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Bog.co.ukThe MC-500 Vixi laser is capable of any combination of red, green, and yellow wavelengths.
By EvangElia PaPavasilEiou, MD, FEBoPhth;anD soM PrasaD Ms, FrCsED, FrCoPhth, FaCs Pattern scanning lasers, first introduced in ophthal- mology during the previous decade, are designed to deliver single laser spots or multiple spots in preplanned array patterns to the retina for the treatment of a variety of pathologic conditions. These devices can save time for the clinician, streamline patient flow for the retina practice, and reduce discomfort from long laser sessions for the patient. A second-generation multi-wavelength laser photoco- agulator system, the MC-500 Vixi Multicolor Scan Laser Photocoagulator (Nidek Co. Ltd.) was introduced at last year’s American Society of Retina Specialists meet-ing in Boston. The laser received US Food and Drug Figure 1. The laser in clinical use. It is a compact unit with a Administration clearance in August 2011 and is now This pattern scan laser allows the practitioner to select photocoagulation. The 577 nm yellow laser is minimally from among 3 wavelengths: 532 nm green, 577 nm yel- absorbed by xanthophylls and well absorbed by oxygenated low, and 647 nm red, as well as combinations of any 2 or hemoglobin, making it the wavelength of choice for lesions all 3 wavelengths simultaneously. This capability enables close to the macula. Good results with dye lasers operating the user to select the necessary color or combination of at this wavelength have been reported.1 Krypton lasers pro- colors to increase efficiency of treatment for a specific ducing the 647 nm red wavelength have historically been indication. We have had the opportunity to use this used for photocoagulation of deep choroidal pathology.
new laser for all forms of retinal treatments for several The combination of the three wavelengths in one months, and we report our initial experience here.
versatile machine with a small footprint (Figure 1) allows the clinician to provide therapy options appropriate for the patient’s pathology. The laser also allows the use of The Vixi is the only pattern scan laser that allows these multiple wavelengths in a variety of grid patterns. selection of multiple wavelengths. The most commonly The MC-500 Vixi includes eight preprogrammed scan employed wavelength in vitreoretinal practice is 532 nm patterns with a memory function for up to 14 patterns green, used for treating retinal pathologies with panretinal (Figure 2). The available patterns include a single spot, Figure 3. All laser parameters can be rapidly adjusted from Figure 2. Various preprogrammed scan patterns are available the touch screen console.
from the touch-screen control unit.
agulation with a selection of colors and scan patterns. Laser squares (from 2-by-2 to 5-by-5 spots), a circle, arcs (of output can be limited to a single wavelength or modulated one-quarter, one-half, or three-quarters of a circle), a to a combination of colors for specific treatments. It is triple arc, a macular grid, a triangle, a line, and a curve. intended to be used in ophthalmic surgical procedures, The macular grid pattern can be used, for example, for including retinal and macular photocoagulation, iridotomy, treatment of the periphery of the macula in quadrants, and, for our glaucoma colleagues, trabeculoplasty. with a fixed inner diameter and spot sizes ranging from The chorioretinal damage and therapeutic effects of dif- 100 to 200 µm. The pattern can also be rotated in incre- ferent laser wavelengths are similar, but each wavelength ments of 15° using an LCD touch screen (Figure 3). The has unique absorption and transmission characteristics 4 most frequently used scan patterns can be saved and that makes it desirable for a particular option. The MC-500 Vixi enables efficient photocoagulation even through The scan spot size is continuously variable from 50 to opaque media. In eyes with cataract, better penetration 500 µm in single mode and from 100 to 500 µm in scan is achieved with the yellow wavelength compared with and automanipulation mode. The actual spot size on the green. In eyes with retinal hemorrhage, better penetration retina changes depending on the laser contact lens used. is achieved with the red wavelength. In case of accidental Spot spacing can be adjusted with the touch screen. For hemorrhage during treatment, the clinician can switch rap- grid photocoagulation, we prefer 2-spot spacing, while for idly to the red wavelength to cauterize the bleeding vessel.
panretinal laser we prefer 1-spot spacing. Continuously Nagpal and colleagues2 reported that pattern scan laser variable size adjustment enables the surgeon to compen- treatment was less time-consuming and less painful for sate for changes due to laser contact lens selection. the patient compared with single-spot 532-nm solid-state The single-spot mode is used in conventional laser green laser. Also, pattern scan laser showed less collateral treatments, and the automanipulation mode can be damage and similar regression of retinopathy compared used to deliver repeated laser emissions with variable with a single-spot 532-nm solid-state green laser. internal times and conventional coagulation settings in For laser eye surgery near the macula, 577 nm yellow is a selectable scan pattern. The automanipulation mode the color of choice. Hemoglobin absorbs yellow light more allows the surgeon to continue laser emission while than other colors, and 577-nm lasers are more effective confirming spot placement. The scan mode is used for than any other wavelength for sealing abnormal blood ves- repeated laser emission with a fixed interval time, high sels 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 choroidal vessel), reducing the risk of hemorrhage. Joondeph and col- In our experience, this laser saves time by requiring fewer leagues3 used 577 nm yellow to treat retinal macro-aneu- sessions, consumes less energy, and provides more versatil- rysms and reported resolution of hemorrhage, exudates, ity than conventional models. It allows us to employ rapid and optimally powered laser emission for laser photoco- Clinical trials have shown that 577 nm yellow is less destructive than green, reducing temperature elevation slit lamps, transforming them into a stage for scanning but still achieving therapeutic goals and preserving visual laser treatments. It can also be provided in combination sensitivity as measured by microperimetry. No controlled with YAG laser and an indirect ophthalmoscope. All clinical trials have demonstrated the clinical advantage of units incorporate the Safety Optics with Low Impact on 1 laser wavelength over another in conventional supra- Cornea (SOLIC) optical design, which ensures low energy threshold retinal photocoagulation, but dye lasers have density on the cornea and lens even with large spot sizes.
been used to exploit the 577 nm yellow peak of oxyhe- The color LCD touch screen has an intuitive menu moglobin to improve the comfort and convenience of clearly indicating scan patterns and photocoagulation standard clinical retinal photocoagulation. Yellow 577 nm data. Ten sets of photocoagulation data (including color, laser light provides excellent lesion visibility, low amounts power output, emission time, and interval time) applied of intraocular light scattering and patient pain, and high to various clinical cases can be registered, and this can choriocapillaris absorption for more uniform effects in be helpful especially for repeated treatments and for patients with light or irregular fundus pigmentation. patients participating in clinical trials. The laser also has Studies have found that differences in efficacy of the a convenient power foot switch and is available with resorption of hard exudates, visual outcomes, and resolu- both front and rear dual ports for improved cable man- tion of focal diabetic macular edema between different agement. This solid-state laser provides longevity, space types of laser were not statistically significant, but green saving, and reduction of power consumption by 60% laser can lead to submacular fibrosis or choroidal neovas- Krypton 647 nm red lasers are typically used for treat- ment of deeper choroidal leakage and have less tissue pene- The MC-500 Vixi is an extremely flexible and user-friend- tration. This wavelength can be used in retinal vascular pro- ly technology. Although we have 3 different laser delivery liferative diseases and chorioretinal diseases associated with systems in our retinal treatment clinic suite, this is the laser exudative manifestations.4,5 The 647 nm red krypton laser we now use for most of our cases because of its ease of use, light is not absorbed by the hemoglobin in the retinal hem- the ability to change wavelengths on the fly, and the versa- orrhage or by the macular luteal pigment xanthophyll, and tile patterns that can be adjusted intuitively. n it is transmitted into the choroid, allowing treatment within the macular zone with less damage to the internal retinal Evangelia Papavasileiou, MD, FEBOphth, is a elements than would be seen with other wavelengths.6 Vitreoretinal Fellow with the Wirral University Teaching In cases of subretinal neovascular membrane, therefore, Hospital NHS Foundation Trust, United Kingdom. She krypton red can be the treatment of choice. Feeder ves- reports no financial relationships relevant to this article. sel photocoagulation with krypton red laser may also be Som Prasad, MS, FRCSEd, FRCOphth, FACS, is considered as a treatment option for subfoveal choroi- a Consultant Ophthalmologist with the Wirral dal neovascularization (CNV) secondary to age-related University Teaching Hospital NHS Foundation macular degeneration (AMD).7 Moreover, in cases of Trust, United Kingdom. He is a consultant for retinal angiomatous proliferation (RAP) stage 3, which Bausch + Lomb, Bayer, and Nidek, and has also includes CNV as well as retinal choroidal anastomosis, received travel reimbursements and/or advisory board krypton laser could be the potential treatment of choice.8 fees from Alcon, Novartis and Allergan. Dr. Prasad can be In this subtype of neovascular AMD with particularly reached via email at email@example.com. bad prognosis, this treatment could lead to anatomical closure of the vascular complex and eliminate the risk for 1. Gupta V, Gupta A, Kaur R, Narang S, Dogra MR. Efficacy of various laser wavelengths in the treatment of clinically significant macular edema in diabetics. Ophthalmic Surg Lasers. 2001;32(5):397-405.
development of tears in the retinal pigment epithelium.9 2. Nagpal M, Marlecha S, Nagpal K. Comparison of laser photocoagulation for diabetic retinopathy using 532-nm However, it may have the disadvantage of requiring more 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. retreatments compared with 532 nm green.
With the Vixi we can start treatment with 1 color and 4. Khairallah M, Brahim R, Allagui M, Chachia N. Comparative effects of argon green and krypton red laser photoco-agulation for patients with diabetic exudative maculopathy. Br J Ophthalmol. 1996;80(4):319-322.
continue it with another. The laser is flexible enough to 5. Olk RJ. Argon green (514 nm) versus krypton red (647 nm) modified grid laser photocoagulation for diffuse be used in almost all clinical cases. The automanipulation 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.
and scan modes allow mode selection appropriate for 7. Shiraga F, Ojima Y, Matsuo T, Takasu I, Matsuo N. Feeder vessel photocoagulation of subfoveal choroidal neovas- cularization 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 In addition to conventional single spot delivery, the for retinal angiomatous proliferation (RAP) in age-related macular degeneration (AMD). [Article in German] Klin scan capability allows a wide range of multicolor laser Monbl Augenheilkd. 2008;225(5):392-396.
9. Krieglstein TR, Kampik A, Ulbig M. Intravitreal triamcinolone and laser photocoagulation for retinal angiomatous pattern deliveries. The laser can be used with existing proliferation. Br J Ophthalmol. 2006;90(11):1357-1360.
Debate over exposing chemical risks Industry cites terror fears; environmentalists want word out By Ann Davis THE WALL STREET JOURNAL SOUTH KEARNY, N.J., May 30 C In the next two months, Greenpeace plans to post on the Internet a color map showing how a terrorist attack on the Kuehne Chemical Co. bleach plant here could unleash a lethal cloud of chlorine vapor over New York City. NOT