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From the editor

Cataract surgery in patients with diabetes

Srinivasan, Sathish FRCSEd, FRCOphth, FACS

Journal of Cataract & Refractive Surgery: November 2017 - Volume 43 - Issue 11 - p 1369-1370
doi: 10.1016/j.jcrs.2017.10.030
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Cataract continues to be the leading cause of blindness according to the Global Burden of Disease, Injuries and Risk Factors Study.A The World Health Organization estimates that the number of cases of blindness from cataract will increase to 40 million in 2025 as a result of aging population and longer life expectancies.1 The cataract surgical rate is defined as the number of cataract operations performed per million of the population in 1 year and is a proxy indicator to the access of cataract services in a country.2 There is robust evidence to demonstrate that the cataract surgical rate uptake has been on an upward trend over the past decade in both developed and underdeveloped countries.3

Diabetes mellitus (DM) is among the most prevalent and morbid chronic diseases, affecting millions worldwide. According to the Global Burden of Disease report, the prevalence of diabetes rose from approximately 333 million in 2005 to approximately 435 million in 2015, an increase of 30.6%.4 The data from 3 population-based studies—the Beaver Dam Eye Study,5 the Blue Mountains Eye Study,6 and the Visual Impairment Project7—have shown an increased association between diabetes and cataract. This increased incidence is higher in patients with late-onset type 2 DM.8 Overall, up to 20% of cataract operations are estimated to be performed in diabetic patients.9

Cataract surgery in patients with diabetes presents a unique set of problems to the operating surgeon. Anterior segment changes include changes in the cornea (increased epithelial fragility, reduced corneal sensitivity, altered epithelial and endothelial barrier functions, and impaired corneal wound healing).10 Diabetic neuropathy and changes in the iris pigment epithelium due to the accumulation of glycogen can lead to miosis and poor intraoperative pupil dilation during cataract surgery.11 Prevention of macular edema in diabetic patients having cataract extraction has been the Achilles heel for cataract surgeons. In the past, intracapsular and extracapsular cataract surgery have been shown to increase the incidence of macular edema or worsen diabetic retinopathy.12,13 However, the modern small-incision phacoemulsification procedure seems to provide good and safer outcomes in diabetic eyes,14,15 presumably as a result of shortened surgical times and less inflammation and damage to the blood–aqueous barrier.

Macular edema after cataract surgery (cystoid macular edema or Irvine-Gass syndrome) occurs as a result of breakdown of the blood–retinal barrier and increased perifoveal capillary permeability, resulting in accumulation of fluid in the outer plexiform and inner nuclear layers of the retina. One of the difficulties in assessing and managing macular edema after cataract surgery in diabetic patients arises from the fact that 2 clinical forms of macular edema can be present, either alone (postsurgical) or in combination (postsurgical and diabetic macular edema). Although clinical examination and fluorescein angiography have been used in the past to diagnose macular edema, optical coherence tomography (OCT) (time domain and spectral domain) has become the gold standard tool for assessing the macula.16

The United Kingdom Prospective Diabetes Study number 3517 clearly demonstrated that in patients with type 2 DM, the risk of diabetic complications was strongly associated with previous hyperglycemia. Patients with a median hemoglobin A1c (HbA1c) of 7.0% showed a substantial reduction in the risk for microvascular complications. Moreover, each 1.0% reduction in HbA1c was associated with a 37% decrease in the risk for microvascular complications.

In this issue Ylinen et al. (pages 1376–1382) in a prospective Finnish population study, evaluated the macular thickness preoperatively and postoperatively with spectral-domain OCT in 93 diabetic patients having uneventful cataract surgery. They also collected data on the patients’ HbA1c and by both univariate and multivariate analysis found that higher serum levels of HbA1c correlated well with increased central retinal thickness as measured by OCT postoperatively.

In the past few years, several new treatments have been tried to address the issue of macular edema after cataract surgery in both diabetic and nondiabetic patients. However, until recently there has been no well-designed randomized clinical trial evaluating all the treatment strategies. In 2012, the European Society of Cataract and Refractive Surgeons (ESCRS) sponsored the PREvention of Macular Edema after Cataract Surgery study to establish an evidence-based treatment for postoperative macular edema in both nondiabetics and diabetic patients. This study, led by Dr. Rudy Nuijts from the Netherlands, recruited 1135 patients from 13 clinical sites across Europe. The results, presented by Nuijts and WieldersB at the annual meeting of the ESCRS in Lisbon, Portugal, in 2017, showed diabetic patients receiving topical nonsteroidal antiinflammatory and topical corticosteroid combined with a subconjunctival injection of 40 mg of triamcinolone have the lowest chance of developing macular thickening after cataract surgery. As we await formal publication of this work in the peer-reviewed literature, I believe that the past decade has provided not only advanced imaging technologies such as OCT but also robust clinical data both in the ophthalmic and nonophthalmic literature that helps us better guide our treatment strategies for diabetic patients.

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Figure:
Sathish Srinivasan, FRCSEd, FRCOphth, FACS

References

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Other Cited Material

A. Bourne RR, Stevens G, White RA, Flaxman S, Mascarenhas M, Price H, Leasher J, Pesudovs KI, Taylor HR; GBD Study Vision Loss Expert Group, “The Global Burden of Disease Study: The Impact of Vision Loss: Prevalence and Trends of Blindness and Visual Impairment Over the Past 28 Years,” presented at the annual meeting of the Association for Vision and Research in Ophthalmology, Fort Lauderdale, Florida, USA, May 2012. Abstract available at: http://iovs.arvojournals.org/article.aspx?articleid=2354749. Accessed October 26, 2017
B. McGrath D. PREMED highlights benefit of combination treatment for CME. EuroTimes October 2017. Available at: http://www.eurotimes.org/premed-study-highlights-benefit-combination-treatment-prevent-cme/. Accessed October 26, 2017
© 2017 by Lippincott Williams & Wilkins, Inc.