16 Posterior Polar Cataract Posterior polar cataracts (PPCs) are a challenge for every cataract surgeon due to their propensity for posterior capsule dehiscence and weakness. Although the initial reported incidence of posterior capsule rupture (PCR) ranged from 26 to 36%,1,2 subsequent improvements in understanding of techniques2–17 and technology have led to a reduction in the rates of PCR to 6 to 7%.8,9 Depending on the clinical presentation, PPCs can be divided into three categories: (1) polar cataracts without evident posterior capsule dehiscence (Fig. 16.1); (2) polar cataracts with preexisting posterior capsule dehiscence (Fig. 16.2); and (3) spontaneous dislocation. PPCs without evident dehiscence account for 97% of all polar cases and are the most common presentation in patients under 40 years of age. This chapter describes the difficulties associated with PPC emulsification and different surgical strategies to improve safety, reduce posterior capsule rupture, and enhance the predictability of outcomes in emulsifying PPCs. It also discusses the role of femtosecond laser–assisted cataract surgery to improve safety in these cataracts. Both the novice and the experienced surgeons will find useful practical tips that they can use when faced with PPCs. The discussion addresses the clinical presentation, the principles for safe removal of PPCs, as well as the different surgical approaches to deal with PPCs. Most commonly, PPCs present with glare disability in bright light conditions. Two types of PPCs have been described in literature: stationary and progressive.18 The stationary type is characterized by a central, dense, disk-shaped opacity located on the posterior capsule with concentric rings around the central plaque opacity that look like a bull’s-eye. It has a cone-shaped projection in the subcapsular region or central posterior cortex. This type of PPC is compatible with good vision. In the progressive type of PPC (Fig. 16.3), changes take place in the posterior cortex in the form of radiating rider opacities. Patients with progressive opacity become more symptomatic as the peripheral extensions enlarge. Normally the patient seeks help in the third or the fourth decade of life. PPCs are present bilaterally in 90% of our cases in adults and 70% in a study conducted by Gavriş and colleagues.19 Often, a posterior capsule defect is observed as an elliptical-shaped defect (Fig. 16.2), which is generally vertically oriented with a central bull’s eye–shaped opacity. Coexisting anomalies have not been reported in the literature, except for a report of coexisting retinitis pigmentosa in the Siatiri and Moghimi10 study. It has been suggested that the size of the polar opacity has a significant impact on the risk of posterior capsule rupture.16 In the same study, in eyes with polar opacities of 4 mm or more, seven eyes (30.43%) had posterior capsule rupture, whereas in eyes with polar opacities of less than 4 mm, two eyes (5.71%), had PCR.16 Further, PCR was found to be more common in patients younger than 40 years and in the eyes that underwent extracapsular cataract extraction as compared with phacoemulslfication.15 The final surgical goal for every surgeon is to be able to safely remove the entire cataract and implant an intraocular lens (IOL), preferably in the capsular bag. To protect the inherently weak posterior capsule, the strategy for posterior polar emulsification involves the following: Several surgical approaches have been proposed for emulsification of PPCs. Our preferred approach is usually a temporal, clear corneal incision. The smallest size of the incision compatible with the surgeon’s phaco tip, sleeve, and comfort level should be selected. We prefer a 2.2-mm incision, as it facilitates maintenance of a closed chamber during surgery. High molecular cohesive ophthalmic viscosurgical devices (OVDs) should be used during capsulorrhexis. While making the capsulorrhexis, a moderate size should be aimed at so that in the eventuality of inadequate posterior capsule support, a sulcus IOL can be placed. Cortical cleaving hydrodissection should be avoided in PPCs, as it can lead to a rapid buildup in hydraulic pressure and blowout of the posterior capsule.1,2,6 Instead, several authors have recommended performing hydrodelineation to create a mechanical cushion of the epinucleus.2,5,8,10,20 The rationale is to create a mechanical cushion that separates the nucleus from the fragile posterior capsule and thereby prevents transmission of mechanical and fluidic forces to the weakest part of the capsule. Similarly, viscodissection has also been performed to protect the posterior capsule.5,6 A dispersive OVD is injected between the epinucleus and the posterior capsule to create a plane of separation and generate space that cordons off the polar opacity during phacoemulsification, and reduces transmission of mechanical forces to the potentially weak capsule. In addition to hydrodelineation, Fine and coauthors6 also perform hydrodissection in multiple quadrants injecting tiny quantities of fluid gently, such that the fluid wave is not allowed to spread across the posterior capsule. Fig. 16.1 (a,b) Posterior polar cataract (PPC) characterized by a central, dense, disk-shaped opacity located on the posterior capsule with concentric rings around the central plaque opacity that look like a bull’s-eye. We published the inside-out delineation in PPCs,9 in which a central trench is sculpted. Then, specially designed right- and left-angled cannulae are placed at a chosen depth in the trench, and fluid is injected (Fig. 16.4). A golden ring within the lens is evidence of successful delineation (Fig. 16.5). Fluid injection is performed in both right and left walls of the trench. The advantage of this technique is that as fluid is injected at a desired depth, under direct vision, a desired thickness of epinucleus cushion can be achieved, and inadvertent subcapsular fluid passage is prevented, which can often happen with conventional hydrodelineation (Fig. 16.6). Nucleus removal should be performed within the cushion of the epinucleus, so that there is a mechanical so that there is a mechanical layer that protects the posterior capsule. Whatever the nucleus division technique, the surgeon should ensure that a closed chamber is maintained at all times. OVD should be injected into the anterior chamber before withdrawal of any instrument to prevent collapse of the anterior chamber.2 Low aspiration flow rate (AFR) and bottle height (BH) should be used in accordance with the slow-motion technique.21 The collapse of the anterior chamber and forward bulge of the PC is prevented throughout the procedure by injecting a viscoelastic before the instrument is withdrawn (Fig. 16.7). In dense nuclear sclerosis, Lim and Goh22 suggest performing a pre-chop of the anterior epinucleus prior to mobilizing, segmenting, and emulsifying the dense endonucleus. Lee and Lee7 use the lambda technique to sculpt the nucleus, followed by cracking along both arms and removal of the central piece. Perhaps one of the most crucial steps during which PCR occurs is removal of the epinucleus. The epinucleus should first be stripped off the capsule using the phaco tip with minimal AFR (14 to 16 cc/min) and vacuum (around 100 mm Hg). At this point, no attempt should be made to completely remove the epinucleus, and the central area is left attached.2,4,6 Then, multiquadrant hydrodissection is performed using special angled cannulae (Fig. 16.8). Because separating the epinucleus from the fornices creates a cleavage plane, passage of fluid does not cause buildup of hydraulic pressure. Therefore, even if there is a preexisting or intraoperative PCR, there is minimal enlargement of this rupture. The epinucleus is then completely aspirated. We prefer bimanual irrigation and aspiration (I/A), as it provides access to cortex all around without causing incision distortion or anterior chamber shallowing. Posterior capsule polishing should be avoided due to the possibility of a fragile capsule.
Clinical Presentation
Risk Factors for Posterior Capsule Dehiscence in Posterior Polar Cataracts
Surgical Strategies in Posterior Cataract Emulsification
Inside-Out Delineation
Nucleus Removal
Epinucleus Removal
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