Figure 1 Implantable
miniature telescope [IMT (by Dr. Isaac Lipshitz)]
positioned in the capsular bag projects a
magnified image onto the macula. Part of the
telescope tube projects anteriorly into the
anterior chamber.
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San Diego—An
implantable miniature telescope in the capsular bag
provides a permanent visual prosthetic device for
patients who are legally blind from bilateral
age-related macular degeneration (AMD). While there is a
learning curve, an early assessment of the implantation
indicates that anterior segment surgeons are familiar
with the standard phacoemulsification and manual
extracapsular surgical skills used for this procedure,
according to David F. Chang, MD.
The IMT (by Dr. Isaac
Lipshitz), is composed of two lenses within a glass tube
measuring 4.4 mm in length and 3.6 mm in diameter. It is
positioned within the capsular bag by means of an
attached polymethylmethacrylate carrier platform that
has long, C-loop haptics. When implanted, it provides
the patient with 2X to 3X magnification.
"Importantly, the
device [developed by VisionCare Ophthalmic Technologies
Inc. with inventors and company founders Isaac
Lipshitz, MD, and Yossi Gross] has been optically
engineered to provide the patient with a much wider
visual field when compared with that provided by a
comparable external telescope," said Dr. Chang, clinical
professor of ophthalmology, University of California,
San Francisco, and a private practitioner in Los Altos.
Figure 2 The implantable
telescope with the PMMA carrier and
haptics.
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During the American Society of
Cataract and Refractive Surgery annual meeting, he
reported 3-month data from the multi-center FDA phase
II-III trial, which had enrolled 204 patients by last
fall. All patients had poor visual acuity bilaterally as
a result of AMD.
Implantation
procedure
Dr. Chang explained the
device is implanted in only one eye, intending for the
patient to use the magnified image for central vision
tasks. The fellow eye without the telescope provides
peripheral vision. The natural crystalline lens is
removed using a standard phacoemulsification procedure,
and the telescope is placed within the capsular bag.
Part of the telescope
tube protrudes into the anterior chamber through the
pupil. High-resolution ultrasound biomicroscopy has
confirmed that there is at least 2 mm of corneal
clearance.
"Once the crystalline
lens has been removed, the limbal incision is enlarged
to 11 mm, as would be done for a manual extracapsular
procedure. The telescope cannot be implanted unless both
the capsulorhexis and capsular bag are intact. The
capsulorhexis should be larger than usual (approximately
6.5 mm)," Dr. Chang explained.
Figure 3 Slit lamp image of
the implanted telescope in the capsular bag viewed
through a dilated pupil. Anterior capsular
fibrosis is visible, showing capsulorhexis
fixation of the flat carrier
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"Because of the high vertical
profile of the device, the major concern during
implantation is corneal touch and endothelial cell loss.
Therefore, the incision must be adequately large, and a
generous amount of retentive ophthalmic viscosurgical
device (OVD) should be used.
"In addition, the
implant should be inserted with a relatively swift and
decisive motion," he added. "Otherwise, with such a
large incision, all of the OVD will leak out, resulting
in collapse of the cornea."
At the 3-month
examination, the mean endothelial cell loss was about
18% to 20%; however, there was a trend toward less cell
loss with greater surgical experience.
The device was found
to center extremely well within the capsular bag.
"We have not had any
cases of corneal decompensation. Two of the telescopes
were explanted because of problems with the optics," he
reported.
The 3-month data
indicated that 89% of the patients had gained at least
two lines on an ETDRS chart, and 75% had gained at least
three lines of distance or near vision.