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New System for Fiberoptic-Free Bimanual Vitreous Surgery
Masayuki Horiguchi, MD;
Yoshihisa Kojima, MD;
Yoshiaki Shimada, MD
Arch Ophthalmol. 2002;120:491-494.
ABSTRACT
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Objectives To describe a new system for fiberoptic-free bimanual vitrectomy and
to present the outcome of 37 eyes with preretinal membranes due to diabetic
retinopathy or proliferative vitreoretinopathy that underwent surgery using
this system.
Methods The system consists of a 40-diopter aspheric field lens suspended from
the operating microscope and a prismatic inverting device. The aspheric lens
is placed above the cornea, and the illumination from the operating microscope
creates an inverted image of the fundus, which is made erect by an inverter
system. No fiberoptics are required, and both hands are free to use 2 microinstruments.
Main Outcome Measures The practical utility of this system and its surgical results and complications.
Results The system was used successfully in all cases. Membrane dissection and
hemostasis were performed without incident. An improvement in visual acuity
of 2 or more lines was found in 30 of 37 eyes. Five eyes did not reveal change
of 2 or more lines, and 2 eyes had a decrease in visual acuity of more than
2 lines. There was no evidence of phototoxicity.
Conclusion This system is very useful for bimanual vitrectomy.
INTRODUCTION
THE TECHNIQUE of bimanual vitrectomy is very useful for removing difficult
preretinal membranes in cases of diabetic retinopathy and other vitreoretinal
diseases.1-5
Furthermore, the bimanual technique is also used in intraocular lens replacement6 and foveal relocation surgical procedures.7-8 Several instruments have been developed
to facilitate the bimanual technique,9-10
and self-illuminated devices are common.7-8,11-12
However, the instruments for self-illumination are expensive and have limitations;
for example, the choice of possible instruments is limited, and the area of
illumination is restricted.
We have developed a new system for bimanual vitreous surgery without
the necessity of a self-illuminating device. We have combined the optical
system of a wide-angle microscope with a binocular indirect ophthalmoscope
and have used the operating microscope for intraocular illumination instead
of a fiberoptic bundle. The illumination from the microscope and a newly designed
aspheric 40-diopter (D) lens placed above the cornea create an inverted image
of the fundus in the same way as an indirect ophthalmoscope. A prismatic inverting
system returns the image to the upright position. This system allows an excellent
view of the fundus, and because the hand normally used to hold the fiberoptic
illumination probe is not needed, 2 vitrectomy instruments can be used simultaneously.
We describe the new system and its results.
MATERIALS AND METHODS
ILLUMINATION-OBSERVATION SYSTEM
This system consists of a 40-D aspheric lens and a prismatic inverting
optical system. The 40-D aspheric lens is used as a field lens. It is attached
to the microscope (OM610; Topcon, Tokyo, Japan), and when both hands are required,
the lens can be swung into place between the objective lens of the microscope
and the cornea. The illumination from the microscope gives an inverted image
of the fundus, and the inverting device allows us to see an erect image.
Figure 1 shows a photograph
of the new system. The refractive power of the lens is critical. When the
refractive power is less than 40 D, the distance from the cornea to the eyepiece
of the microscope is too great to easily perform a vitrectomy; when it is
higher, the lens is too close to the cornea, and the light reflections from
the lens and cornea interfere with the view of the fundus. The diameter of
the lens is also important. The diameter of the commercially available 40-D
lens is about 35 mm, and if used for observing the fundus during vitrectomy,
the edges of the lens interfere with the movement of the surgical instruments.
The diameter of the new lens is 25 mm, small enough to avoid contact with
the surgical instruments.
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Figure 1. The new system for fiberoptic-free
bimanual vitrectomy.
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We used a commercially available prismatic inverting system (Ocular
Instruments Inc, Bellevue, Wash). The binocular convergence angle of the optical
axes of the operating microscope is about 4.1° (pseudophakia and phakia)
when a planoconcave contact lens is used on the cornea, but with this system
the angle is about 6.9°, which enhances the stereoscopic view of the fundus.
However, the pupil size should be larger than 5.0 mm to obtain a wide stereoscopic
operating field. An iris retractor can be used in eyes with a small pupil.
The light source of the microscope was a 50-W halogen lamp, and the
light intensity on the surface of the retina was 30 mW/cm2. The
lens and suspending components are sterilized prior to attachment to the microscope
before surgery.
PATIENTS AND SURGICAL PROCEDURES
This system was used during vitrectomy in 31 eyes with proliferative
diabetic retinopathy and 6 eyes with rhegmatogenous retinal detachment associated
with proliferative vitreoretinopathy between October 2000 and March 2001.
Twelve patients had a tractional macular detachment, 19 had only a preretinal
membrane, and 18 had preretinal or vitreous hemorrhage in addition to a preretinal
membrane or detachment.
We first performed a 3-port pars plana vitrectomy with the wide-angle
view system to remove the vitreous cortex because the visibility of the extreme
periphery was better with a wide-angle view than with our new system. We then
removed the membrane using a bimanual technique. In cases without vitreous
detachment, we tried to create a posterior vitreous detachment first; when
it was difficult, we removed the vitreoustogether with the proliferative membrane.
Gas or silicone tamponade was used when necessary.
RESULTS
SURGICAL PROCEDURES
We successfully performed bimanual vitrectomy with this system in 37
patients. Preoperatively, 23 of 37 eyes were phakic, 10 were pseudophakic,
and 4 were aphakic. In 18 of 23 phakic eyes, a phacoemulsification or lensectomy
was performed prior to the vitrectomy (combined surgery) because of a significant
cataract.
PRACTICAL UTILITY OF THE SYSTEM
The diameter of the area that could be observed with this system was
about 40° (Figure 2), which
is smaller than the field obtained with the wide-angle view system but larger
than that with the planoconcave contact lens. The field of view with this
system was sufficient for membrane removal in the posterior pole, and more
peripheral lesions could be treated by rotating the eye or indenting the sclera.
However, lesions in the extreme periphery, where stereoscopic viewing is difficult,
could not be treated using this system.
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Figure 2. The operating field obtained using
the new system after removal of the preretinal membrane in a patient with
proliferative diabetic retinopathy.
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Although the light reflection from the 40-D lens, crystalline or intraocular
lens, or cornea sometimes interfered with the view, it was not difficult to
eliminate most of it by moving the microscope and/or the eye, as is done with
an indirect ophthalmoscope. The reflected light was less in aphakic eyes than
in phakic or pseudophakic eyes. The small light at the center of the field
cannot be removed. However, this small reflection is always present in the
center of the cornea when anterior segment surgery is performed with a microscope.
The 40-D lens was located about 2.0 cm above the cornea, where the fundus
was clearly visible. This did not interfere with the surgeon's manipulation
of the instruments for vitreous surgery. To prevent dehydration of the corneal
surface, the cornea was occasionally moistened with a small amount of irrigating
solution (BSS Plus; Alcon, Fort Worth, Tex). The 2-cm distance between the
lens and cornea was sufficient to allow the irrigation of the cornea, and
the view was kept clear during the operation.
The distance from the cornea to the objective lens of the microscope
is normally about 18 cm during vitrectomy in our hospital, but it was 25 cm
with this system. Thus, the microscope must be moved farther from the eye
to focus on the image of the fundus. The new height of the microscope was
acceptable to all who used it.
Application of This System to Vitrectomy
This system was useful for the following procedures:
- Membrane dissection in proliferative diabetic retinopathy
(Figure 3A).
- Hemostasis in proliferative diabetic retinopathy
(Figure 3B).
- Membrane peeling from the detached retina in proliferative
vitreoretinopathy (Figure 3C).
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Figure 3. A, Bimanual technique using microscissors
and microforceps in a patient with proliferative diabetic retinopathy (PVR).
B, Bimanual technique using a soft-tipped needle and diathermy in a patient
with PVR. C, Bimanual technique using 2 pairs of forceps in a patient with
PVR. One pair was used to grasp the retina while another peeled the membrane.
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Results of Surgery
Although membrane dissection was completed with our new system, 1 patient
with diabetes developed neovascular glaucoma after surgery, and 1 patient
with proliferative vitreoretinopathy experienced a recurrence of the retinal
detachment. Thirty of 37 eyes had an improvement in visual acuity of 2 or
more lines, whereas 5 did not show a change in visual acuity of 2 or more
lines. Two eyes had a decreased visual acuity of more than 2 lines because
of neovascular glaucoma or a recurrent detachment.
COMMENT
This study demonstrates that a new system can be used effectively for
vitrectomy. In our experience, membrane dissection with this system is much
easier than with self-illuminated devices because of the even illumination
of the operating field and enhanced stereopsis. Although some practice is
required to use this system, we believe that any surgeon who has used the
binocular indirect ophthalmoscope will quickly adjust to this system.
Several methods have been used to illuminate the fundus during vitrectomy.
The coaxial light from a microscope has been used for this purpose, but the
external illumination-induced bright reflections at every optical interface
disturb the view of the fundus. Slitlamp illumination has also been used,
but the operating field seems to be too small.13-15
Another method of illumination for vitreoretinal surgery is the use of an
indirect ophthalmoscope, which provides a bright and even illumination but
an inverted image.11 Currently, a fiberoptic
bundle is widely used for intraocular illumination during vitrectomy,16-17 and a wide-angle view system has
recently been developed for observation of the peripheral retina.18-20 With this system,
a lens of more than 100 D is placed on the cornea, and the fiberoptic bundle
provides an inverted image of a wide area of the fundus. An optical system
is used to make the inverted image erect.
The use of both hands would be expedient for several procedures. The
fiberoptic pipe combined with a membrane pick has been used to hold the epiretinal
membrane while several surgeons illuminate the field.1-5
Endoillumination has been combined with an infusion cannula.9
The fiberoptic illuminating system can also be fixed in a scleral port (4-port
technique).6, 10 Diathermy and
self-illuminated instruments such as forceps, scissors, and a fluted needle
have been used as well.3, 7-8,11
Although these techniques have been helpful for vitreous surgery, the
use of fiberoptics for illumination has limitations, such as the cost of the
device, visibility of the fundus, and choice of instruments. The fiberoptics-free
system we have developed using a 40-D lens and a prismatic inverting device
provides an excellent view of the ocular tissues and allows both hands to
be free to use any 2 microinstruments for vitrectomy. Because this system
does not include disposable parts, we believe that the cost is less than other
systems.
The illumination from an operating microscope has been reported to cause
phototoxic damage to the retina during cataract surgery, glaucoma surgery,
and vitrectomy.21-24
This occurs because the intraocular lens focuses the illumination on the fovea.
In our system, however, the light is focused near the cornea and illuminates
a wide area of the fundus. Therefore, the intensity of the retinal illumination
in this system is not as high as with focused illumination. Endoillumination
from a fiberoptic system also causes retinal phototoxicity during membrane
dissection.25-26 The estimated
retinal irradiation in our system is 30 mW/m2, which is lower than
when a fiberoptic bundle is located 6 mm from the retina.27
In owl monkeys,28 the calculated exposure time
of this light to reach the threshold of ophthalmoscopic damage (200 J/cm2) was 111 minutes. Membrane removal was completed within 30 minutes
in our patients, and we have found no evidence of toxic effects from the light.
We believe that this intensity is not toxic.
We conclude that this system is safe and very useful, allowing both
hands to be free for vitreoretinal surgery.
AUTHOR INFORMATION
Submitted for publication July 31, 2001; final revision received December
5, 2001; accepted December 21, 2001.
Dr Horiguchi has applied for a patent (2001-15991, 2001-160177, and
2001-178299) with the Japanese patent office, Tokyo.
Corresponding author and reprints: Masayuki Horiguchi, MD, Department
of Ophthalmology, Fujita Health University School of Medicine, Kutsukakecho,
Toyoakeshi, Aichi 470-1192, Japan (e-mail: masayuki{at}fujita-hu.ac.jp).
From the Department of Ophthalmology, Fujita Health University School
of Medicine, Toyoake, Japan.
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