CHAPTER ONE
INTRODUCTION
1.0 Background:
Diabetes mellitus is recognized as a group of heterogeneous disorders with the common elements of hyperglycaemia and glucose intolerance, due to insulin deficiency, impaired effectiveness of insulin action or both. 1,2,3 It is a common endocrine metabolic disorder and a leading cause of death worldwide. 1,3 There are more than 154 million diabetics globally and its prevalence is on the increase especially in the developing nations. 1,2,3
Majority of those that suffer the disease are reported to be of African and Asian origin. 1,3
This may be the result of genetic predisposition and lifestyle of people in these areas. 1,3
Nigeria being the most populous African country may harbor a substantial number of people with this condition. 2,3, The rapid increase in the number of persons with diabetes mellitus is expected to lead to an increase in the number of persons with complications from it. 1,2,3 One of such complications of diabetes mellitus is retinopathy which is a highly specific vascular complication that affects the retina of the eyes. 1,2 The complications of diabetes mellitus are termed either small vessel (microvascular) or large vessel (macrovascular) disease. 1,2,3 Small vessel disease includes retinopathy, nephropathy and neuropathy. 2,3 Well conducted clinical trials have shown that good control of diabetes and hypertension significantly reduces the risk for retinopathy in diabetics. 2,3 This assertion is further supported by the results of the Diabetes Control and
Complications Trial (DCCT) which demonstrated that tight glucose control will delay the development of small vessel disease. 2,3 . These small vessel diseases usually affect the eyes and the kidneys. In contrast to these, large vessel disease results in diabetic cardiovascular events and diabetic foot ulcers. 2,3
These complications are usually slow, requiring many years to progress to clinically detectable levels. In the case of diabetic retinopathy, there is no exact interval between the time of diagnosis and development of the disease. 2,3 Visual loss is usually noticed in diabetic subjects through complaints made by the affected individuals and further confirmed by visual acuity tests. Not all diabetics are equally at risk of retinopathy.
It is known that vision threatening retinopathy virtually never appears in type 1 diabetic patients in the first 3-5 years of diabetes or before puberty while up to 20% of patients with type 2 diabetes have retinopathy even at the time of diagnosis.
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After 15 years of diagnosis of diabetes, about 2% of persons become blind while about 10% develop severe visual loss. 1,2,3 After 20 years of the disease, more than 75% of the patients will have some form of retinopathy or the other. 1,3 With the surging prevalence of diabetes worldwide, the number of people bearing these complications is expected to rise astronomically. 1,3,4 For instance, the prevalence of diagnosed diabetes in the United States rose from 6.5% between 1999 and 2002 to 7.8% between 2003 to 2006 as shown by an American study.
Developing nations currently witnessing rapid urbanization, industrialization as well as increasing economic capabilities like Nigeria have higher propensity to develop diabetes due to changes in lifestyle. 2,3,4 It is expected that this rise in prevalence of diabetes mellitus brought by urbanization and industrialization will also trigger an increase in the number of new cases of diabetic retinopathy. 1,2,4
In addition to the rising number of diabetics, there is also an increase in the occurrence of some factors known to potentiate the development of retinopathy in diabetics. These are termed risk factors. 2,3,4
Principal among these risk factors are hypertension, poor glycaemic control, increasing level of blood lipids, increasing body mass index, smoking, higher educational status, and alcohol consumption. 1,2 They are modifiable risks since they can, to a large extent be controlled. Age, sex, and race are non modifiable risks to which the individual can hardly influence. The modifiable risk factors are mainly the concern of this study. The non modifiable risk factors though included in the study since they constitute important demographic parameters, are not really the concern of this study. Hypertension for example, has a frequency of 20-40% among diabetics in Nigeria.
Its prevalence in the general population is only 10-15%.
This shows that the occurrence of hypertension is more than twice enhanced in the presence of diabetes. 3,5,6 Fortunately, hypertension is controllable by the use of antihypertensive drugs, regular exercises, avoiding high salt intake, reducing psychosocial stress and avoiding use of excess
alcohol, hence its contribution to retinopathy in diabetics can be put to check by observing these steps. 3,5,6 It has been reported that avoiding tobacco use and the correction of associated hypertension are important therapeutic measures in the management of diabetic retinopathy
. It is expected from this report that tobacco smoking may play a role in the progression of retinopathy in diabetics who smoke. In addition to good glycaemic control and reduction of blood pressure as a means of checking the development of retinopathy in diabetics, proper patient education, aimed at achieving high level of health literacy is also important. In a study to examine the association between health literacy and diabetes outcomes among patients with type 2 diabetes, inadequate health literacy was found to be independently associated with worse glycaemic control and higher rates of retinopathy.
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Diabetic retinopathy is among the target diseases of vision 2020 which is a global initiative of the WHO for the elimination of avoidable blindness.
It is the Right to Sight initiative with the objective of assisting member states in eliminating avoidable blindness by the year 2020.
The global target is to ultimately reduce blindness prevalence to less than 0.5% in all countries or to less than 1% in any community.
For this goal to be achieved in Nigeria and in Imo State there has to be the will on the part of the health care professionals to make systematic observations and then ask research questions that will help to proffer solutions to this growing health concern. This study was designed to show
the prevalence of diabetic retinopathy among adult diabetics that presented to the General Outpatient Clinics of the Federal Medical Centre Owerri. It is hoped that a good understanding of these risk factors and how they affect diabetics in this area will contribute to the development of the discipline of Family Medicine in Nigeria. This is because reports from this study will make the Family Physician to begin to devote time to properly examine the eyes of diabetic patients presenting to him during each encounter and then begin to aim at risk reduction in the patient. This way, he will be accomplishing his role as one who manages his patients in a holistic manner. The assimilation and adoption of these findings will prepare the family physician to target particular diabetics out of a whole lot that present to him daily for closer eye examination, follow up, as well as prompt and appropriate referral to ophthalmologists.
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