This document discusses microincision vitrectomy surgery (MIVS) using smaller gauge instruments for vitreoretinal surgery. It describes the historical development of vitrectomy from larger 20 gauge systems to newer 23, 25, and 27 gauge systems. Key aspects of MIVS instrumentation and techniques are summarized, including trocar/cannula systems, self-sealing wound construction, challenges with smaller gauges, and advances in vitrectomy machines and illumination systems to improve efficiency and safety with MIVS.

1. MICROINCISION
VITRECTOMY SURGERY
(MIVS)
Dr. Anurag Shandil

2. FINANCIAL DISCLOSURES - NIL

3. Small is BIG
Small is big in the world of ocular surgeries.
Anterior segment surgeons: phacoemulsification to phaconit
Posterior segment surgeons: regular vitrectomy to MIVS

4. Defined as 23, 25 or 27 gauge surgery using smaller probes &
using a transconjunctival scleral incision.
The IDEA
came from using 25-G needles
for transconjunctival, pars
plana intravitreal injections
that did not require
conjunctival dissection or
suturing of the sclerotomy.

5. Historically
• Kasner(1962) – Open sky approach
• Robert Machemer (1970 )
-introduced a 17-gauge vitreous
cutter (1.5mm diameter) that required
a 2.3mm scleral incision.
•
“Father of modern vitreous surgery”
Machemer R, Buettner H, Norton E, et al., Vitrectomy: a pars plana
approach, Trans Am Acad Ophthalmol Otolaryngol,
1971;75:813–20.

6. • Connor O’Malley(1975) – (conventional) 20-gauge
“bimanual” vitrectomy using 3 ports
• Eugene de Juan (1990)- invent the 25-gauge with
transconjunctival sutureless vitrectomy (TSV)
• Chen (1996)- self-sealing sutureless sclerotomy for the 20-
gauge
O’Malley C, Heintz RM, Vitrectomy with an alternative instrument system, Ann Ophthalmol, 1975;7:585–8,
591–4.
De Juan E, Machemer R, Charles St, et al., Surgery for stage 5 retinopathy of prematurity, Arch Ophthalmol,
1987;105:21.
Chen JC, Sutureless pars plana vitrectomy through selfsealing sclerotomies, Arch Ophthalmol, 1996;114:1273–
5.

7. • MIVS was introduced in (2002).
• In 2002, Fujii et al developed 25-gauge system and made
commercially available.
• Eckardt (2005)- 23-gauge system
• Oshima et al (2010)– 27-gauge system
Fujii GY, de Juan E, Humayun MS, et al., Initial experience using the transconjunctival sutureless vitrectomy
system for vitreoretinal surgery, Ophthalmology, 2002;109:1814–20.
Eckardt CM, Transconjunctival sutureless 23-gauge vitrectomy, Retina, 2005;25:208–11.
Oshima Y, Wakabayashi T, Sato T, et al., A 27-gauge instrument system for transconjunctival sutureless
microincision vitrectomy surgery, Ophthalmology, 2010;117:93–102.

8. Need for smaller incision
• 20 G vitrectomy uses large incisions 0.9 mm made by MVR
blades.
1. efficient surgery
2. faster recovery time
3. reduced post-operative inflammation
4. better visual outcomes than 20G vitrectomy.
Dilsher SD, Peter KK, Reducing MIVS wound complication risks. May 2011. Available at:
www.revophth.com/content/d/ retinal_insider/i/1494/c/28019/ (accessed 22 June 2015).
Sato T, Emi K, Bando H, et al., Faster recovery after 25-gauge microincision vitrectomy surgery than after 20-
gauge vitrectomy in patients with proliferative diabetic retinopathy, Clinical Ophthalmol, 2012;6:1925–30.
Yanyali A, Celik E, Horozoglu F, et al., Corneal topographic changes after transconjunctival (25-gauge)
sutureless vitrectomy, Am J Ophthalmol, 2005;140:939–41.
Kadonosono K, Yamakawa T, Uchio E, et al., Comparison of visual function after epiretinal membrane removal
by 20-gauge and 25-gauge vitrectomy, Am J Ophthalmol, 2006;142:513–5.

9. TROCAR/CANNULA SYSTEM
Microcannula System –
• Entry Site Alignment system
(ESA) is the key to 23/25/27-
gauge instrumentation.

12. The ESA system components include:
1.trocar-mounted microcannulas
2.cannula plugs
3.infusion line

13. 23 G Trocar cutting diameter of 0.74 mm compared with
0.61 mm for the 25 G.
Length of the stiletto is 9.6 mm compared with 9 mm for the
25 G

14. • T/C Delta – Diff between Outer Dia of Trochar & Inner Dia of
Cannula
– A large T/C delta – risk of tissue caught between Trochar &
Cannula
– Too Small T/C delta – Removal of Trochar could be
difficult & inadvertent cannula removal

15. The EdgePlus trocars
• advanced blade design to create linear wounds.

16. • hump is perpendicular to the horizontal plane of the blade.
• It stretches the tissue in the direction perpendicular to the
horizontal plane of the blade, thus ensuring a slit-like incision.

17. •Integrated Scleral Marker

18. • Microcannula consist of two components –
-Polyamide cannula
-polymer cannula hub
• Thin-walled polyamide tube 3.6 mm in length with an
inner/outer diameter of 0.57/0.62 mm.
• A collar is present at the extraocular portion and can be
grasped with forceps to manipulate the microcannula
• Cannula plugs have a tapered shaft, provides tight fit

19. • Cannula with Valves – Prevent
leakage of fluid when instrument
removed
• Maintain IOP & avoid Hypotony
related complication
• Require precaution in injecting
Silicon Oil
• Valve cannula (DORC). A cap-like
silicone membrane is mounted on
the head of the microcannula. A
slot in the membrane allows the
insertion of instruments

21. • Colour code for alcon ports
1. 20G – YELLOW
2. 23G – ORANGE
3. 25G – BLUE
4. 27G - PURPLE

22. Infusion cannula is a 5mm metallic tube, has an
internal diameter of 0.56 mm in 23 G & 0.42 mm in
the 25 G
Infusion line has a female Luer-lock connector for precise sliding fit
within the microcannula

23. SELF SEALING WOUND CONSTRUCTION
1.Multiplanar incision
2.Smaller wound diameter
3.Non-overlapping conjunctival and scleral wound
Oblique scleral incision advantages :
-better wound closure
-reduce risk of hypotony
-reduced leakage
-better wound apposition

24. • One step oblique incision
- Made with sharp trocar and cannula (Entry Site Alignment
System [ESA] )
• Incisions parallel to limbus are preferred
• Displaces circumferential scleral fibres rather than cutting the
fibres.
• Conjunctival and scleral vessels should be avoided
• Lateral Conjunctival displacement before the scleral incision

25. • Bi-planar incision
- angle of entry : 30 degree , 5 degree
until 50% scleral depth, followed by perpendicular insertion

27. • Two step method (by Eckardt)
- Displaced conjunctiva stabilized with a pressure plate
- A shelved incision is created using a sharp angled stiletto blade.
- Cannula is inserted in the same wound with a blunt trocar.

28. 23G
trocar kit

29. CHALLENGES IN MIVS
• Instrument Rigidity,
Functionality, and Array
• Newer generation 25G and
27G cutters,
endoilluminators, and laser
probes are now stiffer, and
newer forceps are shorter to
increase stiffness.

30. • The 27G cutter shortened from 32mm to 25mm, with similar
rigidity to the 25G cutter.
• Not suited for use in highly myopic eyes with long axial
lengths.
• Tapered stiffening sleeves to increase rigidity of the thinner
27G instruments.

31. • The radius of curvature of curved instruments is also often
blunted in order to accommodate passage through the
narrower internal diameter of the cannulas.
• 25G curved scissors are less efficacious than larger 20G
scissors, and dissection of dense membranes may need to be
completed by other methods.

32. OVERCOMING THE OBSTACLES OF MIVS
1. Stabilizing the smaller gauge instruments with an extra finger
close to the sclerotomy to reduce bending.
2. Optimal positioning of the sclerotomies close to the horizontal
meridian

33. 3. avoiding the supraorbital rim and bridge of the nose
4. wide-angle viewing systems
5. scleral depression, all minimize the need for eye rotation and
problems related to tool flexure.

34. INSTRUMENTATION &
FLUIDICS IN MIVS
• Size OF Cutter

35. • Poiseuille’s law
• The decreased vitreous flow rate
or so-called “cutting efficiency”
observed with smaller gauge
instruments
• Improved by higher cutting
speed devices and high
aspiration levels along with duty
cycle changes.

36. • Cutter speed
• Alcon Accurus – 2500 cpm
• Alcon Ultravit– 7500 cpm
• EVA; DORC International) - 16,000 cpm (cuts per minute)

37. • The chopped vitreous has a lower viscosity than intact gel and
is more easily aspirated even in reduced diameter instruments

38. • same flow rate, higher the cut rate, the smaller the amount of
vitreous (“bite size”) aspirated into the cutter, reducing both
vitreous and retinal traction.

39. • Port Location
–
20 G 23 G 25 G
Port Distance
to end
0.457 mm 0.229 mm 0.356 mm
Port Area
(mm2)
0.254 0.183 0.083

40. • Cutter design
• Hollow inner tube surrounded by a hollow outer tube arranged
coaxially
• Vitreous aspirated in port, inner tube slides forward, shearing
off the vitreous, aspirated through the inner tube
• Cutting mechanism
1. Guillotine style
2. Rotational

42. Drive mechanism
1. Pneumatic
2. Electrical
a. rotational electric motor
b. solenoid drive (overheats at
high cut rates)

43. • New ultravit probe
• Pneumatic dual drive
guillotine cutter
• 7500 cuts per minute
• Increased cut rate, volume
of individual “bite
“decreases , increasing fluid
resistance at port, thus
decreasing vitreo retinal
traction

44. • In Constellation the passive spring return phase was replaced
with a second pneumatic piston that actively pushes the
guillotine blade into the open position.
• This allowed a higher duty cycle at ultrahigh-speed cut rates
up to 7500 cuts per minute and allowed surgeons to vary the
duty cycle.

45. • Duty cycle control
• The duty cycle (the percentage of time the cutter port is open
relative to each cutting cycle)
• It can be controlled in vitrectomy probes which are
pneumatically driven and not electrically driven

46. • Constellation offers 3 duty cycle settings:
1. Core is the maximum port open duty cycle. more than 50%
Best suited for core vitrectomy , higher flow rates desired
2. Shave is the minimum port open duty cycle.
less than 50%
Suited for shaving in periphery or near mobile retina, low
flow rates when desired

47. 3. 50/50, setting between core and shave
cutter is open and close for the same amount of time.
Similar to old electric cutter settings
# Momentary setting
- Footpedal–controlled aspiration with side pedal–controlled
cutting at low cut rates.
- Ideal for removing lens fragments that do not require the
fragmatome.

48. • Dual dynamic drive (3D) vitrectomy mode
1. Simultaneous linear control of cutting rate and vaccum
pressures to produce the resulting flow rate and enhancing
efficiency.
2. Surgeon via footpedal, can change the settings linearly from a
preset start point for cutting and the vaccum to a preset
endpoint.
Proportional vitrectomy mode.
1. High fixed cut rates as the vaccum is varied linearly, thereby
reducing pulsatile traction and enhancing safety

49. Twin duty cycle (TDC) cutter design
• Enhancing Visual Acuity (EVA) vitrectomy system
(DORC,. Zuidland, the Netherlands)
• It has a second port in the internal guillotine blade of the
pneumatic cutter.
• two cutting edges, cuts both forward and backward,
• eliminates any port closed time
• 92% duty cycle independent of cutting speed
• cut rates doubled, reach 16,000 cuts per minute.

52. Vitrectomy pumps
• Peristaltic pumps
• The flow is set and vaccum
varies to maintain flow with
varying viscosity of
substances.
• Slow vaccum production
due to pump inertia and
pulsatile flow.

53. • Venturi system
• The vaccum is set and flow
varies with viscosity of
substances encountered by
the cutter.
• High maximum vaccum can
be set for core vitrectomy
and low vaccum for
peripheral vitreous shaving

54. EVA (Dorc, Zuidland, the Netherlands)
• VacuFlow Valve Timing Intelligence (VTI)
• computer-controlled operating pistons and closure valves
working in small-flow chambers
• allow the surgeon to have adjustable settings for both
peristaltic and venturi controls.

55. Port-based flow limiting
• Reduced flow rate and high cut rates
1. Increased fluidic Stability
2. Reduced cutter induced motion of detached retina
3. It reduces the average vitreous fibre travel between cuts and
therefore limit the traction exerted on the vitreous and retina
4. Reduce post-occlusion surge after sudden elastic deformation
of dense membranes through the cutter port during membrane
delamination..

56. Illumination System –Consist
of Five basic building blocks
• Efficiency of the illumination system - depends on its coupling
efficiency (measure of the power emitted from the optical source
coupled into the fiber)
• HID lamps - metal halide and high pressure sodium
• Xenon lamps currently in Systems from Alcon
• Light emitting diode (LED)
• Laser light source

57. • Endoillumination
1. Light pipes
2. Chandelier lights
3. Illuminated instruments.
Two Categories of Fibres used

58. Handheld light pipes
• Techniques
1. focal bright illumination
2. specular illumination where light shone at a critical angle
causes an almost transparent surface to glow, highlighting
surface irregularities
3. retroillumination by reflecting the endoilluminator off the
surface of the retina, retinal pigment epithelium, choroid,
sclera, or off the cutter.
4. Wide-angle diffuse illumination

59. • Reducing the diameter of a light pipe by 20% theoretically
reduces the amount of illumination by ~35%
• 23G and 25G endoilluminators had reduced light transmission
due to reduced surface area of the fibre optic by 40% and 50%,
respectively.
• High arc lamps (xenon and mercury vapour) provided the high
power output required for small gauge endoilluminators.
• Newer light emitting diode (LED) light sources
- up to 40 lumens without degradation of light output
- can last more than 10,000 hours

60. • Normal Illumination fields range : 50 to 80 degrees.
• Newer generation light probes : > 100 degrees divergence
angle
1. Wider cone angles
2. Allow better peripheral viewing with less probe angulation.
3. Beveled sheath designs on the tips help to minimize glare,
while providing wide-angle illumination.

61. • The Constellation uses a xenon light source that has a radio
frequency identification (RFID) probe that automatically
regulates light intensity based on the probe gauge size, thus
minimizing the likelihood of inadvertent light toxicity.
• The RFID also allows easy connection of chandeliers and
lighted lasers that can be individually selected and controlled
on the platform without needing to unplug other lights.

62. Chandelier illumination
• fixed in the sclera and provides wide-angle diffuse lighting.
• To permit 4-port Vitrectomy for Bimanual Surgery
• Its handsfree & self-retaining design
• Safety : a retinal threshold time in the order of hours, even
when working at full output
• It decreases phototoxicity as distance from retina is increased.
• produces superior video image quality

64. • Disadvantages:
1.Less helpful in identifying dissection planes at the surgical
point of interest
2. Glare after fluid-air exchange.
3. Excessive use of diffuse illumination also reduces the ability to
see transparent structures
4. Shadows cast by instruments in the path of the light impede
visualization
5. Thermal buildup

65. • Apart from the chandelier systems, combined fiber optic light /
laser probe (illuminated instruments)
• Allow to use the laser and light simultaneously

66. Laser options : straight and curved,
illuminated and nonilluminated.
Advantages of curved illuminated laser :
1. Ability for surgeon-independent scleral depression with
simultaneous laser for peripheral retinal breaks.
2. Treat in phakic patients across the eye.
3. Treat all breaks, including the anterior portions of a tear.

67. Wide angle viewing system
WAVs allow a panoramic view of the retina based on the indirect
ophthalmoscopic principle.
- Contact
- Noncontact viewing system.
• Two components:
1. An indirect ophthalmoscope lens placed on or above the
cornea
2. Prismatic stereo reinverter that reinverts the image

68. Intraocular pressure control
• This control allows surgeons to keep IOP within 2 mm Hg of a
preset level.
• Constellation, combined with valved trocars, becomes a
controlled, predictable system.
• The IOP control utilizes flow sensors at the bottom of the
cassette that directly compensate to maintain a set pressure.

69. • The patient’s eye level must be at the same height as the
bottom row of connectors on the cassette. If the patient is
lower than those connectors, increases in IOP will occur.
• IOP increases at a rate of approximately 1.87 mm Hg for every
inch the patient’s eye is below the cassette connectors, and
such unevenness results in decreased aspiration by the same
factor.
• The Constellation has a patient eye level setting, allowing the
surgeon to make this adjustment so that the pressure he or she
sets is the actual pressure in the eye.

70. Complications
• Ocular hypotony
• Endophthalmitis
• increase the risk of intraoperative breakage of 25-gauge
instruments

71. • Although sclerotomies are left unsutured, UBM proves they
heal much more rapidly than conventional sclerotomies.
• There is minimal wound gape on postoperative day one and
the site is undetectable within 2 weeks, compared with a 6–8
week healing time for 20-gauge sclerotomies
Keshavamurthy R et al. BMC Ophthalmol 2006; 6:7

72. 25-Gauge Scleral Tunnel
Transconjunctival Vitrectomy.
Shimada H et al.Am J Ophthalmol 2006;142:871–873
• Compared the intraocular fluid leakage rate between 25G
transconjunctival vitrectomy with scleral tunnels and standard
25G transconjunctival vitrectomy.
• Standard 25G vitrectomy was conducted in 542 eyes and 25G
vitrectomy with scleral tunnels in 337 eyes. The scleral tunnel
was created by inserting trocars at an oblique angle.

73. • The intraocular fluid leakage rate was significantly
lower when scleral tunnels were used in 25G vitrectomy (1%,
five of 337 eyes) compared with standard 25G vitrectomy
(9%, 50 of 542 eyes).
The wound leakage rate was significantly lower when using
(rather than not) scleral tunnels in 25G vitrectomy, both
without air-gas and with air exchange .
The use of scleral tunnels in 25G transconjunctival vitrectomy
reduces the frequency of wound
leakage even when the peripheral vitreous is removed.

74. Rates of hypotony at the first postoperative day in fluid-filled
eyes were 2.3% in a group of 44 patients with the oblique
technique versus 10% in 40 patients undergoing direct
microcannula insertion
Curr Opin Ophthalmol 200718:188–193
UBM demonstrates that sclerotomy sites with oblique cannula
insertion heal much more rapidly than standard 20-gauge
sclerotomies or even those with direct cannula insertion in 25-
gauge surgery
Curr Opin Ophthalmol 200718:188–193

75. Endophthalmitis
• Endophthalmitis-a potentially devastating complication
Open sclerotomies
Easy entry of conjuncrtival flora
• Isolated case reports of endophthalmitis after 25-gauge
vitrectomy
• one case of endophthalmitis among 5498 20-gauge procedures
(0.018%) compared with seven cases among 3103 procedures
performed with 25-gauge instruments (0.23%), a 13-fold
increase with the 25-gauge instrumentation
( American Academy of Ophthalmology 2006 )

76. • To decrease these risks, carefully prep and sterilize the
surgical field with povidone iodine
• Ensure purposeful conjunctival displacement prior to cannula
insertion to misalign the conjunctival and scleral openings
• Consider oblique cannula insertion to facilitate scleral wound
closure, and suture any wound leaks seen following cannula
removal.

77. Outcomes of 140 Consecutive Cases of
25-Gauge Transconjunctival Surgery for
Posterior Segment Disease.
Lakhanpal et al Ophthalmology 2005;112:817-824
• To evaluate the safety and efficacy of 25-gauge
instrumentation for a variety of vitreoretinal conditions on
previously nonvitrectomized eyes.
• One-hundred forty eyes of 140 patients were evaluated at the
Doheny Retina Institute from July 2002 to July 2003
• All patients underwent surgical procedures using the
Millennium 25-gauge Transconjunctival Standard Vitrectomy
system

78. Indications were
• ERM (29),CNVM(13), NCVH(18), TRD(11), BRVO(12),
MH(11), RRD(10), Dislocated IOL(6), DME(6), Vit
Opacity(5)

79. • No intraoperative complications noted.
No cases required conversion to 20-gauge vitrectomy
10 cases (7.1%) needed single-site sclerotomy suture placement
• Mean total surgical time was 17.46 minutes.
• Intraocular pressures remained stable throughout the
postoperative course.
• Five eyes (3.8%) presented on day 1 with shallow choroidal
detachments, but all resolved by day 7, and none required
volume infusion during the postoperative period.
• No detectable inflammation was noted in any eyes by 4 weeks
postoperatively.
• No case of retinal detachment or endophthalmitis was
recorded.

80. 25-gauge vs 20-gauge system for pars plana vitrectomy: a
prospective randomised clinical trial.
British Journal of Ophthalmology 2007;91:945-948
• To compare 25-gauge vs 20-gauge system for pars plana
vitrectomyin a prospective, randomised, controlled clinical
trial.
• Vitrectomy was performed in 60 patients belonging to 2
groups. The main outcome measure was time for surgery,
divided into duration of wound opening,vitrectomy, retinal
manipulation and wound closure

81. • The total duration of surgery showed no significant difference
between the groups
• The 25-gauge group showed significantly shorter duration of
wound opening and wound closure.
• In contrast, the vitrectomy duration was significantly longer in
the 25-gauge group
• Conjunctival injection and subjective postoperative pain
showed significantly lower irritation in the 25-gauge group

82. • The 25-gauge vitrectomy system offered significantly
improved patient comfort during the first postoperative week.
• Duration of surgery was comparable between the two systems
—the shorter time needed for wound opening and closure in
the 25-gauge group being equalised by the longer vitrectomy
duration