America's Healthier Coffee: Vision

Friday, January 4, 2013

Increase In Vision Impairment Linked To Higher Prevalence Of Diabetes

Editor's Choice
Academic Journal
Main Category: Eye Health / Blindness
Also Included In: Diabetes
Article Date: 12 Dec 2012 - 12:00 PST Current ratings for:
Increase In Vision Impairment Linked To Higher Prevalence Of Diabetes
3 stars

Nonrefractive visual impairment, not due to needing glasses, has increased significantly among Americans in recent years, and the higher incidence of diabetes may be responsible.

The finding came from new research, conducted by a team at the Johns Hopkins University School of Medicine, Baltimore, and was published in JAMA, December 12 issue.

Background information in the report stated: "It is estimated that more than 14 million individuals in the United States aged 12 years and older are visually impaired (<20/40). Of these cases, 11 million are attributable to refractive error."

The most frequent reasons Americans experience nonrefractive visual impairment are:

Prior research has demonstrated that people with visual impairment often have diabetes. Since the eye is one of the main organs impacted by diabetes, patients can develop certain visual conditions.

"The prevalence of diagnosed diabetes has increased among adults in recent years, rising from 4.9 percent in 1990 to 6.5 percent in 1998, 7.9 percent in 2001, 10.7 percent in 2007, and 11.3 percent in 2010," the authors explained.

The researchers, led by Fang Ko, M.D., set out to evaluate the prevalence of nonrefractive visual impairment and the risk factors associated with the condition.

Data was gathered and analyzed from the National Health and Nutrition Examination Survey (NHANES), a representative sample of the American population.

Questionnaires, physical exams, and laboratory tests were given to 9,471 and 10,480 subjects aged 20 and older in 1999-2002 and 2005-2008 respectively.

Participants were considered to have nonrefractive visual impairment when their visual acuity was less than 20/40 when measured by an autorefractor - a tool which evaluates a person's refractive error.

Results showed that the prevalence of nonrefractive visual impairment increased 21%, from 1.4% in 1999-2002 to 1.7% in 2005-2008. They also found that non-Hispanic whites experienced a 40% increase, from 0.5% to 0.7%.

The factors that were linked to nonrefractive visual impairment included: povertyolder agelower education leveldiabetes diagnosed at least 10 years agoThe only risk factor that increased in prevalence between the 2 time periods analyzed was diabetes. The incidence of diabetes with more than 10 years since diagnosis increased 22% overall, from 2.8 percent to 3.6 percent. Among non-Hispanic whites aged 20-39, the prevalence of diabetes increased 133%, from 0.3% to 0.7%.

The researchers concluded:

"We report a previously unrecognized increase of visual impairment among U.S. adults that cannot be attributed to refractive error. If the current finding becomes a persisting trend, it could result in increasing rates of disability in the U.S. population, including greater numbers of patients with end-organ diabetic damage who would require ophthalmic care. These results have important implications for resource allocation in the debate of distribution of limited medical services and funding. Continued monitoring of visual disability and diabetes, as well as additional research addressing causes, prevention, and treatment, is warranted."

Written by Sarah Glynn
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

Visit our eye health / blindness section for the latest news on this subject. Prevalence of Nonrefractive Visual Impairment in US Adults and Associated Risk Factors, 1999-2002 and 2005-2008
Fang Ko, Susan Vitale, Chiu-Fang Chou, Mary Frances Cotch, Jinan Saaddine, David S. Friedman
JAMA 2012; doi:10.1001/jama.2012.85685 Please use one of the following formats to cite this article in your essay, paper or report:

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Tuesday, January 1, 2013

Insulin Plus Growth Factor Inhibitor Limits Vision Damage In Diabetic Mice

Main Category: Eye Health / Blindness
Also Included In: Diabetes
Article Date: 21 Dec 2012 - 1:00 PST Current ratings for:
Insulin Plus Growth Factor Inhibitor Limits Vision Damage In Diabetic Mice
1 star

A new therapeutic approach to diabetes that combines insulin and an inhibitor of the epidermal growth factor (EGF) betacellulin could limit the progression of diabetic macular edema (DME), Cleveland Clinic researcher Bela Anand-Apte, MD, PhD, said at the American Society for Cell Biology Annual Meeting, on Dec. 17 in San Francisco.

The study, conducted with insulin-dependent diabetic mice, showed that by thwarting "cross-talk" between insulin and betacellulin (BTC), which promotes the regeneration of pancreatic beta cells that stores and releases insulin, the EGF inhibitor preserved the animals' vascular integrity, she explained.

"These studies suggest that a combinatorial treatment of insulin and EGF inhibition might be a useful therapeutic combination to prevent macular edema, but needs to be determined in people with diabetes," said Dr. Anand-Apte.

Dr. Anand-Apte's idea for disconnecting diabetic progression from retinopathy was suggested by studies in people with type II diabetes whose blood sugar control was no longer stable on oral medications, requiring them to be treated with insulin. She noted that insulin therapy appeared to result in some patients' retinopathy progressing much faster, at least for a time. There was a correlation between starting insulin therapy and developing DME, she said.

Another clue came from an observation made by Judah Folkman, MD, then at Boston Children's Hospital, about pancreatic cancer patients who had undergone a pancreatectomy. Without a pancreas to produce and regulate insulin, these patients developed severe diabetes but rarely if ever developed proliferative retinopathy, even when they survived for more than 10 to 20 years. In the pancreas of people with diabetes, the researchers hypothesized that "cross-talk" occurred between injected insulin and the secretion of a vascular permeability-inducing factor.

Working with collaborators at Case Western Reserve University and the University of Wisconsin, the Anand-Apte lab used a mouse model for diabetes to look at BTC produced in the pancreas by proliferating beta cells. In previous studies, Dr. Anand-Apte had linked BTC to increased vascular permeability in the retina. Treating diabetic mice with insulin produced a spike in levels of a soluble form of betacellulin in the retina. Simply injecting BTC into the vitreous fluid of both hyperglycemic and normal mice also increased vascular permeability.

Looking more closely, the researchers determined that insulin was disrupting tight junctions between retinal pigment cells (RPEs), the barrier layer wrapped around retinal nerves, by driving up BTC expression. Injecting insulin first increased the production of ADAM10, a protein that weakens molecular cell-cell glues. The increase in ADAM10 was followed by up-regulation of BTC. By blocking the production of BTC and ADAM10 with short interfering RNA (siRNA), the researchers discovered they could protect these cell-cell tight junctions.

Substituting a BTC-targeted EGF inhibitor, the researchers finally thwarted the cross-talk between BTC and insulin. The EGF inhibitor preserved vascular integrity in the diabetic mice.

The association of visual impairment and the progression of both type I and type II diabetes appears to strengthen over time. The National Diabetes Information Clearinghouse estimates that of the 25.8 million American who have diabetes, 4.2 million have diabetic retinopathy, and in 675,000 of them, it progresses to its most severe form, proliferative diabetic retinopathy in which abnormal - and leaky blood vessels intrude into the eyeball's clear vitreous gel, causing retinal traction and bleeding that results in decreased sight.

Many people with diabetes with proliferative retinopathy also develop DME, a thickening of the center of the retina. Increased vascular permeability in the blood-retinal barrier allows leakage of lipoproteins into the macula at the center of the retina, reducing sharp vision. The main risk factors for DME, according to the American Academy of Ophthalmology, are increasing duration of diabetes, high blood sugar and blood pressure. Over 10 years, 20% of patients diagnosed with early-onset diabetes and 40% with older-onset diabetes will develop DME.

Article adapted by Medical News Today from original press release. Click 'references' tab above for source.
Visit our eye health / blindness section for the latest news on this subject. This work was supported in part by National Institutes of Health (EY016490, CA106415, and EY015638), Research to Prevent Blindness (RPB) Challenge Grant, and RPB Lew Wasserman award to BA-A.

"Regulation of retinal vascular leakage by insulin: Implications for patients with diabetic retinopathy," Monday, Dec.17, 2012, 12:30-2 pm, Session: Cell-Cell Junctions II, presentation 1351, poster B927, Exhibit Halls A-C

American Society for Cell Biology

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