Because more patients expect excellent visual acuity, today's cataract surgery is both a therapeutic and refractive procedure. We have found that incision size is especially crucial in minimizing surgically induced astigmatism and, therefore, obtaining a good postoperative refractive result. Clinical trials have found that the length of the incision is directly proportional to the amount of induced astigmatism and inversely proportional to its stability over time.1 Today's patients benefit from reduced incision sizes—gradually reduced from 10 mm in intracapsular cataract extraction to 7 mm in extracapsular cataract surgery, and ultimately to the 3.2-, 2.8-, and sub–2-mm incisions now used for phacoemulsification.2,3
Continued advancements in IOL technology, as well as software and surgical instrument size and design, have allowed for further reducing incision size and tissue trauma. They have also promoted faster recovery. Bimanual microincision cataract surgery (B-MICS) is one such advance, allowing for a less invasive variation of traditional coaxial phacoemulsification. With this technique, cataracts may be extracted through incisions of 1.5 mm or smaller.4,5
Coaxial MICS (C-MICS) is another minimally invasive cataract surgery technique. Proposed by a few Italian surgeons as an alternative to bimanual phaco (Aldo Caporossi, MD, personal communication, 2004), this method resembles the coaxial surgical approach but with a smaller incision (2.2 vs 2.8 mm). The only difference between C-MICS and traditional coaxial phaco is the use of a 21-gauge phaco tip, the UltraSleeve (Alcon Laboratories, Inc., Fort Worth, Texas), which allows for instrument insertion through a 2.2-mm incision.
We analyzed these surgical techniques in a clinical trial.
B-MICS
Although all types of anesthesia are compatible with bimanual phaco, local anesthesia remains the most reasonable alternative when compared with regional or general anesthesia in MICS. Microincisions prevent leakage and enable easy instrument insertion.
First, we perform two 1.4-mm trapezoidal incisions in the clear cornea at the 10- and 2-o'clock positions (Figure 1) with a precalibrated diamond knife (Janach, Como, Italy; Figure 2). Then, I usually perform the capsulorrhexis with a cystotome 26-gauge needle. It may be easier, however, to use capsulorrhexis forceps (Figure 3) to enable perfect control of the circular cutting of the anterior capsule. A dispersive and cohesive ophthalmic viscoelastic device is particularly appropriate for B-MICS. To avoid surgical difficulties and complications, the diameter of the capsulorrhexis should be approximately 5 to 6 mm. Additionally, hydrodissection does not require specific instruments for B-MICS; a normal 26-gauge cannula may be introduced through a microincision and placed under the capsulorrhexis. The cannula is then slightly lifted to create a small tent under the anterior capsule. This facilitates the progression of balanced salt solution (BSS; Alcon Laboratories, Inc.; Figure 4). If the nucleus does not turn, the surgeon can repeat the procedure in the opposite quadrant.7
PHACOFRACTURE
For phacofracture, we need dedicated instruments for B-MICS (eg, irrigating chopper; Figure 5, a sleeveless, 21-gauge phaco tip, phaco machines with ultrasound power modulation technologies) that enable discontinuous ultrasound emission and avoid thermal burns in the corneal tunnel.
We use the Sovereign with WhiteStar technology (Advanced Medical Optics, Inc., Santa Ana, California; Figure 6) for micropulse ultrasound emission. There are several other machines, however, that also allow for the optimization of ultrasound power with different technologies.8
We can adopt the usual techniques for phacofracture. We suggest, however, using the divide and conquer or stop and chop technique for normal nuclei and vertical phaco chop for harder nuclei9 (Figure 7). Whatever the phacofracture procedure, the bimanual technique has several advantages over traditional coaxial and C-MICS phaco. First, the irrigating chopper directs the nucleus fragments toward the phaco tip and creates better followability and less turbulence in anterior chamber. Second, the optimization of fluidics allows for great anterior chamber stability. Lastly, a greater visibility of the surgical field for the minimal size of the surgical instruments makes the technique ideal for microphthalmos and infantile cataracts.
The irrigation and aspiration phase is greatly facilitated by bimanual. In this method, the separate aspiration and irrigation probes are introduced through microincisions and into the anterior chamber. The aspiration probe is held in the dominant hand, and the infusion probe is held in the other hand in continuous infusion mode to avoid anterior chamber collapse. This also directs the cortical material toward the aspiration probe and minimizes turbulence.
After performing aspiration on the opposite half of the entry point, the surgeon should change hands, keeping the aspiration probe in the dominant. Then, the surgeon may perform aspiration in the other half of the chamber. I have found that oval-shaped, sectioned 20-gauge probes fit perfectly within the trapezoidal microincisions (Figure 8).
IOL IMPLANTATION
To implant the IOL, we perform a third incision at the 12-o'clock position between the two microincisions. If necessary, one of the incisions may be enlarged for IOL implantation. There are now many microincision IOLs that can be easily introduced into the posterior chamber with a dedicated injector (Figure 9). We usually perform a simple suture hydration last, although it is also possible to close the major incision with a 10-0 nylon suture.
COAXIAL MICROPHACOEMULSIFICATION
Our technique for C-MICS is the following: After local anesthesia, we use a precalibrated diamond knife to perform two 1.4-mm incisions at the 10- and 2-o'clock positions. Then, we create a capsulorrhexis with a cystotome. After hydrodissection, we enlarge one of the incisions to 2.2 mm with a precalibrated steel knife and perform phacoemulsification with a 20-gauge, 30° angled probe with the UltraSleeve (Figure 10). Finally, we perform bimanual I/A of the residual fragments with an oval sectioned 20-gauge probe and implant the IOL through the 2.2-mm incision used for phacoemulsification (Figure 11). I finish with suture hydration.
We prefer B-MICS over C-MICS for treating both normal and complicated cataracts. The bimanual technique has the great advantages of smaller instruments and bimanuality, with the possibility of better managing microphthalmos, infantile cataracts, and complicated cases (eg, intraoperative floppy iris syndrome, uveitic cataracts, traumatic cataracts).
In a controlled, prospective clinical trial,6 we studied 100 eyes (50 patients) with grade 2 to 4 nuclear or corticonuclear cataract. Fifty eyes were randomized for B-MICS and the 50 fellow eyes underwent C-MICS. Gian Maria Cavallini, MD, performed all surgeries using the Sovereign WhiteStar (Table 1). All patients provided informed consent before surgery.
A clear corneal incision was made in the superior sector, and a flexible hydrophobic acrylic IOL (Acri.Tec Acri.Smart 48S; Carl Zeiss Meditec AG, Jena, Germany) was implanted using a 2-mm injector.
Follow-up at 1 day, 1 week, and 1 and 3 months was performed by the same surgeon who performed the preoperative evaluations. Intraocular pressure and BCVA were measured. A fundus evaluation and complete biomicroscopy of the anterior segment was also performed.
We found no early intra- or postoperative complications. Additionally, there were no signs of corneal thermal burn, zonular dehiscence, capsule rupture, iris damage, or endophthalmitis. IOL rupture occurred in two cases (one in each group), but neither require removal. In two other cases (one in each group), the IOL ruptured completely and required removal and replacement. The only statistically significant difference between the groups was the total volume of the balanced salt solution (P=.004) and total surgical time (P=.045) (Table 2).
CONCLUSIONS
The volume of balanced salt solution and surgical times were lower in the bimanual versus coaxial group. This difference may be related to the instruments and technique used for C-MICS. The 1.4-mm incisions are well suited to the 20-gauge bimanual I/A cannula. Additionally, using a 20-gauge cannula with a 2.2-mm incision in C-MICS results in greater wound leakage and, therefore, the use of more balanced salt solution. Although statistically significant, the difference in balanced salt solution volumes between the two techniques was not clinically relevant and did not affect the endothelial cell count, pachymetry, or inflammation. The continuous improvement in B-MICS—in terms of control of fluidics and intraoperative leakage—could result in further reduction of intraoperative corneal damage compared with coaxial. Although not statistically different, the effective phaco time values were lower in the bimanual group (mean 3.86 ±2.91 seconds vs 4.94 ±2.99 seconds).
We can assert that these phacoemulsification techniques are equally valid, as postoperative visual rehabilitation was quick and satisfactory in both groups. Therefore, B-MICS and C-MICS are both effective and safe techniques for cataract surgery. Bimanual microphacoemulsification, however, gives the surgeon greater control of fluidics and reduces surgical times. Further clinical trials are necessary to confirm these data, but I think that B-MICS is really the technique of the future. It opens the door to the possibility of performing cataract surgery through increasingly smaller incisions.
Luca Campi, MD, is an Ophthalmology Assistant at the Institute of Ophthalmology, University of Modena, Italy. He states that he has no financial interest in the products or companies mentioned. Dr. Campi may be reached at tel: +39 059 4222442; fax: +39 059 371532.
Gian Maria Cavallini, MD, is the Director of the Institute of Ophthalmology, University of Modena, Italy. She states that she has no financial interest in the products or companies mentioned. Dr. Cavallini may be reached at cavallini.gianmaria@unimore.it.
Cristina Masini, MD, is a University Researcher at the Institute of Ophthalmology, University of Modena, Italy. She states that she has no financial interest in the products or companies mentioned. Dr. Masini may be reached at tel: +39 059 4222442; fax: +39 059 371532.
Simone Pelloni, MD, is an Ophthalmology Practionary at the Institute of Ophthalmology, University of Modena, Italy. He states that he has no financial interest in the products or companies mentioned. Dr. Pelloni may be reached at tel: +39 059 4222442; fax: +39 059 371532.
