Today, patients with cataracts can choose from several types of
artificial lenses, which are surgically implanted in the eye to replace
cloudy lenses that obstruct vision. A new vision simulator could help
these patients see how the world would look with each type of implanted
artificial lens, before they have surgery.
In The Optical Society's journal for high impact research, Optica,
researchers in Spain describe and demonstrate their new hand-held device
called the simultaneous vision simulator, or SimVis. With SimVis,
patients can experience how a certain implanted lens would affect their
vision by simply looking through the device.
“There are many different intraocular lenses in the market, which
provide different balances of near and far vision,” said Aiswaryah
Radhakrishan, researcher at the Instituto
de Optica, Consejo Superior de Investigaciones Científicas, Spain.
“We have discovered a way to simulate these intraocular lenses and
demonstrated a prototype device that allows patients to test different
solutions before surgery and choose the one that best suits their needs.”
Choosing the right lens
In the last decade, lens companies have designed intraocular lenses that
not only replace the cloudy lens of the eye but can also correct the
patient’s vision, to reduce the need for glasses. This correction is not
perfect, however. The natural lens is stretched by muscles in the eye to
change its shape, and thus its focal length, to shift from having
up-close and far objects in sharp focus on the retina. Current implanted
intraocular lenses do not have this capability to change shape like
this. Instead, standard intraocular lenses are monofocal, i,e, they
correct only far vision, which creates sharp vision for far-away objects
but blurred vision for objects close by. Patients would then wear
glasses to correct near. There are also newer multifocal lenses that
focus both near and far objects onto the retina at the same time but
with some loss of image quality and contrast for both near and far
distances. The choices for monofocal, and, particular multifocal
intraocular lenses keeps growing as more designs enter the market.
“Currently, the decision on which intraocular lens is implanted during
cataract surgery is typically based on the explanations and experience
of the surgeon,” said Carlos Dorronsoro, first author of the paper. “But
it is difficult for patients to imagine the new visual experience
provided by some of these lenses, therefore, it is very difficult to
make the decision.”
The SimVis uses an optoelectronic tunable lens that changes shape in
response to an applied electric current. To simulate multifocal lenses,
the shape of this tunable lens can be switched so quickly that the
resulting oscillations in focal positions can’t be perceived by human
vision. A patient looking through the device would see near and far
distances in focus at the same time, as well as experiencing the loss of
image quality and contrast that comes with multifocal lenses.
The amount of time the plastic lens remains in a particular focus can be
used to vary the lens power dedicated to that state. For example, a
bifocal lens with 70 percent far and 30 percent near power is simulated
by inducing the far state for 14 milliseconds and the near state for 6
milliseconds and then repeating this pattern continuously.
Testing the vision simulator
The researchers asked nine volunteers to use the SimVis to compare seven
different lenses providing monofocal, bifocal or trifocal corrections
while looking at a poster of a landscape, a laptop, a tablet, and a
smartphone, with high contrast text and eye charts placed at different
distances. Based on the lens simulations, the testers indicated clear
preferences for certain corrections.
“The favored or rejected lenses were different for different testers,
suggesting the need for this kind of simulation prior to surgery to
customize the selection of lenses according to patient requirements,”
said Dorronsoro. “Clinical use of the SimVis could provide an
evidence-based way to assess the subjective needs and preferences of
patients before they undergo cataract surgery.”
The researchers are now working on a binocular version of the SimVis
that is smaller and can simulate different lenses in each eye. Appearing
much like a virtual reality helmet, this new version of the SimVis will
also be lighter and have a wider field of view than the device
demonstrated in the Optica paper. The researchers are working to
complete the necessary clinical validations so that the binocular
version of SimVis can be sold commercially by next year.
Paper: C. Dorronsoro, A. Radhakrishnan, J.R. Alonso-Sanz, D.
Pascual, M. Velasco-Ocana, P. Perez-Merino, S. Marcos, "Portable
simultaneous vision device to simulate multifocal corrections," Optica,
3, 9, 918 (2016). DOI: 10.1364/optica.3.000918.
Optica is an open-access, online-only journal dedicated to the
rapid dissemination of high-impact peer-reviewed research across the
entire spectrum of optics and photonics. Published monthly by The
Optical Society (OSA), Optica provides a forum for pioneering
research to be swiftly accessed by the international community, whether
that research is theoretical or experimental, fundamental or applied. Optica
maintains a distinguished editorial board of more than 40 associate
editors from around the world and is overseen by Editor-in-Chief Alex
Gaeta, Columbia University, USA. For more information, visit Optica.
About The Optical Society
Founded in 1916, The Optical Society (OSA) is the leading professional
organization for scientists, engineers, students and entrepreneurs who
fuel discoveries, shape real-life applications and accelerate
achievements in the science of light. Through world-renowned
publications, meetings and membership initiatives, OSA provides quality
research, inspired interactions and dedicated resources for its
extensive global network of optics and photonics experts. For more
information, visit osa.org/100.
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