Microincisional cataract surgery (MICS) and operating through incisions of 1.5 mm or less are no longer new concepts in cataract sur- gery. Understanding this global concept im- plies that it is not only about achieving a smaller incision size, but also about making a global transformation of the surgical proce- dure towards minimal aggressiveness.
The incision size has been an important is- sue of investigation for many years, starting from reducing the size from 10 mm in intra- capsular surgery to 7 mm in extracapsular cases, and finally from 3.4 mm to 2.8 mm us- ing the phacoemulsification technique. The need to reduce the incision size was mainly for the purpose of reducing the induced
astigmatism, as modern cataract surgery is also refractive surgery. The other essential factor in the development of a new technique was how we could reduce the amount of ener- gy being liberated inside the eye when using ultrasound emulsification. Until now the amount of energy being liberated or the pow- er used to operate a cataract inside the eye has not been determined. As it is a source of me- chanical, wave-shock, constitutional and thermal damage, this energy and power de- livered inside the eye has an effect on the oc- ular structures. The thermal effects of this liberated energy affect all the intraocular structures, endothelial cells, corneal stroma, and incisions.
Jorge L. Alio, Ahmed Galal, Jose-Luis Rodriguez Prats, Mohamed Ramzy
CORE MESSAGES
2 Microincisional cataract surgery (MICS) utilizing incisions of 1.5 mm or less implies not only a smaller incision size but also a global trans- formation of the surgical procedure towards minimal aggressive- ness.
2 MICS surgery using ultrasound or laser offers the advantage of having a superior biological effect on the ocular structures com- pared to conventional phacoemulsification procedures.
2 With the new developing technology of phacoemulsification ma- chines and the power settings, together with adequate instruments, all the cataract grades are amenable to MICS. Refractive lens ex- change using MICS has the advantage of preventing induced astig- matism and wound complications.
21
The main issues and steps involved in the transition from phacoemulsification to MICS may be summarized as follows:
1. Fluidics optimization: MICS surgery should be performed in a closed environ- ment. Because the probe fits the incision exactly, fluid outflow through the incision is minimal or absent. Taking into account the closed chamber concept, we need to optimize the probe function and diameter to balance the outflow and inflow that is taking place every second in this new envi- ronment [1].
2. Bimanuality and separation of functions:
The use of both hands simultaneously is another factor that added to the success of MICS surgery. The surgeon should be aware that working with two hands means working with irrigation and aspiration separately. In this way, irrigation and aspi- ration not only become part of the proce- dure, but also become instruments in the hands of the surgeon [1].
3. New microinstruments: The newly devel- oped microinstruments have been de- signed to perform their function, while at the same time acting as probes. They do not necessarily need to be similar to the traditional choppers or forceps, which were mostly manufactured or created in the extracapsular era. These new specifi- cally designed instruments, coordinated with the fluidics and combined with the new maneuvers, will improve efficiency compared with normal phacoemulsifica- tion that has been performed until now through “small” incisions [1].
4. Lasers: Lasers have become a technologi- cal possibility in performing cataract sur- gery. It is true that their capability of han- dling very hard nuclei is subject to debate.
However, the elegance of laser, the very low levels of energy developed inside the eye, and the possibilities of improving the effi- ciency of this technology in the future makes them attractive for the MICS sur- geon.
5. Ultrasonic probes: Ultrasonic probes have to be modified in order to be used without sleeve. Taking off the sleeve is not the only way to use the probes in performing mi- crosurgery [2, 3]. These probes should be designed to be used more efficiently, ma- nipulating through microincisions with- out creating any tension in the elasticity of the corneal tissue. Furthermore, the fric- tion created between the probe and the corneal tissue should be avoided with the special protection and smoothness of the external profile of the probe.
6. New intraocular lens (IOL) technology:
The technological development that en- ables operation of cataracts through a 1.5- mm incision should be adequately bal- anced with the development of IOL technologies capable of performing this surgery with IOL implantation though this microincision. At present, different IOLs of new designs, new biomaterials and new technologies are available for implantation through microincisions. Should we change the material, develop the optic technology, or both?
21.1 MICS Surgical Instruments Surgical instruments are important for safe and adequate MICS surgery. With a minor movement of the surgeon’s fingers, the metal instruments respond more than expected, uniting the fingers and the instruments to achieve excellent manipulation during MICS surgery (Fig. 21.1).
The instruments are finger-friendly and each has its own function. Once the surgeon becomes accustomed to them, they will be a new extension to his or her fingers inside the eye [1].
1. The MICS microblade is a diamond or stainless-steel blade that can create a trapezoidal incision from a 1.2- to 1.4-mm microblade (Katena Inc., Denville, NJ, USA) [1].
2. The MICS capsulorrhexis forceps (Katena Inc., Denville, NJ, USA) has microtriangu- lar tips that can be used to puncture and grasp the capsule to perform the capsulor- rhexis with a single instrument. It can also be used for other intraocular maneu- vers such as grasping the iris to perform small iridotomies or to cut pre-existing synechia in the anterior or posterior chambers [1].
3. Alio MICS prechoppers are for bimanual use and, as opposed to the single-handed prechopping technique, can be used for all types of cataracts regardless of the hard- ness. The tip has a blunted square hook that should be introduced gently under- neath the anterior capsular rim, with one instrument opposite the other [1].
4. The MICS hydrodissector or irrigating fin- gernail (Katena Inc., Denville, NJ, USA) fa- cilitates manipulation of the nucleus frag- ments, as well as functions as an irri- gating instrument. It can also be useful to
divide the nuclear fragments further.
The forward-directed pointing tip, which has a highly blunt point-like end, is like a fingernail – hence its name. The irrigating fluid exits through a large port (1 mm) di- rected under the tip. This feature helps to push away the posterior capsule to obtain stable fluidic control in the anterior cham- ber when combined with the phacoemulsi- fication or MICS aspirating tip. The flow rate or the free irrigation flow of this in- strument is 72 cc/min, which is considered the highest flow of any instrument per- forming the same function in the market.
This generates anterior chamber stability regardless of the high vacuum level in MICS [1].
5. The MICS irrigating chopper (Katena Inc., Denville, NJ, USA) was designed to chop medium to hard cataract if prechopping has not been performed. It has a sharp pointed triangular-shaped tip, which is an- gled downward to “chop” off segments of the nucleus. The irrigating fluid exits through a large port (1 mm) directed un- der the tip of the instrument [1].
6. The MICS aspiration handpiece (Katena Inc., Denville, NJ, USA) has a bullet-shaped tip designed for easy entry through a para- centesis incision and a 0.3-mm diameter aspirating port close to the tip in the inte- rior part of the curvature. This design works to maintain the fluid balance in the anterior chamber when used with the MICS irrigating fingernail and MICS chopper, and while aspirating the residual cortex [1].
7. The intraocular manipulator (Katena Inc., Denville, NJ, USA) is multifunctional and efficiently helps in iridolenticular synechia dissection, IOL manipulation and other in- traocular maneuvers such as vitreous knuckles or stabilization of the IOL. The conical base is the same diameter as the in- ternal MICS incision in order to maintain the stability of the anterior chamber, thus preventing viscoelastic outflow [1].
Fig. 21.1. MICS surgical instruments
8. MICS scissors (Katena Inc., Denville, NJ, USA) have a 23-gauge (0.6-mm) shaft, so they fit exactly through a very small para- centesis. They have extremely delicate blunt-tipped blades, which are ideal for cutting synechia and capsular fibrosis and membranes, as well as for performing small iridotomies [1].
21.2 Low-Ultrasound MICS 21.2.1 Mackool Tips
Mackool tips generate less heat at the incision compared to non-Mackool tips. The thick- ness of the polymer sheathing the tip is only 50–75 microns, which is much less than that of the infusion sleeve; its thermal conductivi- ty is also much less than that of conventional infusion sleeve material. This tubing system also prevents the spraying effect caused by the solution coming out of the irrigating tip, which occurs when power settings higher than 30% are used for MICS.
Most of the tips are three-quarters of an inch long and have a 45° angulation. Soft and moderately hard nuclei up to +2 hardness can be easily emulsified by using low-ultrasound MICS (LUS-MICS); prechopping will shorten the time of surgery and the energy delivered inside the eye. Hard nuclei of grade 3 or over are more amenable to LUS-MICS, which is ca- pable of emulsifying hard nuclei of any den- sity.
21.2.2 Incisions
After the surgical field has been isolated and an adjustable eye speculum (Duckworth &
Kent, England) has been inserted, the positive corneal meridian is marked and two trape- zoidal incisions of 1.2 mm internally and 1.4 mm externally are performed using the Alio corneal keratome. An external incision of 1.4 mm will be adequate for instrument
manipulation. The two incisions are per- formed in clear cornea 90° apart, at 10 and 2 o’clock, followed by the injection of 1% pre- servative-free lidocaine diluted 1:1 in bal- anced salt solution.
21.2.3 Prechopping (Counter Chopping Technique)
After the capsulorrhexis is performed using Alio’s capsulorrhexis forceps, the prechop- ping is performed. This is a bimanual tech- nique, requiring the use of both hands with the same efficiency. This technique allows manual cut and division of the nucleus, with- out creating any grooves prior to the MICS procedure. In order to protect the endotheli- um and to perform an adequate counter chopping technique, more dispersive or cohe- sive viscoelastic material is injected. The technique of counter prechopping could be applied to all surgical grades of cataract den- sity (up to grade +5). A chopper is introduced through one of the two incisions, depending on the surgeon’s preference.A nuclear manip- ulator is introduced through the other inci- sion to decrease the stress on the capsule and zonules being inserted beneath the anterior capsulorrhexis edge. The rounded microball tip of the nuclear manipulator will protect the posterior capsule during the prechopping procedure. The tips of the nuclear manipula- tor and the chopper should be aligned on the same axis, together with the hardest point of the nucleus along the direction of the lens fibers; appropriate force is then applied between the two instruments. After cracking the nucleus into fragments, the nucleus is rotated and the maneuver is repeated on the other axis to crack the nucleus into four quadrants. Once the fragments have been obtained, the MICS Mackool tip and Alio hydromanipulator fingernail are intro- duced to manipulate and emulsify the frag- ments [1].
21.2.4 Low-Ultrasound MICS Surgical Steps
The MICS technique can be performed using either phacoemulsification (LUS-MICS) or a laser (laser-MICS). After termination of pre- chopping, the Accurus or Infiniti machine is adjusted according to the settings described previously. The LUS-MICS tip and Alio’s hy- dromanipulator fingernail are introduced through the two incisions and an inferior seg- ment is mobilized and brought in contact with the MICS tip, assisted with Alio’s hydro- manipulator, in order to be emulsified. After the elimination of the first hemi-nucleus, the second prechopped hemi-nucleus is rotated to the distal portion of the bag and Alio’s hy- dromanipulator is used to mobilize the seg- ments, making them easy to emulsify. Using this technique reduces the tendency for the nuclear material to come up into the anterior chamber during the procedure, and main- tains its position within the epinuclear cover.
Following the emulsification of all the nu- clear segments, the epinuclear rim is trimmed in the different quadrants to remove all the cortical material remaining in the cap- sular bag. An adequate ophthalmic viscosur- gical device is injected deep in the capsular bag to reform the bag and prepare it for IOL implantation; this helps to force the Viscoat anteriorly, facilitating its removal to prevent a postoperative rise in intraocular pressure [1].
21.3 MICS versus Phacoemulsi- fication: a Clinical Study In a prospective, comparative, clinically con- trolled, masked study of a consecutive series of 100 eyes (50 patients), 50 eyes were operat- ed with the MICS technology and 50 eyes were operated using conventional pha- coemulsification. The patients had a mean age of 65.5 (45–86) years. Mean cataract grade was 3.01 with the lens opacities classification system III grading scale [4].
21.3.1 Inclusion Criteria
Patients ranging between 40 and 90 years:
1. Cataract eyes with a grade of 1–4 2. Normal clear corneas
3. Low or a minimal degree of astigmatism 4. Normal anterior segment
5. Normal retina and posterior segment 6. Normal intraocular pressure
Eyes with any ocular pathology were ex- cluded.
21.3.2 Pre- and Postoperative Examinations
All patients had a full ophthalmologic exami- nation, preoperatively, at 1 week, 1 month and 3 months postoperatively:
1. Uncorrected and best corrected visual acuity
2. Anterior and posterior segment examina- 3. Intraocular pressure measurementtion 4. Endothelial cell count using the SP 2000 P
TOPCON machine
5. Laser flaremeter using the FC 1000KOWA laser flaremeter
6. Cataract density evaluation
21.3.3 Operative Parameters
Only one memory and prechopping tech- nique was used in both groups:
1. Phacoemulsification parameters:
(a) Aspiration: 550 cc/min (b) Power: 20–30%
(c) Flow rate: 20 cc/min 2. MICS operative parameters:
(a) Aspiration: 550 cc/min (b) Power: 20–30%
(c) Flow rate: 20 cc/min
The eyes included in the study were divided into the following two groups:
1. Group I: MICS versus regular phacoemul- sification (100 eyes) in the following pa- rameters:
(a) Incision size (b) Cataract grade (c) Endothelial cell count (d) Laser flare
(e) Pachymetry
(f) Mean emulsification time (g) Mean power
(h) Mean effective phacoemulsification time 2. Group II: MICS versus regular phacoemul- sification (40 eyes of 24 patients) in the fol- lowing parameters:
(a) Postoperative astigmatism (b) Intraoperative saline consumption
21.3.4 Results of LUS-MICS
Microincision cataract surgery using ultra- sound or laser offers the advantage of having a superior biological effect on the ocular structures compared with conventional pha-
coemulsification procedures. A study of the parameters that control the procedure in both techniques found the following.
Working in a closed compartment while operating through the microincisions is char- acteristic of MICS surgery. The pressure of the anterior chamber was found to be higher in MICS surgery than in conventional pha- coemulsification.
The vacuum used during surgery was found to be higher in MICS surgery, which is essential in performing this type of surgery.
The percentage of phacoemulsification differed according to the machine used. The grades of cataract operated with different machines were compared.A lower percentage of phacoemulsification was performed when using MICS 30- and 300-burst modes (Accu- rus system), but using the 300-burst mode de- livered less power to the ocular tissue when the power was calculated (Fig. 21.2).
Microincision cataract surgery offers the advantage of lowering the percentage of cells loss during the procedure. Comparing the re-
Fig. 21.2. Comparison of MICS with conventional phacoemulsification
sults of endothelial cell count pre- and post- operatively, there was no statistically signifi- cant difference between the numbers, al- though the cell loss was reduced in MICS surgery. The flare and inflammatory cells de- veloping after the procedure were also found to be equal and even lower after MICS sur- gery (Table 21.1).
21.3.4.1 Group I
This group included 100 eyes of 50 patients divided in the following way:
1. Phacoemulsification: 50 eyes 2. MICS: 50 eyes
The means and standard deviations of the cataract grade, incision size, endothelial cell
count, flare and cells in the anterior chamber, phacoemulsification time, percentage power and effective phacoemulsification time are shown in Table 21.2.
Table 21.1. Comparison of flare and inflammatory cell values between MICS and conventional phacoemulsi- fication
Conventional phaco- MICS surgery emulsification (mean ± SD) (mean ± SD)
Preoperative Flare value 5.8 6.3 3.8 3.3
Inflammatory cells 0.74 1.5 0.5 0.8
First month Flare value 9.9 11.1 5.7 3.3
Inflammatory cells 1.5 1.5 1.3 1.2
Third month Flare value 5.2 3.5 5.2 2.3
Inflammatory cells 0.9 1.1 0.6 0.5
Table 21.2. Comparisons between MICS and phacoemulsification
MICS Phacoemulsification p value
Mean cataract grade 2.95 (0.99 SD) 3.05 (0.93 SD) 0.745
Mean incision size 1.7 (0.21 SD) 3.3 (0.25 SD) 0.001
Mean endothelial cell loss (%) 11.37 (13.24 SD) 15.65 (19.96 SD) 0.330
Mean flare value 14.51 (17.01 SD) 12.37 (16.79 SD) 0.669
Mean anterior chamber cells 11.2 (11.99 SD) 14.11 (17.59 SD) 0.363 Mean phacoemulsification time 0.38 (0.41 SD) 0.41 (0.44 SD) 0.259
Mean power (%) 5.28 (3.91 SD) 19.2 (10.98 SD) 0.001
Mean effective phacoemulsification time 2.19 (2.77 SD) 9.2 (12.38 SD) 0.001
Table 21.3. Mean changes in pachymetry
MICS Phaco-
emulsification
Preoperative 549.7 551.7
(34.3 SD) (33.23 SD)
1 day 599.4 600.6
(56.11 SD) (71.25 SD)
1 month 552.7 554.8
(31.86 SD) (33.73 SD)
3 months 554.8 552.3
(34.44 SD) (34.61 SD)
21.3.4.2 Group II
Twenty eyes (11 patients) operated with MICS were compared to 20 eyes (13 patients) operated with phacoemulsification. The eyes included in this group provided data about astigmatic changes and saline consumption, which were compared between the two tech- niques.
1. Astigmatic changes: using vector analysis to detect the postoperative changes in astigmatism:
(a) MICS group:
(i) Seventeen eyes had a change of ≤0.5 D (ii) Three eyes had a change ranging be-
tween 1 and 0.5 D
(b) Phacoemulsification group:
(i) Four eyes had a change of ≤0.5 D (ii) Six eyes had a change ranging be-
tween 0.5 and 1.0 D
(iii) Ten eyes had a change of more than 1 D 2. Saline consumption and pachymetry: the differences between the two groups are illustrated in Tables 21.3 and 21.4.
21.4 Advantages of MICS
Performing small incisions in cataract sur- gery has a number of theoretical advantages:
1. Fast visual recovery and improved visual outcome
2. Decrease in postoperative astigmatism 3. Reduction in the anatomical healing time 4. Fewer complications
5. IOL insertion through microincisions is now possible
6. Reduction in the operating time
MICS can be performed using laser energy, which is as safe as ultrasound energy. The use of either source of energy permits:
1. Visual acuity improvement on the first postoperative day
2. Reduction of the inflammatory reaction postoperatively
3. Lower percent of in endothelial cell loss Improving both techniques will open the way to emulsification of all grades of nucleus den- sity; this could be achieved by improving the safety and the fluidity of the low-ultrasound phacoemulsification and laser, with the pos- sibility of obtaining greater aspiration and more vacuum that helps to maintain continu- ous contact between the crystalline lens to be removed and the laser aperture.
21.5 Conclusions
Microincision cataract surgery today is be- coming a popular technique in crystalline lens surgery. With the new developing tech- nology of phacoemulsification machines and power settings, together with adequate instruments, all the cataract grades are amenable to MICS. Refractive lens exchange using the MICS technique has the advantage of preventing induced astigmatism and wound complications.
Table 21.4. Comparison of mean surgical time and saline consumption between the two groups
MICS Phacoemulsification p value
Mean surgical time 4.4 (1.67 SD) 3.13 (2.29 SD) 0.121
Mean saline consumption 92.77 (34.52 SD) 113.84 (30.96 SD) 0.198
References
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