A central posterior polar cataract may significantly affect visual function, even if the opacity is small and localized. The central opacity clinically manifests in the early stages of the disease—when patients are relatively young—and early lens removal is always advised to avoid interference with the patient's daily life.
Disturbing symptoms, such as glare and blurry vision, may indicate presence of a posterior polar cataract; patients may also experience difficulty driving at night, working outdoors or on a computer, and reading small print. However, these patients still may have 20/20 visual acuity. Most posterior polar cataracts are relatively soft because they present at a young age.
A preexisting posterior capsular opening may be strongly suspected if the initial slit-lamp examination demonstrates particulates within the slit beam or a circular hazy ring just behind the concavity of the posterior capsule (Figure 1). These cataracts have a different appearance than routine posterior subcapsular axial opacities that occur in young adults—they resemble a characteristic onion peel or a bull's eye pattern with white calcific borders. The concentric morphology occupies both the posterior subcapsular and posterior cortical regions (Figure 2).
RECOMMENDED PRECAUTIONS FOR REMOVAL
We recommend cataract removal the moment the patient presents with visually disturbing symptoms. Long waits serve no purpose, and an early procedure makes the surgeon's job easier and the prognosis better. We recommend phacoemulsification for all cases. It is best to presume that the posterior capsule is breached or compromised beneath the area of the posterior polar cataract before proceeding with surgery.
Several surgical precautions must be considered in a young patient with a posterior polar cataract. First, the two incision ports must be separated by at least 2 clock hours to create the right vector force angle between the two instruments and thus allow the nucleus to be scooped out. The lens capsule tends to be more elastic in younger eyes, which may cause a wider capsulorrhexis tear than anticipated. By using a high-viscosity ophthalmic viscosurgical device (OVD) and aiming for a smaller capsular opening than you actually want, a continuous capsulorrhexis of the desired size can be achieved. However, to prevent the nucleus from pushing into the vitreous, do not over-inflate or over-pressurize the chamber. This is especially likely to occur if there is a preexisting opening in the posterior capsule. The capsulorrhexis should be no larger than 5.25 or 5.5 mm; the opening should be large enough to scoop the nucleus out and adequate enough for the IOL to be placed in the capsular bag if the posterior capsular breaks. Even though defects in the posterior capsule do not exist in every case, it is better to prepare for a break than to lose the lens into the vitreous.
INSTRUMENTS AND PARAMETERS
We use a blunt, bevel-up, 23-gauge curved cannula to perform the hydroprocedure in various deep planes. We create various rings, always avoiding the sudden gush of fluid and maintaining steady pressure on the syringe. It is important not to over-hydrodissect or place too much pressure on the posterior capsule because vigorous hydrodissection or viscodissection may perforate an intact but abnormally thin central posterior capsule. This may cause serious extension to an already open posterior capsule. Capsular-cortical cleavage is strongly contraindicated in such cases.
Parameters are modified from our standard settings (ie, bottle height, 90–100 cm; flow, 28–30 cc/min; vacuum, at least 240 mm Hg). We lower the bottle height (70–80 cm), flow rate (24 cc/min), and vacuum (180 mm Hg) to provide a relatively deep, pressurized anterior chamber in a lower pressure setting. This minimizes turbulence and hydrostatic pressure and may also avoid hydrodissection and breach of a potential capsular tear or weakness. It helps to maintain steady, unoccluded flow dynamics and provide surge control.
We have performed more than 160 successful posterior polar cataract removals over 4 years. Our current technique is the safest modified technique we have tried. With complication rates less than 5%, we still can manage small posterior capsular openings (Figure 3), frequently without vitreous loss, and place the IOL safely in the bag.
TECHNIQUE
Our devised nuclear scoop technique begins with hydrodelineation in a slow, gradual, and controlled manner in different directions and planes. The beveled cannula is embedded into various nucleus layer, at times bevel down, to create a controlled cleavage of the inner nucleus from the epinuclear plate. More than one delineation ring is achieved, with the golden ring reflex as the central-most, smallest ring of nucleus. More often than not, the smallest nucleus may be delivered through the rhexis opening.
Our nuclear scooping technique may be performed on a wide variety of nuclear densities when the vacuum level is set accordingly: lower for softer nuclei and higher for denser nuclei. It has the advantages of directing most intraocular manipulative forces toward the equator, thus minimizing stretching of the posterior capsule; sculpting; and maximizing the time the tip is occluded. It also minimizes intraocular fluidic currents, further reducing the chance of inadvertent hydrodissection.
Soft to moderate cataracts (grades one and two). At this stage, we distend the chamber with a high-viscosity OVD and position the blunt fork manipulator slowly behind the innermost and smallest nuclear ring. The manipulator is negotiated over to the capsulorrhexis margin (Figure 4) by pressurizing the force vectors toward the lens equator and upward (Figure 5).
Once the manipulator has been inserted into the innermost ring of the nucleus, it is slowly nudged forward and upward, thus freeing the nuclear bulk from the epinuclear plate in a scooping manner. This is achieved once there is slight movement of nucleus (Figures 6 through 8). The capsulorrhexis margin may be used as a lever, and the nucleus is slowly lifted from the epinuclear plate, which is not to be disturbed at this stage. Using the phaco tip in low to moderate vacuum mode, with the bevel down, the nucleus is lifted. A bowl of cortex and the epinuclear plate are left adherent to the capsule, including the cataract at the posterior pole. Later, this is removed centripetally. The soft nucleus is then emulsified using low power settings.
Firm nucleus. Most times, a firm nucleus can be delivered out by slowly lifting it from the rhexis margin in a single piece. Using the phaco probe, bevel downward and in vacuum mode, you can retrieve the nucleus from the nuclear bed. It may then be held in this position by placing the blunt manipulator behind it (Figure 9); emulsification should occur with low phaco powers (20–30%) in the supracapsular plane. To avoid trampolining the chamber, try to keep the tip occluded as much as possible. Some occlusion breaks may occur for repurchase of the nucleus. Proceed circumferentially rather than centrally to avoid such fluctuations.
Very soft cataracts. Sometimes, especially in very soft cataracts, the nucleus may break into two or more pieces, which makes phacoemulsification simpler. In these cases, pull out the phaco probe and reform the anterior chamber with OVD through the sideport incision. Then, use the blunt manipulator to nudge the pieces out of the capulorrhexis, one at time, followed by supracapsular phacoemulsification. Repeat the same maneuvers for the other half of the nucleus (Figure 10).
Hard nucleus. Usually, posterior polar cataracts do not have a hard nucleus, meaning the nucleus is easily aspirated without manual cracking or chopping. However, if you do come across a hard nucleus in these cases, aggressive nuclear chopping/cracking techniques should be avoided because they involve wide separation of fragments and central chopping, which exerts more pressure posteriorly. Such maneuvers stress the posterior capsule and can extend the presumed posterior capsular defect.
Nuclear cracking must only be resorted to in relatively hard cataracts. Use the manual cracking method with an OVD for nuclear segmentation (Figure 11). Because this method relies more on lens segmentation and the application of limited opposing vector forces to disassemble the nucleus toward the lens equator, it avoids the transmission of force to the posterior capsule. Once cracked, the two pieces may be scooped from the bed, one at a time, using the blunt manipulator under the protection of OVD. They are independently emulsified over the capsular plate (Figures 12 and 13).
Extremely hard nuclear cataracts. We prefer the phaco peripheral chop technique because it will not stretch the capsule; it requires peripheral rather than central chopping force vectors. The phaco chopper should reach the edge of the golden ring—never beyond, as this may stretch the epinuclear plate and precipitate a tear in the posterior capsule.
At this point, the entire lens is removed, and the surgeon must be careful to minimize the risk of extension to the presumed capsular opening. Two scenarios may exist. (1) If the epinucleus is already separated and floating, proceed as follows: Continue to aspirate the epinucleus with the ultrasound tip by simple low flow aspiration, followed by IOL insertion. (2) If the epinuclear plate is stuck on the posterior capsule, proceed as follows: Elevate it in one quadrant at a time (Figure 14) using the phaco tip with moderate vacuum (90–100 mm Hg) and flow (22–24 cc/min). Free the epinucleus circumferentially in a flower petal manner; however, do not aspirate it but pull it toward the center of the capsular bag in a centripetal manner. Make sure that the central part of the plate is left intact and removed last. You can also use the I/A tip to address the remainder of the epinuclear shell one quadrant at a time. Go circumferentially around the epinucleus, mobilizing the periphery and allowing the central floor to remain in place. The adherent part of the cortex and epinuclear plate is aspirated. Once complete, circular loosening of the cortex and epinuclear plate is achieved.
If a central plaque of lens cells remains adherent to the posterior capsule after cortical removal, it may be left in its place. No aggressive movement is advised; if there is residual plaque, avoid polishing the central portion because it is frequently weak and opens easily.
Capsular tear. If the posterior capsule has been compromised and the opening is small and round, posterior capsulorrhexis is unnecessary. However, if the margins of the opening are not smooth and continuous, a posterior capsulorrhexis should be performed before IOL insertion.
LENS IMPLANTATION
IOL insertion must be slow and gradual, even if there is no capsular break. Even the slightest force on the weak posterior capsule may be enough to cause a break.
We prefer implanting a foldable IOL using a uniplanar delivery system. If the capsular tear has not distended and is small with no vitreous disturbance seen, we place the IOL in the bag. Alternatively, if the capsule is open or vitreous has presented, the latter must be managed with dry vitrectomy. For beginners, it is a good idea to implant the IOL in the sulcus, over the capsulorrhexis, without attempting in-the-bag implantation.
Even if the posterior capsule remains intact, central scarring of the capsule is sometimes evident and may necessitate (1) primary posterior capsulorrhexis (only recommended for expert surgeons) before lens implantation or (2) Nd:YAG capsulotomy several months postoperatively. The surgeon's goal is to maintain enough capsular bag to safely implant the posterior chamber IOL. If this is possible, the lens should be fixated in the capsular bag. Several methods allow the IOL to be inserted without further damaging the capsular bag. We prefer a bimanual technique in which the trailing haptic is compressed with a curved, Y-hook manipulator in the left hand.
Kamal B. Kapur, MBBS, MS, is the Medical Director of Sharp Sight Laser Centres, New Delhi, India. Dr. Kapur states that he has no financial interest in the products or companies mentioned. He may be reached at tel: +91 22461146 or +91 22461134; fax: +91 22461150; e-mail: kbkapur@yahoo.com.
Samir Sud, MBBS, DNB, practices at the Sharp Sight Centers, New Delhi, India. Dr. Sud states that he has no financial interest in the products or companies mentioned. He may be reached at tel: +91 22461146 or +91 22461134; fax: +91 22461150.
