American Academy of Ophthalmology Web Site: www.aao.org
Original URL:

April 2008

 
News in Review
A Look at Today's Ideas and Trends
News in Review is edited by Brian A. Francis, MD.
 
 

Low-Cost Chip for High-Contrast TV

Researchers at the Schepens Eye Research Institute have developed a new technique for enhancing the image contrast on digital television—making TV viewing easier and more pleasurable for low vision patients, according to the Journal of the Optical Society of America.1 If the new technology catches on at next year’s Consumer Electronics Show, it may soon be an integral part of many digital televisions—without adding much to the cost of HDTVs, according to developer Eli Peli, OD, professor of ophthalmology at Harvard Medical School and senior scientist at Schepens.

Currently, digital television has six times more pixels than analog TV sets, allowing a wider screen, more detail, greater image stability and richer color. The digital signal is able to carry all the data necessary to provide great breadth and depth of visual (and auditory) information because it is compressed with a “coder.”

All digital televisions have a “decoder,” which translates the compressed digital signal into images and sound. When Dr. Peli’s enhancement technique is integrated into a standard decoder, the viewer can use the handheld remote control to adjust the contrast of fine details in the TV picture to a greater degree than is possible with a standard decoder.

“Many low vision patients miss the fine details of pictures and movies, so that they can’t recognize characters,” Dr. Peli said. “And this impacts their ability to follow TV programs. Our new technology should make TV viewing much easier for low vision patients.”

Dr. Peli and fellow researchers tested the new technology in 24 subjects with vision impairment (mostly macular degeneration) and six with normal vision. In the study, each subject adjusted the level of enhancement of eight four-minute videos in four different categories—including one video with low motion, another with high motion, a cartoon and a nighttime scene. The patients were given a remote control, which allowed them to increase or decrease the image contrast.

The researchers found that the level of enhancement selected by those with visual problems correlated with the amount of contrast sensitivity loss they had experienced due to their visual impairment. But even subjects with normal vision preferred pictures with some enhancement.

The technology can also be programmed onto computer chips, and Dr. Peli is now working with Analog Devices Inc. to create a prototype chip. He’ll then test the chip in another study—probably in a few months’ time—and Analog Devices Inc. will present the prototype chip at the Consumer Electronics Show in January.

“The cost is really minimal, so it should be an advantage to consumers,” Dr. Peli said. “We’re hoping that it will become standard in chips for digital TV making it widely available.”

For low vision patients, such a technology could be quite useful, according to Rebecca K. Morgan, MD, a vision rehabilitation specialist and clinical professor of ophthalmology at the University of Oklahoma in Oklahoma City. “Many low vision patients have compromised contrast sensitivity levels—yet TV viewing is an important pastime for them. If the new technology truly is affordable, it could be very helpful to low vision patients.”

—Barbara Boughton

___________________________

1 Fullerton, M. et al. J Opt Soc Am 2007;24(12):B174–B187.

Top

Glaucoma Update 

ALT and SLT Meet MLT

Until recently, doctors who wanted to perform laser trabeculoplasty on their primary open-angle glaucoma patients have had to choose between argon laser trabeculoplasty (ALT) and selective laser trabeculoplasty (SLT). But the former has the disadvantage of damaging the trabecular meshwork, leaving no option for repeat treatment. SLT, while both sparing and repeatable, is performed with a $60,000 SLT-only laser.

A third choice, micropulse laser trabeculoplasty (MLT), may offer a more benign treatment than ALT, at a fraction of SLT’s cost.

Last spring, Antonio M. Fea, MD, professor of ophthalmology at the University of Turin, Italy, reported a 75 percent success rate using MLT in a pilot study with 32 eyes with OAG and IOP exceeding 22 mmHg.1 While the mechanism of MLT’s action isn’t completely understood, it is believed that the thermal injury to the cell triggers a cellular cascade, stimulating a healing response.

Robert J. Noecker, MD, vice chairman and director of the glaucoma service at the University of Pittsburgh Medical Center, said MLT appears to create the same biologic upregulation as achieved by SLT or ALT.

MLT, performed with the Iridex IQ 810 infrared laser, emits short 300-µsec pulses of laser, followed by longer 1,700-µsec rests. The short pulses minimize the time in which laser-induced heat can spread to adjacent tissues, while the much longer rest allows tissue to cool back to baseline temperature, hopefully minimizing photothermal effects in the trabecular meshwork. The Iridex laser is currently used in glaucoma therapy to perform diode laser cyclophotocoagulation using the G-probe.

In a recent study of cadaver eyes, Dr. Noecker found that MLT does not cause craters or burn spots on the trabecular meshwork, as ALT does. But MLT does produce a mild thermal effect that isn’t observed in SLT.2

Dr. Noecker prefers SLT, which he regards as the gold standard, claiming its only drawback is that it uses a somewhat expensive SLT-only machine. But he will perform MLT in his satellite offices that are equipped with the IQ 810, rather than send patients to the main office for SLT.

Dr. Fea said that he offers MLT to patients on maximally tolerated medical therapy, or to those patients intolerant to medication. “Whenever I use MLT, I inform the patients especially about the fact that, as with any laser treatment, the results may fade after a while, and that laser might mean getting rid of eyedrops—or some eyedrops—but not getting rid of IOP measures, optic nerve imaging and visual field testing.”

Dr. Noecker said the multipurpose IQ 810, which was FDA-approved in September 2004, is an interesting new technology that provides an affordable ($33,995) alternative to SLT.

—Miriam Karmel

___________________________

Drs. Noecker and Fea report no related financial interest. ___________________________

1 Fea, A. M. et al. Micropulsed laser trabeculoplasty: a pilot study. Paper presented at the International Glaucoma Symposium, March 30, 2007, Athens, Greece.
2 Noecker, R. J. Abstract presented at the American Glaucoma Society, March 6–9, 2008, Washington, D.C.

Top

Retina Report 

Double Lenses May Bring Sight to Some

Frustrated by the lack of options for his patients suffering vision loss from age-related macular degeneration, Shafiq U. Rehman, MBChB, FRCOphth, consultant ophthalmic surgeon, Yorkshire Eye Hospital, United Kingdom, investigated a double intraocular lens implant introduced by researchers at the University Eye Clinic, San Paolo Hospital, in Milan, Italy.1

After learning the technique, Dr. Rehman in December 2007 implanted the IOL-VIP (intraocular lens for visually impaired people) in a 75-year-old man with 20/250 vision. One month after surgery, the patient had 20/50 vision. Dr. Rehman said, “We will treat his other eye soon, and he may be able to resume driving.”

The IOL-VIP System consists of a biconcave high minus-power IOL in the capsular bag, and a biconvex high plus-power IOL in the anterior chamber, creating an intraocular Galilean telescope. Dr. Rehman said, “The lenses can be rotationally aligned to divert the image falling onto the macula away from the most damaged part of the macula and onto a less damaged area.”

Dr. Rehman added that the procedure, which is similar to cataract surgery, takes 30 minutes and can be performed under simple eyedrop anesthesia. He continues to recruit and introduce this approach, which has been approved in Europe, to appropriate candidates—individuals with stable macular disease with vision between 20/60 and 20/250.

Stephen S. Lane, MD, clinical professor of ophthalmology, University of Minnesota, Twin Cities, and a medical monitor and investigator for an implantable miniature telescope (IMT) designed to enlarge retinal images of the central visual field,2 is familiar with the IOL-VIP system. “It represents one of several devices being developed worldwide to help patients who can no longer benefit from the latest AMD drugs or photodynamic therapy because of extensive scarring,” Dr. Lane said.

Dr. Lane is convinced that devices such as the IMT or IOL-VIP system have great potential for patients with end-stage AMD because “technology doesn’t stand still. Advances in technology will make these low vision devices more viable. However, the question is whether relatively smaller companies working on these devices can stay in business to develop the next generation, especially in America, where we don’t have FDA approval.”

While the IOL-VIP system has been approved for use in patients in Europe, the miniature telescope studied by Dr. Lane and others is scheduled to have a hearing before the FDA panel this month.

—Lori Baker Schena

___________________________

1 Orzalesi, N. et al. Ophthalmology 2007;114:860–865.
2 Hudson, H. L. et al. Ophthalmology 2006;113:1987–2001.

Top

Patient Care 

Probing the Glaucoma Patient’s Personality

Over the years, researchers delving into the minds of glaucoma patients have characterized them as everything from neurotic1 to excitable2 to perfectionistic.3 Now, a team at the University of California, Davis, has added to that list a tendency toward hypochondriasis, hysteria and health concerns.4

In a prospective study, 50 open-angle glaucoma patients and 50 controls were given the Minnesota Multiphasic Personality Inventory-2 test. Though the groups did not differ significantly when it came to medical problems, the glaucoma patients had more somatic complaints and concerns about health compared with controls.

Why? The researchers speculated that there may be something inherent in the diagnosis of glaucoma that triggers feelings of ill-being.

The findings may have implications for adherence. “Such feelings may make it difficult for them to take their medications on time, or they may be more forgetful about taking their meds,” said lead author Michele C. Lim, MD.

Next, the researchers plan to study the relationship between personality type and medication adherence.

For now, Dr. Lim said the bottom line is: “A personality type ‘profile’ may exist for people with open angle

— Miriam Karmel

___________________________

1 Holtmann, H. W. Klin Monatsbl Augenheilkd 1974;165:604–610.
2 Demours, A. P. Test-Book of Ophthalmology (St Louis: Mosby, 1941),3339.
3 Zimet, C. N. and A. S. Berger. Psychosom Med 1960;22:391–399.
4 Lim, M. C. et al J Glaucoma 2007;16(8):649–654.

Top