Introduction

Glaucoma is a disease of public health importance, ultimately resulting in irreversible blindness.1 It is characterised by a progressive optic neuropathy with loss of vision, which is asymptomatic until the advanced stages of the disease. Elevated intraocular pressure (IOP) is the only treatable risk factor in glaucoma, and it is an important parameter in the diagnosis and monitoring of the disease.1 Recent projections predict 111.8 million people will have glaucoma by the year 2040, and African and Asian populations are expected to be disproportionately affected.2 3 In the recent Lancet Global Health Commission on global eye health, glaucoma was reported to have caused blindness in 3.61 million people (uncertainty interval (UI) 2.81 to 4.42 million) and moderate or severe vision impairment in a further 4.13 million (UI 3.24 to 5.18 million).4

The diagnosis of glaucoma usually requires specialist equipment, especially when trying to detect and confirm the presence of early asymptomatic disease. Resourcing primary and secondary healthcare facilities in low-resource settings with expensive high-tech equipment is challenging, particularly when it comes to eye care. Additionally, highly trained health workers are needed to operate such devices. In contrast, portable devices are used in remote areas during ophthalmology outreach programmes and screening exercises.5 Their compact, low maintenance and battery-operated characteristics make them more suitable in areas where bulky high-tech equipment is not available or difficult to transport. Tests using portable devices such as the Eyecatcher perimeter, icare tonometer, portable fundus cameras and more have shown promising results when compared with conventional equipment in eye care.5–10

In high-income countries, portable devices are now being used to monitor glaucoma by assessing IOP at home using devices such as the icare HOME.11 The possibility of remote visual field assessment by patients using portable, easy-to-operate devices has also been demonstrated in some studies.7 8 However, the situation is different in low-income and middle-income countries (LMICs), where the initial diagnosis of glaucoma is challenging due to lack of specialised diagnostic equipment and personnel.

The primary healthcare (PHC) system has been adopted universally in LMICs, with the aim of addressing basic health needs in the community.12 It serves as the first point of care for individuals with conditions needing treatment and/or referral for further management, providing health education on common diseases in communities and basic rehabilitation services if required.13 In the World report on vision, the WHO calls on countries to place a renewed emphasis on incorporating primary eye care (PEC) services into PHC.14 This is being increasingly implemented worldwide, with varying effect in different regions. In South Asia, PEC services are often provided by local non-governmental organisations through networks of PEC facilities, staffed by qualified eye care workers, provided with relevant equipment. However, in many sub-Saharan African countries, such as Nigeria, there is a lack of PEC centres in most regions. The few available centres are often donor driven or initially run by NGOs before handing over to the State, and they lack basic equipment and expertise to screen, diagnose and or manage glaucoma.4 14 15 Equipping PHCs with portable devices which are reliable and easy to operate in the detection of glaucoma could make a great impact in identifying people with glaucoma and refer appropriately for further management in specialised centre before blindness ensues.

Individuals with advanced glaucoma are challenging to manage, as stringent IOP control is required to prevent visual field progression and loss of vision.16 Primary open-angle glaucoma tends to present with more severe visual field defects in African origin populations, and particularly in West African populations, compared with Caucasian populations.17 18 Hence, vigorous treatment needs to be instituted. Treatment options include long-term daily eye-drops, surgery, laser or combined therapy to lower the IOP.18 19 In the LMIC context, the cost of long-term glaucoma treatment is relatively high and many patients cannot afford it and have no medical insurance cover. Therefore, glaucoma treatment and the frequent follow-up appointments are often paid out of pocket.3

The task of preventing vision loss from progressing to end-stage glaucoma is difficult for the health system, the patient and caregivers. Individuals with advanced disease have poor vision and usually need family members or friends to accompany them to the hospital, requiring them to take time off from work. Earlier diagnosis helps to mitigate some of these issues, as it provides for more time to explore treatment options. The diagnosis of glaucoma is not straight forward, as both structural and functional changes of the optic nerve head have to be considered and IOP readings sometimes need to be taken at more than one sitting.

Considering the challenges highlighted above in making the diagnosis of glaucoma in LMICs, the use of portable devices may play an important role in its earlier detection. These devices could be used in community health centres and could serve as a screening tools. Glaucoma cases detected could then be promptly referred to specialised centres for further investigations and management. Known or suspected cases could also periodically have their IOP checked (this being the only modifiable risk factor in management of glaucoma) and possibly visual fields to check for progression of the disease in these community health centres if these portable devices are available.

A preliminary search of MEDLINE was conducted and no current or underway systematic reviews or scoping reviews on this topic were identified. The objective of this scoping review is to assess the nature and extent of the literature in which portable devices have been used in the diagnosis/detection, management and monitoring of glaucoma.