Diabetic Retinopathy Study (DRS)

Diabetic Retinopathy Study (DRS)


Does PRP (argon or xenon arc) prevent severe vision loss in eyes with diabetic retinopathy?


Patients were included in the study if they had PDR in at least one eye or severe NPDR in both eyes, and had VA of 20/100 or better in each eye.

Severe NPDR was defined as the presence at least 3 of the following:

1.     Cotton wool spots

2.     Venous beading

3.     Intraretinal microvascular abnormalities (IRMA) in at least 2 contiguous overlapping photographic fields

4.     Moderate-to-severe retinal hemorrhages and/or MA’s

Patients were excluded if they had undergone previous PRP or had a macula-threatening TRD.


This was a randomized, prospective multicenter clinical trial.  1742 study subjects were enrolled.  One eye from each subject was randomly assigned to PRP and the other eye assigned to no PRP.  The PRP eyes were randomized to either argon blue-green laser (800-1600, 500 micron spots) or xenon arc (200-400, 4.5 degree spots).

The primary outcome measure was severe vision loss, defined as VA < 5/200 on two consecutive follow-up exams, 4 months apart.


PRP reduced the risk of severe vision loss by at least 50% as compared to untreated control eyes.   The greatest benefit was seen in eyes with high-risk PDR.  Study follow-up was over 5 years.

High-risk PDR was defined as any one of the following:

1.     NVD ≥ 1/3 disc area

2.     Any NVD with vitreous hemorrhage

3.     NVE ≥ ½ disc area with vitreous hemorrhage

High-risk PDR was also defined as three or more of the following high-risk characteristics (HRC’s):

1.     Presence of vitreous hemorrhage or pre-retinal hemorrhage

2.     Presence of any active neovascularization

3.     Location of neovascularization on or within one disc diameter of the optic disc

4.     NVD > 1/3 disc area or NVE > ½ disc area

Eyes with high-risk PDR had significantly greater risk of severe visual loss and demonstrated the greatest benefit from PDR.

No clear benefit was demonstrated for PRP in eyes with severe NPDR or in eyes with PDR without high-risk characteristics.

Risks of treatment include small reductions in visual acuity or visual field.  Harmful effects of argon laser treatment were less than those seen with xenon arc treatment.  In the argon laser treatment group, a decrease in VA of 1 or more lines was seen in 11% of eyes; visual field loss was seen in 5%.


PRP reduces the risk of severe vision loss compared with no treatment in eyes with high-risk PDR.

Eyes with high-risk PDR should receive prompt treatment with PRP.  Eyes with two or fewer high risk characteristics (HRC’s) still benefit from PRP, but the benefit is small and risks of treatment may outweigh the benefits.  However, consider earlier treatment with PRP for older-onset diabetic patients.