face off
Illumination
in Vitrectomy
COORDINATED
BY ABDHISH BHAVSAR, MD
Welcome
to Face Off, a column that explores controversial topics in the diagnosis
and management of retinal diseases. Our typical format has involved covering several
topics in each issue with one retina specialist voicing one line of thought in favor
of the treatment or surgery and another retina specialist voicing an opposing line
of thought. In this issue, we will explore the topic of illumination in vitrectomy.
While
we are not recommending any particular treatment for patients, the column will be
a nice exercise in exploring pro and con aspects of treatment decisions that we
face on a regular basis. This column should be interpreted in the spirit of a debate
society.
The 2 topics in this issue are:
► Use of xenon light sources for primary
illumination
►
Use of accessory illumination sources
USE
OF XENON LIGHT SOURCES FOR PRIMARY ILLUMINATION
FOR
DAVID CHOW,
MD
I
don't think any of us really care if its xenon, halogen, metal halide, or mercury
vapor as the light source. What matters to all of us as clinicians, is the safety,
brightness, and color of the light. Clearly, the newer xenon and mercury vapor light
sources have a significantly higher power capability compared to older halogen and
metal halide light sources.
Clinically, this translates into the ability to operate with 25-g
light probes that are brighter than our older 20-g halogen light probes, midfield
probes that are as bright as older standard probes with twice the field of view,
chandeliers that provide global viewing and allow "true" bimanual surgery, and significant
improvements in lighted instruments.
From the safety standpoint, all of the above light sources can
be made safe — it is just a matter of how you filter the light. Filtering out
more and more of the lower wavelengths of blue light improves the safety calculation
of the light source (aphakic hazard sum) but does so with a shift in the chromatic
characteristics of the light source, often making the light look more yellow or
shifting toward green. So it is a trade-off between improving safety by filtering
out lower wavelengths and producing a light whose color is acceptable to clinicians.
As the light sources get brighter and brighter the shift will likely have to be
toward improving safety with the corresponding shift in color. I routinely use a
chandelier on every retinal detachment or diabetic dissection and cannot imagine
returning to an older light source where this would be basically a waste of time.
Safer and brighter — Why wouldn't you want a xenon light source?
USE OF XENON WITH ICG STAINING
OF ILM ONLY
AGAINST
STEVE
CHARLES, MD
Safe,
ISO-compliant, xenon light sources are needed for a number of reasons: smaller fibers
for 25-g and illuminated tools with less light throughput; wide divergence-angle
illuminators with a long working distance, such as chandeliers like the Tornambe
Torpedo (Insight Instruments Inc., Stuart, Fla); 30-70 beam splitters, 3-CCD cameras,
which are 1/3 as light sensitive as 1-CCD cameras; and darkly pigmented patients
with dense vitreous hemorrhages.
I do not agree with using yellow light because the retinal pigment
epithelium (RPE) and choroid have black pigment (melanin). The retina, epiretinal
membrane (ERM), internal limiting membrane (ILM), and vitreous are colorless —
all meaning that contrast is worse with yellow light and tissue identification is
more difficult, especially for macular xanthophyll. Although blue and UV photons
are much more energetic than yellow photons, yellow photons are closer to the 550
nm peak sensitivity of the patient's cone system and the phototoxicity peak sensitivity.
I am opposed to using indocyanine green (ICG) for ILM peeling because of toxicity
and phototoxicity especially when brighter light sources such as xenon and mercury
vapor are used at excessive brightness settings.
USE OF ACCESSORY ILLUMINATION
SOURCES
FOR
FRANK
HJ KOCH, MD
I
always use either the Tornambe Torpedo chandelier or a multi-port illumination system
(MIS) as I perform bimanual surgery most of time. Having 2 active instruments in
the eye makes the surgery safer and quicker. Current Alcon (Fort Worth, Texas) xenon
or metal halide light sources are more than sufficient to drive these chandelier
systems. Why have one hand tied behind your back when it is not necessary?
Unlike a direct light pipe, these chandelier systems keep light
toxicity to a bare minimum due to the distance of the chandelier light exit to the
central retina. Instead of starting with a straight light pipe and then adding a
chandelier system to a case if the need arises, I always use the chandelier first
and then add a straight light pipe, which is seldom necessary.
USE OF ACCESSORY ILLUMINATION
SOURCES
AGAINST
NADER
MOINFAR, MD
Advances
in fiber optic technology and the proven benefits of less invasive surgery have
propelled the use of illuminated bimanual surgical techniques. Bimanual dexterity
can be complicated with accessory light sources. Cases that were daunting because
of poor illumination can now be efficiently and safely overcome with direct bimanual
illumination. Today's wide-field direct illumination obviates the need for accessory
illumination sources, therefore reducing sclerotomy-related complications and surgical
times, and proving again the adage that "less is more." RP
The ideas and opinions expressed in Face
Off do not necessarily reflect those of the editor, the editorial board, or
the publisher, and in no way imply endorsement by the editor, the editorial board,
or the publisher.
Abdhish
R. Bhavsar, MD, is an attending retina surgeon at the Phillips Eye Institute, director
of clinical research at the Retina Center, PA, in Minneapolis, and adjunct assistant
professor at the University of Minnesota. He also serves as state chair of the Minnesota
Diabetes Eye Exam Initiative. E-mail him about Face Off at
bhavs001@umn.edu.
Retinal Physician, Issue: November 2006