21 Postvitrectomy Considerations in Phacoemulsification Pars plana vitrectomy (PPV) was first introduced by Machemer et al1 in 1971, and it has since undergone many important advances in instrumentation and technique. Modern PPV is widely performed employing a microincisional transconjunctival sutureless technique. A few low-powered and short-term studies report a lower incidence of cataract formation after these surgeries, compared with older techniques, possibly due to reduced balanced salt solution (BSS) consumption, lower intravitreal flow, and reduced operative time.2–5 However, it is well accepted that cataracts develop in up to 76% of eyes within 2 years after PPV, which makes them the most common complication of the procedure.6,7 Although there are no known causative factors, risk factors may include older age, preexisting nuclear sclerosis, light toxicity from operating microscope, intraoperative oxidation of lens proteins, intraoperative lens touch (mechanical trauma from surgical instruments), duration of exposure to irrigating solution, diabetic retinopathy, and injection of silicone oil or intravitreal expansile gas.2,8–12 As the indications for PPV expand due to improved surgical techniques and results, this patient population is more likely to present to the anterior-segment surgeon’s clinic with increasing frequency. These patients are more likely than the general age-matched population to have associated ocular or systemic comorbidities and sequelae of prior surgery, including but not limited to conjunctival and episcleral scarring, corneal endothelial cell loss, poor pupillary dilation, zonular weakness, preexisting posterior capsular compromise, low scleral rigidity (high myopes), denser nuclear (brunescent) cataracts, and cystoid macular edema (CME).2 Phacoemulsification can be performed safely in this patient population, but there are important issues to consider preoperatively, intraoperatively, and postoperatively. There are no randomized clinical trials on outcomes of cataract surgery in eyes that previously underwent vitrectomy, but only retrospective case reports and nonrandomized prospective case series.13 Effective management of the challenges presented by coexisting ocular pathology requires a thorough understanding of the potential complications. The most important consideration in the process also happens to be the most basic, and that is the decision to perform the surgery. A comprehensive discussion with the patient of risks and benefits is of utmost importance. The surgeon should discuss the indications for the procedure as well as the chances of success. It is necessary for the cataract surgeon to be as familiar with the patient’s retinopathy as the retinal specialist, allowing for a collaborative informed decision to be made by the surgeon and the patient. Explain to the patient that removing the cataract will provide a better view into the eye for the ophthalmologists and may provide improved peripheral vision and color perception for the patient. Improved central visual acuity is not always probable, so knowing the patient’s best corrected visual acuity prior to the development of the cataract is helpful. The potential acuity meter is a low-tech but highly effective tool in predicting post-surgical visual acuity. Explain that even with an uncomplicated cataract surgery, visual potential will be limited by the underlying retinal disorder. In addition to describing the risks that are inherent to a standard phacoemulsification procedure, emphasize that the patient may experience postoperative diplopia, anisometropia, central scotoma, or metamorphopsia. Cataract surgery in eyes with retinal disease may increase the occurrence of neovascular events, such as neovascularization in age-related macular degeneration, and secondary glaucoma. To minimize intraoperative surprises and make an educated recommendation, the surgeon should perform a thorough preoperative exam that centers around slit-lamp biomicroscopy. This discussion addresses issues that are specific to the postvitrectomized eye, and assumes that findings pertinent to a standard candidate for phacoemulsification are screened for, such as corneal guttae and pseudoexfoliation material. The surgeon should obtain a baseline intraocular pressure reading by applanation tonometry. Also, note the presence of silicone oil bubbles or vitreous strands in the anterior chamber or iridophacodonesis, which may represent posterior capsular compromise or zonular weakness or dehiscence. Remember that these eyes have been previously entered through the pars plana, which puts them at a higher risk for zonular trauma. Also look for inflammatory cells that may represent ongoing healing from PPV or an underlying uveitis. Preoperative topical or oral steroids and topical nonsteroidal anti-inflammatory drugs should be considered. Allow ample time after dilating the patient in the clinic to assess maximal pupillary dilation. Some surgeons like to start long-acting preoperative topical cycloplegics several days before surgery, but intraoperative 1% preservative-free lidocaine with epinephrine, combined with viscomydriasis and slow-motion fluidics settings works well, employing an iris expansion device such as the Malyugin ring (MicroSurgical Technology [MST], Redmond, WA) as necessary. Posterior capsular compromise should be suspected if a posterior capsular plaque is present or if a history of rapidly progressive postvitrectomy cataract exists. If an advanced cataract precludes a satisfactory view to the retina, perform a B-scan. In addition to looking for retinal pathology, also look to see if there is an abnormally large lens thickness or an outpouching of the posterior lens surface, suggesting a defect in the posterior capsule and an intumescent lens. Optical biometry like the Zeiss IOL Master (Zeiss, San Diego, CA), which uses partial coherence interferometry and infrared light, has been shown to be more accurate than ultrasound biometry in vitrectomized eyes.14 A high percentage of vitrectomized eyes are highly myopic or staphylomatous. Therefore, the true axial length (AL) through the visual axis of these eyes is best measured as the patient fixates on a laser target, as opposed to an operator holding an ultrasound probe against the eye.15 In silicone oil-filled eyes, the correction factor for AL calculations is smaller as infrared light travels through different media compared with ultrasound waves.14 The AL is often overestimated using ultrasound biometry in a silicone oil-filled eye, and thus the patient is left with unintended postoperative hyperopia. To facilitate appropriate IOL power calculations, always consult with the retina specialist regarding the expected duration that silicone oil will remain in the eye. No matter which method is used, alterations in the anatomy of vitrectomized eyes present challenges to biometry technologies. Ultrasound measures AL in reference to the retinal internal limiting membrane, whereas optical biometry measures AL in reference to the retinal pigment epithelium.16 If there remains a question about the validity of one method after comparing the measurements to those in the fellow eye, for example, it may be a good idea to obtain both ultrasound and optical biometry for comparison.2,17 Avoid silicone IOLs due to the possibility of future air-fluid exchange or silicone oil fills, which can cause interface issues18 (Fig. 21.1). These interface issues are less likely but still possible with polymethylmethacrylate (PMMA) lenses or hydrophobic and hydrophilic acrylic lenses.19 Consider surface modified heparin-coated IOLs to prevent these interface issues.20 Fig. 21.1 Silicone oil emulsification on silicone intraoperative lens (IOL). (Courtesy of Paula F. Morris, CRA, FOPS, Moran Eye Center.) Have IOL power calculations prepared for both single-piece monofocal acrylic lenses and three-piece monofocal acrylic lenses in the event that sulcus placement with or without optic capture in the bag is necessary. Consider an IOL with a 360-degree square edge design with at least a 6.0-mm optic diameter to maximize the viewing area. Postoperatively, this can make the difference between missing and catching a small peripheral retinal tear. The Alcon acrylic lenses (Alcon Laboratories, Fort Worth, TX) are particularly tacky and may enable a more transparent IOL–capsulotomy interface. In silicone oil–filled eyes, consider plano-convex IOLs like the Duralens II DL60L (Abbott Laboratories, Abbott Park, IL) with the plano surface facing posteriorly to minimize postoperative refractive surprises. Avoid multifocal optics, which can decrease contrast sensitivity in an eye that may already have impaired photoreceptor functionality.21 They will also impair the ophthalmologist’s view to the fundus for necessary peripheral retinal examination.22 The Crystalens (Bausch & Lomb, Rochester, NY) is a multifocal silicone IOL, so this lens should be avoided for multiple reasons. A clear corneal incision is preferred due to the presence of conjunctival scarring that would make a scleral tunnel incision more difficult. However, a scleral tunnel may be preferred in particularly challenging cases requiring a rigid IOL or a larger incision and a nonphacoemulsification extracapsular lens extraction technique. Consider such a technique if posterior capsular compromise is noted preoperatively, as any fragments liberated during phacoemulsification will fall rapidly to the posterior segment due to lack of vitreous support. If this were to happen, cleanup is best left to a vitreoretinal surgeon using a pars plana approach. Warn patients of temporary amaurosis from preservative-free intracameral lidocaine causing “retinal block” in postvitrectomized eyes, due to enhanced posterior diffusion through weakened zonules.23 The decreased physiological barrier between the anterior and posterior segments is also why anterior-segment neovascularization and posterior-segment inflammation are more of a concern postoperatively. Intracameral lidocaine works well to minimize discomfort from excessive stretching of the iridozonular apparatus. This stretching may occur due to zonular weakness as the lens moves in the anterior-posterior direction as infusion is suddenly activated in the eye. Similarly, excess deepening of the anterior chamber when entering the eye with infusion may occur, due to loose zonules and a fluid-filled vitreous cavity instead of semi-solid viscous vitreous. Do not overinflate the anterior chamber with viscoelastic prior to capsulorrhexis. Increased posterior pressure may be provided by performing a retrobulbar or peribulbar block prior to the procedure. Intraoperative miosis and posterior synechiae should be dealt with in such a way as to minimize intraocular manipulations. In a stepwise fashion, intracameral mydriatics, posterior synechialysis, viscomydriasis, and a Malyugin ring or iris hooks may be used. Tightly sealing the main and side-port wounds is more important than in standard phacoemulsification surgery because of the lower threshold for instability of the anterior chamber from egress of fluid through the wounds. However, do not make them too long, and maintain the irrigation ports of the phacoemulsification and irrigation and aspiration (I/A) instruments well inside the anterior chamber and away from the wound. Corneal striations and premature wound hydration will prevent adequate visualization, which is particularly important if you are working in a deep anterior chamber.
Preoperative Discussion
Preoperative Examination
Intraocular Lens (IOL) Selection
Intraoperative
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