American Academy of Ophthalmology Web Site: www.aao.org
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September 2004

 
News in Review
 
 

Topical Meds Aid Vulnerable Group

Eye Exams Could Become Dangerous in Face of SARS

Why Some Women Don’t See Red; They See Red-Orange

Improvements Afoot at the VA, but More Advocacy Ahead


Topical Meds Aid Vulnerable Group
The verdict is in: Topical medication does indeed delay or prevent the onset of primary open-angle glaucoma in African-Americans, and this is the patient population most susceptible to blindness from the disease.

That conclusion, published in the June issue of Archives of Ophthalmology,1 settled a question that had been left hanging when the Ocular Hypertension Treatment Study reported its results in 2002. At that time, follow-up on the 408 African-American study subjects was too short to determine the impact of topical medication on this subset of patients.

In the new report, the OHTS investigators found that the medications reduced the African-American patients’ risk of developing POAG by 50 percent. The median time of follow-up was 78 months.

This finding provides support for the idea that screening and early treatment of ocular hypertension in African-Americans would reduce the visual disability they disproportionately suffer from glaucoma, said Eve J. Higginbotham, MD, lead author of the study and chair of ophthalmology at the University of Maryland, Baltimore.

But the study also contains nuances that go beyond this ophthalmic truism. For instance, Dr. Higginbotham said, race didn’t appear to be as important to an African-American’s risk of developing glaucoma as was an accumulation of other risk factors.

“The risk of converting from ocular hypertension to glaucoma was much higher in the presence of multiple risk factors. The no-treatment group among African-Americans had a 16.1 percent conversion rate, vs. 8.4 percent in the treated group,” she said.

The African-American subjects achieved their target IOP in both eyes at 87.6 percent of study visits, compared with 84.8 percent among other study participants. Yet among those who received medication, the risk of developing POAG—even after being adjusted for length of follow-up—was twice as high for African-Americans as it was for other participants.

“So the treatment goals were met, but perhaps the pressure reduction when you have multiple risk factors needs to be greater,” Dr. Higginbotham said. “The medications worked as well, but the other risk factors had an impact on the course of the disease. This observation would suggest the IOP goal should be lower, however additional studies are needed to test that hypothesis.”

Bottom line: African-American patients need individualized care, she said. “You need to go beyond the skin color to specific measurable risk factors, and then tailor treatment based on that assessment.”

Eydie G. Miller, MD, clinical associate professor at the Scheie Eye Institute in Philadelphia, agreed. “The conversion rate to glaucoma in treated African-American participants was higher despite a 23 percent IOP reduction that resulted in a mean IOP of 19.2 mmHg—nearly the same IOP results as those obtained in the other participants,” she writes in an accompanying editorial. “So we need to focus on what puts those particular patients at higher risk . . . [including] corneal thickness, cup-disc ratio, age and pattern standard deviation.”

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1 Higginbotham, E. J. et al. Arch Ophthalmol 2004;122:813–820.

In the Clinic
Eye Exams Could Become Dangerous in Face of SARS
A study on how to detect severe acute respiratory syndrome (SARS) has yielded a conclusion worthy of note for ophthalmologists: The coronavirus that causes the disease has been found to populate the tears of early stage SARS patients.

In the spring of 2003, as experts at the World Health Organization were rushing to cope with a global outbreak of the emerging disease, doctors at Tan Tock Seng Hospital in Singapore used swabs to take tear samples from 36 consecutive patients with suspected SARS.

Eight of those patients ultimately were diagnosed as “probable SARS” because they met WHO’s case definition for the disease. (See sidebar box Defining Symptoms of SARS, right. And for more information about the disease visit www.who.org or www.cdc.gov.)

Polymerase chain reaction testing showed the virus’ RNA in the tears of three of those patients, all of whom were tested within nine days of symptom onset. In the other five probable SARS cases, the tears contained
no viral RNA, but all those patients had been tested late, a mean of 19.4 days after symptoms began. However, the difference was not statistically significant.

Writing in the July issue of the British Journal of Ophthalmology, the authors alert ophthalmologists that, during outbreaks of SARS in their regions, it would be prudent to strengthen infection control practices for even routine ophthalmic exams of patients who show possible symptoms.1

“Ophthalmologists examine patients at close distances and inadvertent physical contact with patients’ eyes is inevitable. This is a potential hazard to health care workers . . . ,” the authors write. “There is a potential possibility of transmission to other patients through the use of reusable eye equipment such as the Goldmann applanation tonometer, trial contact lenses, trial frames and even reusable pinhole devices, which come into close contact with the patients’ eyes.”

To prevent transmission when seeing suspected SARS patients, they recommend carefully disinfecting all eye equipment, using strict hygiene during exams and adopting the “M3G” barrier method for all personnel (mask, gown, gloves and goggles).

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1 Loon, S. C. et al. Br J Ophthalmol 2004;88:861–863.

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Defining Symptoms of SARS

Suspect cases

  • Fever above 100.4 degrees Fahrenheit (38 degrees Celsius)
  • Respiratory symptoms
  • History of contact with a case of probable SARS
  • Travel to an area where SARS has been recently identified

 

Probable cases

  • Chest x-ray showing pneumonia or acute respiratory
    distress syndrome

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Source: WHO

Research Report
Why Some Women Don’t See Red; They See Red-Orange
When is red not red? When the genetic variability in a woman’s red-opsin genes allows her to distinguish subtle variations in reddish shades that others can’t see, according to scientists studying how evolutionary pressures maintain genetic variability.

In a study of the region on the X chromosome that codes for the red-opsin photopigment, the scientists found that chance alone couldn’t account for the nine active red-opsin gene variants and 74 “silent” but similar polymorphisms they found in 236 men from around the world.

Previously, these altered opsins have been shown to shift the sensitivity of red cones toward red-oranges,
up to 5 nanometers from the 560 nm wavelength considered normal for red photoreceptors.

The scientists theorize that, from an evolutionary perspective, a woman with different red-opsin genes on her two X chromosomes would be able to distinguish subtle differences in shades of red—giving her an advantage in gathering food in prehistoric societies. Today, such a woman might have better depth perception or chromatic visual acuity than others do.

Writing in the online edition of the American Journal of Human Genetics,1 the researchers attribute the variations in opsin genes to a process called gene conversion, in which dividing cells substitute small groups of nucleic acids (with as few as 50 kilobase-pairs) into a chromosome. This differs from recombination, in which chromosomes exchange much larger segments of DNA that can cause severe genetic deficiencies.

“Gene conversion is the vehicle for generating a high level of mutations in one region of a chromosome. And natural selection maintains it,” said Brian Verrelli, PhD, coauthor of the study and assistant professor in
the Center for Evolutionary Functional Genomics at Arizona State University. “So it’s like the two of them are working together, first to generate diversity, and then to keep it there.”

“If gene conversions were constantly happening over thousands of years, and they didn’t have an effect on the evolutionary fitness of the population, then the variation would eventually disappear,” he added. “But if it does affect the fitness of the population, then natural selection will keep it there.”

Dr. Verrelli, whose coauthor is Sarah A. Tishkoff, PhD, assistant professor of biology at the University of Maryland, noted that there have been studies showing that some women can see better than others. “What we’re now learning is that part of the reason for this could be the variability in the red opsins,” he said.

Such ideas suggest a possible confounder for contemporary studies of the quality of vision after LASIK or cataract surgery. And, from a practical standpoint, what might the genetic variability mean for color vision?

First, it would explain why one person’s red is another person’s red-orange, he said. And it gives insight on certain unscientific gender differences. Or, as Dr. Verrelli titled one of his lectures on the subject: “Why Women Dress Better Than I Do.”


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1 Verrelli, B. C. and S. A. Tishkoff. Am J Hum Genet 2004;75(3).
(E-pub ahead of print.) 


From the DC Office
Improvements Afoot at the VA, but More Advocacy Ahead

The U.S. department of Veterans Affairs announced on July 30 a new policy requiring optometric laser surgery to be performed only under the supervision of an ophthalmologist. This VA limitation follows months
of debate on the issue and concerns raised by the Veterans Eye Treatment Safety Coalition, led by the Academy, congressional leaders and veterans’ service organizations.

The VETS Coalition has been fighting for nothing short of surgery by surgeons and remains dedicated to that principle and to the right of veterans to the highest quality of care. “This directive represents a significant step by the VA to resolve a serious patient safety issue; however, the VETS Coalition does not believe that optometrists, practitioners who do not attend medical school or fulfill surgical residencies, have the proper training and education to perform invasive eye surgery,” said Michael D. Maves, MD, MBA, executive vice president for the American Medical Association.

The VETS Coalition has sought to work with VA leadership on resolving this veterans’ safety issue and will continue to do so. In light of the VA’s intention to proceed with this directive’s approach despite VETS Coalition concerns, there remain several minimum-level provisions that must be addressed before implementation to reduce the likelihood of a bad surgical outcome for veterans subject to optometric surgery. These include establishing minimum optometric education and training standards and requiring direct ophthalmic supervision. In its current form, the directive does not adequately define supervision, so it could range anywhere from “direct,” in which a U.S.-licensed ophthalmologist is in the operating room, to a mere reporting structure.

“We believe that an ophthalmologist-led team is the best way to ensure quality eye care for veterans, but allowing optometrists to perform invasive eye surgery—even with ophthalmologic supervision—lowers the bar and goes against the standard of care in 49 out of 50 states and in the U.S. military,” said H. Dunbar Hoskins Jr., MD, executive vice president of the Academy.

—Sandra Remey