Review of retinal cameras for global coverage of diabetic retinopathy screening

Abstract

The global burden of diabetes has resulted in an increase in the prevalence of diabetic retinopathy (DR), a microvascular complication of diabetes. Lifelong repetitive screening for DR is essential for early detection and timely management to prevent visual impairment due to the silent sight-threatening disorder. Colour fundus photography (CFP) is helpful for documentation of the retinopathy as well as for counselling the patient. CFP has established roles in DR screening, detection, progression and monitoring of treatment response. DR screening programmes use validated mydriatic or non-mydriatic fundus cameras for retinal imaging and trained image graders identify referable DR. Smartphone-based fundus cameras and handheld fundus cameras that are cost-effective, portable and easy to handle in remote places are gaining popularity in recent years. The images captured with these low-cost devices can be immediately sent to trained ophthalmologists for grading of DR. Recent increase in numbers of telemedicine programmes based on imaging with digital fundus cameras and remote interpretation has facilitated larger population coverage of DR screening and timely referral of those with sight-threatening DR to ophthalmologists. Good-quality retinal imaging and accurate diagnosis are essential to reduce inappropriate referrals. Advances in digital imaging such as ultra-wide field imaging and multi-modal imaging have opened new avenues for assessing DR. Fundus cameras with integrated artificial intelligence (AI)-based automated algorithms can also provide instant DR diagnosis and reduce the burden of healthcare systems. We review the different types of fundus cameras currently used in DR screening and management around the world.

Fig. 1. Rural Teleophthalmology.

A Retinal imaging inside a mobile telemedicine van in Chunampet village, south India, performed by a local trained technician.  B Retinal image with Topcon TRC NW200 non-mydriatic desktop fundus camera.

Fig. 2. Retinal imaging with hand-held fundus camera.

A Retinal imaging with Zeiss Visuscout 100 handheld fundus camera. B Retinal image of sight-threatening diabetic retinopathy with post laser status centre involving diabetic macular oedema taken with Visuscout camera.

Fig. 3. Comparison of retinal imaging between  conventional fundus camera and smartphone based fundus camera.

A Fundus image of branch retinal vein occlusion in conventional desktop camera. B Fundus image of branch retinal vein occlusion in smartphone-based Fundus on Phone (FOP) mydriatic camera.

Fig. 4. Diabetic retinopathy screening in camps.

A Retinal imaging with Fundus on Phone (FOP) non-mydriatic (NM) smartphone-based camera in a DR screening camp. B Retinal image of sight-threatening diabetic retinopathy taken with FOP NM camera.

Fig. 5

A MII RetCam. B Retinal image of sight-threatening diabetic retinopathy taken with MII Retcam.

Fig. 6. Wide field retinal imaging in diabetic retinopathy.

Ultra-wide field fundus image of post panretinal laser photocoagulation proliferative diabetic retinopathy with fresh pre-retinal haemorrhage taken with Optos Daytona plus camera.