Articles about Eye Health and Disease 2001
Study Shows Effectiveness of a New Treatment for
Macular Degeneration (Transpupillary ThermoTherapy - TTT)
Age related Macular Degeneration (AMD) is a common cause
of visual loss in Caucasians over age 50. Often, the disorder is
divided into a "dry" type and a "wet" type. The
dry type consists of deposits being present in the retina known as drusen.
These deposits themselves usually do not lead to a significant loss of
vision, but they are associated with development of the "wet"
type. In this type, an abnormal blood vessel grows under the retina
and hemorrhages or scars, leading to a major loss of central (reading)
vision. This vessel is referred to as a "choroidal neovascular
membrane (CNV)". If the membrane is very well defined and
identifiable under the retina, it might be treatable using laser, or the
newer "photodynamic therapy". However, in many cases the
vessels are poorly outlined and defined under the retina (an
"occult" choroidal neovascular membrane), making treatment
difficult or impossible.
Transpupillary thermotherapy (TTT) is an effective treatment of occult
wet AMD, according to study results presented at the recent American
Academy of Ophthalmology meeting (11/01). More than 100 patients with
occult neovascular membranes associated with wet AMD underwent TTT with
the IRIS Medical OcuLight SLx laser from IRIDEX Corporation. Some key
results:
• Of the 83 patients available for 6-month follow-up, visual acuity
stabilized or improved in 63 patients (76%) and worsened (2 or more line
loss) in 20 patients (24%). Fluid under the retina was reduced in
90% of cases.
• Of the 48 patients followed for 9 months, visual acuity stabilized or
improved in 38 patients (79%).
In the study, laser treatment consisted of a large laser spot adequate to
cover the abnormal vessels, typically 3000-6000 micrometers diameter (3-4
mm), delivered over a period of 1 minute. Patients were evaluated for
visual acuity (stable or improved vision was defined as a loss of one
line, any improvement in vision or no change in the vision) and the need
for additional treatment. The TTT protocol is a Minimum Intensity Protocol
(MIP) that uses sub threshold photocoagulation to close CNV while sparing
the retina itself. The protocol uses the OcuLight SLx laser and Large Spot
Slit Lamp Adapter to produce favorable therapeutic responses in clinical
studies with minimal side effects and preservation of vision in patients
with occult CNV secondary to AMD. In cases where a traditional laser
is used, the retina would be destroyed along with the abnormal vessels,
leading to a loss of vision.
Retreatments with TTT are needed about 20% of the time, usually within
2 to 4 months.
(For more information about macular degeneration, go to:
Macular Degeneration.)
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