there are many types of glaucoma including open-angle, closed-angle, and normal tension glaucoma; primary open-angle glaucoma is the most frequent encountered in the US 2,3. Primary open angle glaucoma is often labeled as the “silent thief of vision” due its characteristic painless and slow progression of mostly peripheral vision loss1. There are many barriers that prevent patients from seeking appropriate eye care including, but not limited to, geographic, educational, socioeconomic, and cultural considerations. 2,3
Tele-glaucoma helps overcome these barriers by relying on remote consultation or screening tools. Tele-glaucoma can be applied for screening or consultation. When applied for remote screening tele-glaucoma can to detect glaucoma in order to initiate prompt treatment. When applied for remote consultation glaucoma patients can be followed remotely over time in order to monitor treatment over time.
Early action is pivotal in preventing glaucoma’s blinding complications. Glaucoma patients can particularly benefit from a tele-medicine approach because patients tend to be older and thus loss of vision can severely affect their mobility, and consequently, their quality of life. By delivering glaucoma care remotely, tele-glaucoma shows promise in providing patients with access to specialized ocular care. This can also be very useful for remote rural or underserved areas and has the potential to revolutionize the current healthcare paradigm of “first come, first serve.”2 Furthermore, current healthcare models do not distinguish between patients with progressive glaucoma who require timely intervention and health care access and those who do not need imminent care. Tele-glaucoma by identifying the most advanced or progressing patients may transform current clinical practice by prioritizing the delivery of care to patients who require the most urgent intervention. 2
US and International Initiatives
Several tele-glaucoma clinical studies are ongoing in the US and internationally. 4 In the US, tele-glaucoma is making a significant impact on providing care to rural veterans as well as homeless veterans in a program piloted by the Atlanta VA clinic. This program is called Technology-based Eye Care Services (TECS). On average, veterans are more vulnerable than the general population for eye diseases like glaucoma because enrollees are usually older patients and are thus less likely to see eye care professionals regularly. TECS successfully illustrated that tele-glaucoma allowed veterans to seek timely access to eye care and significantly reduced the cost of eye exams for both the patient as well as the VA health care system. Other tele-glaucoma studies include trials in Philadelphia at Wills Eye Hospital and in Newark at Rutgers New Jersey Medical school.
Global efforts in tele-glaucoma are also being made, with many initiatives based in Africa due to a disproportionately high prevalence of glaucoma cases in African populations. Given that the general awareness of glaucoma may be low, and the disease is mostly painless and harder to detect; many patients remain undiagnosed, and thus, untreated. Tele-glaucoma has the potential to bridge this gap by delivering care to those who would otherwise be unable to seek it.
Additionally, the American Academy of Ophthalmology has recognized the value of telemedicine and has sponsored a task force on tele-ophthalmology. For example, tele-ophthalmology has proven to successfully improve and extend ophthalmic care in diabetic retinopathy and retinopathy of prematurity. With advances in intraocular pressure monitoring and optic nerve analysis, the Academy's goal is to expand this successful initiative to the realm of tele-glaucoma in order to improve the detection and treatment of glaucoma and have a positive impact on qualities of life and patient outcomes. 
Tele-glaucoma is an integral part of tele-ophthalmology which aims to detect the leading vision threatening diseases (cataract, glaucoma, age-related macular degeneration, and diabetic retinopathy). Ophthalmic evaluation for visual acuity, non-contact tonometry, structure (including OCT), and function testing can be mobilized with a small footprint to allow travel to satellite or remote sites. There are 2 major modalities within tele-glaucoma: store and forward versus telepresence.
Store and forward telemedicine refers to collecting relevant data from patients without real time live interaction with a physician. Store and forward tele-medicine is especially applicable to specialties such as ophthalmology because diagnoses are largely based on documented information and images. Images and test results are gathered into a single file at the screening site and then sent to the appropriate professionals via a secure encrypted Internet connection. Once received, the data are analyzed by a specialist as if the data was collected in person at the clinic. By not requiring specialists on site, the store and forward modality furthers the reach of tele-glaucoma in remote regions.
In contrast, the telepresence modality places a specialist directly in contact with the screening team. The same images and data are collected, but live consultations allow providers to disseminate immediate diagnoses, treatment suggestions, and expert referrals, as needed. This “real time” tele-medicine modality is especially useful for clinicians who see many patients and for patients who need more immediate medical attention. 6,9 Telepresence also has the potential to circumvent the problem with patients failing to follow-up afterwards with an ophthalmologist after their screening encounter.
During telemedicine for glaucoma, intraocular pressure measurement must avoid the use of topical anesthetics (requires presence of a supervising physician, nursing staff, and carries the potential risk of adverse effects). Current technologies are available that allow for remote IOP measurement. For example, non-contact tonometry, or "air puff" tonometry, can be used to noninvasively measure IOP.  Although puff tonometry correlates with application tonometry discrepancies may occur. Optical coherence tomography (OCT) is also a common imaging tool that can be brought to screening sites to assess glaucomatous structural damage. OCT is a noninvasive tool that allows screeners to acquire cross sectional images of the retina and optic nerve head (ONH) without dilating the pupil. Spectral domain (SD)-OCT can be used to diagnose thinning of the retinal nerve fiber layer (RNFL) and ganglion cell-inner plexiform layer (GCIPL), as well as ONH structural changes. Thus, SD-OCT is a valuable clinical tool in diagnosing glaucoma and following its progression at screening sites.
Additionally, non-mydriatic digital color fundus photos are obtained as part of a complete ocular evaluation during screening or consultation. Incorporating software digital filters to process images has been shown to facilitate the identification of ocular pathology. This may assist screeners in identifying abnormalities on images during screening . 
New, wearable and portable brain-computer interface devices are making headway in detecting visual field changes from glaucoma. Some cellphone-based technologies rely on head-mounted displays to detect electrical brain potential signals associated with visual field stimulation. This technology can successfully discriminate between healthy and glaucomatous eyes. The portability and ease of use makes these technologies a promising asset for tele-glaucoma functional testing in the future.
Finally, the new and evolving field of robotics has applications during tele-glaucoma by allowing a remotely present physician virtual and physical presence with the screening team and the subjects being evaluated. Additionally, the field of artificial intelligence with deep learning algorithms continue to show an impressively high performance (aROC, sensitivity and specificity) in identifying ocular pathology (like diabetic retinopathy and glaucoma). Hybrid deep learning methods have also been used in conjunction with OCT to distinguish healthy eyes from eyes with early glaucoma. With further improvement and wider adoption of these algorithms, artificial intelligence systems have the potential to change the face of tele-glaucoma, and ultimately, telemedicine as a whole.
Challenges and Future Directions
Patient retention and follow-up after glaucoma detection remains problematic. Many patients do not follow up as recommended. Furthermore, glaucoma patients are often elderly and face vision loss and mobility restrictions which can hinder traditional glaucoma care. Tele-glaucoma can offer solutions to the afore mentioned challenges.
Tele-glaucoma shows promise in delivering effective screening solutions, especially for remote and underserved communities. The regulatory and reimbursement policy challenges remain an obstacle to the wider implementation of tele-glaucoma. 
Glaucoma affected 60.5 million people worldwide in 2010 and is projected to impact 79.6 million by 2020. Tele-glaucoma has the potential to remotely diagnose and plan treatment at the time of encounter. Tele-glaucoma has the potential to alleviate some of the obstacles to traditional glaucoma care, including the transportation of elderly visually disabled patients. Tele-glaucoma also has the ability to prioritize the delivery of care to the patients that need it more urgently- thus reducing risks of irreversible damage to vision in those patients.
- 1 Parihar, J. K. S. Glaucoma: The ‘Black hole’ of irreversible blindness. Med. J. Armed Forces India 72, 3–4 (2016).
- 2 Kassam, F., Yogesan, K., Sogbesan, E., Pasquale, L. R. & Damji, K. F. Teleglaucoma: Improving Access and Efficiency for Glaucoma Care. Middle East Afr. J. Ophthalmol. 20, 142–149 (2013).
- 3 Damji, K. F. Strengthening Institutional Capacity for Glaucoma Care in Sub-Saharan Africa. Middle East Afr. J. Ophthalmol. 20, 107–110 (2013).
- 4 Shahid, K. et al. Ocular Telehealth Screenings in an Urban Community. Telemed. E-Health 18, 95–100 (2012).
- Rural and Remote Health. Available at: https://www.rrh.org.au/journal/article/4045 (Accessed: 27th June 2018)
- Damji, K. F. et al. STOP Glaucoma in Sub Saharan Africa: enhancing awareness, detection, management, and capacity for glaucoma care. Expert Rev. Ophthalmol. 12, 197–206 (2017).
- Kiage, D., Kherani, I. N., Gichuhi, S., Damji, K. F. & Nyenze, M. The Muranga Teleophthalmology Study: Comparison of Virtual (Teleglaucoma) with in-Person Clinical Assessment to Diagnose Glaucoma. Middle East Afr. J. Ophthalmol. 20, 150–157 (2013).
- Telemedicine for Ophthalmology Information Statement - 2018. American Academy of Ophthalmology (2018). Available at: https://www.aao.org/clinical-statement/telemedicine-ophthalmology-information-statement. (Accessed: 27th June 2018)
- Bonnardot, L. & Rainis, R. Store-and-forward telemedicine for doctors working in remote areas, Store-and-forward telemedicine for doctors working in remote areas. J. Telemed. Telecare 15, 1–6 (2009).
- Store-and-forward teledermatology results in similar clinical outcomes to conventional clinic-based care, Store-and-forward teledermatology results in similar clinical outcomes to conventional clinic-based care. J. Telemed. Telecare 13, 26–30 (2007).
- Szirth, B., Khouri, A., Bhagat, N. & Shahid, K. New Concepts in Screening for Vision Threatening Disease. Invest. Ophthalmol. Vis. Sci. 48, 1578–1578 (2007).
- Raina, U. K., Rathie, N., Gupta, A., Gupta, S. K. & Thakar, M. Comparison of Goldmann applanation tonometer, Tono-Pen and noncontact tonometer in children. Oman J. Ophthalmol. 9, 22–26 (2016).
- Bussel, I. I., Wollstein, G. & Schuman, J. S. OCT for glaucoma diagnosis, screening and detection of glaucoma progression. Br. J. Ophthalmol. 98, ii15–ii19 (2014).
- Xia, T., Patel, S. N., Szirth, B. C., Kolomeyer, A. M. & Khouri, A. S. Software-Assisted Depth Analysis of Optic Nerve Stereoscopic Images in Telemedicine. Int. J. Telemed. Appl. 2016, 7603507 (2016).
- Kolomeyer, A. M. et al. Software-Assisted Analysis During Ocular Health Screening. Telemed. E-Health 19, 2–6 (2013).
- Nakanishi, M. et al. Detecting Glaucoma With a Portable Brain-Computer Interface for Objective Assessment of Visual Function Loss. JAMA Ophthalmol. 135, 550–557 (2017).
- Ting, D. S. W. et al. Development and Validation of a Deep Learning System for Diabetic Retinopathy and Related Eye Diseases Using Retinal Images From Multiethnic Populations With Diabetes. JAMA 318, 2211–2223 (2017).
- Muhammad, H. et al. Hybrid Deep Learning on Single Wide-field Optical Coherence tomography Scans Accurately Classifies Glaucoma Suspects. J. Glaucoma 26, 1086–1094 (2017).
- Thomas, S.-M. et al. The Effectiveness of Teleglaucoma versus In-Patient Examination for Glaucoma Screening: A Systematic Review and Meta-Analysis. PLOS ONE 9, e113779 (2014).