**1. Introduction**

The rising number of persons living with diabetes worldwide has significant implications for global blindness. Diabetes is a condition of public health importance and paramount health concern in our time, with about 463 million adults worldwide living with diabetes as of 2019 [1]. The prevalence of diabetes for all age groups worldwide is 2.8% in 2000 and will increase to 4.4% in 2030 [2]. Projections suggest that the total number of individuals with diabetes will more than double from 171 million in 2000 to 366 million by 2030 [2]. Diabetic retinopathy (DR) is a microangiopathy and a significant finding amongst people living with diabetes. About 140 million patients are estimated to have diabetic retinopathy, and 10% of this number, i.e., about 14 million, have impaired vision. Diabetic macular edema (DME) is the commonest cause of visual impairment amongst persons living with diabetes [3].

The prevalence of DME is influenced by the type of diabetes and the use or non-use of insulin treatment [4]. The ten-year incidence of DME is highest amongst older onset patients on insulin, in which a rate as high as 25% has been reported. In research examining the prevalence and risk factors for DME in the United States, non-Hispanic blacks had a higher odd of developing DME than non-Hispanic whites [5]. There was a more significant burden of DME among non-Hispanic blacks, individuals with high hemoglobin A1c, and those with a longer duration of diabetes. It would appear that race plays a vital role in developing DME.

Development of DR and DME is associated with well-researched risk factors, including long duration of diabetes, suboptimal glycemic control as evidenced by elevated HbA1c, hypertension, obesity, elevated serum lipid levels, anemia, pregnancy, associated kidney disease, and smoking [6–10]. DME patients are at increased risk of cerebrovascular accidents (stroke) and cardiovascular disease (CVD) when compared to other DM patients without DR [11]. Also, DME has been shown to negatively impact the quality of life (QoL) of the patient [12]. The most feared complication of all the complications associated with diabetes is a loss of vision [13].

The management of a patient living with diabetes requires the input of a multidisciplinary team [14, 15]. It includes such psychosocial support as can be provided by the family, peers, and even the workplace. This kind of support will help improve patient compliance to treatment and result in an overall healthier patient. There are physician and patient challenges in the care of DR and DME. Physician challenges include managing wide variations in patient responses to treatment, the complex comorbidity profile of the high-risk population, and the suboptimal outcomes associated with delayed initiation of treatment with intravitreal anti-VEGF therapy. Obvious patient challenges include compliance to treatment and clinic attendance for monitoring, the cost of treatment and medical insurance, the burden associated with long-term follow-up and management, problems with access to health care and treatment (especially amongst the low and medium-income), and the time spent on treatment, visits, and follow-up, particularly for the working-age population. Nonetheless, to prevent visual impairment and blindness from DR and DME amongst patients living with diabetes, timely intervention is required. It is possible through the early detection of treatable retinopathy.

### **2. Screening for DR and DME**

DR and DME occur in DM patients, and risk factors are as outlined previously. Therefore, this disease lends itself to early detection through screening of at-risk persons. DR is a progressive disease. The early stages of DR, which can be asymptomatic, can progress to more advanced sight-threatening forms of the disease. The role of ophthalmic screening for early detection of vision-threatening disease in atrisk patients living with diabetes is an essential and practical strategy for preventing vision loss from DR and DME. Though systematic screening is preferred and has proven to reduce rates of blindness from DR effectively, few nations have this in place. In most countries, only some form of opportunistic screening is available or no screening at all [16].

There are different real-world examples of the benefit gained through DR screening. The English national health service (NHS) diabetic retinopathy screening program is a successful model of a screening program that has evolved from opportunistic to effective systematic screening [16]. The UK's systematic screening has effectively reduced the prevalence of DR-related blindness in the UK. The UK national screening program was established in 2004 to provide standardized, quality-assured DR screening across England. All patients living with diabetes

#### *Current Management of Diabetic Macular Edema DOI: http://dx.doi.org/10.5772/intechopen.100157*

above the age of 12 years are invited at least annually for an ophthalmic screen. Those patients at higher risk could have more frequent visits, while those at least level of risk could be considered for more extended visits. Screening is done by qualified screeners who carry out two-field retinal photography, using an updated list of persons living with DM. Images are then digitally transferred to a centralized location for retinal grading by qualified individuals (graders). A comprehensive quality-assurance system is set up, including regular auditing of grading carried out by individuals grading within the English screening program. The UK's screening program has a coverage of 83% and screened close to 3 million persons in 2018/2019. The entire program has reported successes, such that after seven years of the program, a review of the causes of blindness in the UK showed that DR was no longer the most common cause of blindness amongst the working-age [17]. This UK experience of DR screening provides compelling evidence that systematic diabetic retinopathy screening, coupled with timely treatment of sight-threatening disease, can reduce vision impairment and blindness.

For a DR screening program to be effective, it should be composed of the following seven component pathways, 1. identifying the population eligible for screening; 2. invitation and information; 3. testing; 4. referral of screen positives and reporting of screen-negative results; 5. appropriate diagnosis; 6. intervention, treatment, and follow-up; 7. reporting of outcomes [16].

The entire framework of the screening program should be based on the following, resources and infrastructure, a pathway for screening, quality of screening, and equity in access to high-quality screening. In addition, standardization of the process, quality assurance, and auditing of the screening program should be implemented to ensure effectiveness and a high level of sensitivity for timely detection of sight-threatening disease and appropriate referral. Although there are well-designed guidelines for DR screening, considerable gaps exist in deciding the best screening methods and how often to screen, infrastructure and resources for screening, and the fact that several patients living with diabetes fail to keep screening appointments. In addition, in several low- and mid-income countries, healthcare coverage is not countrywide. There is a scarcity of updated information on persons living with diabetes who are the targets of such DR screening programs [16].

In consideration of the economic aspect of DR screening, issues relating to the overall cost-effectiveness of ophthalmic care, the cost-effectiveness of systematic versus opportunistic screening, how screening should be organized and delivered, how often screening should be performed, have all been raised. It has been shown that systematic screening for DR is cost-effective in terms of sight years preserved than no screening [18]. In addition, teleophthalmology screening offers remote screening by trained paramedics in out-of-hospital facilities, including rural and hard-to-reach communities [19, 20]. Other remote screening initiatives include healthcare kiosks and smartphone tele screening, which provide teleophthalmology solutions for a broader range of patients, including in underserved locations and rural communities. In countries with inadequate primary care systems, without a routine systematic screening program, a holistic approach to screening for diabetes is recommended to prevent end-organ damage. This holistic approach should include at least retinal screening, foot examinations, blood pressure monitoring, urine albumin testing, HbA1c, and lipid testing [19]. A significant side benefit of DR screening is that it can also identify other ophthalmic conditions, including cataracts, glaucoma, and other retinal and retinovascular diseases.

In recent times, the entry of artificial intelligence (AI) algorithms further provides immediate grading and feedback on fundus photographs acquired by trained personnel in an out-of-hospital location (including primary care clinics and pharmacies) [21–23]. These AI-backed systems feature automated retinal image

analysis (ARIA) [24, 25]. The image to be graded or analyzed can be acquired using digital fundus cameras, and now even handheld mobile devices, including smartphones, can be used. Internet access is required to upload the image for grading to the AI software. The software then compares the uploaded image with cloud-based images. It can provide information on if there is a presence of sight-threatening DR or not with a high level of sensitivity and specificity. This AI software-based screening is the future of DR screening. Utilizing ARIA, detection of DR can be done without the need for human image graders. ARIA, in turn, standardizes the process, is more efficient, and covers a larger area within a shorter period. The EMERALD Study is a recent multicenter study conducted in 13 centers within the UK [26]. This study examined the sensitivity, specificity, and acceptability of an alternative pathway using spectral-domain OCT to detect DME and 7-field Early Treatment Diabetic Retinopathy Study [ETDRS] and ultra-widefield fundus images for PDR. These images were interpreted by trained nonmedical staff (ophthalmic graders) to detect reactivation of previously treated disease. The authors compare this alternative pathway with the current standard of care (face-to-face examination by ophthalmologists). They concluded that this new alternated pathway has acceptable sensitivity and offers a significant release of resources.

At this time, home screening using optical coherence tomography (OCT) device has been explored, "Home OCT device" [27]. Success and experience gained from using the Foresee Home Device in monitoring eyes with AMD have evolved into the idea that patients at risk of DME can be monitored remotely from their homes using the Home OCT device, reducing the number of hospital visits [28]. Home OCT can be combined with home monitoring of visual acuity and other aspects of visual function. This innovative idea also provides information on DME's entire clinical evolution and history, which is missed between clinic visits for several patients. The patient uses the Home OCT device to scan the macula for early disease detection constantly. Therefore, home teleophthalmology and home monitoring combined can detect early disease, lead to intervention early in the disease process, and prevent vision loss from DR and DME. This home screening and monitoring of DME is another current reality in the COVID 19 era and provides a way out for a future lockdown, as happened during the COVID 19 pandemic.

To conclude, DR screening of at-risk patients living with diabetes is essential for the early detection of sight-threatening disease to enable timely, effective treatment. With increasing numbers of patients diagnosed with diabetes, DR-related visual disabilities will likely increase in the coming years. An interdisciplinary organized public health approach will provide the best approach to achieving screening for many patients. Collaboration amongst all different partners is required to reduce the incidence of vision loss resulting from DME and DR. This multidisciplinary approach will ensure that relevant information about diabetes and the eye screened is shared with the screened patient and across the system responsible for diabetes care. This will facilitate integrated care for the patient. Other incidental findings diagnosed during eye screening, such as cataracts or glaucoma, should be referred to the appropriate eye care team.
