Treatment Of Established Disease

Laser panretinal photocoagulation (PRP) of the retina is the primary treatment for PDR (Fig. 8). Its value was proven in the Diabetic Retinopathy Study (DRS), which randomly assigned PRP to one eye of 1758 diabetic patients with advanced retinopathy. The DRS found that photocoagulation reduces the risk of severe visual loss by 50% or more (30). The question of when to apply PRP was further delineated by the ETDRS. One eye of each patient was assigned randomly to early photocoagulation and the other to deferral of

Figure 7 Fibrosis of the neovascularization results in traction on the retina.

photocoagulation (21). Based on the ETDRS, early photocoagulation is not recommended because severe visual loss is uncommon in treated and untreated eyes; moreover, PRP is associated with significant loss of visual acuity and peripheral vision, especially in the first few months after treatment (25). The DRS did identify high-risk characteristics for which PRP is clearly beneficial: (i) eyes with neovascularization and preretinal or vitreous hemorrhage and (ii) eyes with neovascularization on or within one disc diameter of the optic disc equaling or exceeding 1/4 to 1/3 disc area in extent even in the absence of preretinal or vitreous hemorrhage (30).

Early laser therapy has been found to be helpful in one exception, macular edema. In this setting, the ETDRS found early focal photocoagulation increased the chance of visual improvement, decreased the frequency of persistent macular edema, and caused only minor visual field loss. Therefore, focal laser treatment should be considered for eyes with macular edema that involves or threatens the fovea (21).

Anecdotal reports suggest intraocular injection of triamcinolone acetate into the vitreous is helpful in eyes with macular edema; however, there are no randomized clinical trials proving its efficacy in diabetic patients (25,31,32). In addition, it has been associated with elevations in intraocular pressure leading to glaucoma, cataract formation, endophthalmi-tis, vitreous hemorrhage, and retinal detachment (33,34). Despite these risks, the anecdotal evidence of its efficacy has made it a valuable option for the treatment of refractory macular edema.

Figure 8 Panretinal photocoagulation is present in the retinal periphery for 360 degrees.

Laser therapy, unfortunately, is at times unable to deter the progression of neovascularization and secondary vitreous hemorrhage and traction retinal detachment. In these cases, the risk of severe visual disability rises dramatically and surgical intervention is necessary with vitrectomy. The timing of vitrectomy is important as found in the Diabetic Retinopathy Vitrectomy Study (DRVS). The DRVS enrolled 370 eyes with advanced, active PDR and visual acuities of 10/200 or better and randomly assigned the eyes to either early vitrectomy or conventional management. It found that if vitrectomy was delayed until central retinal detachment occurred, only 28% of eyes had a visual acuity of 10/20 or better at 4 years; whereas, 44% had a 10/20 visual acuity or better if vitrectomy was preformed early (25,35). The major indications for vitrectomy are macular-involving/threatening traction retinal detachment, combined traction-rhegmatogenous (i.e., torn) retinal detachment, and nonclearing vitreous hemorrhage (2).

If vitreous hemorrhage occurs, it can be managed conservatively with observation and laser treatment, surgical vitrectomy, or pharmacologic vitrectomy. Pharmacologic vitrec-tomy can be preformed with hyaluronidase (Vitrase) injection, which has shown therapeutic utility in clinical trials (36). A recent case report found that the anti-VEGF antibody beva-cizumab (Avastin) caused marked regression of neovascularization and rapid resolution of vitreous hemorrhage (37) (Fig. 9).

Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

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