Blood Glucose Control and Vision Outcome in Diabetes
There is now compelling evidence that tight control of blood glucose levels in diabetes decreases the risk of diabetic retinopathy (retinal damage) and other microvascular (small blood vessel) disease.
The Diabetes Control and Complications Trial Research Group, initiated in 1982, has reported data on 1441 patients (age range: 13 to 39) with insulin-dependent diabetes (IDDM) from 29 centres followed from 3 to 9 years. A "primary prevention cohort" had no diabetic retinopathy at baseline and a "secondary-prevention cohort had mild retinopathy. Patients were randomly assigned to "intensive" (multiple daily insulin injections or infusion by pump with continal adjustment of dosage) or "standard" (once or twice daily insulin with conventional monitoring ogf blood glucose levels) therapy groups. Six monthly retinal photographs were graded for retinopathy. Other outcomes measured nephropathy, neuropathy, neuropsychologic disorders, macrovascular disease and quality-of-life.
Data at all time intervals showed significantly improved blood sugar and glycated haemoglobin levels with "intensive" therapy. Most importantly, the risk of progression of retinopathy was definitely less in the intensive therapy group by 36 months and, after 5 years, the risk was 50% less. Intensive therapy substantially reduced the risk of nephropathy (kidney damage), neuropathy (nerve damage) and, probably, macrovascular (major blood vessel) disease.
Adverse effects were relatively minor except for an increased rate of hypoglycaemia (very low bllod sugar). As with other studies, a transient worsening of retinopathy was noted during the first year of intensive therapy but tended to regress toward baseline by 18 months. The incidence of vision threatening complications of diabetes, including macular oedema (retinal swelling) and neo-vascularization (new, abnormal blood vessel formation), was dramatically decreased by intensive insulin therapy
| standard therapy | intensive therapy | |
| sustained microaneurysms | 90% |
70% |
| 9 year incidence of neovascularization |
24% | 8% |
| 9 year incidence of macular oedema | 44% |
27% |
| Secondary cohort requiring laser | 14.2% |
5.5% and required fewer sessions |
|
Stable retinopathy at 5 years with respect to baseline retinopathy |
33% | 51% of primary cohort |
|
32% | 45% of secondary cohort |
Conclusions:
References
The Diabetes Control and Complications Trial. N Engl J Med 1993;329:977-86
The Diabetes Control and Complications Trial. Arch Ophthalmol 1995;113:36-51
The Diabetes Control and Complications Trial. Ophthalmology 1995;102:647-61
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