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Diabetic retinopathy
All people with diabetes mellitus are at risk those with Type I diabetes (juvenile onset) and those with Type II diabetes (adult onset). The longer a person has diabetes, the higher the risk of developing some ocular problem. Between 40 to 45 percent of Americans diagnosed with diabetes have some stage of diabetic retinopathy. After 20 years of diabetes, nearly all patients with type 1 diabetes and >60% of patients with type 2 diabetes have some degree of retinopathy. Prior studies had also assumed a clear glycemic threshold between people at high and low risk of diabetic retinopathy.

However, it has been shown that the widely accepted WHO and American Diabetes Association diagnostic cutoff for diabetes of a fasting plasma glucose = 7.0 mmol/l (126 mg/dl) does not accurately identify diabetic retinopathy among patients. The cohort study included a multi-ethnic, cross-sectional adult population sample in the US, as well as two cross-sectional adult populations in Australia. For the US-based component of the study, the sensitivity was 34.7% and specificity was 86.6%.

For patients at similar risk to those in this study (15.8% had diabetic retinopathy), this leads to a positive predictive value of 32.7% and negative predictive value of 87.6%. Published rates vary between trials, the proposed explanation being differences in study methods and reporting of prevalence rather than incidence values. During pregnancy, diabetic retinopathy may also be a problem for women with diabetes. It is recommended that all pregnant women with diabetes have dilated eye examinations each trimester to protect their vision.[citation needed]

Diagnosis

Diabetic retinopathy is detected during an eye examination that includes:

  •  Visual acuity test : This test uses an eye chart to measure how well a person sees at various distances ( i.e. ,
  •  Digital Retinal Screening Programs : Systematic programs for the early detection of eye disease including diabetic retinopathy are becoming more common, such as in the UK, where all people with diabetes mellitus are offered retinal screening at least annually. This involves digital image capture and transmission of the images to a digital reading center for evaluation and treatment referral. See Vanderbilt Ophthalmic Imaging Center and the English
  • visual acuity).
  •  Pupil dilation : The eye care professional places drops into the eye to widen the pupil. This allows him or her to see more of the retina and look for signs of diabetic retinopathy. After the examination, close-up vision may remain blurred for several hours.
  •  Ophthalmoscopy : This is an examination of the retina in which the eye care professional: looks through a device with a special magnifying lens that provides a narrow view of the retina, or wearing a headset with a bright light, looks through a special magnifying glass and gains a wide view of the retina. Note that hand-held ophthalmoscopy is insufficient to rule out significant and treatable diabetic retinopathy.
  •  Optical coherence tomography (OCT) : This is an optical imaging modality based upon interference, and analogous to ultrasound. It produces cross-sectional images of the retina (B-scans) which can be used to measure the thickness of the retina and to resolve its major layers, allowing the observation of swelling and or leakage.
  • National Screening Programme for Diabetic Retinopathy
  •  Slit Lamp Biomicroscopy Retinal Screening Programs : Systematic programs for the early detection of diabetic retinopathy using slit-lamp biomicroscopy. These exist either as a standalone scheme or as part of the Digital program (above) where the digital photograph was considered to lack enough clarity for detection and/or diagnosis of any retinal abnormality.


The eye care professional will look at the retina for early signs of the disease, such as: leaking blood vessels, retinal swelling, such as macular edema, pale, fatty deposits on the retina (exudates) – signs of leaking blood vessels, damaged nerve tissue (neuropathy), and any changes in the blood vessels.

Should the doctor suspect macular edema, he or she may perform a test called fluorescein angiography. In this test, a special dye is injected into the arm. Pictures are then taken as the dye passes through the blood vessels in the retina. This test allows the doctor to find the leaking blood vessels.

   
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