SCATTERINGS | NEWS
The Ohio State University
Scientists have known for years that
the crystalline lens of the human eye
loses its ability to focus on nearby objects
with advancing age; many people first
notice the condition, called presbyopia,
when they reach their 40s and can no
longer read without glasses. However,
researchers have not yet reached consensus about the exact cause of the condition: Is it an actual sti ening of the lens
material, a change in the muscles and
ligaments that alters the surface curvature
of the lens, or something else?
Using a non-invasive light-scattering
approach from materials science, a
team from Ohio State University
(Columbus, Ohio, U.S.A.) found no
appreciable change in the bulk modulus—a key measure of resistance to
compression—in lenses from people over
a 40-year age range. e scientists presented their results at a recent American
Physical Society meeting in Pittsburgh,
Physics professor Ratnasingham
Sooryakumar, graduate student Sheldon
Bailey and their colleagues tested cata-ract-free lenses from Ohio State’s organ
bank; the human donors’ ages ranged
(From left) Optometry professor Mark Bullimore,
physics professor Ratnasingham Sooryakumar
and physics graduate student Sheldon Bailey
in their Ohio State University lab.
from 30 to 70 years. ey also tested
intact bovine eyes of undetermined age.
Sound waves travel faster in sti er
materials; these pressure fluctuations
cause small density changes, which lead
to corresponding changes in the refractive index of the material. e researchers assessed the high-frequency acoustic
response of the lenses by measuring
the Brillouin scattering from a 514-nm
e results showed that the bulk
modulus does not change appreciably with age, Sooryakumar said. e
findings contradict two studies from
2004 and 2007, in which groups from
Australia and the Netherlands measured
a large increase in the shear modulus
in the human lens starting at around
age 35. However, those researchers used
mechanical techniques that required
cutting each lens into slices or pieces.
Granted, the bulk and shear moduli
of a material are mathematically related
to each other, but the di erent findings
clearly indicate that more research is
needed into the causes of presbyopia.
Ultimately, the condition may have
multiple contributing factors.
“What I believe we have done is to
raise questions about what is going on
with the tissue at the microscopic scale,”
Sooryakumar said. “Ultimately, we hope
that this will help to provide additional
insight into the biological structure and
the clinical consequences of aging on
— Patricia Daukantas
DID YOU KNOW?
Malaria-carrying mosquitoes may be the next target of the laser “death ray.” According to a report in the Wall Street Journal, scientists in Bellevue, Wash. (U.S.A.),
are building a WMD—or weapon of mosquito destruction. The device incorporates
laser parts bought on eBay and guided by a desktop computer.
The idea came from Lowell Wood, an astrophysicist who worked with the late
Edward Teller on the anti-missile defense program of the 1980s (OPN, February
2009, p. 14). So far, the team at Intellectual Ventures LLC, a think tank founded by
former Microsoft Corp. executive Nathan Myhrvold, has devised a contraption that
res off shots of laser light at mosquitoes con ned to a glass box some 30 m away.
A pair of Dutch lmmakers had made a spoof of an anti-mosquito laser system
several years ago, but the idea Myhrvold’s group is pursuing came out of a serious
brainstorming session. Myhrvold’s former boss, Bill Gates, has been funding research to
combat malaria, which kills 1 million people annually, mostly in tropical rural lands. Female
Anopheles mosquitoes transmit the malaria parasite through their bites.
The trickiest part of the so-called “photonic fence” appears to be getting the laser power
adjusted so that it zaps mosquitoes without exterminating bene cial insects, harming humans or wasting energy.