Vitrectomy: Development And Steps
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This document provides an overview of vitrectomy, including a brief history, the key steps in a simple vitrectomy procedure, and descriptions of the equipment used. It discusses trocars and cannulas, sclerotomies, illumination sources, viewing systems, vitreous cutters, and vitreous removal. Advantages of smaller gauge vitrectomy instruments are also summarized.
Vitrectomy: Development And Steps
- 1. Vitrectomy: Development and Steps Dr Samarth Mishra Moderator: Dr Kumar Saurabh
- 2. Brief history of vitrectomy Steps for simple vitrectomy Trocars and cannula Sclerotomy Illumination source Viewing systems Cutters Vitreous removal Closure of ports
- 3. "can we touch the vitreous and go unpunished" ?? • Such was the vitreous sanctity in 1960s and early 1970s • David Kasner, through cornea removed opaque vitreous with primary amyloidosis ( 2 patients ) • He developed open sky vitreous surgery technique • Machemer introduced pars plana vitrectomy (PPV) in 1971. • Vitreous infusion suction cutter(VISC), 17-gauge (1.42mm diameter)
- 4. Experiment to remove the egg white by a rotating drill inserted into a tube. Machemer: working in garage could remove egg albumin through a small opening in the egg shell
- 5. 3 port Vitrectomy • Connor O'Malley, 1972: Proposed three port vitrectomy • 1990: De Juan; 25G instrumentation for use in paediatric eyes • Peyman : 23G vitrectomy probe, primarily intended for vitreous and retinal biopsies • 2002, Fujii et al introduced 25G transconjunctival vitrectomy system using microtrocars and cannulas • Eckardt in cooperation with DORC (The Netherlands),2005, developed 23G vitrectomy instrumentation as an alternative to 25G system • 23G combines considerably higher stiffness and stability than 25G • 2010: 27G sutureless vitrectomy system by Oshima
- 6. Advantage of small G vitrectomy instruments : • Less surgical trauma • Self-sealing and sutureless • More efficient with reduced operating times • Decreased corneal astigmatism • Faster postoperative recovery and increased patient comfort • Reduced conjunctival scarring, conjunctival preservation in patients with prior/ pending glaucoma surgery • Suited to the narrower spaces of paediatric eyes References: Textbook of vitreous microsurgery (5th ed), Peyman, Textbook of Ryan’s retina (6th ed) , Principle and practice of vitreoretinal surgery
- 7. Disadvantage: • Reducing the instrument diameter reduced the infusion and aspiration rates obtained • Hagen-Poiseuille’s Law : The volume flow rate along a pipe is directly proportional to the fourth power of the pipe’s radius. • Affects the functionality and efficiency Vitreous microsurgery; 22 SECTION II ■ Surgical Technology and Techniques
- 8. Simple vitrectomy • Basic requirements : • Vitrectomy machine • Light source • An air pump • Operating microscope • Lens viewing system
- 9. SET UP Positioning of the patient • The first critical step • Eye should be in primary position. • Small shoulder roll under the patient facilitates slight extension of the neck doughnut-shaped rubber ring (‘tennikoit’ ring) • Surgeon rests the wrists on the support frame around the patients head throughout the operation
- 10. • Level of support is just above the patient’s ears • Eye should be cleaned with povidone-iodine (5%) and draped as for any surgery. • The sterile adhesive drape used to cover the patient is pushed down into the space between the patient’s head and the hand support. • This forms a trough to collect fluid that could otherwise spill onto the floor.
- 11. Surgical preparation of the eye • 20G vitrectomy system requires a conjunctival incision performed at the limbus, both nasal and temporal • Nasal incision extends from the horizontal approximately 1.5-2 clock-hours superiorly • Temporal incision usually extends for 4 clock-hours • If a sew-in contact lens system is used, a suture is placed at the 3 and 9 o'clock positions at the limbus. • 4-0 silk/ Mersilene suture is used. References: Textbook of vitreous microsurgery (5th ed), Peyman, Textbook of Ryan’s retina (6th ed) , Principle and practice of vitreoretinal surgery
- 12. Trocar/Cannula System • The outer diameter of vitrectomy instruments is given in “Gauge”. • Higher the gauge number, the smaller the outer diameter of an instrument. • The trocar/cannula system theoretically creates less traction on the vitreous base during instrument entry and exit. • Cannulas maintain the alignment between the conjunctiva and sclera. • Less traumatic to wound borders (than the repeated insertion and withdrawal of instruments) • 20G: 0.89mm • 23G: 0.64mm • 25G :0.51mm • 27G: 0.4mm Source: Alcon laboratories
- 13. Cannula systems • Valved and non-valved cannulas • Open sclerotomies can cause vitreous incarceration and subsequent drag when instruments are reintroduced. • In bullous retinal detachment, the retina can be pushed into the sclerotomy by the fluid egressing through the open sclerotomy. • Seen as a grey membrane in the sclerotomy wound References: Textbook of vitreous microsurgery (5th ed), Peyman, Textbook of Ryan’s retina (6th ed) , Principle and practice of vitreoretinal surgery
- 14. Sclerotomy • 20-gauge vitrectomy requires limited peritomy • Incisions are made with a 20G MVR blade perpendicular to sclera and aimed towards center of vitreous cavity to avoid damaging lens and retina • In higher gauge, the conjunctiva above the sclerotomy is typically displaced and in • Aphakic 3.0 mm from limbus • Pseudophakic and phakic: 3.5 - 4.0 mm • It is anterior to the ora serrata to prevent a retinal tear and posterior to the vascularized pars plicata to avoid hemorrhage References: Textbook of vitreous microsurgery (5th ed), Peyman, Textbook of Ryan’s retina (6th ed) , Principle and practice of vitreoretinal surgery
- 15. • ZORRO’S INCISION : Blade is inserted at an angle of 10 to 15 ° and enters vitreous without straightening • POLLACK: Suggested a biplanar incision, where the trocar is inserted at an angle of 5° to the sclera until 50% depth, and then raised to an angle of 30° to sclera • All blades used for incisions must be sharp, so that when introduced into the eye, they do not push or drag pars plana epithelium or vitreous base ahead of them, causing a retinal tear or dialysis, • Sclerotomies should ideally be ~160 degrees apart to facilitate manipulation in the vitreous cavity References: Textbook of vitreous microsurgery (5th ed), Peyman, Textbook of Ryan’s retina (6th ed) , Principle and practice of vitreoretinal surgery
- 16. Video • The first incision is for the infusion cannula(ITQ), just inferior to the lateral rectus • If the cannula is placed too far inferiorly, it presses against the lid speculum • In 20G , 7-0 vicryl mattress suture, which secures the base flanges of the infusion cannula, is placed before entering the eye References: Textbook of vitreous microsurgery (5th ed), Peyman, Textbook of Ryan’s retina (6th ed) , Principle and practice of vitreoretinal surgery
- 17. Illumination source • To illuminate the material being removed • Employs yellow light but may use white light • A fibreoptic cable encased in a plastic handpiece connected to the vitrectomy light source • Intensity of light pipe should be set at the minimum that allows visualization • Minimises the risk of phototoxicity • Should be placed as far to the retina as possible to reduce the intensity of the light at the retinal surface References: Textbook of vitreous microsurgery (5th ed), Peyman, Textbook of Ryan’s retina (6th ed) , Principle and practice of vitreoretinal surgery
- 18. • Light probe is held just inside the sclerotomy for a wider area • The farther into the eye the endoilluminator is held , the smaller is its cone of illumination • Light pipe positioned to point towards tip of vitreous cutter such that the light illuminates the tip and the material ahead of it.
- 19. Fixed (chandelier/ torpedo) illumination • Inserted at the pars plana and fixed to the sclera • Torpedo minilight (Insight Instruments, Stuart, Florida, USA), the Awh 25-gauge chandelier (Synergetics, Inc, St Charles, Missouri, USA) and the Twinlight (DORC Zuidland, The Netherlands). 29/30G Dual chandeliers Sakaguchi, Hirokazu, et al. "A 29/30-gauge dual-chandelier illumination system for panoramic viewing during microincision vitrectomy surgery." Retina 31.6 (2011): 1231-1233.
- 20. Infusion cannula • ITQ • Used to deliver the BSS into the vitreous cavity. • The cannula is usually 2, 4, or 6 mm in length • Standard pars plana vitrectomy will employ a 4 mm infusion cannula. References: Textbook of vitreous microsurgery (5th ed), Peyman, Textbook of Ryan’s retina (6th ed) , Principle and practice of vitreoretinal surgery
- 21. • Longer infusion cannula preferred in: • Aphakic / pseudophakic patients/ • Patients with high myopia/ • Peripheral retinal elevations (such as choroidal detachments) • Reduces the risk of the cannula entering the subretinal space • A 2-mm cannula is employed to reduce the risk of lens damage. Taken from : https://www.retinalphysician.com/issues/2011/september-2011/surgical-precision References: Textbook of vitreous microsurgery (5th ed), Peyman, Textbook of Ryan’s retina (6th ed) , Principle and practice of vitreoretinal surgery
- 22. • Infusion cannula is placed through a sclerotomy ITQ • MVR blade is kept perpendicular to the sclera and aimed towards the midvitreous cavity • Reduces the risk of hitting the lens or damaging the retina . • MVR blade is visualized directly in the vitreous as it passes through the pars plana. • The 6-0 Vicryl suture can be left in place following removal the infusion cannula at the conclusion of surgery • Some prefer to use a 6-0 nylon or Mersilene suture, which is cut at the conclusion of the surgical case and then replaced with a 6-0 Vicryl suture following removal of the infusion cannula.
- 23. • Slip knot can be used so that the knot can be loosened and the infusion cannula removed at the conclusion of the procedure without replacing the suture • Visualize the position of cannula in the vitreous cavity before turning on the infusion. • Grasp the infusion cannula with smooth forceps and gently push the cannula toward the central vitreous caviry while tilting the eye toward the cannula itself • Light pipe is used to see of the infusion tip References: Textbook of vitreous microsurgery (5th ed), Peyman, Textbook of Ryan’s retina (6th ed) , Principle and practice of vitreoretinal surgery
- 24. • If tip not visualized, the indirect ophthalmoscope can be tried In cases of opaque media or where the infusion cannula tip is not visualized: • Initial vitrectomy is commenced with infusion line connected to a hand-held infusion needle (20-gauge bent cannula/ bent butterfly needle) whose tip can be seen, until the media is clear enough to see the cannula • Infusion needle is held in the non-dominant hand through a superior sclerotomy • In a choroidal detachment, initial infusion can be provided through a 22-gauge needle and the detachment drained prior to fixing the infusion cannula. References: Textbook of vitreous microsurgery (5th ed), Peyman, Textbook of Ryan’s retina (6th ed) , Principle and practice of vitreoretinal surgery
- 25. If choroidal tissue is noted completely/ partially covering the infusion cannula tip after fixing: • The infusion is withheld and this tissue is cleared with an MVR knife prior to starting the fluid. • After the infusion is turned on, incisions are made in SNQ and STQ for the vitrectomy instrument and fiberoptic endoilluminator probe
- 26. Viewing system • Employs a neutralising lens • Most commonly used is handheld contact lens attached to an irrigating handpiece ( held on the cornea by the assistant ) • Sew-on contact lens : Held in place by sutures sewn at the limbus ❖ Disadvantage: blood may migrate under it and reduce visualization • BSS / viscoelastic solution couples the lenses to cornea • Lenses of various strengths and configurations allow viewing of the macula or with the aid of prism lenses the retinal periphery • High minus lenses (Biconcave lenses ) are used for Air – Fluid exchage Macular Lens References: Textbook of vitreous microsurgery (5th ed), Peyman, Textbook of Ryan’s retina (6th ed) , Principle and practice of vitreoretinal surgery
- 27. Vitreous cutter • Allows high-speed cutting of formed vitreous and controlled removal of the vitreous gel with low suction • Electrical: Use electric energy to drive the motor, heavier • Pneumatic:Utilize pressurized air pulses to drive the diaphragm and inner tube forward, light weight A) Guillotine-type mechanism, which in most cases is driven pneumatically by the vitrectomy machine B) Rotatory cutters the inner tube rotates within the outer tube to cut the vitreous. C) Oscillatory cutters are similar to rotatory type, but the rotation is not 360°. They rotate 180° to one side to cut the vitreous and again 180° to other side again
- 28. ` • Most currently available vitreous cutters feature a side-cutting port with the guillotine action in the vertical plane • Some newer vitreous cutters have side-cutting port closer to the tip of the steel and use horizontal cutting mechanism. • Cut rates on older systems go upto 1,500cpm. • Current vitreous cutters are capable of delivering cut rates of up to 16,000 cpm.
- 29. • The vitreous cutter is connected to the vitrectomy machine through two lines. • First goes from the cutter to the cutting drive on the machine • This line plugs into the vitrectomy machine at the port labeled 'cutter'. • The second line is the aspiration line from the vitreous cutter to the vitrectomy machine • Priming mode allows to prime the cutter before its use • Higher the cut rate, the smaller the amount of vitreous (“bite size”) aspirated into the cutter, reducing both vitreous and retinal traction
- 30. Vitrectomy machine Infusion system allows control of intraocular pressure (lOP) during surgery • A) Gravity fed system • Rely on gravity (The height of the bottle) • Bottle is positioned ~18 inches above the eye level to maintain normal lOP • B) Gas forced infusion • BSS is attached to an air pump that regulates the pressure • Forces BSS into the eye through infusion tubing. • Usually set at a pressure of 20-30 mm of Hg
- 31. Vitrectomy Systems Use Two Types of Pumps: A) Flow rate control (Peristaltic pumps) • keeps fluid turnover in the eye exactly at the rate controlled by the pedal • Vacuum adjusts itself to the lowest level required B) Vacuum control (Venturi pumps) • keeps the suction vacuum of the pump exactly at the level controlled by the pedal • fluid turnover depends on vacuum, size of aspiration path and condition of material being aspirated. References: Textbook of vitreous microsurgery (5th ed), Peyman, Textbook of Ryan’s retina (6th ed) , Principle and practice of vitreoretinal surgery
- 32. Vitreous removal • Bimanual technique. • Instruments should be held lightly with the surgeon’s fingertips. • Light probe positioned to point toward the tip of the vitreous cutter • Cutting port of the vitrector should face the vitreous to be cut, so as to reduce vitreous traction and aid visualization. • Ports are cleared first proceeding furthur to core vitrectomy • Initial goal is to remove vitreous near the sclerotomy sites to make subsequent intravitreal manipulation safer and to clear the axial media to improve visualization for ensuing surgery
- 33. • Instruments is held steady in the vitreous cavity • Moved only systematically and purposefully to the minimal extent required • Vitreous is allowed to come to the vitreous cutter. • When the vitreous appears to cease migrating toward the vitreous cutter, the cutter is advanced further posteriorly in the central vitreous cavity to engage any remaining posterior vitreous. • Excessive wandering movements can lead to vitreous traction and peripheral retinal breaks
- 34. • Vitrectomy proceeds in an anteroposterior fashion. • If there are media opacities, they should be removed from the central vitreous. • Any reflection of the light off the cutter can be minimized by changing the angle of illumination from the fiberoptic source. References: Textbook of vitreous microsurgery (5th ed), Peyman, Textbook of Ryan’s retina (6th ed) , Principle and practice of vitreoretinal surgery
- 35. • After anterior and central core of the vitreous are sufficiently removed, the posterior hyaloid status is noted. • If there is a CPVD: Opening is created in the posterior hyaloid at one side and this is followed out to the periphery and circumferentially • In partial PVD; a complete PVD should be induced from the disc outward, over attached retina and away from the macula. References: Textbook of vitreous microsurgery (5th ed), Peyman, Textbook of Ryan’s retina (6th ed) , Principle and practice of vitreoretinal surgery
- 36. Truncation of cone • After removal of the anterior vitreous cortex, the second objective is removal of the posterior vitreous cortex • Eyes requiring vitrectomy usually have total vitreoretinal contact/ partial PVD with conical vitreous configuration, or total PVD with frontal plane configuration. Entry is made nasally • The portions of posterior cortex extending between areas of vitreoretinal adherence are known as bridging • Here tangential traction occurs • Both the conical surface and the bridging portions, must be removed to relieve traction
- 37. Removal of the adherent posterior hyaloid • The posterior hyaloid is attached to the optic nerve, the retinal vessels, over the macula, and to areas of old retinal scarring • Extreme caution is necessary when removing the posterior hyaloid. • Any undue traction on the hyaloid will be transmitted to the vitreous base and can result in retinal tears or detachment. • Anteroposterior pulling has to be avoided as it can cause retinal tears. • The posterior hyaloid is typically engaged in the peripapillary region, where the potential for damage to the retina is least. References: Textbook of vitreous microsurgery (5th ed), Peyman, Textbook of Ryan’s retina (6th ed) , Principle and practice of vitreoretinal surgery
- 38. Video
- 39. • A soft-tipped extrusion cannula with active suction used for this • A silicone-tipped cannula cut to approximately 3 mm is attached to suction through the aspiration line of the vitrectomy machine and is brought to the peripapillary region • May use vitreous cutter on low aspiration to engage the posterior hyaloid. • Barbed MVR blade or other pick may also be used. References: Textbook of vitreous microsurgery (5th ed), Peyman, Textbook of Ryan’s retina (6th ed) , Principle and practice of vitreoretinal surgery
- 40. How to confirm the engagement of the posterior hyaloid— • 1.) The infusion line will stop dripping. No fluid will be seen to enter the eye and the BSS bottle will not drip • 2. ) ‘Fish-strike' sign : Bending of the soft tipped cannula as it is moved to and fro over the retinal surface. • When the posterior hyaloid is completely detached: Weiss ring will be present in the central vitreous cavity. • Undue traction to the elevated hyaloid is avoided, because this may increase the risk of peripheral retinal tears References: Textbook of vitreous microsurgery (5th ed), Peyman, Textbook of Ryan’s retina (6th ed) , Principle and practice of vitreoretinal surgery
- 41. • The posterior hyaloid should be removed from posterior to anterior using the vitreous cutter. • The peripheral vitrectomy should proceed toward the vitreous base, with or without scleral depression, depending on the underlying pathologic condition. • Triamcinolone acetonide staining helps to visualize the posterior cortex Taken from: Retinal Reattachment: General Surgical Principles and Techniques
- 42. Shaving and trimming of the vitreous base • Scleral depression with a cotton-tipped applicator or scleral indentors • Done by the assistant • Easiest and safest at the crest of the indentation mound where it is visible • Attention should be paid to the infusion tip intermittently. References: Textbook of vitreous microsurgery (5th ed), Peyman, Textbook of Ryan’s retina (6th ed) , Principle and practice of vitreoretinal surgery
- 43. • Inadvertent displacement of the infusion from depression can cause complications • It is important for assistant to reduce the amount of depression as the suction increases, • This is because of the propensity of the peripheral retina to collapse toward the vitreous cutter as the eye becomes soft. • Vitrector suction should be reduced in the periphery to avoid retinal pull and inadvertent breaks. • High cut rates of 2,500–5,000 cpm are safer for trimming the peripheral vitreous
- 44. Closure of sclerotomy ports • Superonasal and superotemporal sclerotomies are closed first • For 20G or leaking ports, 7-0 Vicryl suture used. • Permanent closure with nylon/ Mersilene suture can be done. • Infusion to be clamped temporarily while the sclerotomies are being sutured. • The infusion cannula is then removed from its sclerotomy and the preplaced 6-0 Vicryl suture is pulled up and tied down tight • If a temporary suture was not used, the infusion cannula should be removed and a suture placed in the sclerotomy to ensure permanent closure. • 25-gauge vitrectomy, a transconjunctival self-retaining cannula system, creates self- sealing incisions for vitreoretinal surgery. References: Textbook of vitreous microsurgery (5th ed), Peyman, Textbook of Ryan’s retina (6th ed) , Principle and practice of vitreoretinal surgery
- 45. Hypersonic Vitrectomy (VITESSE ) (B+L) • Ultrasound-based • 27 kHz to 31 kHz • 100% open 100% of the time • Liquefies tissue in a highly-localized zone at the edge of the port • Rather than being cut, the vitreous is reduced to the viscosity of water and aspirated, using much lower energy with greater efficiency • Causes less traction and turbulence Source: Bausch + Lomb Surgical , St Louis, MO
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