Combined Cataract Surgery With Pars Plana Vitrectomy: The Vitreoretinal Surgeon's Perspective
Combined treatment has many advantages. We present our recommended approach.
Kevin K. Suk, MD • Timothy G. Murray, MD, MBA, FACS
|Kevin K. Suk, MD, practices at the Retina Institute of California in Arcadia. Timothy G. Murray, MD, MBA, FACS, is professor of ophthalmology at the Bascom Palmer Eye Institute in Miami. Neither author reports any financial interest in any products mentioned in this article. Dr. Murray can be reached via e-mail at TMurray@med.miami.edu.|
The development and progression of cataracts is an almost invariable consequence of pars plana vitrectomy, with up to 80% of vitrectomy patients developing or having progression of significant cataracts.1-3 A majority of these eyes will then subsequently undergo cataract extraction.
The indications for vitrectomy have expanded over the years to include a variety of vitreoretinal diseases, including diabetic retinopathy, epiretinal membrane, macular hole and retinal detachment, all of which increase in prevalence with advancing age. The prevalence of cataracts also increases with age and with diabetic retinopathy, such that they are frequently comorbid with vitreoretinal diseases.
In many cases, intraocular tamponade is used as an adjunct during vitreoretinal surgery, which further contributes to the formation and progression of cataracts.4,5 In the United States, cataract and vitreoretinal pathology are usually addressed separately. In this approach, the two surgeries are performed in sequence by the anterior-segment and vitreoretinal surgeons, which ultimately delays the final visual outcome and prolongs patient recovery.
Another disadvantage of the sequential approach is that cataract surgery in a previously vitrectomized eye is more technically challenging, which can increase the potential for intraoperative complications. There is also concern regarding the possible recurrence or exacerbation of vitreoretinal diseases after cataract surgery.
PHACOEMULSIFICATION IN THE VITRECTOMIZED EYE
Loss of vitreous support in a previously vitrectomized eye results in an unstable posterior capsule that is unusually mobile and flaccid.6,7 Vitrectomy may also weaken the zonules,6,8 which, in combination with a flaccid posterior capsule, may allow the lens-iris diaphragm to move excessively. Fluctuation of the anterior-chamber depth can make surgical maneuvers during phacoemulsification difficult and can increase the risk of complications.
Figure 1. Note the preplacement of 23-gauge valved cannulas using a midline placement approach. Valved cannulas will enhance fluidic stability during both the anterior and posterior segments of the combined procedure.
In particular, an unstable posterior capsule that is excessively mobile can increase the risk of inadvertent damage during phacoemulsification. Unfortunately, it is difficult to identify which eyes will behave this way prior to surgery, as they do not exhibit lens dislocation or phacodenesis preoperatively.9
The posterior capsule may also have occult tears from the previous vitrectomy, and a cataract developing within weeks of the vitrectomy should raise suspicion for damage to the posterior capsule during surgery.10,11
Poor mydriasis is also not uncommon,12 sometimes necessitating the use of iris hooks.
Posterior capsule plaques are also frequently encountered during surgery in previously vitrectomized eyes, and they can be difficult to remove without risking damage to the posterior capsule.8-10,13
Finally, the cataracts encountered after vitrectomy tend to be characterized by denser nuclear sclerosis.9 The increased energy needed to phacoemulsify these lenses can increase intraoperative and postoperative corneal edema, as well as inflammation.9
COMBINED PHACO AND VITRECTOMY
Outside of the United States, cataract and vitreoretinal pathology are frequently addressed simultaneously by a single surgeon. A combined approach minimizes the surgical and economic burden of multiple surgeries, as well as the anesthesia and its antecedent risks. Additionally, combination surgery allows for faster patient recovery and earlier visual rehabilitation.14,15
Removing the cataract prior to vitrectomy optimizes visualization of the posterior pole, which is important when peeling preretinal membranes and the internal limiting membrane. Visualization of the anterior retina is also improved.
A known complication of macular surgery is the formation of iatrogenic retinal tears, which usually occur during the induction of a posterior vitreous detachment.16 As the majority of these retinal tears are found in the periphery,16 small tears that may appear in the anterior retina can be more readily identified and more easily treated when the cataract is removed.
Removal of the cataract additionally allows for better access to the vitreous base without the risk of touching the lens. More extensive removal of the anterior vitreous may be required in complex cases of diabetic tractional retinal detachment and in proliferative vitreoretinopathy. In vitrectomy for macular hole, a more complete vitrectomy allows for a larger gas fill and a longer duration of tamponade, which may improve the closure rate.17
Several studies have demonstrated the efficacy and safety of combined surgery for a variety of indications, including macular hole,14 ERM,15 proliferative diabetic retinopathy18 and other complex vitreoretinal diseases.19
A few concerns, however, are unique to the combined approach. Combined surgery may elicit a more intense postoperative inflammatory response20,21 and some surgeons have reported a higher rate of posterior capsule opacification 14,20,21 and posterior synechiae formation.20-22
The inflammatory response may also induce morphologic changes to the ciliary body; a shallow anterior chamber and narrowing of the angle have been observed to occur more frequently after combined surgery compared to vitrectomy alone.23 Aggressive control of postoperative inflammation may minimize these events.19,24
Finally, use of an intraocular tamponade, such as gas, in combined surgery may increase the risk of intraocular lens–related complications, such as pupillary capture and lens decentration.20,25 Moreover, anterior displacement of the intraocular lens may induce a myopic shift in the refractive outcome.26
Advances in surgical platforms have enhanced combined surgery. Currently, the Constellation Vision System (Alcon Laboratories) is used for all combined cases at the Bascom Palmer Eye Institute. In addition to the platform used, careful attention to surgical technique is important when addressing the unique aspects of combined phacoemulsification and vitrectomy.
Figure 2. Use of torsional phacoemulsification in a standard phaco/chop approach. The posterior infusion is placed but “clamped.”
We approach the eye superiorly. This approach provides a seamless transition between the anterior and posterior portions of the surgery. To that same end, a single surgeon addresses both the cataract and the vitreoretinal pathology.
Trocar placement is the important first step in combined surgery. After the first trocar is placed inferotemporally, and the infusion cannula is inserted, the superior trocars are placed approximately 150º apart. This provides excellent access to the anterior segment.
Some surgeons prefer to perform phacoemulsification first and to insert the trocars afterwards. A disadvantage of this approach is that the globe is more difficult to keep rigid when inserting the trocars. A long, angled incision is key to proper wound construction and is aided by flattening the sclera during trocar entry.
The pressure on the globe necessary to flatten the sclera can cause the corneal incision to leak and destabilize the eye when the trocars are inserted after phacoemulsification. By inserting the trocars first, a closed system is maintained, making it easier to keep the globe rigid during wound construction. Valved cannulas also help to maintain a closed system and the stability of the globe. After the trocars are inserted, the main corneal incision is created superiorly, and the paracentesis is made approximately 90º away. The cataract is then removed with phacoemulsification.
An advantage of the Constellation surgical platform is the Ozil torsional handpiece. Torsional ultrasound allows for increased phacoemulsification efficiency and followability and potentially less corneal trauma and edema.
In our approach, the IOL is inserted immediately after phacoemulsification — prior to vitrectomy. It improves surgical time and efficiency; in particular, if a fluid-air exchange is performed or intraocular tamponade is used, the IOL needs to be inserted prior to these maneuvers. We also find that, when a wide-angle viewing system is used, the IOL does not interfere with the surgeon's view during the subsequent vitrectomy.
The IOLs we typically use are acrylic, foldable, three-piece lenses (Alcon Acrysof MA 60AC or MA 50BM lens). They have a 6.0- and 6.5-mm optic, respectively, and an open-loop design with a haptic angulation of 10º. The larger optic size, in conjunction with an appropriately sized anterior capsulorhexis, may help prevent papillary capture and other IOL-related complications during fluid-air exchange and gas tamponade.
As mentioned above, gas tamponade after combined surgery is also associated with myopic refractive error, presumably due to anterior displacement of the IOL. Using an IOL with an angulated haptic, such as these, can minimize the anterior displacement of the lens and the consequent myopic shift, compared to an IOL without angulation.27
Additionally, it is preferable to use partial coherence interferometry (IOLMaster; Carl Zeiss Meditec) to measure the axial length when calculating the IOL power. The alternative, ultrasound biometry, measures axial length from the cornea to the vitreoretinal interface, whereas the IOLMaster measures from the cornea to the retinal pigment epithelium. In the presence of macular thickening, axial length measurements with ultrasound biometry would result in a myopic refractive error.
The optimal placement of the IOL is in the capsular bag. However, a known complication of cataract surgery is rupture of the posterior capsule, which occurs at a rate of 0.82% to 2.1% during combined phacoemulsification and vitrectomy.28-31 In the event of a posterior-capsule rupture, vitrectomy is performed to remove the anterior hyaloid and to separate the vitreous from the nuclear material. Any residual nuclear material is then removed using the 23-gauge vitreous cutter with a low cut rate and low aspiration “dense” mode on the Constellation Vision System). The IOL lens can then usually be implanted into the ciliary sulcus.
If the anterior capsulorhexis is intact, the IOL can be placed in the sulcus and the optic captured. The IOL is placed in the sulcus with the haptics situated 90º from the posterior-capsule rupture. Next, one side of the optic, 90º away from the optic-haptic junction, is pushed behind the anterior capsulorhexis with a lens manipulator, such as a Sinskey hook.
Figure 3. Note bag/bag placement of the IOL (preference for a three-piece acrylic IOL) and 10-0 nylon sutured, biplaned clear corneal wound.
Once that side of the optic is placed under the anterior capsule, the other side is similarly pushed under the 'rhexis to capture the optic. This provides more stability to the IOL, compartmentalizes the anterior chamber and places the IOL in the plane of the bag.
At the commencement of phacoemulsification, the viscoelastic that is injected to facilitate lens insertion is kept in the anterior chamber, and the main corneal incision is secured with a 10-0 nylon suture. These steps help stabilize the anterior chamber and prevent fluctuations of the irislens diaphragm during vitrectomy.
It is our practice to inject intravitreal triamcinolone acetonide (0.4 mg/0.1 mL) at the end of vitrectomy after all of the trocars are removed to reduce postoperative inflammation. In a review of 114 eyes that received intravitreal triamcinolone after combined phacoemulsification and vitrectomy for a variety of complex vitreoretinal pathologies, there were no cases of fibrin or increased anterior-chamber inflammation.19 Another study showed that the use of intravitreal triamcinolone at the end of vitrectomy reduced morphologic changes to the ciliary body induced by inflammation.24
In summary, combined cataract and vitreoretinal surgery is effective and efficient, and offers many advantages over the sequential approach. Such a strategy minimizes surgical trauma, reduces the risk of complications and allows for faster visual rehabilitation, while improving visualization and maximizing surgical access to the anterior retina. A few concerns specific to combined surgery, such as increased postoperative inflammation and IOL-related complications, can be avoided by using optimal surgical techniques. RP
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