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Innovations in Screening Technology

The availability of portable hand-held non-nonmydriatic fundus cameras (which can capture retinal images without the need to apply medication to enlarge the pupils) is another advancement that may improve the uptake of screening, particularly in primary care setting. Non-nonmydriatic imaging is quick and causes less discomfort and therefore may be more readily accepted by the patients and more convenient to the health care provider.⁷⁷ Several studies, conducted in high-resource countries, have reported that non-mydriatic cameras provide an effective and cost-effective approach for DR screening. ^{78, 79}

Another emerging technology is the use of smartphones for screening of Diabetes-related Retinopathy. Smartphones are an attractive option for the capture, interpretation and transmission of retinal images due to their widespread accessibility, portability and relatively low cost. ^78-80 . Preliminary studies evaluating the use of smartphone technology for Diabetes-related Retinopathy screening have shown encouraging results ⁸¹, but further work is needed to improve image quality and validate their use by non-ophthalmology personnel.⁸⁰

The use of automated grading software to evaluate digital retinal photographs is another approach that may help reduce the costs of Diabetes-related Retinopathy screening, by removing the requirement for manual (human) grading by specialist readers. A pilot study conducted in Scotland that evaluated an automated system designed to assess image quality, and detect the presence of quality, showed that automated grading displayed similar effectiveness to manual grading, but was less costly ⁸². The use of automated grading systems for the assessment and detection of Diabetes-related Retinopathy has since been evaluated in several other countries, and is likely to play a major role in Diabetes-related Retinopathy screening in the future ^83,84.

Innovations in Imaging Technology

The past few years has seen several advances in the management of diabetes-related eyes diseases, particularly in the diagnosis and treatment of Diabetes-related Retinopathy and Diabetes-related Macular Edema.

The standard method for the detection of Diabetes-related Retinopathy and Diabetes-related Macular Edema is a comprehensive dilated eye examination with stereoscopic colour fundus photographs taken over time in order to monitor changes in the retina.

Other imaging techniques, such as optical coherence tomography (OCT) and fluorescein angiography also play a role in the diagnosis and management of complications of Diabetes-related Retinopathy, particularly for Diabetes-related Macular Edema.

OCT is a non-invasive technique that uses light to capture detailed 3-dimensional images showing the structure of the retina making it more suitable for the detection of Diabetes-related Macular Edema than fundus photography, which only provides 2-dimensional images. OCT is commonly used in clinical practice to confirm the diagnosis and monitor the treatment of Diabetes-related Macular Edema. However, its role as a screening test for Diabetes-related Retinopathy (in addition to fundus photography) is still unclear, in part due to the low availability of OCT machines and personnel to operate them⁸⁵. Several newer versions of OCT have been introduced including:

Spectral-domain-OCT (SD-OCT): provides detailed images of morphological abnormalities in the retina; this approach is already widely used in clinical practice

OCT-Angiography: this a relatively new approach allowing detailed visualisation of blood vessels in the retina and choroid layer of the eye, which can help monitor DR progression. An advantage of OCT-angiography is that its non-invasive and does not require injection of drugs to help visualise the blood vessel, which is required for fluorescein angiography) ⁸⁶.

Swept source-OCT (SS-OCT): captures images of structures across a wider area than is reached with SD-OCT (including vitreous, retina, choroid, and sclera), and offers faster scan speeds.

Other imaging modalities that may play a more prominent role in the management of Diabetes-related Retinopathy and Diabetes-related Macular Edema in the future, include:

Ultra-Widefield Color Fundus Photography: Compared with traditional single-field fundus photography, ultra-widefield imaging can capture higher quality images from a larger area of the retina, including the peripheral retina (the part that provides our side vision), which is often affected by Diabetes-related Retinopathy. Studies have shown that this approach improves diagnosis and classification of DR ⁸⁷. The availability of ultra-widefield cameras has led to the increased use of ultra-wide field fluorescein angiography, a technique which allows better visualisation of the blood vessels in the peripheral retina, improving the detection and classification of Diabetes-related Retinopathy ⁸⁸.

Retinal oximetry is a non-invasive technique that can be used to measure the oxygen saturation of retinal blood vessels. Diabetes-related Retinopathy is caused by damage to the retinal blood vessels and the reduced blood supply can lead to a deficit of oxygen (hypoxia) in the inner retina. This oxygen deficit has been linked to the development of Diabetes-related Retinopathy, and also to high oxygen levels in the retinal blood vessels. Therefore, measurement of higher oxygen saturation in blood vessels through the use of retinal oximetry may in the future provide a method of detecting the early development of Diabetes-related Retinopathy before it appears in other imaging modalities ⁸⁹.

Fundus Autofluorescence is a non-invasive imaging technique that uses the fluorescent properties of lipofuscin, a naturally occurring compound found within the cells of retina to generate high-contrast retinal images that can be used in the diagnosis and management of several retinal disorders. Fundus autofluorescence has been shown to compare favourably to OCT and fluorescein angiography for the detection of macular oedema, and is likely to play a role in the diagnosis and follow-up of Diabetes-related Retinopathy in the future.

Technologies to improve the implementation of screening

Other technological advances that are likely to increase the implementation of screening of Diabetes-related Retinopathy in the future include the availability of portable fundus cameras, and the use of smartphone-based camera for the capture of retinal images ⁸⁷. These advances will be particularly useful in rural areas of developing countries when incorporated into a tele-screening programme.

The incorporation of automated Diabetes-related Retinopathy image assessment systems that help to eliminate the requirement of manual (human) experts to assess and grade images are also likely to have a significant impact. These systems have demonstrated the potential to reduce the cost of screening. Several different automated grading platforms have been developed over the past few years, and some of the more recent platforms employ artificial-intelligence software, one of which was recently approved by the US FDA (https://www.eyediagnosis.net/idx-dr)

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