June 01, 2007
8 min read

International effort needed to sort out causes of eye disease, expert says

A portion of Ocular Surgery News’ ARVO coverage is found below.

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FORT LAUDERDALE, Fla. — As global populations live longer, increasing and varying rates of ocular disease pose an international health care challenge, according to an analyst here at the Association for Research in Vision and Ophthalmology meeting.

Gerald Chader, PhD of the Doheny Eye Institute, Los Angeles, discussed “Eye Diseases in Diverse Populations.”

Public policy must support eye care programs to prevent blindness and vision loss, Dr. Chader said.

Ocular diseases occur in diverse populations and, within those populations, across socioeconomic, ethnic, gender, geographical and environmental lines, he said.

AMD is the leading cause of vision loss in Europe but less prevalent in Asia, Dr. Chader said, and African and African-American populations have lower rates of AMD than other groups.

AMD is on the rise in Japan and in coastal cities in China, he said. He speculated on whether modern, Western lifestyles may account for that phenomenon, while more traditional lifestyles and diet persist in inland areas.

Globally, cataract ranks as the leading cause of severe vision loss and blindness, according to the World Health Organization, Dr. Chader said.

Women in Tibet have a higher rate of cataract than their counterparts in other countries. Cataract accounts for 75% of all blindness in Tibet, he said.

Glaucoma is the second-leading cause of blindness worldwide, Dr. Chader said. However, differences in the incidence and type of glaucoma vary among nations. For example, he said, open-angle glaucoma is more prevalent in Asian populations.

Globally, diabetic retinopathy is the leading cause of poor vision among young adults, Dr. Chader said. The Latino Eye Study in Los Angeles showed that 20% of subjects were underdiagnosed for diabetes. Of that group, 25% had undiagnosed diabetic retinopathy, he said.

Myopia is on the rise in Asia, particularly among Chinese children, according to the Sydney Myopia Study, Dr. Chader noted.

Public policymakers and the international ophthalmic community need to focus on the causes of eye disease and invest in prevention and treatment initiatives, he said.

Most of these items appeared originally as daily coverage from the meeting on OSNSuperSite.com. Look for more in-depth coverage of these and other topics in upcoming issues of Ocular Surgery News.

Experts: Ethics should guide clinical trial participation

Physicians and researchers involved in pivotal clinical trials need to exercise constraint and observe a strict code of ethics, advised several speakers.

George O. Waring III, MD, FACS, FRCOphth, Morris Waxler, MD, and Barbara Hart discussed “Professional responsibility vs. product liability: Do clinical trials cross the line?”

Dr. Waring has participated in several clinical trials. Dr. Waxler served for 26 years as a medical monitor for the U.S. Food and Drug Administration. Ms. Hart is a clinical trial consultant for drug and device makers.

Dr. Waring called for a symbiotic but ethical relationship between physicians and pharmaceutical and device manufacturers. “Rather than have an ‘us vs. them’ circumstance, it would be better to have an ‘us’ circumstance,” he said.

Current FDA regulations allow a medical monitor to be a clinical trial investigator. However, the trial is conducted amid various concerns regarding potential bias, conflicts of interest, patient safety, disclosure of information and liability, Dr. Waring said.

It is unusual but not impossible for a paid medical monitor to serve concurrently as an investigator. But he or she must disclose all pertinent information in accordance with FDA regulations, he said.

Ms. Hart noted that clinical trials operate amid two dilemmas. One dilemma is the conflict between congressional mandates and patient autonomy; the second is between safety and effectiveness and product availability, she said.

Individuals who play multiple roles in the clinical trial process must be transparent, with all scientific, financial and career information subject to open scrutiny. Regulatory approval assures that a product’s benefits outweigh the risks, but it does not mitigate or eliminate conflict of interest, she said.

The informed consent process as required by law does not require investigators to disclose financial information to trial participants, Dr. Waxler said.

“Patients don’t care” whether or not a physician has a vested interest in a drug, device or surgical procedure that may help the patient, Dr. Waring said.

Still, even a small sum of money may alter how some physicians handle disclosure, report trial data and advise patients, Dr. Waring said.

Drs. Waring and Waxler agreed that close collaboration between physicians and industry leads to beneficial innovation.

Multifocal IOL evaluation: Stray light tests possible alternative

Contrast sensitivity and stray light tests may be viable alternatives to night driving simulations for evaluating multifocal IOL safety, according to a speaker here.

Bruce A. Drum, PhD, and colleagues compared clinical vision tests with visual performance in simulated night driving at the University of Iowa’s National Advanced Driving Simulator. The study included 55 subjects aged 30 to 60 years who had uncorrected visual acuity ranging from 20/10 to 20/40. The driving test was designed to evaluate the distance at which subjects could identify road signs and obstacles, according to the study.

The driving, contrast sensitivity and stray light tests were performed at baseline and with “fog” created with diffusing goggles to simulate multifocal IOL light-scattering properties. Driving and contrast sensitivity tests were administered with and without glare.

Data showed that glare and fog similarly affected driving performance and clinical test results. Intraocular stray light was increased 73% by light filters and by 100% by moderate fog filters. The fog filters also reduced sign and obstacle recognition distances by about 12%, Dr. Drum said.

Paradoxically, combined glare and fog improved sign recognition more than either factor alone, he noted.

Both fog filters reduced contrast sensitivity slightly. Glare alone did not affect contrast sensitivity, but selectively increased the effect of fog on contrast sensitivity loss, according to the study.

“These patterns suggest that contrast sensitivity and stray light tests may provide alternatives to driving simulation studies for evaluating multifocal IOL safety,” the authors said in the study.

Economics, epidemiology play symbiotic roles in treatment

Cost-effectiveness, cost-utility and epidemiological data determine health care analysis and policy, according to a health care economist speaking here.

Emily W. Gower, PhD, described how epidemiology “informs” economics and how economics “motivates” epidemiological research at the meeting.

Economic models include two components: cost-effectiveness and cost-utility, she said. Cost-effectiveness represents the benefit derived from a health care service weighed against the cost for the service. Cost-utility represents the value gained from a service, such as improvements in quality of life, she said.

Cost-utility also accounts for the number of years a patient expects to live and the number of years that patient is willing to “trade” for improved vision, Dr. Gower noted.

Costs per quality-adjusted life-year (QALY) gained factor into cost-effectiveness. For example, a medical service with a cost of $100,000 per QALY gained is not considered cost effective. Cost-effectiveness utility models are derived from clinical trial data and epidemiological analyses. However, data on utility values are lacking, she said.

The Centers for Medicare and Medicaid Services does not currently recognize cost effectiveness data but is considering policy changes, she noted.

OCT can aid pre-LASIK keratoconus screening, researcher says

Optical coherence tomography can be a useful tool for preoperatively detecting keratoconus or forme fruste keratoconus in patients undergoing LASIK, according to a study presented here.

Yan Li and colleagues at the University of Southern California, Los Angeles, and the Cole Eye Institute, Cleveland, performed optical coherence tomography (OCT) using the Visante OCT device (Carl Zeiss Meditec) in 37 eyes of 21 patients with keratoconus. They compared their findings with a control group of 36 eyes in 18 patients.

The researchers found that keratoconic corneas were significantly thinner, averaging 452.6 µm vs. 546 µm at the thinnest point on normal corneas. Also, the thinnest spot on the corneal map was inferiorly displaced by about –0.81 mm compared with –0.12 mm for normal corneas, according to the study.

In addition, keratoconic corneas were significantly more asymmetric, the study authors noted.

The results indicate that OCT can be useful for diagnosing keratoconus either alone or in combination with pachymetry and corneal topography, Mr. Li said.

Paintball guns can cause devastating eye injuries

Paintball gun-related eye injuries are often severe and normally require surgical intervention, according to a poster study presented here.

Kyle Alliman, MD, and colleagues at Bascom Palmer Eye Institute performed a retrospective study of 36 eyes in 36 patients treated at the center. The researchers found that young men who were not wearing eye protection were usually the group to receive paintball-related injuries.

Of the 36 patients, 31 were men (86%) and 35 patients (97%) were not wearing eye protection at the time of injury, according to the study.

Initial treatment involved the primary repair of a ruptured globe in 25% of cases, and 56% of cases were initially managed medically. However, surgery was eventually needed in 81% of cases and eight eyes (22%) required enucleation.

“[Final] visual acuity correlated strongly with vision at presentation,” the authors said. At presentation, 28 eyes (77%) had 20/200 or worse visual acuity. Final visual acuity was 20/40 or better in 13 eyes (36%) but was 20/200 or worse in 18 eyes (50%), according to the study.

“Paintball-related ocular injuries are frequently severe and visually devastating,” the authors said. “The vast majority of patients required surgical intervention at some point during their ophthalmic care.”

Friedenwald Award

Ilene K. Gipson, PhD, received the Friedenwald Award here in recognition of her contributions to the basic and clinical understanding of ocular cell biology, particularly regarding the ocular surface and the cornea.

Dr. Gipson focused her award lecture, titled “The Ocular Surface: The Challenge to Enable and Protect Vision,” on recent research into microbiological factors influencing dry eye syndrome.

According to Dr. Gipson, researchers have so far identified 19 mucin genes, which are expressed by ocular surface epithelial cells and play a key role in preventing and treating dry eye. In particular, one mucin, known as MUC16, has a key role in corneal pathology, as bacteria will adhere to corneal cells that lack MUC16. Thus, the mucin acts as a barrier against various pathogens, Dr. Gipson said.

Burgeoning knowledge and understanding promise to yield new treatments for corneal diseases such as dry eye, she noted.

Spherical aberrations persist after LASIK with laser- or microkeratome-created flaps

Spherical aberration increases and remains elevated for at least 1 year after LASIK regardless of whether flaps are created using a femtosecond laser or a mechanical microkeratome, according to a study presented here.

Jay W. McLaren, PhD, and colleagues conducted the paired-eye study comparing wavefront-measured errors after LASIK performed using either technology for flap creation.

Femtosecond lasers offer precise cutting with little damage to surrounding tissue. They also allow flaps to be created in any desired geometric configuration, Dr. McLaren said.

However, the study data show that the femtosecond laser induced lasting spherical aberration similar to that resulting from microkeratomes, he said.

The study included 20 patients who underwent non-wavefront-guided LASIK for myopia or myopic astigmatism. One eye of each patient was randomly assigned to flap creation by femtosecond laser and the other eye was assigned to flap creation by microkeratome, Dr. McLaren said.

The targeted flap thickness was 120 µm in the femtosecond laser group and 180 µm in the microkeratome group. All flaps had a superior hinge, he said.

Preoperative spherical equivalent refractive error averaged –3.7 D ± 1.6 D in the femtosecond laser group and –3.7 D ± 1.7 D in the microkeratome group.

In the femtosecond laser group, the researchers found that spherical aberration significantly increased from 0.27 µm ± 0.09 µm preoperatively to 0.42 µm ± 0.16 µm at 1 month follow-up. Spherical aberration also similarly increased in the microkeratome group, from 0.26 µm ± 0.09 µm preoperatively to 0.39 µm ± 0.15 µm at 1-month follow-up, according to the study.

Spherical aberration remained elevated at 1-year follow-up in both groups.

The researchers also found that coma had increased at 6-months follow-up in the femtosecond laser group, but it was no longer markedly elevated at 1 year.

No significant increase in coma was seen among eyes treated with the manual microkeratome, Dr. McLaren said.

Eye geometry for horizontal coma, spherical aberration

Internal optics compensate for off-axis horizontal corneal coma in IOL-implanted eyes, according to study data presented here.

Susana Marcos, PhD, and colleagues investigated whether compensation for coma occurs in pseudophakic eyes with spherical aberration-correcting IOLs. They also sought to identify the eye geometry causing compensation.

“It is well-known that in young eyes, positive spherical aberration of the cornea is partially compensated by internal [spherical aberration],” the authors said in the study abstract. “Aspheric [IOLs] have been introduced to mimic this effect in pseudophakic eyes. Compensation of horizontal coma has also been shown to occur in young eyes and the active/passive nature of this effect has been debated.”

The patient group included 38 eyes of 21 patients implanted with two types of aspheric IOLs with negative spherical aberration. Researchers used a laser ray tracing system to measure total aberrations and videokeratoscopy to identify corneal aberrations. They also measured IOL tilt and decentration using a custom Purkinje imaging system. They referred tilt to the pupillary axis and decentration to the pupillary center, according to the study.

Data showed that spherical aberration was reduced with respect to corneal values in all eyes. Total horizontal coma was also markedly reduced in all eyes, according to the study.

A note from the editors:

To facilitate bringing news to readers rapidly, for OSN SuperSite articles and meeting wrap-up articles, OSN departs from its editorial policy and typically does not send these items out for source corrections.