Prevalence of diabetic retinopathy in the United Arab Emirates: a cross-sectional survey

Diabetic retinopathy (DR) is a complication of diabetes mellitus (DM) that affects the blood vessels of the retina and leads to blindness. The progression of retinopathy is gradual, advancing from mild abnormalities, characterized by increased vascular permeability, to moderate and severe non-proliferative diabetic retinopathy, characterized by the growth of new blood vessels on the retina and posterior surface of the vitreous [1].

DR is one of the most serious complications of diabetes. For example, the Wisconsin epidemiological study of diabetic retinopathy (WESDR) concluded that 3.6% of those diagnosed with type 1, and 1.6% of those diagnosed with type 2 DM were legally considered blind. For type 1 DM, blindness was mostly (86%) due to diabetic retinopathy. For type 2 DM, blindness was related to retinopathy in 33% of the cases [2]. The prevalence of DR is probably around 30% in type 2 DM, but notably was above this level in five out of six studies reported from the Asian and pacific island nations of the Western Pacific Region [3]. The annual incidence of retinopathy requiring opthalmological follow up or treatment has been reported to average 1.5% after one year [4]. The same source estimates that 6–9% of patients with proliferative retinopathy or severe non proliferative disease would become blind each year [4]. Moreover, growing evidence also suggests that after 15 years of diabetes, approximately 2% of patients develop blindness, while about 10% develop severe visual handicap [4]. Thus, the early detection of sight-threatening retinopathy and the timely intervention with laser photocoagulation has been shown to be effective in preventing severe visual loss.

Several factors have been identified as determinants for the development of DR and its progression; including, type and duration of DM, age, gender, glycemic control, hypertension, body mass index (BMI), smoking, serum lipids and presence of microalbuminuria (MA) [[5–8] and [9]].

Despite the potential risk of DM complications in general and the grave burden imposed by DR in particular, no study was carried before to estimate the impact of the problem in the UAE. To our best knowledge this effort constitutes the first attempt to estimate the prevalence and determinants of DR among diabetics in Al-Ain district, UAE, with the specific objective of identifying high risk groups for DR amendable to timely intervention, in order to facilitate the planning of screening services. Al Ain city is located in the interior of Abu Dhabi Emirate and constitutes the second largest city (approximately 400,000 populations).

The International Diabetes Federation (IDF) in 2003 ranked the UAE's prevalence rates for type 2 DM and impaired glucose tolerance (IGT) as the second highest in the world (20% for DM and 26% for IGT) [3] implying that the disease and its complications such as retinopathy might constitute a sizable health care burden to the UAE population. Despite that, little is known about the true impact of DM and its complications, including diabetic retinopathy, in the UAE population. While the prevalence of DR in Al-Ain, UAE (19%) is clearly lower than that reported in other populations such as the US (40–45 % [13]), Saudi Arabia (31%), Oman (42%) and Egypt (42%) [14, 15] and [16], it was substantially higher than the equivalent rate reported in a similar study in Kuwait (8%) [17]. The substantial heterogeneity in reported prevalence of retinopathy may partly be real, for example due to differences in the age structure of different population, but may also be due to differences in study methodology and population sample.

Our findings clearly demonstrate that, as elsewhere, DR is a common health problem and may well be among the leading causes of blindness in UAE adults. It is well established that nearly all patients with DM – of both type 1 and type 2 – are at high and increasing risk for the disease [2, 13]. The fact that the majority of our study population (63%) were illiterate further reveal and emphasize the seriousness and complexity of the problem in the UAE. Therefore, additional care needs to be taken to illiterate patients to have a comprehensive annual eye examination with pupil dilation while treating doctors should also be reminded to closely follow DM treatment guidelines and refer all diabetics to ophthalmologist for management and treatment as indicated to preserve vision.

The analysis of the sample population showed that DR increases with patients' age and disease duration, which is consistent with findings elsewhere [5, 6, 11, 12], and [18]. Comparatively, the duration of diabetes is known to reflect total glycemic control and risk factors exposure over time [2, 18]. While this may suggest avenues for primary prevention, the true prospects for that are currently unknown. For example, Aiello et al [13] in a longitudinal study have shown that after 20 years duration, nearly all type 1 DM patients and approximately two thirds of type 2 DM end up developing retinopathy regardless of their diabetic control. However, the analysis revealed that DR in the study sample was marginally significantly associated with hypertension, which is largely held as a significant risk factor in most studies [7, 19]. Thus, improved monitoring and control of hypertension among DM patients in the UAE, which has always been shown to slow the progression of retinopathy, particularly among those with poorly controlled diabetes, is strongly recommended [20].

As reported elsewhere, the presence of microalbuminuria was highly significantly associated with DR in the study population (OR 2.04; 95% CI: 1.03–4.07). MA is a well known predictor for diabetes cardiovascular complications and therefore, DM patients should be targeted for screening for early detection and treatment [21, 22].

The prevalence of retinopathy was also higher in DM patients with other chronic DM complications such as coronary artery disease (p = 0.002), peripheral neuropathy (p = 0.001) and peripheral vascular disease (p = 0.009). However, a multivariate stepwise logistic regression analysis on these chronic complications showed only marginal significant association after adjusting for sex and duration which is consistent with studies in the neighboring countries such as Sultanate of Oman [23]. Surprisingly, and unlike findings elsewhere [18], the degree of glycemic control did not show any significant association with DR in the study sample.

Our study has few limitations. First, the assumption that DM patients with blindness and cataract had diabetic retinopathy as the primary cause, may have slightly led to some over estimation of the prevalence of retinopathy. Second, it is known that DM is notoriously under-diagnosed, and therefore while our sample probably adequately reflects DR among diagnosed DM patients; it is likely that this proportion still reflects only the top of the iceberg.

Our study documented for the first time the prevalence, type and determinants of diabetic retinopathy in the UAE. This complication was related to the patient's age, male gender, type of DM, disease duration and presence of hypertension, MA and other chronic complications of diabetes. As such it is important to recommend introducing early screening program for DR for all diabetic patients, and especially those with associated hypertension, microalbuminuria and those with long disease duration.

Notwithstanding that the rate of DM in the population is high, and the fact that a high rate of undiagnosed diabetes exits in the UAE, it is highly recommended that urgent efforts should be made to improve health education to DM patients. It is established that the knowledge of the retinopathy status of an individual is just one in a whole process of care in diabetes. The implicit 'gold standard' for identifying and grading retinopathy remains, the retinal examination by the ophthalmologist. Several studies [2, 24] have demonstrated the cost effectiveness of screening for retinopathy and established that screening for DR saves vision at a relatively low cost; much lower and safe than with later interventions like involving intra-ocular surgery in the absence of a screening program. Equally, the enormous potential debilitating indirect costs of retinopathy on patients could be curbed with increased productivity and decreased disability. Much awareness, management and attention to the complication is therefore needed in the UAE.