Ординатура / Офтальмология / Английские материалы / Retinal and Vitreoretinal Diseases and Surgery_Boyd, Cortez, Sabates_2010

161.Jennings PE, Chirico S, Jones AF, Lunec J, Barnett AH. Vitamin C metabolites and microangiopathy in diabetes mellitus. Diabetes Res 1987;6:151-4.

162.Pecoraro RE, Chen MS. Ascorbic acid metabolism in diabetes mellitus. Ann N Y Acad Sci 1987;498:24858.

163.Bursell SE, Clermont AC, Aiello LP, et al. Highdose vitamin E supplementation normalizes retinal blood flow and creatinine clearance in patients with type 1 diabetes. Diabetes Care 1999;22:1245-51.

164.Anderson RA, Roussel AM, Zouari N, Mahjoub S, Matheau JM, Kerkeni A. Potential antioxidant effects of zinc and chromium supplementation in people with type 2 diabetes mellitus. J Am Coll Nutr 2001;20:212-8.

165.Roussel AM, Kerkeni A, Zouari N, Mahjoub S, Matheau JM, Anderson RA. Antioxidant effects of zinc supplementation in Tunisians with type 2 diabetes mellitus. J Am Coll Nutr 2003; 22:316-21.

166.Cheng HH, Lai MH, Hou WC, Huang CL. Antioxidant effects of chromium supplementation with type 2 diabetes mellitus and euglycemic subjects. J Agric Food Chem 2004;52:1385-9.

167.Vine AK. Hyperhomocysteinemia: a risk factor for central retinal vein occlusion. Am J Ophthalmol 2000;129:640-4.

168.Pianka P, Almog Y, Man O, Goldstein M, Sela BA, Loewenstein A. Hyperhomocystinemia in patients with nonarteritic anterior ischemic optic neuropathy, central retinal artery occlusion, and central retinal vein occlusion. Ophthalmology 2000;107:1588-92.

169.Abu El-Asrar AM, Abdel Gader AG, Al-Amro SA, Al-Attas OS. Hyperhomocysteinemia and retinal vascular occlusive disease. Eur J Ophthalmol 2002;12:495-500.

170.Lahey JM, Kearney JJ, Tunc M. Hypercoagulable states and central retinal vein occlusion. Curr Opin Pulm Med 2003;9:385-92.

171.Cahill M, Karabatzaki M, Meleady R, et al. Raised plasma homocysteine as a risk factor for retinal vascular occlusive disease. Br J Ophthalmol 2000;84:154-7.

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172.Cahill MT, Stinnett SS, Fekrat S. Meta-analysis of plasma homocysteine, serum folate, serum vitamin B(12), and thermolabile MTHFR genotype as risk factors for retinal vascular occlusive disease. Am J Ophthalmol 2003;136:1136-50.

173.Sottilotta G, Oriana V, Latella C, et al. Role of hyperhomocystinemia in retinal vascular occlusive disease. Clin Appl Thromb Hemost 2007;13:104-7.

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During the last century, ophthalmology has been exploring new horizons both in the diagnosis and treatment of different pathologies, particularly in vitreoretinal surgery. These advances have been achieved mostly due to a better understanding of the various diseases as well as to the technological upgrades in the instruments utilized for vitreoretinal surgery.

Small Incision Vitrectomy

Surgery

In recent years, vitrectomy surgery has seen major advancements in technology, quality and safety. The advent of the 25 gauge vitrectomy has enabled both surgical outcomes and shorter, more comfortable recovery for patients.

Microincision vitrectomy surgery (MIVS) is one of the most significant innovations in vitreous surgery since posterior vitrectomy was developed by Robert Machemer, MD, in the 1970. MIVS is defined as a combination of 25or 23-gauge instrumentation and a transconjunctival sutureless procedure. The indication of MIVS was limited to macular surgery for several years after its introduction because of several disadvantages, including flexible instruments, lower aspiration rate, and insufficient illumination. The stiffness of instruments, cutting rates, and aspiration rates have been improved and the introduction of brighter light sources, such as xenon lamps, has improved illumination. As a result of these improvements, the indications for MIVS have expanded to include complicated cases with proliferative diabetic retinopathy and PVR (Figure 1).

Improvements to instrumentation and illumination have also influenced surgical techniques. A small-gauge vitreous cutter on which the port is positioned closer to the tip allows for epiretinal membrane delamination.

Microincision vitrectomy surgery (MIVS) with 25or 23-gauge instrumentation is undoubtedly one of the most impressive evolutions in the surgical retina field of the past three decades.1,2 Similar to the trend toward minimally invasive intervention in phacoemulsification for cataract surgery, smaller incisions in vitrectomy without peritomy and suturing have the potential to facilitate early visual recovery, diminish ocular surface irregularities, and decrease patient discomfort,

operating time, postoperative inflammation, andsurgically-inducedastigmatism.Therefore, MIVS is also known as “minimally-inva- sive” vitrectomy surgery. In contrast to the above-described benefits of MIVS, however, wound-sealing–related complications, such as hypotony, choroidal detachment, and a higher incidence of endophthalmitis, are major concerns of small-gauge vitreous surgery.

The transconjunctival 25-gauge system is anotherwell-employedMIVSsystem.Although reduced illumination and cutting efficiency were concerns with 25gauge early on, brighter light sources, such as xenon (Accurus High Brightness Illuminator,Alcon Laboratories Inc., Fort Worth, TX;) and the Constellation Vision System have addressed these concerns.

The 25-gauge vitreous cutter on the Accurus (Alcon Laboratories, Inc.) is highly efficient and is capable of 2,500 cpm. The high cutting rate and a port closer to the tip of the cutter have allowed surgeons to use 23/25-gauge for more challenging cases such as diabetic traction retinal detachments.3,4 During diabetic vitrectomy, a smaller gauge

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vitreous cutter can conformal cutter delamination and foldback delamination of epiretinal membranes (Figure 2). Recent improvements in this equipments and the creation of stiffer instruments via shortening the shaft length and increased availability of accessories, will further expand the surgical indications of 23/25-gauge MIVS in many countries.

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Alcon Constellation Vision

System

The Constellation is the culmination of over three decades of evolutionary development of vitreous cutters and fluidics, new and improved tools, xenon illumination sources, phaco technology, new laser technology, systems integration, efficiency systems, and advanced user interface design. The author is the principle architect of the Alcon Constellation Vision System (Figure 3).

The VISC and RotoExtractor were single port, large incision, so-called full function, slow speed, rotary, electric cutters with as-

piration provided by a syringe operated by the assistant. The Berkley Bioengineering Ocutome 800, developed by Conor O’Malley, MD and Ralph Heinz was the first three-port, 20-gauge (0.89mm) system and had the first lightweight, pneumatic probe and surgeon foot pedal to control on-off aspiration; a major advance. Berkley Bioengineering subsequently was acquired by Coopervision and Coopervision was later acquired by Alcon Laboratories. The Coopervision Ocutome 8000, developed by Carl Wang, his engineering team, and myself, had the first linear suction (now used on all vitrectomy and phaco machines), an integrated light source, and a connected fragmenter. The MidLabs MVS system, developed by Carl Wang and I, had

the first disposable pneumatic cutter; a crucial improvement over reusable cutters with low performance cutting. After the original MidLabs was acquired by Alcon Laboratories I started InnoVision and began development of the OCM. The OCM had a dual actuation InnoVit cutter with limited angle rotary cutting at 1500 cuts/minute, linear diathermy, tool ID, an articulated arm with integrated tubing management, servo controlled IOP, a graphical user interface with soft keys, integrated xenon illuminator, integrated fragmenter, auto-gas mixing, auto fluid-air exchange valving, and power scissors. The InnoVision OCM technology was never commercialized

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and was later acquired by Alcon Laboratories and I became a consultant for Alcon. Many of the OCM concepts were improved upon and incorporated into the highly successful Accurus system which included an advanced graphical user interface with soft keys and global functions, VGFI (vented gas forced infusion), integrated fragmenter, silicone injector (VFC), and a halogen light source. 25-gauge and later 23-gauge tools were developed for the Accurus platform and are now in their third generation (Figure 4). A non-integrated EyeLite 532nm diode pumped laser and later a non-integrated xenon source were developed to use with the Accurus system.

The Constellation incorporates new, improved implementations of all the concepts incorporated in the OCM as well as the Accurus and adds many new capabilities. The vitreous cutter is the pivotal component of any vitreoretinal surgery system; the Constellation UltraVit cutter utilizes dual pneumatic actuation (no spring return axial cutter) like the InnoVit and currently operates at 5000 cuts/minute. Because it is diaphragm driven it eliminates the friction of the InnoVit piston, provides the familiar axial cutter format, and scales better to 23, 25 and even 27 gauge form factors. The cutter is driven using a proprietary variable duty cycle technology dependent on the dual actuation system. Variable duty cycle control enables use of a biased closed approach to produce increased port-based flow limiting when working in close proximity to the retina; so-called vitreous shaving. Alternatively, port-based flow limiting can be decreased by using a biased open approach enabling greater flow rates when doing core vitrectomy. The aspiration system has an low latency response time to a foot pedal command for vacuum decrease or increase because of a new, triple proportional valve aspiration system and cassette design. Sensor-based, fast response, digital flow control and flow limiting facilitate working safely near the retinal surface. The aspiration system provides continuous linear (proportional) reflux as well as micro-reflux for all aspiration tools enabled by routing the infusion system through the vacuum cassette.

The Constellation utilizes a real-time operating system and distributed processor architecture to ensure reliability as well as

2X faster response time than the Accurus. It has a switched Ethernet architecture with 42 printed circuit boards, a Pentium CPU, five microprocessors, many FPGAs, and uses over 600,000 lines of code. The electronics have power back up for situations such as the cord being pulled out or power failure in the OR to facilitate rapid resumption of surgery.

Integrated pressurized infusion using a two chamber system and servo control of the intraocular pressure (IOP) is unique to the Constellation and is especially valuable in high flow scenarios such as removal of dislocated dense lens fragments using the fragmenter with 23 or 25G infusion. IOP compensation is accomplished by sensing fluidic resistance in the infusion circuit during push priming by sensing flow and pressure. The infusion pressure is automatically increased as flow increases during surgery to control the IOP within +/- 2 mmHg. IOP compensation will reduce sudden IOP decrease and resultant bleeding after dense epiretinal membrane deforms through the cutter port. It is likely that IOP compensation will enable use of lower average infusion pressures. The infusion system has automatic bottle out warning and enables changing bottle with no interruption in fluid flow or bubbles.

The Constellation can be configured with one or two, dual port xenon illumination sources to facilitate use of illuminated tools, chandeliers, and Torpedoes. The new xenon illuminator design is more efficient and produces 2X longer, 400 hour lamp life. The author typically uses 12-16% intensity settings

because the efficient xenon source and fiber coupling technology. The xenon optical system produces greater than 25 lumens using 23G and 25G fibers at 200 hrs. Radio frequency identification (RFID) connectors on the illumination tools automatically adjust the initial xenon source intensity depending on specific tool characteristics: light throughput, typical working distance, and divergence angle. This set-point is 8-10 lumens which is the optimal light intensity for all tools in 20, 23, and 25G. The surgeon can increase Illumination, if needed, to the maximum FDA allowed output.

RFID in the tool connectors activates parameter and mode setup decreasing setup time as well as workload and training requirements for the circulator. RFID also activates a new time saving, push prime system for the vitreous cutter and any connected extrusion tools. A sterile articulated arm incorporating a tubing management system enables priming and testing of all infusion and aspiration components before the patient is anesthetized, prepped, and draped; significantly decreasing setup time and eliminating the need for a Mayo stand to support the tubing and surgical drape. Embedded wizards and digital instructional video facilitate faster setup especially when using less experienced personnel.

The Constellation is usually configured with an embedded PurePoint 532nm laser. The PurePoint laser is a novel, advanced, thin-disk 532 nm solid state laser. The thindisk laser engine reduces thermal lensing, which are changes in the index of refraction

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of the Nd Vanadate lasing medium as it heats up. The thin-disk design produces a more constant laser output especially with higher powers and firing rates because of thermal stability. The lithium triborate frequency upconversion crystal (1064 nm to 532 nm), thermal electric cooler, and all optomechanical components are solder mounted in a fixed, mechanically and thermally stable position. A separate foot pedal controls laser power and standby/ready/standby control with voice verification eliminating dependence on the circulator. The Constellation graphical user interface eliminates the need for a separate display and controls.

An Auto Infusion Valve replaces the stopcock used for fluid-air exchange eliminating delay while air travels through 84 inches of tubing and bubbles. The auto infusion valve can be controlled by the surgeon’s foot pedal or the scrub tech using the Constellation sterile graphical user interface.

Auto Gas Syringe Fill system enables filling the syringe from attached tanks of SF6 and C3F8 reduces gas wastage, ensures sterility, and eliminates the need for the circulator to assist the scrub tech. A software applet calculates how much air to add to the gas to produce the surgeon’s desired concentration of gas in air.

The VFC power silicone/perfluorocarbon liquid injector supports simultaneous aspiration and has RFID to automatically configure the Constellation mode.

Advanced phaco technology including Ozil torsional phaco is embedded in the Constellation to support both combined phacoemul- sification-vitrectomy (phaco-vit) procedures as well as phaco only procedures. The Constellation, digital, fast, non-pulsatile flow control is superior to conventional peristaltic pump technology for phaco procedures.

The Constellation has proportional control of new, higher frequency, 1.5 MHz, sinusoidal diathermy system producing 10 watts maximum. Higher frequency diathermy produces a more focused lesion possibly reducing retinal damage. Proportional control eliminates the need for the nurse or scrub technician to adjust the power and facilitates optimal intensity.

Power forceps with linear (proportional) control as well as power scissors with singlecut and multi-cut modes support disposable Alcon Grieshaber disposable DSP ILM and end-grasping forceps as well as vertical and curved scissors tips. Bimanual surgery (is supported by single pedal linear control of power forceps to grasp and stabilize epiretinal during the initial segment of pedal travel followed by control of the power scissors with further depression of the pedal.

Turnover time is greatly reduced because RFID on all tools initiates automated push-

prime, testing and setup. The articulated arm system enables sterile setup and testing prior to or in parallel with. RFID and a barcode reader identify all consumables without RFID generate consumable use data for a wireless printer or LAN based connection. Surgical parameters and steps, laser log, and consumable use reports are generated automatically and printed on wireless printer for inventory control, cost accounting, billing, analysis, or incorporation into an operative note.

In summary, the Alcon Constellation Vision System addresses all the needs of the vitreoretinal and cataract surgeon using the most advanced surgical and efficiency technologies.

References

1.Fujii GY, De Juan E Jr, Humayun MS, et al. A new 25-gauge instrument system for transconjunctival sutureless vitrectomy surgery. Ophthalmology. 2002;109:1807–1812.

2.Eckardt C. Transconjunctival sutureless 23-gauge vitrectomy. Retina. 2005;25:208–11.

3.Kadonosono K, Yamakawa T, Uchio E, et al. Fibrovascular membrane removal using a highperformance 25-gauge vitreous cutter. Retina. 2008.

4.Oshima Y, Shima C, Wakabayashi T, et al. Microincision vitrectomy surgery and intravitreal bevacizumab as a surgical adjunct to treat diabetic traction retinal detachment. Ophthalmology. 2009.