EyeNet Magazine



   
 
News in Review
A Look at Today’s Ideas and Trends
By Linda Roach, Contributing Writer
Edited by Brian A. Francis, MD
 
 

• Retinopathy May Occur in Prediabetics
• Carbohydrate Intake Linked to Cortical Cataract
• Bariatric Surgery May Affect Eye Health
• Have You Checked Your Tonometer Today?
• Sports Zone: Basketball Sounds Good


Retinopathy May Occur in Prediabetics

A patient might not meet the formal definition for type 2 diabetes but could still be experiencing the earliest form of diabetic retinopathy, the leaders of the Diabetes Prevention Program (DPP) study reported at the American Diabetes Association’s 65th Annual Scientific Sessions in June.

A random sampling of DPP subjects, all prediabetic at the beginning of the study, found that 8 percent had retinal microaneurysms indicative of early diabetic retinopathy. Within this group, the number of microaneurysms was small in the prediabetic subjects, and slightly more severe in those who had developed type 2 diabetes in the previous one to five years.

The finding pushes against the boundaries of conventional wisdom about the timing of diabetic damage to retinas. Until now, patients considered prediabetic—currently defined by plasma glucose levels of 110 to 125 milligrams/deciliter on a fasting blood test (plus a confirmatory test)—have been considered at risk for early cardiovascular damage, but not for retinopathy. (The DPP used a bottom threshold for defining prediabetic glucose levels of 95 mg/dL.)

“Now we know that diabetic retinopathy does occur in prediabetes,” said the vice chairman of the DPP study, Richard F. Hamman, MD, DrPH. “This suggests that changes in the eye may be starting earlier and at lower glucose levels than we previously thought.

“These observations may lead diabetes experts to reconsider the diagnostic thresholds used to define diabetes,” he said. Dr. Hamman is professor and chairman of preventive medicine and biometrics at the University of Colorado.

Indeed, those thresholds have moved steadily downward. Until 1997, the dividing line between prediabetes and outright disease was a fasting plasma glucose of 140 mg/dL, compared with 126 currently. 

If patients with glucose levels as low as 95 mg/dL can be subject to early retinopathy, what might this mean for ophthalmic practice guidelines? Currently, the Academy’s Focal Points module on diabetic retinopathy1 recommends, for type 2 diabetics over age 30, a retinal exam at the time of diagnosis but not before. Said Donald S. Fong, MD, MPH, coauthor of that Focal Points publication, “In response to the DPP findings, ophthalmologists will likely change their practice in two ways. First, we would carefully examine the eyes of and refer for testing patients at high risk of diabetes and/or impaired glucose tolerance. Second, we would work closely with our primary care colleagues to ensure patients with any retinopathy are appropriately tested and the impaired glucose tolerance managed. This is because people with impaired glucose tolerance are at an increased risk for heart disease and stroke.” Dr. Fong is a vitreoretinal surgeon and director of clinical trials research for Kaiser Permanente Southern California.

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1 Fong, D. S. and F. L. Ferris. Focal Points: Practical Management of Diabetic Retinopathy (San Francisco: American Academy of Ophthalmology, 2003).


Nutrition & Vision

Carbohydrate Intake Linked to Cortical Cataract

The higher a woman’s diet is in carbohydrates, the more likely she is to develop cortical cataracts, according to a new study.¹

The study of 417 women between the ages of 53 and 73 found that women who ate 200 grams or more daily of carbohydrates were 2 1/2 times more likely to develop the cataracts than were women whose diets had less than 185 grams. The women were a subset of the long-running Nurses’ Health Study in Boston.

“It seems that by controlling the amount of carbohydrate, we can achieve a significant reduction in the personal cataract burden,” said Allen Taylor, PhD, senior author of the study and director of the laboratory for nutrition and vision research at the USDA Human Nutrition Research Center on Aging at Tufts University.

He noted that ophthalmologists should make their patients aware of the link between high carbohydrate intake and cataracts.

One ophthalmologist doubts the research will affect his practice. “We’re not going to take a history of what patients eat and convince them to try and change their diet, because it may cause cataracts,” said Stephen S. Lane, MD, clinical professor of ophthalmology at the University of Minnesota.

Randall J. Olson, MD, professor and chairman of ophthalmology and visual sciences and director of the John A. Moran Eye Center at the University of Utah, however, takes a different view.

He noted that cataract surgery is the most frequent surgical procedure in ophthalmology and the single largest expenditure of Medicare dollars. “I think that understanding the elements of prevention is extremely important,” he said. Medicine, he noted, is largely focused on treatments as opposed to prevention. “We better be more concerned about prevention,” he said.

—Harvey Black

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1 Chiu, C. J. et al. Amer J Clin Nutr 2005;81(6):1411–1416.

Sports Zone: Basketball Sounds Good
Three Johns Hopkins University students have designed a basketball that would let blind players “see” the ball and play the game.

Their basketball system for the blind has two parts: a piezoelectric sound emitter attached behind the backboard, which sends out pulses of sound, and a second, smaller emitter enclosed inside a special ball. The latter device transmits a continuous tone at a different frequency. It is enclosed in an airtight cylinder—which normally houses a small pump—inside a Spalding Infusion basketball.

Mike Bullis, business services development manager for Blind Industries and Services of Maryland, who is blind, caught three passes and sunk two out of three baskets during a trial run of the system.

“There are people all over the country who are waiting for something like this,” Mr. Bullis said afterward. “Right now, blind kids can play with a ball, but only if someone is there to find it if it rolls away.”

Two of the engineering students who designed the system had a special reason for being pleased with these comments. Alissa Burkholder and Ashanna Randall played for four years on the Johns Hopkins women’s basketball team, before graduating last spring.

“I’ve been playing basketball since second grade, so it’s something I’m really interested in,” Ms. Burkholder said. “This project is something that can help a community of people experience something I’ve enjoyed, too.”

She also had a family stake in the outcome: Her father, Thomas O. Burkholder, MD, is an ophthalmologist in Allentown, Pa. What did he think about his daughter’s work on behalf of the visually impaired? “My parents were impressed that we actually got the product to work,” she said.

Blind Industries and Services of Maryland, which commissioned and sponsored the students’ project, hopes to nurture the system to market, Mr. Bullis said. He is working with engineers at Spaulding to lower the basketball emitter’s pitch, to eliminate echoes caused by its high frequency. Eventually, he hopes the idea can be adapted for soccer balls and volleyballs, too.


Cornea Report

Bariatric Surgery May Affect Eye Health

Atlanta corneal specialist W. Barry Lee, MD, was puzzled. The 39-year-old woman had what four other physicians labeled as severe dry eye, which had progressed to xerophthalmia and a visual acuity of 20/800 by the time he saw her. But neither the medical history nor his close questioning revealed any obvious reason for her condition.

“Then she said, ‘Oh, I forgot to tell you. I had a gastric bypass done three years ago,’” Dr. Lee recalled. She admitted that she stopped taking the recommended multivitamin pills within a few months of the surgery because they upset her surgically altered, 7-ounce-capacity stomach.

A blood test showed her vitamin A level was virtually zero, explaining why she was exhibiting a vision condition more commonly seen among malnourished residents of poor countries (5 micrograms per deciliter compared with normal levels of 38 to 106 µg/dL). Liquid vitamin A supplementation eliminated her nyctalopia, and her visual acuity improved to 20/40 in six months. By last summer, a year after Dr. Lee first saw her, she was seeing 20/20 again.

In a paper on the case in June’s Ophthalmology, Dr. Lee and three coauthors warned that the growing incidence of gastric bypass surgery might bring similar patients into their offices.¹ And Slater et al. reported last year that 52 percent of bariatric surgery patients were deficient in vitamin A within a year of surgery, and 69 percent by four years.²

“There’s no way I could have seen the only case of this,” Dr. Lee said. “There must be other cases in this country that are going undiagnosed. One of my coauthors [Jason P. Harris, MD] is a gastric bypass surgeon, and he had no idea that this complication existed.”

Especially if the patient doesn’t tell the ophthalmologist about the gastric bypass surgery, less severe cases of vitamin A deficiency are easy to miss, Dr. Lee said. “This patient told me, ‘I’ve been telling the other four doctors that I can’t see at night, and they just said it was because I was nearsighted,’” he said.

“Early xerophthalmia looks just like dry eye, and it can be really tough to know the difference,” he added. “If patient are just a little deficient, they may complain about tearing, dry eye, and their vision may be a little bit decreased. In very mild cases, they probably will say they’re not seeing very well at night.”

Dr. Lee suggests that clinicians be alert for apparent dry eye in which the conjunctiva has a Bitot’s spot and the patient complains about worsening visual acuity, especially at night. “Check their vitamin A level right away,” he recommended.

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1 Ophthalmology 2005;112(6): 1031–1034.
2 J Gastroin Surg 2004;8:48–55.

 


Glaucoma Update

Have You Checked Your Tonometer Today?

How often do you check the calibration of your Goldmann applanation tonometer? It’s probably not often enough, say British ophthalmologists who checked the units at their institution over a four-month period.¹

By the end of the study, none of the 33 tonometers tested in the hospital’s outpatient and casualty departments had calibration errors within ±0.5 mmHg, the range the manufacturer (Haag-Streit) considers acceptable. Furthermore, 17 out of the 33 had calibration errors greater than ±2.5 mmHg by then. 

Consequently, the authors recommend that the frequency of scheduled error-checks be increased from annually, which is often the rule today, to monthly. However, the acceptable level of error before returning them for recalibration should be increased to ±2.5 mmHg, they say. Their measurements showed that 48.5 percent to 65.5 percent of the devices met that standard.

“A balance must be achieved between practical tolerance limits and clinical accuracy,” they write.

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1 Sandhu, S. S. et al. J Glaucoma 2005;14(3):215–218.

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