EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/153099
20 EW CATARACT August 2013 Complicated cataract cases Small, scarred pupil and previous filtering surgery by Kevin L. Waltz, OD, MD T here are several issues cataract surgeons confront when they operate on post-trabeculectomy eyes. The principle and most concerning is accelerated failure of the glaucoma filter. The drop in intraocular pressure that usually accompanies cataract surgery mitigates this concern, in part. Normal, ocular hypertensive, and glaucomatous eyes alike experience the pressure-lowering benefit of cataract surgery.1 More mundane concerns for posttrabeculectomy eyes include, but are not limited to, hyperfiltration through the bleb if it is relatively new, miotic pupil, posterior synechiae, flaccid iris, shallow anterior chamber, the consequences of previous conjunctival surgery, and astigmatism. Fresh blebs may overfiltrate, causing Tenon's capsule to absorb a significant volume of irrigating fluid, placing the cataract surgeon under water in no time. Overhanging blebs may have to be trimmed back if they restrict access to the peripheral cornea. Posterior synechiae may need to be broken to provide access to the cataract. Miotic pupils may need to be opened by pharmacologic means, viscomydriasis techniques, pupil stretch,2 pupil expansion rings, or hooks. Shallow anterior chambers are common in angle closure and combined mechanism glaucoma. The surgeon needs to be familiar with methods for deepening the chamber, be it with viscoelastics or by performing a limited vitrectomy. Lastly, most eyes with glaucoma filters have good visual potential. These patients have the same desire for good refractive outcomes as other patients. Meticulous attention to biometry, intraocular power calculation, and the management of astigmatism are essential. In this issue, Kevin Waltz, OD, MD, provides some of his insights into the management of cataract in the post-trabeculectomy eye. While the number of these eyes is declining, they will continue to be an important part of ophthalmic practice for decades to come. W hile the number of patients undergoing trabeculectomy is declining in general,1 cataract patients still present who have undergone previous filtering surgery. Previous trabeculectomy presents a number of potential challenges during cataract surgery including posterior synechiae and corneal astigmatism. In addition, it is necessary to keep turbulence during cataract surgery to a minimum so as not to compromise the function of the bleb. When there are a number of challenges at the start of a case, any small deviation can cause surgical plans to be changed in a major way. As a surgeon, I never want to start a case such as this without 100% confidence in my equipment. An 80-year-old white male patient presented who had been previously diagnosed with glaucoma and had undergone trabeculectomy in both eyes. As a result, he had posterior synechiae, his pupils did not dilate well, and I had no way of assessing his ciliary zonules prior to surgery. The prior trabeculectomies had also left this patient with significant corneal astigmatism that he wanted corrected via a toric IOL. The patient understood the complicated nature of the case. The capsular bag and ciliary zonules must be intact to receive a toric IOL. I could not evaluate the zonules and capsular bag until the time of surgery. With the patient fully aware of the complexity and uncertainties of the surgery, I turned my attention to planning how to achieve the best outcomes possible for him. Such a surgery requires a viscoelastic. I decided to use Healon Endocoat (Abbott Medical Optics, AMO, Santa Ana, Calif.) for the initial part of the surgery. I performed a temporal clear corneal incision and a superior paracentesis within the clear cornea away from the filtering bleb. All incisions were made in the clear cornea to preserve the conjunctiva, a process generally considered important in cases of cataract surgery with previous glaucoma surgery. Excessive trauma to the eye or problems with loss of the vitreous can jeopardize the efficacy of the filtering bleb, necessitating a very efficient cataract surgery. In addition, excessive trauma may cause miosis of the pupil during surgery, which is why a preoperative nonsteroidal anti-inflammatory drug and viscoelastic are suggested. Following the initial incisions, the anterior chamber was inflated with Healon Endocoat. Once the chamber was stabilized, posterior synechiolysis was performed using a pair of Kuglen hooks. The pupil was enlarged sufficiently that a Malyugin ring (MicroSurgical Technology, Redmond, Wash.) was not necessary. After the pupil was stretched with the Kuglen hooks, I further enlarged it with the injection of additional Healon Endocoat. A good dispersive viscoelastic tends to keep the pupil stable throughout surgery. I then completed a capsulotomy followed by hydrodissection in a normal fashion. As the pupil was still not that wide, I injected additional viscoelastic between the phaco handpiece and the temporal iris to discourage any rubbing and subsequent iris atrophy. The dispersive nature of the viscoelastic allows it to stay in the intended location. The pupil was very small and dilation was limited due to scarring. The pupil was stretched with two opposing metal instruments and then further dilated with the OVD. Kevin Miller, MD, Complicated cataract cases editor References 1. Tong JT, Miller KM. Intraocular pressure change after sutureless phacoemulsification and foldable posterior chamber lens implantation. J Cataract Refract Surg 1998; 24:256-62. 2. Miller KM, Keener Jr GT. Stretch pupilloplasty for small pupil phacoemulsification. Am J Ophthalmol 1994; 117:107-8. Watch this video on your smartphone or iPad using your QR code reader. (Scanner available for free at your app store.) The phaco is now complete and the eye is ready to receive the IOL. Note the clear cornea, the non-traumatized iris, and the well-centered capsulotomy. These are all possible due to the protective qualities of the OVD. Source: Kevin L. Waltz, OD, MD