22 Posterior Capsulotomy, Bag-in-the-Lens and Evolving Techniques
A new method is being described with a potential to reduce posterior capsule opacification and thus the need for treatment of secondary cataract. The posterior capsulotomy, different techniques of which are presented in this chapter, uses an anatomical feature, Berger’s space, to prevent future lens epithelium migration. In the bag-in-the-lens (BIL) technique, the anterior and posterior capsules are placed in the intraocular lens’ flange after creation of both an anterior and a primary posterior capsulorhexis. The main advantage of the femtosecond laser–assisted technique for performing the BIL intraocular lens implantation is the safety and reproducibility of creating perfect anterior and posterior capsulotomies with the proper size, centration, and symmetry. Performing a minicapsulotomy before the “real” capsulotomy has proven to be helpful in intumescent cataracts with their increased intracapsular pressure.
Keywords: anterior hyaloid membrane, bag-in-the-lens technique, Berger’s space, intumescent cataracts, minicapsulotomy, posterior capsule opacification, posterior capsulotomy, rescue technique
There is some irony in the fact that cataract surgery as we know it—whether performed “conventionally” with phacoemulsification alone or with the femtosecond laser—is not only the most frequent invasive intervention in modern medicine, but arguably also the most successful—and at the same time it paves the way for what seems to be the second most-frequent intervention: the treatment of posterior capsule opacification (PCO), occasionally also named secondary cataract or after-cataract. Fong et al described a 3-year PCO incidence of 38.5% 1; other authors have reported even higher rates. Certain groups are particularly prone to develop PCO; in pediatric patients, this late complication is widely regarded as almost inevitable. 2
The causes of PCO are lens epithelial cells (LEC) left behind in the capsular bag. These cells most likely induce the opacification of the posterior capsule by a variety of mechanisms, among them proliferation, migration, epithelial-to-mesenchymal transition (EMT), collagen deposition, and lens fiber regeneration. 3 A number of modifications have been tried to reduce the prevalence of PCO somewhat like different surgical techniques, changes in intraocular lens (IOL) design and material, the use of a plethora therapeutic agents, and attempts to eliminate the LECs without ever conquering the problem. All these recent changes have delayed the onset of PCO rather than eliminating the problem. 4
The standard treatment of PCO is Nd:YAG (neodymium:yttrium aluminum garnet) laser capsulotomy, which is easy and quick but not without the potential for complications. A number of complications have been reported in the literature following Nd:YAG laser posterior capsulotomy. Among these are an elevated intraocular pressure (IOP), iritis, injury to the cornea, and damage to the IOL. There were cases of cystoid macular edema as well as of disruption of the anterior hyaloid surface, an increased risk of retinal detachment, and sometimes IOL movement or dislocation. 5 Minor effects on the eye’s refraction after Nd:YAG laser capsulotomy have been described; they tend to vanish, however, after about 3 months. 6 Furthermore, the patients’ visual acuity decreases slowly over time before the diagnosis of PCO is made and organizational effort is necessary to plan the Nd:YAG treatment. Because primum nil nocere is the physician’s guiding light since the days of Hippocrates, 21st century cataract surgeons strive hard to do everything in their power to prevent PCO and thus spare their patients another procedure.
22.2 Primary Posterior Laser-Assisted Capsulotomy
The answer might be found in the anatomy of the eye. Normally, Berger’s space is a tiny anatomical void between the posterior capsule and the anterior hyaloid membrane. At the very end of cataract surgery after IOL implantation, this small lacuna usually turns out to be larger than before—and larger than expected—but until recently there was no way to reliably visualize and assess this structure intraoperatively. The advent of the femtosecond laser has changed that. A unique feature of the femtosecond laser systems is a new quality of imaging. The Catalys system, for instance, comes with a three-dimensional (3D) spectral-domain optical coherence tomography (OCT). This imaging system visualizes the ocular surfaces and employs algorithms to process the image, to automatically detect surfaces, and to create safety zones. The fluid-filled patient interface of the laser system increases the IOP only minimally and allows an uncomplicated docking after the eye was opened. 7 The anatomy of the anterior segment, minutes after IOL implantation, has never been examined in 3D before. In the topography revealed by the 3D OCT at this moment and in an additional application of the femtosecond laser at the end of the procedure lies a new option to prevent PCO.
The femtosecond laser has proved its worth in performing a posterior capsulotomy that can overcome the difficulties that a manual capsulorhexis poses to the surgeon. 8 Primary posterior laser-assisted capsulotomy (PPLC) has been performed by using different techniques. Whichever is employed, at first, regular laser cataract surgery is completed. Anterior capsulotomy, lens fragmentation, and optional corneal incisions are performed. Next, the patient is undocked from the laser system and placed under the operating microscope where lens material is removed and then the anterior and posterior lens capsule surfaces can be polished using bimanual irrigation and aspiration after removal of cortical remnants.
The capsular bag and the anterior chamber are filled with ophthalmic viscosurgical device (OVD). An acrylic IOL (one piece, two piece, or plate haptic) is implanted and the bimanual irrigation and aspiration handpieces are used to remove the OVD in front of and behind the IOL. A round blunt cannula is used to inject a small quantity of OVD homogeneously behind the IOL optic. With minimal pressure on the optic, the OVD spreads evenly behind the IOL. The corneal incisions are hydrated and the eye is docked again to the laser system. 3D spectral-domain OCT is performed and the ocular surfaces are detected by the software. On the axial and the sagittal OCT view, the anterior and the posterior surface of the IOL can be easily identified. The anterior capsulotomy edges can be seen as two thin, white lines between the iris and the anterior lens surface.
Technique 1: The anterior hyaloid membrane is connected to the posterior capsule (▶ Fig. 22.1).
Technique 2: The anterior hyaloid membrane is not connected to the posterior capsule (▶ Fig. 22.2).
Fig. 22.1 Intraoperative three-dimensional optical coherence tomography planning screen of the primary posterior capsulotomy. The vitreous is attached to the posterior capsule. IOL, intraocular lens; OVD, ophthalmic viscosurgical device.
Fig. 22.2 Intraoperative three-dimensional optical coherence tomography planning screen of the primary posterior laser capsulotomy. The vitreous is not attached to the posterior capsule. The treatment can be performed without damaging the intraocular lens (IOL) or the anterior hyaloid membrane. OVD, ophthalmic viscosurgical device.
22.2.1 Technique 1
If the posterior capsule is directly attached to the anterior hyaloid membrane, the inferior third of the cylindrical capsulotomy treatment zone is placed on the posterior capsule by adjusting the surface first so that the anterior capsule fit is matched with the posterior capsule surface. Depending on the size of Berger’s space, an incision depth between 400 and 800 μm is programed to stay within Berger’s space. The pulse energy is set to 8 to 10 μJ and the capsulotomy diameter is usually 3.5 mm or greater. On the infrared camera view, the posterior capsulotomy is centered to the IOL optic or the anterior capsulotomy. After confirmation of the treatment zones, the laser delivers pulses into the vitreous and then, moving in an anterior direction, hits the anterior hyaloid membrane and the posterior capsule. Small bubble formations can be seen while the laser targets the vitreous and the OVD between posterior capsule and IOL. After undocking, the patient is rotated under the operating microscope for inspection. In most cases, the cut posterior capsule disc curls up and can be seen as a triangle or square lying on the anterior hyaloid surface. No further manipulations on the eye are necessary.
22.2.2 Technique 2
If the posterior capsule is not connected to the anterior hyaloid surface, similar to technique 1, the incision depth of the treatment zone is adapted to the size of Berger’s space and should be set between 400 and 800 μm. The inferior third of the cylindrical treatment is placed on the posterior capsule. The pulse energy is set to 7 to 10 μJ and the aimed capsulotomy diameter is 3.5 mm or greater. The infrared camera image is used to center the posterior capsulotomy to the anterior capsulotomy. After confirmation of the treatment zones, the laser application is started in Berger’s space without cutting into the vitreous. Two circles of bubbles can be seen on the infrared screen. One imitates the treatment circle, and the other moves to the center of the circle. After the laser treatment is finished, the free posterior capsulotomy falls down onto the intact anterior hyaloid surface. This can be confirmed on the OCT images after rescanning the eye intraoperatively (▶ Fig. 22.3). After undocking, the patient is swiveled back to the operating microscope for further inspection. The free posterior capsule disc can be seen as a triangle or a square (▶ Fig. 22.4). With minimal movement of the eye, the posterior capsule moves out of the visual axis. No further manipulations are necessary.
Fig. 22.3 Optical coherence tomography image of the anterior segment immediately after primary posterior laser capsulotomy. The posterior capsule lays on the anterior hyaloid membrane. IOL, intraocular lens.