EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/78710
22 EW NEWS & OPINION May 2012 Complicated cataract cases Phaco with weak zonules: Part 1 by David F. Chang, M.D. L ike many conditions that affect the eye, zonulopathy can be in- herited or acquired. Inherited forms do not always manifest at birth. Common inherited conditions include pseudoexfoliation syndrome, retinitis pigmentosa, Marfan syndrome, and ho- mocystinuria. Zonular weakness or dial- ysis is also a common complication of blunt and penetrating ocular trauma and previous eye surgery. Eyes that undergo multiple vitrectomies are at particularly high risk for zonular weakness, espe- cially if the anterior cortical gel has been stripped. In some eyes the reason for zonular weakness may simply be unknown. In the Ophtec (Boca Raton, Fla.) capsular tension ring (CTR) study, the most common indication for CTR implantation was idiopathic zonular weakness unassociated with pseudoex- foliation syndrome. In this month's column, David F. Chang, M.D., presents part 1 of a two- part series on phacoemulsification in eyes with zonular weakness. He dis- cusses intraoperative clinical findings and strategies for managing loose zonules during the early steps of cataract surgery, including capsu- lorhexis and hydrodissection. He ex- plains the application of capsular tension rings and capsule retractors, devices that are especially helpful in weak zonule cases. Since zonular is- sues confront all cataract surgeons from time to time, this information is universally applicable. In the June issue of EyeWorld, Dr. Chang will discuss pearls for nuclear emulsification and cortical cleanup in eyes with weak zonules. Kevin Miller, M.D., Complicated cataract cases editor W eak zonules compli- cate every step of the cataract procedure and challenge sur- geons to diagnose and manage intraoperative zonulopathy. This two-part article will discuss sur- gical pearls for phaco in these cases. Capsulorhexis The capsulorhexis step provides the first opportunity to directly assess zonular integrity. The peripheral an- terior capsule is normally immobile but will demonstrate "pseudoelastic- ity" by seemingly stretching as the capsular flap is pulled.1 This is not true capsular elasticity but rather due to the failure of the zonules to immobilize the peripheral lens cap- sule. The lack of zonular circumfer- ential traction due to diffuse zonular weakness will create difficulty incis- ing the anterior capsule, as though the cystotome were dull. If the cystotome tip depresses rather than incises the central anterior capsule, a halo-shaped light reflex may be noted. Finally, there may be signifi- cant phacodonesis as the cystotome first perforates and tears the anterior capsule. Weak zonules significantly increase the risk of a radial anterior capsular tear because of this pseu- doelasticity. Because the zonules do not adequately immobilize the ante- rior capsule, the peripheral capsule moves along with the flap as it is being torn. While a large diameter capsulorhexis would be helpful for phaco, making a smaller opening re- duces the risk of a peripheral exten- sion if one is struggling to control the tear. Because capsular retractors or a capsular tension ring (CTR) re- quire a continuous curvilinear cap- sulotomy, the overriding importance of achieving an intact capsulorhexis dictates erring on the side of a smaller diameter that can be second- arily enlarged after the IOL has been implanted. The capsule tear-out rescue technique of Brian Little, F.R.C.S., is particularly helpful for controlling a tear that wants to run radially because of weak zonules and pseudoelasticity.2 Hydrodissection When there is diffuse zonular laxity, the nucleus is more difficult to rotate because of deficient capsular rotational stability and counter fixa- tion. One should therefore suspect significant circumferential zonular weakness if, despite proper hydrodis- section technique, the nucleus does not rotate easily. Overly forceful efforts to rotate the nucleus may shear already weakened zonules. This may potentially create a large zonular dialysis or dislocate the crystalline lens even prior to insertion of the phaco tip. One alternative is to use two in- struments to bimanually rotate the nucleus. In this situation, the second instrument tip, rather than the cap- sular bag, becomes the counter fixat- ing fulcrum around which to rotate the nucleus. However, when severe zonular laxity is diagnosed during the capsulotomy step and the nu- cleus cannot be easily rotated fol- lowing hydrodissection, the safest strategy is to insert capsule retractors as described below (Figures 1-5). By Figure 1. MST capsule retractors have a looped tip that reduces the risk of puncturing the equatorial capsule and are inserted through paracentesis sites. They are packaged in sets of three and are inserted after capsulorhexis completion Figure 2. Hydrodissection is delayed until after insertion of capsule retractors to reduce the risk of extending the trau- matic zonular dialysis with nuclear rotation Figure 3. Initiation of irrigation propels the nucleus posteriorly, resulting in over tightening of one of the capsule retractors. Seeing this, the surgeon should loosen the tight retractor before resuming phaco Figure 4. Compared to a CTR, capsule retractors do not impede cortical aspiration