October 2016

 

RETINA

 

Management of capsule rupture at cataract surgery


by Steve Charles, MD

 
   
Ruptured capsule
Ruptured capsule at cataract surgery Source: Byron Wood, Vitreous Microsurgery, Fifth Edition

Tips for avoiding a retinal break or detachment after cataract surgery

In spite of extraordinary advancements in cataract surgery techniques and technology, rupture of the posterior capsule, posterior dislocation of lens material, and the need for anterior vitrectomy still occur at a substantial rate. It is likely that femtosecond laser-assisted cataract surgery will reduce the incidence of capsular rupture, but widespread adoption will take years. The relatively low incidence of capsular rupture can produce the unintended consequence of poor preparation and even hasty, unwise actions. Anterior vitrectomy began with the pioneering work of David Kasner in the late 1960s, using cellulose sponges and scissors to remove anterior vitreous. This approach was based on the concept that the critical problem was vitreous incarceration in the cataract wound. Unfortunately, it was not recognized that severe intraoperative vitreoretinal traction is inherent in cellulose sponge anterior vitrectomy. Lifting the sponge and adherent vitreous to enable scissors cutting as well as wicking cause marked acute vitreoretinal traction. Anterior vitrectomy is never “simple,” as some surgeons have incorrectly stated. Anterior vitrectomy is performed in close proximity to the vitreous base, a zone of permanent adherence of vitreous to peripheral retina with 1/100 the tensile strength of posterior retina. The majority of post-cataract surgery retinal breaks occur at the posterior edge of the vitreous base. Aspirating liquid vitreous without a cutter is hazardous, liquid vitreous is illusory, severe vitreoretinal traction always occurs from pulling on the collagen fiber matrix.

Vitreous cutters are far safer than cellulose sponge vitrectomy. Cellulose sponges should never be used to test for vitreous during cataract surgery or penetrating keratoplasty or removal of vitreous at the site of traumatic corneal-scleral lacerations. Vitreous cutters must be used with the highest possible cutting rates to minimize pulsatile vitreoretinal traction. I coined the term “pulse flow” to describe the volume of vitreous that goes through the cutter port with each open/close cycle. High cutting rates produce lower pulse flows, less acceleration, and therefore less force on the vitreous. High cutting rates confine energy to the region near the port while lower cutting rates produce remote effects, i.e., retinal breaks. The lowest effective aspiration flow rate or vacuum should be used to reduce non-pulsatile vitreoretinal traction. Technique is crucial as well; the vitreous cutter should never be pulled back while vitreous is engaged; the safest technique is “continuous engage and advance,” a term I coined. Infusion should always be used for anterior vitrectomy; so-called “dry vitrectomy” inherently produces hypotony, scleral infolding often misinterpreted as choroidal effusion, miosis, and occasionally, catastrophic suprachoroidal hemorrhage. The infusion should always be separated from the vitreous cutter incision; the infusion sleeve causes turbulence, which reduces vitrectomy efficiency as well as causes damage to the corneal endothelium. The vitreous cutter should be placed through one sideport incision or the pars plana and a 23-gauge angulated infusion cannula or anterior chamber maintainer through another sideport; the cutter should never be placed through the phaco incision. Separating the cutter from the infusion reduces turbulence, endothelial damage, iris trauma, and is more efficient with respect to removing vitreous. Although many surgeons are not comfortable with pars plana vitrectomy, this approach removes all vitreous from the anterior segment without damage to the corneal endothelium or iris, eliminates vitreous to the wounds, and is effective at removing residual cortex. If a pars plana vitrectomy approach is utilized, the phaco wound should be sutured to prevent iris prolapse. Although trocar-cannula systems have revolutionized sutureless, transconjunctival vitreoretinal surgery, they are unnecessary for pars plana approaches to anterior vitrectomy. The primary purpose of trocar-cannula systems is to maintain misalignment of the conjunctiva that was intentionally displaced from the sclerotomy site and allow tool exchange without wound damage. Neither of these advantages is relevant to the cataract surgery setting. It is better to make a small circumferential conjunctival incision 3.5 mm posterior to the limbus and enter with a 23-gauge MVR blade; a scleral tunnel is not recommended. Creation of a scleral tunnel in a soft eye can result in suprachoroidal introduction of the cutter. Although some manufacturers have advocated 25-gauge vitrectomy for this setting, 23-gauge is a better choice because of tool stiffness in the context of topical anesthesia and eye movement. I use 25/27-gauge vitrectomy for all posterior vitrectomy cases, but these procedures are performed with a retrobulbar or occasionally peribulbar block. Visualization is essential for safe, effective anterior vitrectomy; triamcinolone particulate marking is ideal for this purpose. Triesence (Alcon, Fort Worth, Texas) is preservative-free.

Many anterior segment surgeons incorrectly think that vitrectomy causes cystoid macular edema (CME); however, extensive pars plana posterior vitrectomy never causes CME, which refutes the vitreous removal hypothesis for CME causation. CME is associated with anterior vitrectomy after capsule rupture in cataract surgery not because of vitreous removal but due to iris trauma from cellulose sponges, iris retractors and surgical manipulation. Cellulose sponges imbibe infusion fluid and liquid vitreous, swell, and traumatize the iris as they are lifted out of the vitreous cavity. In addition, direct iris trauma occurs when they are used to test for vitreous. Sweeping the wound is also a dangerous maneuver; acute vitreoretinal traction results from this maneuver. It is far safer to remove vitreous from the wound with the cutter.

When capsule rupture occurs, the first step is to inject OVD before removing the phaco probe to stabilize the anterior chamber and prevent lens material from moving posteriorly. A viscoelastic barrier is ideal for prevention of vitreous mobilization into a capsular defect and the phaco wound while removing remaining lens material and implanting an intraocular lens. Posterior dislocation of lens material never damages the retina; inappropriate action by the surgeon is the real cause of retinal damage in this situation. The phaco probe can give the illusion of anterior vitrectomy because it liquefies hyaluronan gel, but it doesn’t break up collagen fibers. Using the phaco probe in vitreous in an attempt to prevent lens material from falling posteriorly is a very dangerous practice. Jagged, hard nuclear fragments will never damage the retina if dropped unless a surgeon manipulates them. Similarly, using a lens loop in the vitreous is to be avoided; vitreoretinal traction is inevitable with this technique. Some surgeons have advocated irrigating posterior dislocated lens material in an attempt to mobilize it anteriorly, apparently unaware that forceful irrigation is used to create retinal detachment in experimental models. If lens material becomes dislocated into the vitreous cavity the cataract surgeon should perform an anterior vitrectomy and then remove residual cortex anteriorly without producing vitreoretinal traction.

If the capsular defect is small, an IOL can be implanted in the capsular bag. If there is insufficient posterior capsular integrity to support in-the-bag implantation, sulcus implantation with an appropriate IOL is often possible. If there is insufficient capsular support for sulcus implantation, the surgeon can use an anterior chamber lens unless the patient has Fuchs’ dystrophy or significant glaucoma. Although many surgeons use sutured or glued IOLs, I urge caution. Many cases of late weakening and breakage of sutures, endophthalmitis from erosion of the suture through a scleral flap and the conjunctiva, and even suprachoroidal hemorrhage from suture passage through the pars plicata have been reported. Iris suturing can lead to uveitis, hyphema, glaucoma, and CME.

If posterior lens material is present, the cataract surgeon should suture the cataract wound after vitreous and cortex cleanup to prevent iris prolapse at a subsequent posterior vitrectomy for removal of the lens material. Only in special circumstances should pars plana vitrectomy and removal of the posterior lens material be performed during the same procedure. A clear cornea and well-dilated pupil are needed for optimal visualization; complicated cataract surgery does not always provide this. Endoillumination, a fundus contact lens or wide-angle viewing system, a 7,500–10,000 cuts/minute cutter, and a fragmenter are required for posterior vitrectomy and removal of lens material in addition to requisite training and experience. Adequate visualization behind the equator is not possible without endoillumination and fundus visualization optics. Using the phaco probe in the vitreous cavity is unwise; it is too short and not the correct diameter for 20/25 sclerotomy adaptors. The current Alcon fragmenter is 20 gauge and has exactly the same phaco power as the phaco probe, albeit without Ozil. A complete core vitrectomy should be performed before removing lens material with the fragmenter to avoid vitreoretinal traction. Triamcinolone particulate marking facilitates more efficient and complete vitrectomy. Suction only mode is utilized to lift lens material away for the retinal surface; the first arc of pedal travel controls vacuum with the Constellation Vision System (Alcon). The second arc of pedal travel proportionally controls ultrasonic power. Continuous aspiration and ultrasound energy is mandatory to prevent scleral burns and plugging. Power should be stopped instantly if so-called lens milk indicating plugging occurs; scleral burns will occur very rapidly without fluid flow. The fragmenter must then be back flushed outside the eye while ultrasonic power is applied. Careful examination of the retinal periphery must be done to find any retinal breaks so endolaser retinopexy and fluid-gas exchange with SF6 can be performed. Liquid perfluorocarbon is unnecessary in the vast majority of cases but can be used to float a rock hard, black nucleus into the anterior chamber after core vitrectomy is performed. In summary, patients have very high expectations with modern cataract surgery and are not mentally prepared for a retinal detachment. It is essential to focus on the inescapable fact that many, if not most, retinal detachments after cataract surgery are driven by incorrect intraoperative management and therefore preventable.

Editors’ note: Dr. Charles practices at Charles Retina Institute, Germantown, Tennessee. He has financial interests with Alcon.

Contact information

Charles: scharles@att.net

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