Review of Diabetic Studies


Diabetes is one of the leading causes of blindness. We see many patients with diabetes so it’s important to know how to treat diabetic retinopathy.  We need to understand and know when to refer the patient to an ophthalmologist for further treatment.

Diabetes Control and Complications Trial (DCCT)

->  Objectives

  • To determine whether intensive treatment with the goal of maintaining blood glucose concentration close to the normal range could decrease the frequency and severity of these complications.

-> Results / Conclusions

  •  “Normoglycemic re-entry” is the slight worsening of retinopathy for a period of 18 months after intensive blood glucose control. After 18 months, the retinopathy stabilizes & improves.
  • Maintaining an HbA1c value of around 7% reduced the risk of long-term retinopathy, neuropathy and nephropathy by about 50%

Diabetic Retinopathy Study

-> Objectives

  • To determine if laser photocoagulation prevents severe vision loss from proliferative diabetic retinopathy.
  • To determine whether a difference exists in the efficacy and safety of argon versus xenon photocoagulation for treatment of proliferative diabetic retinopathy.

-> Methods

  • One eye of each patient was randomly assigned to laser photocoagulation, and the fellow eye was assigned to follow-up only (no treatment).
  • The eye chosen for the treatment group was randomly assigned to either argon laser therapy or xenon arc photocoagulation therapy.
  • Treatment included panretinal photocoagulation (PRP) and any focal treatments necessary for neovascularization of the iris (NVI) or elsewhere (NVE)
  • The outcome measure was severe vision loss defined as VA <5/200 on two consecutive follow-up visits, 4 months apart.

->  Results/Conclusions

  • Photocoagulation reduces the risk of severe visual loss by more than 50% compared to no treatment eyes.
  • In high-risk proliferative diabetic retinopathy, benefits outweigh the risks of photocoagulation.
  • Argon laser and xenon laser photocoagulation reduced the risk of severe vision loss by more than 50%.


(Image courtesy of Wikipedia)

Early Treatment of Diabetic Retinopathy Study (ETDRS)

->  Objectives

  • To determine the efficacy of laser photocoagulation and aspirin for preventing or delaying the progression of early diabetic retinopathy to severe stages of visual loss and blindness.
  • To determine guidelines for when to initiate photocoagulation treatment.
  • To monitor closely the effects of diabetes mellitus and of photocoagulation on visual function.
  • To produce natural history data that can be used to identify risk factors and test etiologic hypotheses in diabetic retinopathy.

->  Methods

  • One eye of each patient was randomly treated with immediate photocoagulation. Treatment of the other eye was reserved until high-risk proliferative retinopathy developed.
  • All patients entered the study with either moderate or severe NPDR or mild  PDR in both eyes.

-> Results / Conclusions

  • Aspirin had no effect on patients with mild to severe nonproliferative or early proliferative diabetic retinopathy.
    • It did not progress to high-risk proliferative stage.
    • Aspirin did not  increase risk of vitreous hemorrhage or decreased vision but it decreased risk of cardiovascular disease.
  • Focal photocoagulation
    • For patients with macular edema, it was shown to reduce the risk of moderate vision loss, to increase the likelihood of moderate visual gain, and to decrease retinal thickening.
  • Panretinal photocoagulation
    • It should not be performed in cases of mild to moderate NPDR.
    • It should be considered in cases of severe NPDR and early PDR, especially with NIDDM (non-insulin-dependent diabetes mellitus).
    • It should be performed in all cases of high-risk PDR.
    • Early vitrectomy should be considered in cases of advanced PDR.
    • All patients with diabetic retinopathy should be carefully followed.

Even though we refer patients for treatment, as a primary eye care provider we have to educate our patients on treatment options. Therefore, it’s important to know outcomes from each study.  Come visit next month for a case of infection!


Johnson, D., Meadows, J., Moose, H. Persson, T. Beta Sigma Kappa Pocket Reference Manual for Evidence-based Clinical Decision Making

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