Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Doctors focus on pupil size for safety of laser vision correction

07.05.2003


Exactly how a person’s eyes respond to low levels of light is even more crucial than doctors have thought in deciding who is and who isn’t a good candidate to have laser vision correction surgery, according to results announced today at the annual meeting of the Association for Research in Vision and Ophthalmology in Ft. Lauderdale. The findings should help doctors choose patients who are likely to fare well with the surgery, and to forego recommending treatment for others.


Dr. Scott MacRae taking light measurements along the roadways in Rochester.


Dr. Scott MacRae taking light measurements along the roadways in Rochester



In the earliest days of laser vision correction, some patients complained of worsened night vision after the surgery – some reported significant glare from light sources such as headlights at night, while others saw halos around bright lights. Occasionally, though much more rarely, patients undergoing the procedure still report such side effects.

Ophthalmologist Scott MacRae, M.D., professor of Ophthalmology and Visual Science at the University of Rochester Medical Center, recently studied the role of a patient’s pupil size in determining a patient’s outcome from the surgery. In a study of 340 patients, he found that generally the larger a patient’s pupils, the more likely that person is to have a problem with laser vision correction. MacRae also discussed the results at the recent annual meeting of the Association for Cataract and Refractive Surgery in San Francisco.


“This is not a problem for most people,” says MacRae, “but as the procedure becomes more common, we have to make sure that we remain vigilant to protect and enhance people’s eyesight.”

MacRae is part of a team that has used a technology known as adaptive optics to discover dozens of previously unknown subtle imperfections in the eye, and he has found that those imperfections loom more important as the pupil size gets larger. He reports that if a surgeon treats a large enough swath of the eye for such patients, those imperfections are minimized. His study shows that it’s essential that doctors treating patients with large pupils consider creating an especially large treatment zone.

He found that doctors must be especially careful when using a laser to correct vision on people whose pupils dilate to six millimeters or more, a group that comprises about 40 percent of the population. If physicians treat too small an area of the cornea, patients are likely to have a problem when their eyes are most dilated – at night.

To understand the problem, think of a window washer who should clean an entire window even when the inside blind is partway down. When the blind goes up, a person looking through the window wouldn’t get a clear view unless the previously covered section of the window was washed too. Likewise, MacRae says, surgeons must treat a large part of the cornea so that when the pupil widens, the entire pupil transmits light clearly.

Pupil size is especially critical if a person is extremely near-sighted. MacRae says that generally, people with pupils larger than seven millimeters should be checked very thoroughly before having the surgery done.

MacRae measures every patient’s pupils three different times using three separate instruments. He also makes three measurements of the thickness of the cornea, another crucial element in deciding who is a safe candidate. Overall he advises against surgery in more than 20 percent of patients who inquire about the surgery, especially patients who have large pupils and are extremely nearsighted.

“Oftentimes I’ll have a patient who is initially upset because I won’t treat them, but they become grateful as they realize that we’ve done what is best for them in the long run,” he says. “When the pupil dilates, aberrations can be troubling. You have to be really careful. Patients need to be wary of surgical centers that trivialize these issues.”

In recent months MacRae has taken to driving around Rochester-area roads at night to measure just how much light typically enters a person’s eye, to get a grasp on how wide their pupils are while they’re on the road. He has found that conditions change markedly from one street to the next – information that perhaps won’t surprise drivers but which hasn’t been tapped by ophthalmologists whose patients report night driving as one of their biggest concerns.

“There is tremendous variation, depending on where your eye is looking,” MacRae says. “Country roads can be nearly completely dark, while city streets are often brightly lit.” He found that the amount of light entering a driver’s eye on a country road during a rainy night might be 200 times less than what he or she encounters driving through a busy intersection seconds later. He also found that a typical night driver frequently confronts situations where he or she has less than one-tenth the amount of light that doctors, in their offices, assume their patients encounter at night.

Tom Rickey | EurekAlert!
Further information:
http://www.urmc.rochester.edu/

More articles from Health and Medicine:

nachricht New leukemia treatment offers hope
23.09.2016 | King Abdullah University of Science and Technology

nachricht Alzheimer’s: Cellular Mechanism Provides Explanation Model for Declining Memory Performance
21.09.2016 | Deutsches Zentrum für Neurodegenerative Erkrankungen e.V. (DZNE)

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: OLED microdisplays in data glasses for improved human-machine interaction

The Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP has been developing various applications for OLED microdisplays based on organic semiconductors. By integrating the capabilities of an image sensor directly into the microdisplay, eye movements can be recorded by the smart glasses and utilized for guidance and control functions, as one example. The new design will be debuted at Augmented World Expo Europe (AWE) in Berlin at Booth B25, October 18th – 19th.

“Augmented-reality” and “wearables” have become terms we encounter almost daily. Both can make daily life a little simpler and provide valuable assistance for...

Im Focus: Artificial Intelligence Helps in the Discovery of New Materials

With the help of artificial intelligence, chemists from the University of Basel in Switzerland have computed the characteristics of about two million crystals made up of four chemical elements. The researchers were able to identify 90 previously unknown thermodynamically stable crystals that can be regarded as new materials. They report on their findings in the scientific journal Physical Review Letters.

Elpasolite is a glassy, transparent, shiny and soft mineral with a cubic crystal structure. First discovered in El Paso County (Colorado, USA), it can also be...

Im Focus: Complex hardmetal tools out of the 3D printer

For the first time, Fraunhofer IKTS shows additively manufactured hardmetal tools at WorldPM 2016 in Hamburg. Mechanical, chemical as well as a high heat resistance and extreme hardness are required from tools that are used in mechanical and automotive engineering or in plastics and building materials industry. Researchers at the Fraunhofer Institute for Ceramic Technologies and Systems IKTS in Dresden managed the production of complex hardmetal tools via 3D printing in a quality that are in no way inferior to conventionally produced high-performance tools.

Fraunhofer IKTS counts decades of proven expertise in the development of hardmetals. To date, reliable cutting, drilling, pressing and stamping tools made of...

Im Focus: Launch of New Industry Working Group for Process Control in Laser Material Processing

At AKL’16, the International Laser Technology Congress held in May this year, interest in the topic of process control was greater than expected. Appropriately, the event was also used to launch the Industry Working Group for Process Control in Laser Material Processing. The group provides a forum for representatives from industry and research to initiate pre-competitive projects and discuss issues such as standards, potential cost savings and feasibility.

In the age of industry 4.0, laser technology is firmly established within manufacturing. A wide variety of laser techniques – from USP ablation and additive...

Im Focus: New laser joining technologies at ‘K 2016’ trade fair

Every three years, the plastics industry gathers at K, the international trade fair for plastics and rubber in Düsseldorf. The Fraunhofer Institute for Laser Technology ILT will also be attending again and presenting many innovative technologies, such as for joining plastics and metals using ultrashort pulse lasers. From October 19 to 26, you can find the Fraunhofer ILT at the joint Fraunhofer booth SC01 in Hall 7.

K is the world’s largest trade fair for the plastics and rubber industry. As in previous years, the organizers are expecting 3,000 exhibitors and more than...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Experts from industry and academia discuss the future mobile telecommunications standard 5G

23.09.2016 | Event News

ICPE in Graz for the seventh time

20.09.2016 | Event News

Using mathematical models to understand our brain

16.09.2016 | Event News

 
Latest News

Chains of nanogold – forged with atomic precision

23.09.2016 | Life Sciences

New leukemia treatment offers hope

23.09.2016 | Health and Medicine

Self-assembled nanostructures hit their target

23.09.2016 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>