Featured Research

from universities, journals, and other organizations

Doctors Focus on Pupil Size for Safety of Laser Vision Correction

Date:
May 8, 2003
Source:
University Of Rochester Medical Center
Summary:
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.

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.

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 are large. 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. Pupil size is especially critical if a person is extremely near-sighted.

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.

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.


Story Source:

The above story is based on materials provided by University Of Rochester Medical Center. Note: Materials may be edited for content and length.


Cite This Page:

University Of Rochester Medical Center. "Doctors Focus on Pupil Size for Safety of Laser Vision Correction." ScienceDaily. ScienceDaily, 8 May 2003. <www.sciencedaily.com/releases/2003/05/030507080508.htm>.
University Of Rochester Medical Center. (2003, May 8). Doctors Focus on Pupil Size for Safety of Laser Vision Correction. ScienceDaily. Retrieved July 23, 2014 from www.sciencedaily.com/releases/2003/05/030507080508.htm
University Of Rochester Medical Center. "Doctors Focus on Pupil Size for Safety of Laser Vision Correction." ScienceDaily. www.sciencedaily.com/releases/2003/05/030507080508.htm (accessed July 23, 2014).

Share This




More Health & Medicine News

Wednesday, July 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Courts Conflicted Over Healthcare Law

Courts Conflicted Over Healthcare Law

AP (July 22, 2014) Two federal appeals courts issued conflicting rulings Tuesday on the legality of the federally-run healthcare exchange that operates in 36 states. (July 22) Video provided by AP
Powered by NewsLook.com
Why Do People Believe We Only Use 10 Percent Of Our Brains?

Why Do People Believe We Only Use 10 Percent Of Our Brains?

Newsy (July 22, 2014) The new sci-fi thriller "Lucy" is making people question whether we really use all our brainpower. But, as scientists have insisted for years, we do. Video provided by Newsy
Powered by NewsLook.com
Scientists Find New Way To Make Human Platelets

Scientists Find New Way To Make Human Platelets

Newsy (July 22, 2014) Boston scientists have discovered a new way to create fully functioning human platelets using a bioreactor and human stem cells. Video provided by Newsy
Powered by NewsLook.com
Gilead's $1000-a-Pill Drug Could Cure Hep C in HIV-Positive People

Gilead's $1000-a-Pill Drug Could Cure Hep C in HIV-Positive People

TheStreet (July 21, 2014) New research shows Gilead Science's drug Sovaldi helps in curing hepatitis C in those who suffer from HIV. In a medical study, the combination of Gilead's Hep C drug with anti-viral drug Ribavirin cured 76% of HIV-positive patients suffering from the most common hepatitis C strain. Hepatitis C and related complications have been a top cause of death in HIV-positive patients. Typical medication used to treat the disease, including interferon proteins, tended to react badly with HIV drugs. However, Sovaldi's %1,000-a-pill price tag could limit the number of patients able to access the treatment. TheStreet's Keris Lahiff reports from New York. Video provided by TheStreet
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins