with dyslipidemia [10]. Further clinical trials are currently underway examining the effects of statins.

Aspirin Treatment

The Early Treatment Diabetic Retinopathy Study (ETDRS) investigated whether aspirin (650 mg/ day) could retard the progression of retinopathy. After examining progression of retinopathy, development of vitreous hemorrhage, or duration of vitreous hemorrhage, aspirin was shown to have no effect on retinopathy, and there are no ocular contraindications to the use when required for cardiovascular disease or other medical medications.

Laser Photocoagulation

Laser photocoagulation therapy has proven effective in reducing DR progression, and pars plana vitrectomy can in many cases prevent severe vision loss in patients with advanced stages of DR [22]. Unfortunately, both treatments carry a risk of additional vision loss, and neither is effective at reversing loss of visual acuity.

Panretinal Photocoagulation and Focal/

Grid Laser Photocoagulation

Therapeutic retinal photocoagulation has been practiced for more than 50 years. Since the 1960s, the treatment has become gradually more refined, effective, and safe as new wavelengths and treatments have entered clinical practice.

Two large National Institutes of Healthsponsored trials, and the Early Treatment Diabetic Retinopathy Study (ETDRS), provide the strongest support for the therapeutic benefit of photocoagulation. The DRS tested whether scatter (panretinal) photocoagulation (PRP) surgery could reduce the risk of vision loss from PDR [23]. There were 1,758 participating patients. After only 2 years, photocoagulation surgery was shown to significantly reduce visual loss (i.e., best acuity of 5/200 or worse) in 15.9% of untreated

eyes versus 6.4% of treated eyes. The benefit persisted through the entire duration of follow-up and was greatest among patients whose baseline evaluation revealed high-risk characteristics (HRCs) (disk neovascularization or vitreous hemorrhage with any retinal neovascularization). Of control eyes with HRC, 26% progressed to severe visual loss versus 11% of treated eyes. The absolute benefit of photocoagulation was much smaller for eyes that did not have HRC.

To determine the timing of photocoagulation, the ETDRS examined the effect of treating eyes with mild NPDR to early PDR. The rates of visual loss were low with either treatment applied early or delayed until development of HRCs. Because of this low rate and the risk of complications, the report suggested that scattered photocoagulation be deferred in eyes with mild-to-moderate NPDR. When retinopathy is more severe, scatter photocoagulation should be considered and usually should not be delayed, if the eye has reached the high-risk proliferative stage.

The ETDRS also demonstrated the effectiveness of focal photocoagulation in eyes with macular edema. In patients with clinically significant macular edema, 24% of untreated eyes, compared with 12% of treated eyes, developed doubling of the visual angle (e.g., 20/50 to 20/100). Laser photocoagulation in both the DRS and the ETDRS was beneficial in reducing the risk of further visual loss, but generally not beneficial in reversing already diminished acuity.

The recommended therapy is either 1,200– 2,000 burns 500 m in diameter delivered through the Goldmann lens or 1,200–2,000 burns 200 m in diameter delivered through the Rodenstock panfundoscope or Volk SuperQuad lenses. The burns should be intense enough to whiten the overlying retina, which often requires a power of 200–600 mW and duration of 0.1 s (Fig. 21.20).

Focal and grid laser photocoagulation is indicated for CSME, the goal being to limit vascular leakage through a series of focal laser burns at leaking microaneurysms or grid laser burns in regions of diffuse breakdown of the blood-retinal barrier (Fig. 21.21). In some patients with less than high-risk PDR or with severe or very severe NPDR, PRP may be indicated under certain circumstances. The latter include presence of rapidly