NEW INSTRUMENTATION FEATURE STORY

Multicolor ScanLaser Photocoagulator
Provides Efficiencies
in the Clinic
The MC-500 Vixi laser is capable of any combination of red, green, and yellow wavelengths.
BY EVANGELIA PAPAVASILEIOU, MD, FEBO PHTH ;AND SOM PRASAD, MS, FRCSE D , FRCO PHTH , FACS

P

attern scanning lasers, first introduced in ophthalmology during the previous decade, are designed
to deliver single laser spots or multiple spots inpreplanned array patterns to the retina for thetreatment of a variety of pathologic conditions. Thesedevices can save time for the clinician, streamline patient
flow for the retina practice, and reduce discomfort fromlong laser sessions for the patient.
A second-generation multi-wavelength laser photocoagulator system, the MC-500 Vixi Multicolor Scan Laser
Photocoagulator (Nidek Co. Ltd.) was introduced atlast year’s American Society of Retina Specialists meeting in Boston. The laser received US Food and Drug
Administration clearance in August 2011 and is now
available worldwide.
This pattern scan laser allows the practitioner to selectfrom among 3 wavelengths: 532 nm green, 577 nm yellow, and 647 nm red, as well as combinations of any 2 orall 3 wavelengths simultaneously. This capability enables
the user to select the necessary color or combination ofcolors to increase efficiency of treatment for a specificindication. We have had the opportunity to use thisnew laser for all forms of retinal treatments for several
months, and we report our initial experience here.
MULTIPLE WAVELENGTHSThe Vixi is the only pattern scan laser that allows
selection of multiple wavelengths. The most commonly
employed wavelength in vitreoretinal practice is 532 nm
green, used for treating retinal pathologies with panretinal

Figure 1. The laser in clinical use. It is a compact unit with asmall footprint.

photocoagulation. The 577 nm yellow laser is minimallyabsorbed by xanthophylls and well absorbed by oxygenatedhemoglobin, making it the wavelength of choice for lesions
close to the macula. Good results with dye lasers operating
at this wavelength have been reported.1 Krypton lasers producing the 647 nm red wavelength have historically beenused for photocoagulation of deep choroidal pathology.
The combination of the three wavelengths in oneversatile machine with a small footprint (Figure 1) allows
the clinician to provide therapy options appropriate forthe patient’s pathology. The laser also allows the use of
these multiple wavelengths in a variety of grid patterns.
The MC-500 Vixi includes eight preprogrammed scanpatterns with a memory function for up to 14 patterns(Figure 2). The available patterns include a single spot,
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NEW INSTRUMENTATION FEATURE STORY

Figure 2. Various preprogrammed scan patterns are available
from the touch-screen control unit.

squares (from 2-by-2 to 5-by-5 spots), a circle, arcs (ofone-quarter, one-half, or three-quarters of a circle), a
triple arc, a macular grid, a triangle, a line, and a curve.
The macular grid pattern can be used, for example, fortreatment of the periphery of the macula in quadrants,
with a fixed inner diameter and spot sizes ranging from100 to 200 µm. The pattern can also be rotated in increments of 15° using an LCD touch screen (Figure 3). The
4 most frequently used scan patterns can be saved andrecalled from the LCD menu.
The scan spot size is continuously variable from 50 to500 µm in single mode and from 100 to 500 µm in scan
and automanipulation mode. The actual spot size on theretina changes depending on the laser contact lens used.
Spot spacing can be adjusted with the touch screen. For
grid photocoagulation, we prefer 2-spot spacing, while forpanretinal laser we prefer 1-spot spacing. Continuously
variable size adjustment enables the surgeon to compensate for changes due to laser contact lens selection.
The single-spot mode is used in conventional laser
treatments, and the automanipulation mode can beused to deliver repeated laser emissions with variableinternal times and conventional coagulation settings ina selectable scan pattern. The automanipulation mode
allows the surgeon to continue laser emission while
confirming spot placement. The scan mode is used for
repeated laser emission with a fixed interval time, highpower, and instantaneous speed.
PRACTICAL EXPERIENCE
In our experience, this laser saves time by requiring fewer
sessions, consumes less energy, and provides more versatility than conventional models. It allows us to employ rapid
and optimally powered laser emission for laser photoco2 RETINA TODAY APRIL 2012

Figure 3. All laser parameters can be rapidly adjusted fromthe touch screen console.

agulation with a selection of colors and scan patterns. Laser
output can be limited to a single wavelength or modulated
to a combination of colors for specific treatments. It is
intended to be used in ophthalmic surgical procedures,
including retinal and macular photocoagulation, iridotomy,and, for our glaucoma colleagues, trabeculoplasty.
The chorioretinal damage and therapeutic effects of different laser wavelengths are similar, but each wavelength
has unique absorption and transmission characteristics
that makes it desirable for a particular option. The MC-500
Vixi enables efficient photocoagulation even throughopaque media. In eyes with cataract, better penetrationis achieved with the yellow wavelength compared withgreen. In eyes with retinal hemorrhage, better penetrationis achieved with the red wavelength. In case of accidental
hemorrhage during treatment, the clinician can switch rapidly to the red wavelength to cauterize the bleeding vessel.
Nagpal and colleagues2 reported that pattern scan laser
treatment was less time-consuming and less painful forthe patient compared with single-spot 532-nm solid-state
green laser. Also, pattern scan laser showed less collateral
damage and similar regression of retinopathy comparedwith a single-spot 532-nm solid-state green laser.
For laser eye surgery near the macula, 577 nm yellow is
the color of choice. Hemoglobin absorbs yellow light morethan other colors, and 577-nm lasers are more effective
than any other wavelength for sealing abnormal blood vessels while doing minimal damage to the macula. The yellow
wavelength is safer in locations where the inner choroid
is heavily pigmented (for instance, over a large choroidalvessel), reducing the risk of hemorrhage. Joondeph and colleagues3 used 577 nm yellow to treat retinal macro-aneurysms and reported resolution of hemorrhage, exudates,
edema, and serous macular detachment.
Clinical trials have shown that 577 nm yellow is less

NEW INSTRUMENTATION FEATURE STORY

destructive than green, reducing temperature elevation
but still achieving therapeutic goals and preserving visual
sensitivity as measured by microperimetry. No controlled
clinical trials have demonstrated the clinical advantage of
1 laser wavelength over another in conventional suprathreshold retinal photocoagulation, but dye lasers havebeen used to exploit the 577 nm yellow peak of oxyhemoglobin to improve the comfort and convenience ofstandard clinical retinal photocoagulation. Yellow 577 nm
laser light provides excellent lesion visibility, low amounts
of intraocular light scattering and patient pain, and highchoriocapillaris absorption for more uniform effects inpatients with light or irregular fundus pigmentation.
Studies have found that differences in efficacy of theresorption of hard exudates, visual outcomes, and resolution of focal diabetic macular edema between different
types of laser were not statistically significant, but green
laser can lead to submacular fibrosis or choroidal neovascularization.
Krypton 647 nm red lasers are typically used for treatment of deeper choroidal leakage and have less tissue penetration. This wavelength can be used in retinal vascular proliferative diseases and chorioretinal diseases associated withexudative manifestations.4,5 The 647 nm red krypton laser
light is not absorbed by the hemoglobin in the retinal hemorrhage or by the macular luteal pigment xanthophyll, and
it is transmitted into the choroid, allowing treatment within
the macular zone with less damage to the internal retinal
elements than would be seen with other wavelengths.6
In cases of subretinal neovascular membrane, therefore,
krypton red can be the treatment of choice. Feeder vessel photocoagulation with krypton red laser may also be
considered as a treatment option for subfoveal choroidal neovascularization (CNV) secondary to age-related
macular degeneration (AMD).7 Moreover, in cases ofretinal angiomatous proliferation (RAP) stage 3, which
includes CNV as well as retinal choroidal anastomosis,
krypton laser could be the potential treatment of choice.8
In this subtype of neovascular AMD with particularly
bad prognosis, this treatment could lead to anatomical
closure of the vascular complex and eliminate the risk fordevelopment of tears in the retinal pigment epithelium.9
However, it may have the disadvantage of requiring more
retreatments compared with 532 nm green.
With the Vixi we can start treatment with 1 color andcontinue it with another. The laser is flexible enough tobe used in almost all clinical cases. The automanipulationand scan modes allow mode selection appropriate forspecific pathologies.
In addition to conventional single spot delivery, thescan capability allows a wide range of multicolor laser
pattern deliveries. The laser can be used with existing

slit lamps, transforming them into a stage for scanninglaser treatments. It can also be provided in combination
with YAG laser and an indirect ophthalmoscope. Allunits incorporate the Safety Optics with Low Impact on
Cornea (SOLIC) optical design, which ensures low energy
density on the cornea and lens even with large spot sizes.
The color LCD touch screen has an intuitive menu
clearly indicating scan patterns and photocoagulation
data. Ten sets of photocoagulation data (including color,power output, emission time, and interval time) applied
to various clinical cases can be registered, and this canbe helpful especially for repeated treatments and forpatients participating in clinical trials. The laser also hasa convenient power foot switch and is available withboth front and rear dual ports for improved cable management. This solid-state laser provides longevity, spacesaving, and reduction of power consumption by 60%
compared with the previous model.
CONCLUSION
The MC-500 Vixi is an extremely flexible and user-friendly technology. Although we have 3 different laser delivery
systems in our retinal treatment clinic suite, this is the laser
we now use for most of our cases because of its ease of use,
the ability to change wavelengths on the fly, and the versatile patterns that can be adjusted intuitively. nEvangelia Papavasileiou, MD, FEBOphth, is aVitreoretinal Fellow with the Wirral University Teaching
Hospital NHS Foundation Trust, United Kingdom. She
reports no financial relationships relevant to this article.
Som Prasad, MS, FRCSEd, FRCOphth, FACS, isa Consultant Ophthalmologist with the Wirral
University Teaching Hospital NHS Foundation
Trust, United Kingdom. He is a consultant forBausch + Lomb, Bayer, and Nidek, and has also
received travel reimbursements and/or advisory board
fees from Alcon, Novartis and Allergan. Dr. Prasad can bereached via email at sprasad@rcsed.ac.uk.
1. Gupta V, Gupta A, Kaur R, Narang S, Dogra MR. Efficacy of various laser wavelengths in the treatment of clinicallysignificant macular edema in diabetics. Ophthalmic Surg Lasers. 2001;32(5):397-405.
2. Nagpal M, Marlecha S, Nagpal K. Comparison of laser photocoagulation for diabetic retinopathy using 532-nm
standard laser versus multispot pattern scan laser. Retina. 2010;30(3):452-458.
3. Joondeph BC, Joondeph HC, Blair NP. Retinal macroaneurysms treated with the yellow dye laser. Retina.
1989;9(3):187-192.
4. Khairallah M, Brahim R, Allagui M, Chachia N. Comparative effects of argon green and krypton red laser photocoagulation for patients with diabetic exudative maculopathy. Br J Ophthalmol. 1996;80(4):319-322.
5. Olk RJ. Argon green (514 nm) versus krypton red (647 nm) modified grid laser photocoagulation for diffuse
diabetic macular edema. Ophthalmology. 1990;97(9):1101-1112; discussion 1112-1113.
6. Yannuzzi LA, Shakin JL. Krypton red laser photocoagulation of the ocular fundus. Retina. 1982;2(1):1-14.
7. Shiraga F, Ojima Y, Matsuo T, Takasu I, Matsuo N. Feeder vessel photocoagulation of subfoveal choroidal neovascularization secondary to age-related macular degeneration. Ophthalmology. 1998;105(4):662-669.
8. Stoffelns BM, Kramann C, Schoepfer K. Laser photocoagulation and photodynamic therapy (PDT) with verteporfin
for retinal angiomatous proliferation (RAP) in age-related macular degeneration (AMD). [Article in German] Klin
Monbl Augenheilkd. 2008;225(5):392-396.
9. Krieglstein TR, Kampik A, Ulbig M. Intravitreal triamcinolone and laser photocoagulation for retinal angiomatousproliferation. Br J Ophthalmol. 2006;90(11):1357-1360.

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