June 2010




Understanding the impact of diabetes

by Matt Young EyeWorld Contributing Editor

Magnified retina of healthy eye (left) and retina of diabetic eye—mottled (right) Source: Getty Images

Diabetes can impede good visual results after cataract surgery, and new research identifies specific instances when the disease does and doesn’t hinder results. “Cataract surgery improved VA [visual acuity] by an average two lines for patients both with and without diabetes, or with DR [diabetic retinopathy] but no past laser treatment,” according to Jie Jin Wang, Ph.D., Centre for Vision Research, department of ophthalmology, University of Sydney, Sydney, Australia. In diabetic retinopathy eyes treated with laser previously, there wasn’t much gain in visual acuity 12 months post-op, although some eyes did do better, according to the study, which was published online in February 2010 in Acta Ophthalmologica. “Those with a history or signs of preoperative laser treatment, likely indicating prior CSME [clinically significant macular edema] or PDR [proliferative diabetic retinopathy], had none or less VA improvement compared to patients with or without diabetes or with DR but no previous laser treatment, who gained an average 2 LogMAR lines 1 year after phacoemulsification cataract surgery,” Dr. Wang reported.

A closer look

Dr. Wang analyzed 1,192 cataract surgery patients, of whom 324 (27.2%) had diabetes (321 with type 2 and three with type 1) and 136 (42.0%) had DR. “After adjusting for age, gender, diabetes duration and preoperative pinhole VA, the average VA gained 12 months after surgery was 10.8 letters among 868 patients without diabetes, 10.6 letters among 188 patients with diabetes but no DR, 10.0 letters among 95 patients with DR but no past laser treatment, and no letters among 41 patients with DR plus past laser treatment,” Dr. Wang reported. In fact, eyes that had previous laser treatment for DR were six times more likely to have post-op visual acuity less than 6/12 after month 12 compared to eyes with DR but no prior laser treatment. Those diabetes patients with disease duration for less than 15 years had significantly higher mean VA gain than those with diabetes for 15 years or greater.

“This suggests that the effect of diabetes duration on cataract surgery visual outcomes could be independent of the severity of DR,” Dr. Wang reported. Nonetheless, DR severity did play an important role in results after cataract surgery. For instance, VA levels greater than or equal to 6/12 after 12 months were achieved by 44% of eyes with DR and previous laser treatment, which compares unfavorably to 86% of eyes with DR but no previous laser treatment. Dr. Wang suggested that eyes that underwent previous laser treatment experienced little visual improvement likely due to PDR or CSME.

“Previous reports indicate that poor cataract surgery visual outcomes are related to the preoperative retinal status, particularly when PDR and CSME are present,” Dr. Wang reported. Eyes with DR but without prior laser treatment experienced less improvement in visual acuity after cataract surgery in this study than in earlier research. “Previous studies have shown that VA improved by >2 lines in between 74% and 86% of patients with diabetes before surgery,” Dr. Wang noted. “Our finding that 42% of patients, with DR but not previously treated by laser before cataract surgery, gained 2 LogMAR lines is less than these previous reports. These previous studies had relatively small numbers of patients.”

Some of that research also excluded patients with ocular diseases other than cataract and DR, such as CSME, “which could explain a higher proportion achieving VA improvement >2 lines after surgery,” Dr. Wang noted. “These findings provide realistic expectations for diabetic patients needing cataract surgery,” Dr. Wang concluded. Realistic expectations are key, since Eric D. Donnenfeld, M.D., co-chairman, cornea, Nassau University Medical Center, East Meadow, N.Y., said diabetic patients are “notoriously difficult to manage.”

In particular, he said, these patients have increased risk for retinal pathology. “That’s something that needs to be addressed aggressively,” Dr. Donnenfeld said.

Dr. Donnenfeld pretreats these patients with NSAIDs for a week and post-op for three months. Typically a cataract patient would be pretreated with NSAIDs for only three days and then 4 to 6 weeks post-op, he said. He also uses more steroids for diabetics than the average cataract patients, and in particular finds Durezol (difluprednate, Alcon, Fort Worth, Texas) useful, which he said effectively prevents retinal thickening in diabetics according to recent research. Steroids may also be injected intravitreally, or Avastin (bevacizumab, Genentech, South San Francisco, Calif.) may be used to prevent cystoid macular edema (CME) in these patients, he said.

Editors’ note: Dr. Wang has no financial interests related to this study. Dr. Donnenfeld has no financial interests related to his comments.

Contact information

Donnenfeld: 516-766-2519, eddoph@aol.com
Wang: jiejin_wang@wmi.usyd.edu.au

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