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1. Introduction
Diabetic retinopathy (DR) is a sight threatening, microvascular complication of diabetes that affects the retina. It is the most common complication of diabetes [1] and a leading cause of blindness amongst working aged adults in the developed world [2,3,4]. All persons with diabetes are at risk of developing retinopathy, however, persons living with type 1 diabetes (T1DM) have a higher chance of getting DR as compared to persons living with type 2 diabetes (T2DM) [5]. The prevalence of DR is directly linked to that of diabetes. Some studies estimate a DR prevalence of 34.6% [6,7] and find that it is more common in T1DM as compared to T2DM [7]. The exact mechanism of how prolonged hyperglycaemia causes retinopathy is still unclear, however studies have shown that prolonged hyperglycaemia alters retinal perfusion thereby disturbing the normal physiological and homeostatic state of the retina, in turn causing retinopathy [8]. Based on the presence or absence of abnormal blood vessels on the retina, it can broadly be classified into:
- Non-proliferative (NPDR)
- Proliferative (PDR) [9]
These can be further sub-classified into mild, moderate and severe retinopathy. Each level of classification has a different prognosis of vision with worst visual outcome associated with severe proliferative retinopathy. Maculopathy, which occurs when there are changes with the macula, functionally and severely affects vision, but may or may not be present with non-proliferative or proliferative retinopathy. In recent times, the natural history and factors that influence the development of DR have been understood a little better due to large trials and landmark studies in the UK and around Europe, making the management of DR better [10].
After the St. Vincent’s declaration to reduce blindness from diabetes by a third, the United Kingdom (UK) became the first country in the world to offer systematically organised screening for DR to all patients diagnosed with diabetes over the age of 12. This screening programme was implemented in England in 2003 and it reached nationwide coverage in 2008 [11]. The screening programmes within the four UK nations are overseen by a national programme and run at the community level by local programmes [12]. In England, screening is overseen by the National Diabetic Eye Screening Programme (NDESP) [13], in Wales it is the Diabetic Retinopathy Screening...