Both triamcinolone (by injection) and fluocinolone (by implant) have been shown to reduce macular edema and improve visual acuity but with the serious side effects of glaucoma and cataract formation. Many patients required multiple steroid injections and some developed infections. The long-term benefits and safety of these treatments need to be established.
These agents have been shown to benefit patients with ‘wet’ age-related macular degeneration, which shows some similarities with diabetes-related macular edema (DME). One hundred and seventy two patients with DME were randomized to pegaptanib or sham injections and after 36 weeks those on active treatment had visual improvement of 10 letters or more and less need for photocoagulation. Larger trials in diabetic patients of this and other similar agents are under way.
Meta-analysis shows that panretinal laser photocoagulation (PRP) (Figure 15.19) reduces the risk of blindness in eyes with proliferative retinopathy by 61%, and this has now become the cornerstone of treatment of advanced disease. Focal laser photocoagulation can be effective for more discrete neovascularisation or ischemia. There is no evidence that PRP confers benefit until sight-threatening proliferative retinopathy is present.
Similarly, in the ETDRS, focal grid laser photocoagulation to the macula decreased the risk of moderate visual loss due to DME by 50% (95% CI 47–53%) over 3 years in 2244 patients with bilateral disease (Figure 15.20).
Photocoagulation is generally well tolerated but some patients can experience discomfort and need local anesthetic. Up to 23% of patients experience transient or permanent visual loss following PRP. There can also be visual field constriction and night blindness, which can affect eligibility for driving.
These problems emphasize the essentially destructive nature of PRP, which is why prevention of retinopathy is so important and also why there is active research into alternative medical treatment.
Surgical vitrectomy in advanced eye disease results in sustained benefit in terms of visual acuity, with 6/12 (20/40) or greater vision in at least 25% of eyes at 4 years. Improved operative technique with intraoperative imaging has greatly advanced the field and is likely to have improved outcomes.
A 29-year-old woman with type 1 diabetes and coeliac disease had a profound fear of hypoglycaemia. Consequently, she maintained high blood glucose levels and her HbA1c was consistently above 9% (75 mmol/mol). Because of developing retinopathy, she elected to try CSII. There was a dramatic improvement in blood glucose control without hypoglycemia and her HbA1c came down to 6.5% (48 mmol/mol) over 6 months. Regular ophthalmic assessments were scheduled but she missed two appointments. Four months later she presented with acute vitreous hemorrhage in her right eye secondary to advanced proliferative retinopathy. Extensive panretinal photocoagulation has prevented further hemorrhage and preserved vision in her left eye, but she now requires vitreoretinal surgery on the right for traction detachment.
Comment: This case demonstrates the potential for rapid worsening of retinopathy with glycemic improvement. It is essential to arrange frequent eye examinations in this and similar situations (such as pregnancy) and also to impress upon the patient their importance. Panretinal photocoagulation is best carried out before neovascularisation and hemorrhage.
Regular retinal examination is recommended by all national guidelines. The ADA suggests expert examination within 5 years of diagnosis of all with type 1 diabetes aged > 10 years and as soon as possible after diagnosis of type 2 diabetes. The best periodicity thereafter is controversial. The ADA suggests that review could be every 2 or more years if there are several annual assessments with no retinopathy. Studies from Liverpool in the UK suggest that there is a minimal likelihood of progression from no retinopathy to significant change requiring therapy in less than 2 years in patients with type 2 diabetes.
The most effective mode of surveillance has been the subject of intense research and in the UK there is general agreement that digital fundus photography is superior to both optometrist-based slit lamp ophthalmoscopy as well as opportunistic direct ophthalmoscopy performed by diabetologists. The National Screening Committee and the National Service Framework for Diabetes have both recommended annual two-field digital fundus photography for everyone with diabetes and a nationally funded program is now in place. Photographs are graded according to the scale in Box 15.4 and there are set referral targets based upon their score (Box 15.5). At the time of writing, well over 80% of patients were being offered, and most were taking up, annual fundus photography. In pregnancy, women should be screened as soon as possible after booking and at 28 weeks’ gestation. An additional review should occur at 16–20 weeks if the first one reveals any retinopathy.
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This edition first published 2010, © 2010 by Rudy Bilous and Richard Donnelly. Previous editions: 1992, 1999, 2004
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