Normal or Minimal NPDR
The patient with a normal retinal examination or minimal NPDR (i.e., with rare microaneurysms) should be re-examined annually, because within one year 5% to 10% of patients without retinopathy will develop it. Existing retinopathy will develop further by a similar percentage.
Mild to Moderate NPDR without Macular Edema
Patients with retinal microaneurysms and occasional blot hemorrhages or hard exudates should be re-examined within 6 to 12 months, because disease progression is common. The natural history of Type 1 diabetic patients suggests that approximately 16% of patients with mild retinopathy (hard exudates and microaneurysms only) will progress to proliferative stages within 4 years.
Mild to Moderate NPDR with Clinically Significant Macular Edema (CSME)
CSME is defined by the ETDRS to include any of the following features:
- Thickening of the retina at or within 500 µm of the center of the macula
- Hard exudates at or within 500 µm of the center of the macula, when associated with adjacent retinal thickening
- A zone or zones of retinal thickening one-disc area or larger, where any portion of the thickening is within one-disc diameter of the center of the macula
It is now appropriate to subdivide diabetic macular edema according to involvement at the center of the macula, because the risk of visual loss and the need for treatment is greater when the center is involved. Macular edema is best evaluated by dilated examination using slit-lamp biomicroscopy, OCT, and/or stereoscopic fundus photography. Current treatment for diabetic macular edema include Anti-VEGF regimens.
Severe NPDR and Non-High-Risk PDR
In eyes with severe NPDR, the risk of progression to proliferative disease is high. Half of patients with severe NPDR will develop PDR within 1 year, and 15% will have high-risk PDR. For patients with very severe NPDR, the risk of developing PDR within 1 year is 75%. Furthermore, 45% will become high-risk PDR in this same time frame. Therefore, these patients should be re-examined within 2 to 4 months.
The presence of any three of the following features characterizes DRS high-risk PDR:
- Neovascularization (at any location)
- Neovascularization at the optic disc
- Severe neovascularization
- New vessels within one-disc diameter of the optic nerve head that are larger than one-quarter to one-third disc area in size
- New vessels elsewhere that are at least one-half disc area in size
- Vitreous or preretinal hemorrhage
Current treatment for PDR include panretinal laser therapy, Anti-VEGF treatment regimens, and Vitrectomy.