The traumatic cataractous lens poses many unique challenges to anterior segment surgeons. To ensure a successful outcome, we must anticipate and address several issues, some of which are not evident preoperatively. New and evolving technologies are enabling us to approach these complicated cases with more predictability and safety. Although some very helpful devices such as the capsular tension ring are not yet approved for use in the US, novel viscoelastic agents and sutureless, pars plana vitrectomy (PPV) instrumentation are FDA approved and can greatly assist the management of these difficult cases.
A traumatic cataract with vitreous prolapse (Figure 1) involves two special circumstances: (1) the presence of vitreous in the anterior chamber and (2) focal zonular loss with capsular instability. Trauma may also result in corneal scarring and iris irregularity, not to mention posterior segment pathology. These three complications do not directly influence cataract extraction, however, and are not addressed in this article.
Zonular dialysis may also exist in other conditions that are not traumatic, such as pseudoexfoliation or Marfan's syndrome. The difference is that these conditions involve diffuse, progressive zonular disease as opposed to a one-time focal disturbance that occurs upon trauma. Although the surgical approach to cataract extraction may be similar in both scenarios, long-term capsular stability is less likely in the presence of progressive conditions, and surgeons must take this fact into consideration when positioning and fixating IOLs in these cases. This article focuses on the traumatic etiology of zonular loss.
TO PHACO OR NOT TO PHACO?
Your first decision is whether adequate zonular support exists to attempt phacoemulsification. At the slit lamp, carefully evaluate the area of zonular dialysis, the position of the crystalline lens, and the degree of phacodonesis. If the zonular support is minimal and the lens is very mobile, then phacoemulsification is not the best approach. Alternatives include a large-incision intracapsular procedure or, preferably, a PPV/lensectomy. Depending on the patient's age, degree of collateral trauma to the anterior segment, and other surgical factors, you may then either suture in a posterior chamber IOL or implant an anterior chamber IOL. In the future, iris-supported lenses such as the Artisan (OPHTEC, Groningen, The Netherlands) may also prove useful for these cases.
For borderline cases of phacodonesis, re-evaluating the patient with a portable slit lamp while he is supine may help uncover further lens instability. If the plane of the lens tilts significantly into the vitreous, then zonular support may be inadequate for phacoemulsification.
As a general rule of thumb, cataracts with less than 90º (3 clock hours) of zonular loss may be approached with phacoemulsification, but those with greater than 150º of zonular loss may not. Although cases with between 90º and 150º of loss (up to 5 clock hours) are more challenging, surgeons can successfully execute phacoemulsification in these eyes using the techniques and technology available today.
PARS PLANA VITRECTOMY
It is necessary to remove prolapsed vitreous, common in traumatic cases, prior to performing phacoemulsification. Should vitreous get caught in the phaco probe or be placed under any traction, complications such as further vitreous prolapse, an extension of the zonular dialysis, or a retinal detachment may occur.
You may perform the vitrectomy using either an anterior or posterior approach. The latter, while more labor-intensive, is superior because it allows a more physiologic removal of the vitreous. Instead of pulling the vitreous farther anteriorly, a pars plana approach draws the vitreous back toward the vitreous space, thereby clearing the anterior chamber, debulking the anterior vitreous, and preventing a repeated prolapse. Furthermore, if small cortical fragments pass through the zonular defect during the phacoemulsification, you can aspirate them posteriorly with greater safety.
To anterior segment surgeons, however, a pars plana approach is the less familiar option. Typically, we are less accustomed to creating peritomies, suturing an infusion cannula, and managing sclerotomies, and we consider these techniques to be within the domain of vitreoretinal specialists. Fortunately, if you share that view, a technological advance may change your mind and enable you to perform a limited PPV comfortably. The Transconjunctival Standard Vitrectomy System (TSV25) (Bausch & Lomb Surgical, Inc., San Dimas, CA) eliminates the need for a conjunctival peritomy, episcleral cautery, and even sutures. In contrast to traditional, larger, 20-gauge PPV instruments, the 25-gauge TSV25 permits you to create self-sealing transconjunctival sclerotomies and is designed for complete, three-port, posterior-segment surgery.
When treating vitreous prolapse, only a one-port PPV is necessary as opposed to the usual three. Because communication between the anterior and posterior segments exists, you may use an anterior chamber maintainer instead of a posterior infusion cannula. The larger bore of the anterior chamber maintainer provides better inflow of irrigating fluid and allows for superior chamber stability. Place the single PPV port in the quadrant of the zonulysis. Using the TSV25 microcannula over a trocar renders constructing this sclerotomy no more difficult than creating a paracentesis. You may then proceed with the vitrectomy until the anterior chamber is clear. The entry-site alignment cannula allows you to maintain this port's easy accessibility until the conclusion of the case. With the TSV25, you can safely and efficiently expand your temporal, sutureless (maybe even topical) cataract approach to the pars plana and vitreous.
MANAGING ZONULAR DIALYSISThe Necessity of Safety
After clearing the prolapsed vitreous, you must deal with the compromised zonules and capsular instability. Careful steps in each of the three main phases of phacoemulsification can help prevent further zonular dialysis, maintain capsular integrity, and avoid the posterior dislocation of nuclear material. Differing surgical techniques, fluid modifications, and new viscoelastic technologies such as Healon5 (Pharmacia Corporation, Peapack, NJ) can increase procedural safety.
The Capsulorhexis
Performing the capsulorhexis may be difficult in a case of traumatic cataract due to a lack of the usual zonular counter traction forces. To address this situation, initiate the capsular tear in the location of the greatest zonular stability and complete it in the direction of the zonular dialysis. In cases of significant lenticular mobility, you may need to create two semicircular tears that converge. A fine capsulorhexis forceps allows you the most control in these circumstances. A large capsulorhexis of 5.5 mm or more in diameter will allow the lens to prolapse easily. Perform hydrodissection gingerly in order to avoid overfilling the anterior chamber and minimize the rotation of the lens to avoid placing stress on the remaining zonules.
Phacoemulsification
Whichever machine you use, phacoemulsification must proceed under low flow, low vacuum (eg, 30 to 100 mm Hg vs 300 to 500 mm Hg) conditions, whether the nucleus is out of the bag or you are employing an endocapsular approach. The goal is to minimize chamber fluctuation and decrease zonular stress. By moving slowly and using lower vacuum settings, you can ensure that phacoemulsification does not inadvertently trap vitreous or capsular structures. In most cases, a supracapsular approach offers the highest degree of safety. Once you remove the lens from the confines of the capsule, the chances of further capsular tension or damage are minimal.
Throughout this process, viscoelastics play an important role. Liberally inject a dispersive viscoelastic such as Viscoat (Alcon Laboratories, Inc., Fort Worth TX) anteriorly to protect the endothelium and in the area of the zonular compromise to form a barrier to the posterior segment. In addition, it is important to inject Healon5 beneath the lens and into the capsular bag to maintain full capsular expansion. The viscoelastic's rheological properties allow it to be highly viscous, maintain space, and avoid aspiration during low-flow phacoemulsification. The density and greater weight of Healon5 allow you to pressurize the capsular bag and compartmentalize the eye between the anterior and posterior segments.
Hydrodissection is the best method by which to elevate the lens. Avoid techniques such as phaco flip that apply posterior pressure directly on the lens. Next, using low vacuum settings to prevent the aspiration of the Healon5, emulsify the lens in one large piece using a carousel technique. Dividing the lens into multiple fragments risks the loss of one or more of the segments posteriorly through the zonular defect.
I/A
Removing cortex using automated I/A is one of the most challenging steps of the phacoemulsification procedure, because it places the most direct radial force on the zonules. The capsule is floppy and generally collapses toward the aspiration port, both of which raise the risk of damage and further zonular dehiscence. A capsular tension ring offers great assistance during this phase, because it provides a taut capsular equator and reforms the anatomic, fully expanded shape of the capsular bag. This device is unavailable in the US, however.
Alternatively, placing Healon5 within the capsular fornix will maintain its expansion. Splitting the I/A, meanwhile, allows better access to all areas of the capsular fornix and gives you the ability to hold back the capsule with the irrigating instrument while performing aspiration with your other hand. You may also wish to consider using more involved techniques such as the use of modified iris hooks to support the capsule.
If the above I/A techniques prove futile, an IOL placed in the bag can act as a poor man's capsular tension ring. Use a three-piece IOL and place the haptics in the meridian of the zonular loss in order to maximally expand the capsule. Select a lens implant with C-loop, rather than J-loop, haptics. The former shape allows more contact between the haptics and the capsular fornix and thereby better expands the floppy capsule. Further cortex removal can then proceed safely. If the zonules are intact for more than 210º around the lens, then an IOL that is positioned properly within the capsular bag typically remains stable. If the lens/bag complex appears unstable after lens implantation, employ a McCannel suture to secure the haptic to the iris.
CONCLUSION
Traumatic cataracts challenge even the most experienced anterior segment surgeons. With careful planning and the use of the latest technological advances, however, you can manage these difficult cases effectively, safely, and confidently.
