A posterior polar cataract is a dense white opacity that is situated on the central posterior capsule. It consists of characteristic concentric rings around the central opacity (bull's eye). A posterior polar cataract presents a special challenge to the phaco surgeon because of its predisposition to posterior capsular dehiscence during surgery.1,2 Osher et al1 reported a 26% (8/31 eyes) incidence of posterior capsular rupture during surgery in eyes with a posterior polar cataract. We had a rate of 36% (9/25 eyes).2 Hayashi et al3 reported 7.1% (2/28 eyes), whereas Lee and Lee4 reported 11% (4/36 eyes).
To prevent posterior capsular rupture, Osher et al1 recommended using slow-motion phacoemulsification with a low aspiration flow rate, a low level of vacuum, and infusion pressure. Fine et al5 avoided overly pressurizing the anterior chamber with viscodissection to mobilize the epinucleus and cortex, Allen and Wood6 performed viscodissection, and Lee and Lee4 advocated a lambda technique with dry aspiration. We prefer inside-out delineation.7 Combined with modern instrumentation, refined surgical strategies, a better understanding of phacodynamics, and cumulative surgical experience, this technique has enabled us to reduce the incidence of posterior capsular rupture to 8% (2/25 eyes).7
In our opinion, surgery should be delayed as long as possible and undertaken only if the patient finds it difficult to perform routine activities. We believe that the subsequent paradigm should govern the procedure.COUNSELING
During the preoperative examination, the physician should inform the patient of the possibility of the nucleus' dropping intraoperatively due to a posterior capsular rupture, a relatively long operative time, secondary posterior segment intervention, and a delayed visual recovery. In addition, the surgeon should discuss Nd:YAG capsulotomy for residual plaque1-3 and emphasize the possibility of preexisting amblyopia, especially in cases of unilateral posterior polar cataract.3ANESTHESIA
Peribulbar anesthesia with oculopressure to soften the globe diminishes intraoperative posterior pressure.1 With increasing experience, one may use topical anesthesia in a selective manner.
We prefer a closed chamber technique. The contours of the cornea and the globe should be maintained throughout the procedure. Hayashi et al3 performed phacoemulsification, pars plana lensectomy, or intracapsular cataract extraction, depending on the size of the opacity and the density of the nuclear sclerosis.THE INCISION
We create a paracentesis with a 15º ophthalmic knife (Alcon Laboratories, Inc., Fort Worth, TX) and inject Provisc (Alcon Laboratories, Inc.). Next, we make a temporal, corneal, single-plane valvular incision of 2.6mm. A cohesive viscoelastic in the anterior chamber prevents its collapse as well as forward movement of iris-lens diaphragm during surgical entry into the eye. Fine et al5 cautioned against increasing the pressure in the anterior chamber.THE CAPSULORHEXIS
Ideally, the capsulorhexis should be no larger than 5mm. Although a size of 4mm or less could be detrimental if the surgeon must prolapse the nucleus into the anterior chamber, a larger opening may not leave adequate support for a sulcus-fixated IOL if the posterior capsule is compromised.2,5HYDRO PROCEDURES
Cortical cleaving hydrodissection8 can lead to hydraulic rupture and should be avoided.1,2 It is logical instead to perform hydrodelineation to create a mechanical cushion of epinucleus.2-4,6,9,10 Fine et al5 performed hydrodissection in multiple quadrants and gently injected tiny amounts of fluid such that the fluid wave could not extend across the posterior capsule. We employ inside-out delineation to precisely demarcate the central core of nucleus.7INSIDE-OUT DELINEATION
We sculpt a central trench using the slow-motion technique with the Infiniti Vision System (Alcon Laboratories, Inc.). For nuclear sclerosis of grade 3 or less (on a grading system from 1 to 5),11 our preset parameters are ultrasound energy of 30% to 60% (supraoptimal power), vacuum of 60mmHg, an aspiration flow rate of 18mL/min, and a bottle height of 70cm. We are careful not to mechanically rock the lens. Injecting a dispersive viscoelastic (Viscoat; Alcon Laboratories, Inc.) through the sideport incision before retracting the probe prevents the forward movement of the iris-lens diaphragm.
We introduce a specially designed, right-angled cannula mounted on a 2-mL syringe filled with fluid through the main incision and place the tip adjacent to the right wall of the trench at an appropriate depth, depending on the density of the cataract. The tip then penetrates the central lenticular substance, and we inject fluid through the right wall of the trench (Figure 1). The fluid traversing inside out produces delineation. A golden ring within the lens indicates successful delineation (Figure 2). If the delineation is incomplete, the surgeon may inject fluid in the left wall of the trench with another right-angled cannula. The trench allows the surgeon to reach the central core of the nucleus. When fluid reaches a desired depth, it will create an epinuclear bowl that will act as a mechanical cushion to protect the posterior capsule during subsequent maneuvers.
With conventional hydrodelineation, the cannula penetrates the lenticular substance and thus causes the fluid to traverse from the outside inward. It is sometimes difficult to introduce the cannula within a firm nucleus, and the effort can rock and stress the capsular bag and zonules. The surgeon may also inadvertently inject fluid into the subcapsular plane and thereby conduct unwarranted hydrodissection. Inside-out delineation is easy to perform, provides excellent surgical control, reduces stress to the zonules, and precisely demarcates the central core of nucleus.NUCLEAR REMOVAL
We avoid rotating the nucleus, because this maneuver can rupture the posterior capsule. All of our techniques are geared toward facilitating the removal of the nucleus while it is cushioned by the epinucleus. Bimanual cracking and division of the nucleus involve outward movements and can distort the capsular bag. For nuclear sclerosis greater than +2, we use the technique of step-by-step chop in situ and lateral separation12 with 40% to 50% ultrasound, vacuum of 150 to 250mmHg, an aspiration flow rate of 18mL/min, and a bottle height of 70 to 90cm. The resultant fragments are removed with a stop, chop, chop-and-stuff technique.13
For less dense nuclei, we aspirate the entire nucleus within the epinuclear shell. We use an aspiration flow rate of 16mL/min and a vacuum level of 100 to 120mmHg. Traction of posterior lenticular fibers and posterior polar opacity during surgery are sufficient to break the weak posterior capsule. Thus, the slow-motion technique reduces turbulence in the anterior chamber.14 Injecting viscoelastic prior to removing the instrument prevents the anterior chamber from collapsing and the posterior chamber from bulging forward.2,15 Lee and Lee4 described their use of the lambda technique to sculpt the nucleus, after which they cracked along both arms and removed the central piece.EPINUCLEAR REMOVAL
First, we strip off the peripheral lower half of epinucleus using 30% ultrasound, 80 to 100mmHg of vacuum, an aspiration flow rate of 16mL/min, and a bottle height of 80 to 90cm. The central area of epinucleus remains attached.2,5,11 Next, we mobilize the peripheral upper epinucleus (subincisional epinucleus) with gentle, focal, multiquadrant hydrodissection using a right-angled cannula that faces right and left (Figure 3). The fluid wave travels along the cleavage formed between the capsule and lower epinucleus without threatening the integrity of the posterior capsule. Hydrodissection is safe at this stage, because the capsular bag is not fully occupied. In other words, the built-up hydraulic pressure is not sufficient to rupture the posterior capsule. Finally, we aspirate the entire epinucleus, including the central area.
Others have suggested performing viscodissection of the epinucleus by injecting viscoelastic (Healon5 [Pharmacia AB, Stockholm, Sweden]6 or Healon GV [Pharmacia AB] and Viscoat5) under the capsular edge to mobilize the rim of epinucleus. The surgeon then removes this rim with a coaxial I/A handpiece. Alternatively, one may perform manual dry aspiration with a Simcoe cannula.4PSEUDOHOLE
At times, the classic appearance suggestive of a defect may be observed in the posterior cortex when the posterior capsule actually remains intact. This phenomenon is known as a pseudohole.
Bimanual, automated I/A using an aspiration flow rate of 20mL/min and vacuum of 400mmHg optimizes surgical control, preserves the anterior chamber, and aids in the complete removal of the cortex. Fine et al5 reported using coaxial phacoemulsification to protect the posterior capsule with viscoelastic during cortical removal.POLISHING THE POSTERIOR CAPSULE
We avoid polishing the posterior capsule due to its fragility.1-3,5,11 The traction produced by polishing an excessively adherent plaque could eventually rupture an otherwise normal posterior capsule. We prefer to perform an Nd:YAG posterior capsulotomy postoperatively when needed.POSTERIOR CAPSULAR DEHISCENCE
If a defect is present in the posterior capsule, we inject Viscoat over the area before withdrawing the phaco or I/A probe from the eye.15 Then, we perform a two-port, limbal anterior vitrectomy using a cutting rate of 800 cuts/min, vacuum of 300mmHg, and an aspiration flow rate of 25mL/min. Once the anterior chamber is free of vitreous, we aspirate the cortex with bimanual I/A. A posterior capsulorhexis may be performed if the rupture is confined to a small central area.IOL IMPLANTATION
In eyes with a posterior capsular defect, we implant the IOL in the bag only if we can create a posterior capsulorhexis. If the posterior capsular defect is large, we will place the lens over the anterior capsule in the ciliary sulcus. Although others have suggested capturing the optic through the anterior capsulorhexis,5,16 we believe optic capture increases inflammation.17After implanting the IOL, we remove viscoelastic by two-port vitrectomy rather than I/A. Vitrectomy aspirates material in a piecemeal and gradual manner, and it reduces the chance of rapidly aspirating vitreous.
We do not suture the main valvular incision but do suture the paracentesis in eyes with a posterior capsular defect. We will periodically evaluate these eyes for retinal break, cystoid macular edema, and raised IOP.
Abhay R. Vasavada, MBBS, MS, FRCS, is Director of the Iladevi Cataract & IOL Research Centre, Raghudeep Eye Clinic, Memnagar, Ahmedabad, India. He states that he holds no financial interest in any product or company mentioned herein. Dr. Vasavada may be reached at +91 79 7492303; email@example.com.
Shetal M. Raj, MBBS, MS, is Senior Consultant, the Iladevi Cataract & IOL Research Centre, Raghudeep Eye Clinic, Memnagar, Ahmedabad, India. She states that she holds no financial interest in any product or company mentioned herein.
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