Phacovitrectomy: Expanding indications

Cataract surgery may have to be combined with vitrectomy in a variety of clinical situations. It may be an integral part of a vitrectomy procedure, as in the case of a patient with a ruptured lens and a posterior segment intraocular foreign body (IOFB), or, conversely, vitrectomy surgery may be necessary to achieve safe cataract removal, as in the case of a patient with a dislocated lens. Age-related cataract, however, is common in many patients with vitreoretinal disorders, and cataract removal may be necessary simply to complete posterior segment surgery in eyes in which lens opacities obscure the view of the fundus. When pars plana vitrectomy was first introduced in the 1970s, the optimum way to remove associated cataracts was uncertain. Intracapsular and extracapsular cataract surgery resulted in large wounds, with problems of wound leak or even dehiscence during posterior segment surgery. Cataract surgery several weeks before vitrectomy allowed wound healing to occur, but the associated delay risked advancement of the vitreoretinal pathology, with a detrimental effect on the outcome. Pars plana lensectomy with ultrasonic fragmentation introduced the possibility of combined small-incision cataract removal with vitrectomy. However, it was the establishment of phacoemulsification as the routine method of cataract removal in the late 1980s that offered the possibility of efficient combined vitrectomy and cataract surgery, with secure wound construction and stable intraocular lens (IOL) fixation in an intact capsular bag.1–3 Phacovitrectomy is now widely carried out in patients with a variety of macular pathologies as well as retinal detachment, uveitis, diabetes, and IOFBs.4 Initially, phacovitrectomy was reserved for cases in which cataract precluded an adequate view of the fundus during vitrectomy. As confidence in the phacovitrectomy technique has increased and concern about intraoperative miosis and corneal opacity decreased, the indications for combined surgery have grown. Similarly, new generations of combined phaco and vitrectomy machines with dual cassettes allow rapid transition between the 2 modes, resulting in time-efficient surgery. Phacovitrectomy is now considered when lens opacities are mild or even nonexistent,5 particularly in patients older than 60 years of age. This could be called “nonessential” phacovitrectomy. In these cases, cataract surgery is not obligatory for successful completion of the vitrectomy but is done to avoid the need for subsequent cataract surgery and hasten visual recovery. Vitrectomy, particularly in the older-than-60-years age group, frequently results in significant lens opacities, especially if long-acting gases are used as in macular hole surgery.6,7 Phacovitrectomy offers several advantages over vitrectomy followed by subsequent cataract surgery in 2 steps. Only 1 operation is needed and the surgical difficulties and morbidity associated with cataract extraction following vitrectomy are avoided. These include small pupil size, deep anterior chamber with reverse pupillary block, zonule weakness, and resultant increased mobility of the lens–iris diaphragm with posterior capsule tears.8–12 Combining phacoemulsification and vitrectomy improves postoperative retinal visualization without the obscuring effect of the cataract, thus allowing accurate retinal assessment. Visual recovery is also not delayed by subsequent cataract development. Phacovitrectomy also allows more complete anterior vitrectomy and access to the anterior retina and vitreous base without risking lens trauma, important in a number of clinical scenarios such as the management of anterior proliferative vitreoretinopathy. Arguably, a full vitrectomy allows a better gas fill,13 potentially improving tamponade of peripheral retinal breaks, especially inferiorly. Surgery can be carried out successfully via clear corneal or scleral incisions. Corneal incisions have been associated with a lower incidence of fibrinous uveitis and posterior capsule opacity but a higher risk for corneal endothelial dysfunction.14 If a corneal incision is used, the tunnel should be relatively short to avoid interfering with the perioperative posterior segment view. Superior wounds offer convenience and allow the entire operation to be performed with the surgeon positioned at the head of the patient but are associated with higher degrees of postoperative astigmatism and run more risk of interfering with the retinal view because of the oval-shaped cornea. A suture can be used to secure the wound, even in small-incision surgery, to avoid leakage from deep scleral indentation during vitrectomy. Bimanual phacoemulsification techniques potentially allow smaller incision size, ensuring a more secure wound15 provided the wound is not enlarged for IOL insertion before the vitrectomy. Posterior segment intraocular gas pressure can cause significant problems in phacovitrectomy. Anterior dislocation of the IOL optic by posterior gas pressure can lead to optic capture by the iris.16 Similarly, displacement of the anterior capsule onto the iris can lead to posterior synechiae formation postoperatively. There are several strategies to reduce the occurrence of these problems. Sustained postoperative dilation should be avoided. Some clinicians avoid dilation in the immediate postoperative period, and others use short-acting mydriatics to limit synechial formation. Face-down positioning can be encouraged. The capsulorhexis should be large to avoid problems with phimosis but should aim to overlap the optic edges by 0.5 mm only to hold the optic posteriorly. Capsulorhexis can occasionally be difficult in eyes with vitreous hemorrhage and no red reflex. In these cases, trypan blue staining and use of the endoilluminator in the anterior chamber can assist visualization.17 The IOL design is important, and the optic diameter should be large to lessen the risk for optic capture.18 Plate IOLs with broad haptics offer significant advantages to reduce the risk for optic capture as well as superior IOL centration.19 Folding IOLs can be used safely, and they offer the advantage of small wound size.20 Intraocular lens insertion can be performed before or after vitrectomy is completed. The peripheral vitreous base view is more impaired in pseudophakic eyes than in aphakic eyes and is one argument for leaving IOL insertion until the posterior segment surgery is concluded.21,22 However, some surgeons prefer to finish the anterior segment stage of surgery before vitrectomy, avoiding later maneuvers associated with IOL insertion and shortening surgery.4 Intraocular lenses with rounded tapering edges (eg, Quattro Corneal IOLs) offer advantages for trans-IOL vitrectomy by preventing “jack-in-the-box” prismatic effects when the posterior segment is viewed through the edge of the IOL. Posterior capsule opacity appears to be more common after phacovitrectomy than after solitary phaco surgery,5 but primary capsulotomy can be performed with low morbidity using the vitrectomy cutter, avoiding another threat to delayed visual recovery.23 Moreover, posterior capsule opacity is also not infrequent following sequential cataract surgery after vitrectomy.12 Folding acrylic optic materials have several advantages over silicone for phacovitrectomy, including less condensation during fluid–air exchange when primary capsulotomy is done and less possibility of silicone oil adherence if subsequent silicone oil tamponade is used. Fibrinous uveitis is reported in 6% to 15% of patients after phacovitrectomy.5,24–27 It is more common in vitrectomy for proliferative diabetic retinopathy and retinal detachment and after more extensive retinal ablative treatment or retinopexy.26 Subconjunctival and topical steroids can be used at the completion of surgery to lessen the incidence of fibrin formation, but in practice fibrin formation is rarely a significant clinical problem. Patients with macular holes and macular puckers are perhaps the most frequent clinical scenarios in which nonessential phacovitrectomy could be considered because of the high incidence of significant cataract formation after surgery and the age group affected.28 However, not all patients are ideal candidates for nonessential phacovitrectomy with IOL implantation; in some patients, vitrectomy followed by sequential cataract surgery is a better option. In diabetic patients, lens opacities following vitrectomy are paradoxically less common than in nondiabetic patients.29 Diabetic patients appear to have a higher incidence of posterior synechiae,30 posterior capsule opacity,26 and inflammatory anterior uveitis27 following phacovitrectomy than nondiabetic patients, especially if retinopathy is very active, if a large amount of intraoperative laser is needed, or if gas tamponade is used.30 Phacovitrectomy is also thought to result in an increased risk for neovascular glaucoma compared with vitrectomy alone in some reports25 but not others.31,32 Therefore, although phacovitrectomy can be performed successfully in diabetics with significant lens opacities,32,33 diabetic patients are not always ideal nonessential phacovitrectomy candidates. Refractive outcome has not been a major concern in many patients having vitrectomy for significant vitreoretinal pathology because of the poor visual prognosis. However, improvements in technique and instrumentation have led to an increase in the indications for vitrectomy; patients with better levels of preoperative visual acuity are now being operated on.34,35 Refractive outcomes are important in patients with normal or near-normal levels of visual acuity, and the refractive outcome of phacovitrectomy surgery is becoming increasingly important.36 Furthermore, refractive manipulation can often add a further positive feature to the surgery; the opportunity to dispense with distance correction can be a very favorable feature of phacovitrectomy for sight-threatening retinal disease. The absence, therefore, of accurate preoperative biometry could be regarded as a relative contraindication to nonessential phacovitrectomy; for example, in the case of macular-off retinal detachment or substantial macular thickening. Fellow-eye measurements can be used, but incorrect axial length estimations will result in errors in IOL choice and potentially significant unplanned ametropia. Similarly, scleral buckling alters the final refractive outcome in an unpredictable way and would be a further contraindication to nonessential phacovitrectomy. The amplitude of apparent accommodation in pseudophakic patients is virtually equivalent to that of normal accommodation in patients older than 60 years of age; therefore, removal of clear lenses during phacovitrectomy does not significantly disadvantage patients in this age group.37 On its own, vitrectomy has little effect on long-term astigmatism, with any surgically induced changes resolving by 3 months postoperatively.38,39 Surgical compensation is not needed during cataract surgery to correct for any astigmatic effects induced by vitrectomy surgery.38 New small-gauge vitrectomy has even less effect on postoperative astigmatism,40,41 allowing perhaps more rapid postoperative visual recovery. While refractive outcomes have been acceptable and comparable to the outcomes achieved with solitary phaco surgery,36 several authors report a small myopic shift between aimed for and achieved refraction with phacovitrectomy. Several explanations of this have been suggested, including IOL position shift with gas pressure, axial length changes, and inaccuracies in axial length measurement preoperatively.42,43 Vitrectomies are often done in patients with thickened posterior retinas from macular edema, macular pucker, or the edges of elevated macular holes. In these situations, intraocular length can be measured short, the effect occasionally being enhanced by eccentric fixation, resulting in the insertion of an IOL with too high a power and postoperative myopia. In these patients, if postoperative myopia is considered undesirable, aiming for a low-plus final refraction of 0.25 to 0.50 diopter should be considered (Manvikar S, et al. IOVS 2006; 47:ARVO E-abstract 642). Phacovitrectomy is now an established technique to allow combined cataract extraction and vitrectomy and has a low incidence of postoperative and intraoperative problems. The technique is routinely used to avoid postoperative cataract delaying recovery in patients with minimal or no lens opacities preoperatively, particularly in macular hole surgery.