19 Torn Posterior Capsule and Anterior Vitrectomy Rupture of the posterior capsule during phacoemulsification is a rare but serious intraoperative complication and carries the risk of precipitating problems such as retinal detachment that may lead to permanently decreased visual acuity.1 Recent studies report that the rate of posterior capsular rupture, with or without vitreous loss, ranges from 0.45 to 7.9%.2–5 In the event of a posterior capsular rupture, the outcome is heavily dependent on the surgeon’s early recognition and management of the problem. The lens capsule is an elastic, clear, basement membrane composed of type IV collagen produced by lens epithelial cells. The zonular fibers insert on the equatorial lens capsule, anteriorly 1.5 mm onto the anterior capsule and posteriorly 1.25 mm onto the posterior capsule.6 The capsule has variable thickness. Although the capsule is thickest (17 to 23 µm) near the anterior and posterior equator where the zonular fibers attach, it is only 2 to 4 µm thick at the posterior pole. The anterior capsule is considerably thicker than the posterior pole (14 µm in adults), and it continues to increase in thickness with age. The posterior capsule may be particularly fragile in patients with congenital posterior lenticonus and posterior polar cataract7 (Fig. 19.1). Patient factors that increase the risk of capsular rupture have been well identified.8,9 Eyes with long or short axial lengths, that is, with associated deep or shallow anterior chambers, respectively, present certain challenges. In high myopia, the anterior chamber is deeper, drawing the surgeon’s instruments to a more vertical position. The posterior capsule may exhibit a “trampolining” motion due to the thinner, more pliant tissues. Lowering the bottle height and decreasing the vacuum and flow settings can help compensate for this movement. In high hyperopia, the anterior chamber is crowded, decreasing the area in which to work. Furthermore, the posterior capsule is more anterior and closer to the surgeon’s instruments. Dense, mature cataracts described as black or white cataracts present added risk. These lenses bring challenges to performing a capsulorrhexis, require increased phacoemulsification energy, and impede adequate visibility. Such dense cataracts are more prevalent in older patients, and advanced age is an independent risk factor. This risk is likely best explained as a combination of coexisting factors such as zonular weakness, small pupil, and dense lens.10 Management of white cataracts and brunescent cataracts is discussed in Chapters 14 and 15, respectively. Small pupils are a significant predisposing factor for violating the posterior capsule during surgery. Floppy iris syndrome, posterior synechiae, and pseudoexfoliation are some of the most common causes of inadequate pupil size. Small pupils may be a harbinger of further problems, as many causes of small pupils carry other risks such as zonular laxity and iris billowing.11 These problems, and the techniques to address them, are discussed fully in Chapters 4, 5, and 23. Other predisposing factors for capsular rupture may include (1) uncooperative, disoriented, or anxious patients with subsequent inadvertent movements; (2) poor visualization due to unclear media such as corneal disease; (3) preexisting trauma with unseen capsular rupture or zonular damage; (4) previous ocular surgery, especially vitrectomy with or without silicone oil; (5) a history of intravitreal injections, which may have violated the posterior capsule; and (6) an inexperienced surgeon (e.g., a resident). Lastly, the surgeon can reduce the risks by proper positioning and management of the surgical field. Appropriate placement of the surgeon’s hand position in relation to the patient’s brow can improve visualization and decrease torsion of the globe. A temporal position, which is now favored by cataract surgeons, is particularly advantageous if the brow is prominent (e.g., a deep-set eye). Pooling of fluid on the surgical field can be addressed by turning the head temporally to allow fluid to drain. During phacoemulsification the hydrostatic pressure in the anterior chamber is greater than physiological intraocular pressures (IOPs) but ideally is maintained in a constant state. This is the result of the balance of numerous factors: (1) hydrostatic pressure created by the height of the infusion bottle (11 mm for every 15 cm of bottle height) or a phacoemulsification platform with target IOP control, (2) the evacuation of fluid or lens material controlled by the surgeon through vacuum and aspiration, and (3) the egress of fluid through the wounds. When the posterior capsule unexpectedly ruptures, there is a sudden equalization of the hydrostatic pressure between the anterior chamber and the vitreous cavity. This causes an abrupt posterior displacement of the iris and dilation of the pupil as the posterior capsule opens. This is often the first warning of capsular rupture. Another indicator of capsular rupture is that the nucleus seems to “fall away” from the phaco tip. This phenomenon is due to the loss of the support of the posterior capsule and subsequent movement of lens material posteriorly. The apparent loss of the phaco effect and a sudden clear zone that appears near the phaco tip are indicators that vitreous may be caught in the phaco tip. These warning signs are especially important when visualization of the posterior capsule is impaired in scenarios such as poor dilation or dense cataract. Generally, if the surgeon is suspicious that the posterior capsule has ruptured, it probably has. The surgeon is therefore justified in modifying the surgical plan on the suspicion of a tear of the posterior capsule. These signs of posterior capsule rupture can occur not only during phacoemulsification or irrigation and aspiration (I/A), but may also occur during hydrodissection. Aggressive hydrodissection may result in a posterior capsular rupture, especially in the presence of a small or noncontinuous capsulorrhexis. If a posterior capsular rent that developed during hydrodissection is not identified before the infusion of fluid from the phaco handpiece, the lens may be driven into the vitreous.12 To repeat, if the surgeon is suspicious that the posterior capsule may be torn, it probably has. Before any management decisions have been made, the first step should be to stabilize the anterior chamber. The phaco or infusion-aspiration tip should remain in the eye, aspiration should be immediately stopped, and infusion should continue to maintain positive pressure. The second instrument can then be carefully removed so that dispersive viscoelastic can be generously injected to aid in holding the vitreous behind the posterior capsule. After a liberal amount of viscoelastic has been injected, then the phaco tip can be cautiously removed from the eye and the surgeon can prepare for possible vitrectomy. After these steps have been taken, the surgeon can then develop a concise alternative surgical plan with the goal of minimizing the duration of surgery and decreasing the risk of injury to the cornea or retina (Fig. 19.2). The surgeon’s alternative surgical plan hinges on two questions: First, has vitreous migrated into the anterior chamber? Second, does nucleus still remain in the eye? When in doubt, it is prudent to convert to an extracapsular cataract extraction rather than proceed with phacoemulsification. A key factor in the determination as to whether to continue phaco or convert to extracapsular surgery might be the presence of vitreous in the anterior chamber combined with a large piece of nucleus. If vitreous is present immediately after a capsular tear, generally it indicates a large capsular tear combined with syneretic poor vitreous support. Once a posterior capsular rupture is identified, it is of utmost importance to inject a dispersive ophthalmic viscoelastic device (OVD) beneath the lens material to tamponade the vitreous posteriorly and hold all lens fragments anteriorly (Fig. 19.3). The advantage of dispersive viscoelastic is that it resists egress through incisions or by aspiration.13 Additionally, dispersive agents are well absorbed through the trabecular meshwork, which aids in decreasing a spike in postoperative IOP. The clear corneal incision should be sutured and abandoned if large lens material is to be evacuated manually, and a shelved limbal incision should be created after conjunctival peritomy.14 Expanding clear corneal incisions to 10 mm or greater to facilitate removal of large nuclear fragments will result in large amounts of irregular astigmatism that will be challenging to manage. Surgeons commonly underestimate the size of the limbal incision required to remove the largest nuclear remnant. Therefore, it is wise to create an incision larger than thought necessary. Extracting lens fragments using a lens loop, a Sinskey hook and spatula, or a Kansas forceps should be approached cautiously as it may pull the vitreous with it. As a result, much of the nuclear extraction should be attempted by viscoelastic prolapse. External pressure should be avoided, as vitreous will preferentially be expelled. Fig. 19.2 Prevention of enlargement of a capsular tear. The phaco tip remains within the incision with minimal irrigation and no aspiration. The second instrument is removed and replaced with an ophthalmic viscoelastic device (OVD) cannula. Dispersive OVD is injected above and below the nucleus to stabilize the anterior chamber. Then the phaco tip can be removed. Fig. 19.3 Dispersive viscoelastic (teal) is injected below the lens fragments to prevent loss of fragments into the vitreous and to hold the vitreous back. If a posterior capsular tear is found in the later stages of phacoemulsification, the surgeon may decide that continued phacoemulsification is appropriate. Dispersive viscoelastic should be injected initially before removal of the phaco or I/A handpiece. Additionally, dispersive viscoelastic should be injected below the lens nucleus to raise it into the anterior chamber. This may be injected through a side-port incision or through a pars plana incision to perform posterior assisted levitation of nuclear fragments.13 Once nuclear fragments have been successfully floated into the anterior chamber with a layer of dispersive viscoelastic, cautious phacoemulsification may be continued with low vacuum and low irrigation. A second instrument should be used to deliver nuclear fragments into the phaco tip so as not to aspirate vitreous. Resist the temptation to further fragment the nucleus by cracking or other maneuvers, as these smaller fragments are difficult to chase and may then fall posteriorly. (For additional information on this topic, see Chapter 51.) Removing cortex once a posterior capsular tear has been identified also entails special considerations. Low-flow I/A or using a Simcoe extraction cannula will minimize the turbulence that might enlarge the capsular rent and encourage movement of further vitreous anteriorly. If an inadequate amount of dispersive viscoelastic is remaining over the capsular rent, additional viscoelastic should be injected generously. The I/A tip should be brought into contact with the cortex before the initiation of vacuum to avoid aspirating the vitreous preferentially. Stripping the cortex should be performed in a motion toward the capsular tear, as stripping away from the rent will pull the tear further. Ultimately, if the surgeon is concerned that efforts to remove all the cortex are too dangerous, they should be abandoned. A small amount of cortex can be left behind if maneuvers needed to remove it put the patient at unnecessary risk. Alternatively, bimanual I/A can be utilized to provide exquisite control over I/A. This technique provides improved maneuverability and maintains a more stable anterior chamber. If the vitrector is in use, or going to be used, remaining cortex can be aspirated by bimanual vitrectomy with the cutting mode turned off.15 Some posterior capsular tears may present as round holes, usually as a result of damage by the phaco tip. If the rent is visible and size and location allow, it may be converted into a posterior capsule capsulorrhexis (PCC), which was first described by Gimbel et al16 (Fig. 19.4). After creating some tension to the posterior capsule by injecting viscoelastic through the tear into Berger’s space, coaxial microforceps are used to perform the capsulorrhexis. This technique decreases the likelihood of expanding of the tear during subsequent surgical steps. The creation of a PCC may enable the intraocular lens (IOL) to still be implanted in the capsular bag if anterior vitrectomy is performed sufficiently and without expanding the hole. If the decision is made to place a lens in the capsular bag, a single-piece implant may be preferred because it unfolds slowly and in a controlled manner. (Further information is found in Chapter 6.) For a larger capsular defect, a three-piece implant may be placed with capture of the optic through the anterior capsulorrhexis. Unfortunately, the feasibility of creating a PCC may be limited by residual cortex or peripheral location. The surgeon’s ability to perform a PCC is dependent on obtaining good visibility of the torn posterior capsule’s borders and requires a working coaxial microforceps.
Capsular Anatomy
Risk Factors for Capsular Rupture
Signs of Capsule Rupture
First Steps
Conversion to Extracapsular Cataract Extraction
Continued Phacoemulsification
Posterior Capsule Capsulorrhexis
Ento Key
Fastest Otolaryngology & Ophthalmology Insight Engine
