Eyeworld

MAR 2012

EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.

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26 EW NEWS & OPINION Cataract continued from page 24 March 2012 Figure 3A. Use of microrhexis scissors in excising a fibrotic anterior capsular rent to maintain adequate mydriasis throughout the phacoemulsification procedure. It is important to decide on the type of anesthesia. Injection anes- thesia is preferred by many sur- geons, although the procedure can be safely performed under topical anesthesia. Injection anesthesia is preferred in patients with hard cataract and associated comorbid conditions like subluxated cataract, small pupils, etc. When performed under topical anesthesia, the patient may experience discomfort during maneuvers that stretch the zonular apparatus, when there is excessive movement of the lens-iris di- aphragm. This undesirable sensation may be eliminated by intracameral non-preserved lidocaine. Enhanced posterior diffusion of the anesthetic drug through the zonule may cause transient blindness due to tempo- rary retinal block. Intraoperative problems and surgical technique The intraoperative problems to be anticipated during phacoemulsifica- tion include: ocular hypotony, deep anterior chamber, disturbed vitreous dynamics, compromised zonule, poor pupillary dilatation, loose capsular bag, pre-existing posterior capsular rent, posterior capsular plaque, dropped nuclear fragments, and infusion deviation syndrome. Ocular hypotony can be coun- tered by firming the globe with vis- coelastics. An infusion cannula may be placed through an inferotemporal sclerotomy port and the flow used to firm the globe. To prevent excessive deepening of the anterior chamber, it is advisable to perform the surgery at a reasonably low infusion bottle height, and other phaco parameters are also adjusted appropriately. An- other technique is to enter the ante- rior chamber with the phaco probe in a dry manner with prior elevation of the pupillary margin with a spat- ula working from the side-port. The Figure 3B. Use of microrhexis forceps in completing the rhexis in the presence of anterior capsular fibrosis microscope magnification (zoom) can also be adjusted at a low level to enhance the depth of focus. 1. Incision A clear corneal incision is pre- ferred to a scleral tunnel incision. Both the phaco and side-port inci- sions should be carefully fashioned to avoid fluid leakage since fluid dynamics become increasingly important in these eyes. A scleral tunnel incision is pre- ferred if the patient opts for a rigid IOL or in a very challenging case where the surgeon may have to con- vert to a large incision non-phaco technique. A fornix-based conjuncti- val flap (Figure 1) can be dissected, which may be difficult due to the scarring. The conjunctival flap should be anchored at the periphery at the conclusion of surgery. 2. Capsulorhexis Capsulorhexis may be challeng- ing in view of the increased preva- lence of anterior capsular fibrosis in many eyes. The red fundal reflex may also be compromised due to the posterior segment pathology, ad- vanced nature of the cataract at the time of presentation, and a lusterless cornea in some patients. Therefore, it is prudent to stain the anterior capsule with trypan blue dye to en- hance its visibility. A sharp cystotome should be used for capsulorhexis. It is prudent to keep a pair of microrhexis forceps and scissors handy. One may need to incise the fibrotic areas with mi- crorhexis scissors (Figures 3A and 3B). Every effort should be made not to deepen the anterior chamber ex- cessively during injection of vis- coelastic. A rhexis of about 5-5.5 mm should be fashioned. This facili- tates nuclear emulsification, reduces the incidence of posterior capsular opacification and capsular phimosis, and promotes adequate fundus visu- alization during post-op follow-up. 3. Hydrodissection steps Hydrodissection must be slow and gentle, keeping in mind the Figure 4A. Central posterior capsular plaque in a post-vitrectomy cataract possibility of pre-existing posterior capsular rent. Slow and gentle hy- drodissection followed by frequent decompression should be done to avoid a posterior capsular blowout. It is necessary to verify that ade- quate nuclear rotation has been achieved to prevent further stress on the compromised capsulozonular apparatus. In eyes presenting with mature white cataracts after vitrec- tomy, the possibility of lens touch and occult capsular rupture should be kept in mind. In these cases, in- stead of hydrodissection, a gentle hydrodelineation and/or hydro-free dissection may be performed prior to removal of the nucleus. 4. Nucleus management A technique of nuclear emulsifi- cation that is least traumatic to the capsulozonular apparatus should be employed. A direct phaco chop tech- nique is believed to be the least trau- matic and is the author's technique of choice. However, the surgeon may employ any technique that he/she is comfortable with, and these may include the stop-and- chop or divide-and-conquer tech- niques. Post-pars plana vitrectomy cataracts are denser than the senile cataract, and therefore, more time has to be spent in emulsifying the nucleus. Care must be taken not to cause thermal burns to the cornea and not to apply excessive force on the lens while emulsifying it. Notable fluctuation of anterior chamber depth may occur because of increased movement of the lens- iris diaphragm. Excessive fluctua- tions can be reduced by keeping the bottle height low and maintaining irrigation whenever the phaco probe or irrigation-aspiration probes are in the eye. These patients are prone to infusion deviation syndrome wherein the fluid migrates posteri- orly through the weakened zonule. Raising the infusion bottle has the paradoxical effect of further shallow- ing the anterior chamber. Figure 4B. View after posterior capsular rhexis that includes the capsular plaque 5. Cortical clean up Cortical clean up should be thorough and performed using lower I/A parameters and circumfer- ential stripping to reduce stress on the zonule. A bimanual irrigation- aspiration system is very efficient for safe and complete cortex removal. Gentle posterior capsular polishing should be performed to reduce the incidence of post-op posterior capsu- lar opacification. 6. Small pupil strategy As mentioned earlier, a long-act- ing cycloplegic and NSAIDs should be instilled in the post-op period. The surgeon should utilize a step- wise approach to small pupil man- agement (posterior synechiolysis, viscomydriasis, pupillary membrane dissection, stretch pupilloplasty, and iris hooks). The Malyugin Ring (MST, Redmond, Wash.) is also a good option. Intraoperative manipu- lations and anterior chamber depth fluctuation should be minimized. 7. Dense posterior capsular plaques Marked posterior capsular fibro- sis or plaques are quite common in silicone oil-filled eyes. Centrally lo- cated plaques (Figures 4A and 4B) may be visually significant and need to be removed. Many plaques may be removed by capsular polishing or dissection with a 26-gauge needle. Once an edge is created it can be peeled off with Utrata forceps. Very dense plaques may be managed by including them in the primary pos- terior capsulorhexis. 8. IOL implantation The IOL should be implanted in such a position so as to ensure long- term fixation and stability as well as to optimize visualization of the pos- terior segment. Regardless of the IOL design, placement must be gentle, avoiding excessive rotational ma- neuvers. If there is zonular dialysis, use of a capsular tension ring ensures that the capsular bag is evenly distended

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