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UCSB
makes important advances in studies of retinal detachment
15
Dec 2004
Scientists at the University of California, Santa Barbara's
Neuroscience Research Institute are reporting significant
advances in their studies of retinal detachment: --
They have discovered that cellular changes that occur
in the retinas of animals with retinal detachments also
occur in humans. This implies that experimental therapies
that reduce cellular damage in animals have a high likelihood
of being successful in humans. -- They have determined
that oxygen therapy for retinal detachment, which they
pioneered, can be highly successful in animals even
when it is delayed, suggesting that it should be successful
in humans as well. In the January 2005 issue of Investigative
Ophthalmology and Visual Science, the international
team of scientists describes changes that occur in detached
human retinas. In this study, Steven K. Fisher, professor
of molecular, cellular and developmental biology, and
Geoffrey P. Lewis, research scientist, headed the UCSB
effort, collaborating with colleagues at the Moorfields
Eye Hospital and the Institute of Ophthalmology at University
College London. Understanding the "glial" response is
a key aspect of this study. Glial cells are known as
the "supporting cells" of the nervous system. The central
nervous system (CNS) consists of both neurons and glial
cells. Glial cells actually outnumber neurons in the
CNS but their functions are poorly understood. It is
known that glial cells surround neurons, hold them in
place and supply nutrients to neurons. They insulate
neurons from each other and also destroy and remove
dead neurons. The reaction of the glial cells to retinal
detachment is critical to the success of surgery to
correct retinal detachment. The glial response is part
of an important medical condition called "proliferative
vitreoretinopathy" (PVR). This condition is characterized
by the growth of glial cells on the surface of the retina.
In response to unknown stimuli, these cells begin to
contract and can cause the retina to tear or re-detach.
In humans, PVR is the most common cause of failure of
retinal reattachment surgery. It occurs in five to 10
percent of all cases. Essentially the glial cells form
scar tissue in PVR. Scar tissue in one location causes
the re-detachment of the retina, in another it blocks
the regeneration of neurons and vision does not return.
According to this and earlier studies, the data indicate
that glial cell remodeling can play a clear role in
the return of good vision following successful reattachment
surgery. What has been a surprising new result in all
of the recent studies is the extent of neuronal remodeling
that occurs during the time the retina is detached.
"The structural remodeling of retinal neurons in animals
following detachment has been assumed to alter synaptic
connections between nerve cells and in doing so have
an effect on visual outcome including reduced visual
acuity or changes in color vision," said Lewis. Photoreceptors
in the eyes are among the most highly metabolic cells
in the body, using more energy than any others. Because
of this, the UCSB researchers decided to test the use
of extra oxygen to help maintain the cells after a retinal
detachment. First reported by the UCSB researchers in
1999, the therapy has proved remarkably effective and
is now being used by some ophthalmologists prior to
surgery. Recently the UCSB team reported refinements
of these results. Normal room air has about 21 percent
oxygen. In these first studies, the effects of oxygen
were examined under "ideal" conditions. That is, oxygen
therapy at 70 percent was begun immediately after creating
a retinal detachment. However, these ideal conditions
would not likely be encountered in a clinical situation
because it would not be possible to administer oxygen
to human patients immediately after a retinal detachment
occurs. Therefore, a new study was undertaken in which
elevated oxygen was administered 24 hours after creating
a detachment, thus more closely mimicking conditions
commonly encountered in human patients. The results
were published by the UCSB scientists in American Journal
of Ophthalmology last summer. In this case, neuronal
cell death and nerve cell remodeling was greatly reduced
by comparison to the animals breathing normal room air,
although the glial cell response was less affected than
in the experiments with delivery of immediate elevated
oxygen. Assuming that it is desirable to reduce cell
death and prevent the remodeling of nerve cells in detachment
patients, the simple administration of elevated oxygen
between the time of diagnosis and surgical repair may
result in more rapid and improved recovery after reattachment
surgery. Future research will include determining the
effectiveness of this hyperoxia therapy when administered
both before and after reattachment surgery, and methods
for better inhibition of the undesirable cellular effects
that lead to PVR. This research has broad implications
since the cell types involved (neurons and glia) are
the same as those in the brain and spinal cord. The
UCSB effort is one of a handful of research labs in
the world that are studying retinal detachment in this
way. The work at UCSB is unique in that the researchers
have specialized using high resolution microscopy techniques
to precisely map changes in protein expression and morphology
in the cells. NOTE: Steven Fisher is available at 805-893-3637,
or by e-mail at fisher@lifesci.ucsb.edu Geoff Lewis
can be reached at 805-893-3611, or by e-mail at g_lewis@lifesci.ucsb.edu
Contact: Gail Gallessich gail.g@ia.ucsb.edu 805-893-7229
University
of California - Santa Barbara |
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