Exame de Fundo de Olho em Paciente Diabético

Paciente, sexo M, 32 anos.
1) Paciente com história de pancreatite aguda em junho de 2012, tendo sido retirada a cauda do pâncreas no tratamento cirúrgico. Desenvolveu diabetes mellitus após o quadro e faz uso de insulina desde então. Apresenta quadros de hipoglicemia esporádicos que não causam complicações.
Medicamentos em uso: Insulina NPH (20 unidades antes do café-da-manhã); metformina XR (500 mg); glibenclamida (5mg); captopril (25mg); omeprazol (20mg).

Dúvidas:
1) A partir de quando é necessária a investigação de lesões oculares em pacientes diabéticos?
It is estimated that there are 700,000 (approximately 10 per cent of the population) diabetic patients in Hong Kong and there is a trend towards younger adults being diagnosed with diabetes in developed countries. Many studies have shown that poorly controlled, unbalanced diet and lack of regular exercise might contribute to this trend. Diabetic retinopathy is a complication of diabetes and one of the worldwide leading causes of blindness.Early detection with regular examinations and management of the disease are effective measures to reduce the chance of blindness due to sightthreatening retinopathy. Therefore, screening for retinopathy is recommended for all diabetic patients, particularly at the time of first diagnosis. The prevalence of diabetic retinopathy in patients up to one year since the diagnosis of diabetes was 18.2 per cent. This is lower than a previous epidemiological study in Hong Kong. The known duration since diagnosis of selected diabetic patients in our study was up to one year, whereas diabetic patients included in the epidemiological study had a mean known duration of 4.71 years, with a range from 0.1 to 40.6 years. A difference in the known duration of diabetes might lead to the lower prevalence in the present study. Our electronic system records ‘greater than 15’ if the known duration of diabetes is over 15 years, which made it difficult to calculate the mean and range of known duration of diabetes. The prevalence of diabetic retinopathy regardless of the duration since diagnosis in the present study (28.0 per cent) was similar to previous studies in Hong Kong (28.4 per cent) and Victoria, Australia (29.1 per cent); however, it was lower than studies in the United States (33.2 per cent), Singapore (35.0 per cent) and China (37 per cent). Different races such as Black people, Hispanics, Caucasians and Chinese were included in the US study, while the majority of patients recruited in the present study were Chinese. Moreover, sample sizes were generally lower in other studies; there were 778 in the US study, 3,261 in the study in Singapore and 235 in the Chinese study. These factors might account for the differences in prevalence of diabetic retinopathy among these studies. The prevalence was lower in India (18.0 per cent). Insufficient public awareness of diabetic retinopathy and lack of health checks might result in undiagnosed diabetes in the Indian population, and therefore a lower prevalence of diabetic retinopathy might be expected. Modes of diet may also contribute to the difference of prevalence of diabetic retinopathy among countries and this requires further investigation. Similar to other epidemiological studies, our research shows an increase in the prevalence of diabetic retinopathy with longer durations since the diagnosis of diabetes. The percentage of patients with sight-threatening retinopathy with different durations since the diagnosis of diabetes, the percentage in ‘newly diagnosed’ patients was actually higher (6.89 per cent) than other durations except over 10 years. This was mainly due to the major increase in patients with mild and moderate non-proliferative diabetic retinopathy who had a longer duration since the diagnosis of diabetes, rather than those with sight-threatening retinopathy. The onset of diabetes could be years longer than the time of diagnosis. Patients may not be aware of the diabetes until they experience symptoms, such as frequent urination, unusual thirst, extreme hunger, unusual weight loss or extreme fatigue and irritability. Therefore, those labelled as ‘newly diagnosed’ did not mean ‘newly onset’ of diabetes. Considering the alarming prevalence of diabetic retinopathy in newly diagnosed diabetic patients and its percentage of sight-threatening retinopathy, retinal screening should be indicated as soon as patients are diagnosed with diabetes. Tight control of blood glucose is effective in reducing the rate of progression of diabetic retinopathy and therefore the association between blood glucose level and diabetic retinopathy has been investigated. Levels of HbA1c were not available for some patients and random glucose levels are affected by many factors including the time since the last meal. In the present study, blood glucose levels were excluded in our evaluation of risk factors associated with the prevalence of diabetic retinopathy. Blood glucose levels may be controlled by diet, oral medication or insulin injections. There were no insulin users in the present study. All recruited subjects who were not receiving oral medication said they used diet control. Reporting bias might affect this result because many patients knew that an intake of too much sugar and carbohydrates made it difficult to control diabetes. Instead of admitting that they do nothing, they might claim to use diet control. From our results, hypertension had no significant effect on the prevalence of diabetic retinopathy in newly diagnosed diabetic patients. One explanation is that control of tight blood pressure is more important to the progression of established retinopathy than the onset of diabetic retinopathy. Hypertension is a risk factor of macro-vascular and micro-vascular complications and diabetic retinopathy is amicrovascular disease. Tight control of blood pressure in diabetic patients (mean duration was 2.6 years) with hypertension would have less retinal signs microaneurysms, hard exudates and cotton-wool spots) than those with less blood pressure control. These differences were noticed after a 7.5-year follow-up period. From the Action to Control Cardiovascular Risk in Diabetes study, careful glycaemic control and intensive treatment of dyslipidaemia reduced the rate of progression of diabetic retinopathy but intensive blood pressure control did not. Therefore, hypertension seems to have little effect on the prevalence of diabetic retinopathy in newly diagnosed diabetic patients. Cigarette smoking is a risk factor for complications of diabetes, especially cardiovascular disease; however, smoking had little effect on the prevalence and incidence of diabetic retinopathy in this and other epidemiological studies, even though our smoking prevalence was lower. Only patients who were current smokers during attendance at the clinic were classified as ‘ever smoked’. Reporting bias might further decrease the number of smokers because patients might feel guilty about smoking and give misleading information.

Referência Bibliográfica: Lee KM, Sum WM (2011) Prevalence of diabetic retinopathy in patients with recently diagnosed diabetes mellitus. Clin Exp Optom 94: 371–375.

2) Quais as alterações que se espera encontrar ao exame?
In this study, 30.7 per cent of subjects with T2DM were found to have diabetic retinopathy.There was 1.7 per cent (17/1,011), who had sight-threatening diabetic retinopathy that was comparable to a previous Hong Kong study, which we estimated to be 1.9 per cent based on their published data.
For the 891 subjects with T2DM for one year or longer, nearly two-thirds (62.7 per cent) have not had a diabetic retinopathy evaluation since diagnosis. This is much higher than reported for other countries (Melbourne: 20 to 32 per cent; 15 United States: 35 per cent16) and reflects the lack of organised and systematic eye care for people with diabetes in Hong Kong.
Of the 891 subjects with gradable fundus photographs, nearly 2.0 per cent had sight-threatening diabetic retinopathy. Those who had not had a retinal assessment since diagnosis of their T2DM were more likely to develop sightthreatening diabetic retinopathy than those who had a retinal evaluation. This finding supports a previous report that diabetic patients who did not receive eye care show a high prevalence of ocular morbidity.
Another interesting finding in this study is that subjects with other ocular disorders that required further management, such as significant cataract (28.9 per cent), suspected glaucoma (2.2 per cent) and macular hole (0.5 per cent), were generally unaware that they had such disorders. One reason might be that more than half of these subjects (189/328) had not consulted an eye-care provider for an eye examination within the last two years. Another reason might be that, among older people in Hong Kong, it is generally accepted that vision deteriorates with ageing and people would not seek attention until vision had deteriorated to the point where daily routine activities were adversely affected.
The present study clearly indicates that many patients with T2DM did not receive timely eye care. This could be attributed to several reasons. First and possibly the most important reason is the Hong Kong health care system. Our subjects were recruited from a patient population attending government-funded medical clinics. A patient with T2DM under the care of a medical clinic would assume that the system would direct him or her to whatever care is necessary. If the system does not send the patient to have an eye examination, then the patient would assume that he or she does not need one. A previous study has shown that most Hong Kong people are aware that consulting medical professionals might help them prevent agerelated blindness. Nevertheless, only approximately one-quarter of those who had a visual loss in either eye had already sought professional advice. Another Hong Kong-based study revealed that the average waiting period for an ophthalmological evaluation in a local eye hospital was 21 weeks. Clearly, being directed to an appropriate eye-care service and gaining access to that service in a timely manner are key issues that need to be addressed in the Hong Kong health care system.
Second, diabetic retinopathy is typically asymptomatic until the macula is involved.It is understandable that many patients assume that there is no problem with their eyes because their vision is clear. The lack of knowledge on the asymptomatic nature of diabetic retinopathy might be one reason why patients with T2DM do not seek or request regular eye care.
There are several limitations to this study. As the use of a retinal examination in the past was self-reported by the subjects, the data might be misreported and not reliable. In addition, our study group is subject to a degree of bias. Of all the patients referred to our screening clinic, approximately 90.9 per cent actually attend. Those who did not attend give reasons such as ‘already attending the hospital eye service’, ‘do not wish to have the pupil dilation’ or ‘cannot afford the screening fee’. This study also excludes diabetic patients who reside in a nursing home. This group is known to have a high prevalence of sight-threatening diabetic retinopathy. Our data should be interpreted in light of these limitations.
Over 60 per cent of subjects in the present study with T2DM for one year or more have not had a retinal assessment since diagnosis of their DM. The risk of developing sight-threatening diabetic retinopathy appears to be higher for those who have not had a retinal assessment. There is a clear need to promote a more efficient and systematic way to manage the eye and vision care of patients with T2DM in Hong Kong, particularly in the older-onset group.


Referências Bibliográficas: Fung MM, Yap MK, Cheng KK. Community-based diabetic retinopathy screening in Hong Kong: ocular findings. Clin Exp Optom 2011;94:63–66.