EyeWorld Asia-Pacific June 2012 Issue

40 EWAP RETINA June 2012 Critical issues in the management of cataract with diabetes by Wong Tien Yin, MD A review of current data on the clinical management of this increasingly prevalent condition D iabetes is becoming an increasingly critical public health issue as the world population ages. The disease has serious consequences on the health of the eye, but our knowledge of diabetic eye diseases is imperfect. Fortunately, we are learning new things every day as research continues into various aspects of the condition, from risk factors to prevention to treatment. It is therefore timely to keep an eye on developments from this research. Here are some of the critical issues in the management of cataract in patients with diabetes that we have learned in the past few years. Managing diabetic retinopathy (DR) Intensive glucose therapy has been found to reduce the onset of new diabetic retinopathy (DR) by 75%; however, it reduces progression by only 50%, so therapy needs to be started early. It takes more than 3 years for beneficial effects to become manifest, but, on the other hand, metabolic memory means that the effects of glucose control are long- lasting. Blood pressure (BP) control is just as important as glucose control, as demonstrated by the UK Prospective Diabetes Study (UKPDS, Lancet 1998;352:837- 853). Tight BP control has been associated with lowered risk of retinopathy progression (with a risk reduction of 34%, p=0.004), of photocoagulation for clinically significant macular edema (CSME; 42% risk reduction, p=0.016), of retinal photocoagulation (35% risk reduction, p=0.023), of 3-line decrease in vision (47% risk reduction, p=0.004), of blindness in one eye (24% risk reduction, p=0.046), of microalbuminuria (>50 mg/L, 6 years, 29% risk reduction, p=0.009), and of gross albuminuria (>300 mg/L, 6 years, 39% risk reduction, p=0.061). Serum lipids are the third factor, influencing clinically significant versus non-clinically significant macular edema. Two major randomized controlled trials (RCTs) demonstrated the effect of fenofibrate, reducing the need for laser for diabetic macular edema (DME) and proliferative diabetic retinopathy (PDR) by 30% in the FIELD study (Keech et al., Lancet 2007), and reducing the risk of DR progression by 40% (ACCORD-Eye, N Engl J Med , 2010). Liew, Wang and Mitchel ( N Engl J Med , 2011) added that fenofibrate may have anti-VEGF effects. Diabetes and cataract Many studies show earlier onset of cortical and PSC cataract and earlier cataract surgery in patients with diabetes. The Blue Mountain Eye Study found that all three cataract types are associated with diabetes in an age-sex adjusted model, while PSC and cataract surgery were associated with diabetes in a multivariate model. Meanwhile, the Visual Impairment Project, looking at patients with diabetes for more than 5 years, associated the disease with cortical and nuclear cataracts but not PSC in a multivariate model. Diabetes and cataract surgery Consistent findings from various case series and meta- analyses indicate that diabetes may significantly worsen visual outcome after cataract surgery. In addition, preoperative DR/DME influences visual outcome from asymmetric progression in the operated eye. Surgeons should ensure adequate laser treatment prior to surgery—surgery should be delayed until DR/DME is stabilized. If the cataract is moderate to advanced, consider surgery to adequately assess the need for laser or to permit laser therapy. Laser therapy is particularly critical as the risk of DR doubles in patients with diabetes 12 months after cataract surgery. Preventing DR/DME post-cataract surgery Based on the 2008 NHMRC guidelines, panretinal photocoagulation (PRP) is used to treat proliferative DR, but should also be considered for severe nonproliferative DR prior to cataract surgery. By the same guidelines, focal laser used for CSME should also be considered for mild DME before proceeding with cataract surgery. Adjunctive therapy may be needed prior to or during cataract surgery in refractory DME, in microaneurysms (MAs) close to the fovea, and in diffuse DME. Intravitreal triamcinolone (IVTA) provides short-term improvement in vision and structural improvement in terms of macular thickness, but long-term visual outcome may not be better than that achieved with laser in most cases of DME (DRCRNet, Ophthalmology 2008). However, IVTA may be useful for refractory DME (Gillies et al. Ophthalmology 2006). Multiple injections are generally needed and some complications – glaucoma, PSC cataract, endophthalmitis – frequently occur. Anti-VEGF agents, on the other hand, may provide a better option. The basis for anti-VEGF therapy is provided by several studies, including: Aiello LP et al. ( N Engl J Med , 1994), who have shown that VEGF levels are higher in eyes with DME than in eyes with age-related macular dystrophy (AMD); Lowe et al. ( Exp Eye Res , 2007), who have further demonstrated that intraocular VEGF levels correlate with retinopathy severity; Salam A et al. ( Br J Ophthalmol , 2010), who have shown that VEGF mediates blood-retinal barrier hyperpermeability, promoting fenestration in and disrupting intercellular junctions between endothelial cells. In addition, RCTs such as DRCRNet and RESOLVE have shown intravitreal anti-VEGF agents to have superb efficacy and safety. In terms of timing, intraocular injections can be given before, during or after cataract surgery. While the 2008 NHMRC Guidelines recommend giving intraocular injections during cataract surgery, there is no good evidence to favor any one sequence over another. But in choosing between IVTA and anti- VEGF, surgeons should consider the IOP or the presence of glaucoma, the consequences of needing multiple injections, and systemic safety issues such as stroke. CME vs. DME after cataract surgery MAs at the fovea tend to be found with DME more than with CME. Diabetic patients suffering from CME after cataract surgery will have no or only mild DR, while fundus fluorescein angiography (FFA) will reveal a petaloid pattern and disc staining. Cases of DME after cataract surgery will be attended by moderate or severe DR, and an FFA will show MAs without disc staining. In contrast to DME, CME responds to topical steroids or NSAIDs. One final consideration is the consequence of surgery on management options: remember that a small capsulorhexis or capsular phimosis after phacoemulsification makes it difficult to perform laser. Summing up Cataract is a common co- morbidity of patients with DR. Systemic control is important in preventing DR progression after cataract surgery. Adequate laser treatment should be given before performing cataract surgery, and adjunctive therapy with IVTA or anti-VEGF agents should be given if needed during cataract surgery. Finally, ensure an adequate capsulorhexis for retinal assessment and treatment. EWAP Contact information Wong: tien_yin_wong@nuhs.edu.sg