Background 10 27 11 However, utilization of the edge barrier effect has two major shortcomings: (1) overlap of the optic by the anterior capsule leaf induces fibrotic whitening and shrinkage of the latter, thereby reducing the size of the free optic zone (this is especially true if the rhexis opening is small or decentered, be it because of inadequate dimensioning or due to subsequent contraction), and (2) the barrier function can be lacking from the very beginning, or wear off over the years, even when all the three above-mentioned requirements are fully met. 24 15 2 Therefore, the potential for avoiding after-cataract formation by optimizing the edge barrier effect is limited, even when all relevant parameters are fully exploited. In addition, even in those cases where the sharp edge forms a permanent circumferential barrier, visibility of the peripheral retina may be significantly reduced by pearl formation in the intercapsular space outside of the optic rim. 16 3 Rationale The still significant percentage of after-cataract formation requiring YAG-LCT in the longer run, and the problem of dysphotopsia, have fostered the search for better alternatives. Thereby, a new approach was required, since the concept of optimizing the migrational barrier effect of the optic edge is largely exploited. As one option, intraoperative removal of the central posterior capsule by performing a primary posterior continuous curvilinear capsulorhexis (PPCCC) seemed promising, since the posterior capsule serves as a scaffold for centrally migrating LECs. As such, it is not an alternative, but much more supplements the current sharp edge concept by providing a “second barrier of defence” when the optic edge barrier is overcome by migrating LECs. 26 4 1 25 5 1 Fig. 1 Primary posterior capsulorhexis decreases YAG laser capsulotomy rate by removing scaffold for LEC migration; however, residual capsule may still opacify, and LECs may alternatively grow upon optic surface  Thus, a PPCCC constitutes a useful additive surgical measure, but does not fully prevent after-cataract formation. 6 In order to elucidate the suitability of the posterior optic buttonholing (POBH) technique as a routine procedure for senile cataracts, an extensive prospective study comprising a large number of eyes was initiated. In several substudies, a prospective randomized bilateral design was used to elucidate the risk profile compared to the standard in-the-bag implantation of IOLs in detail. For this purpose, the surgical technique of POBH was revised and optimized to be then systematically investigated. From September 2004 to June 2007, over 1000 eyes underwent this POBH procedure. Patients were randomly taken from the waiting list. All prospective comparison studies were approved by the Medical University of Vienna Ethics Committee. Technique Discussion Section 2 3 4 9 Fig. 2 crescent-shaped blue areas red lines bold line red area hatched line  Fig. 3 Retroillumination photography of buttoned-in IOLs (HOYA AF-1): note perfect autocentration of optic and run of posterior capsule rim  Fig. 4 HOYA AF-1-type IOL preferred because of continuous haptic–optic junction and “hopper loop” haptic. POBH causes optic to position (by approximately 1 mm) more posteriorly (compared to standard in-the-bag placement), thereby stabilizing the vitreous body  13 5 19 Fig. 5 “Aspiration curette” for effective and safe debridement of anterior LEC layer additionally reduces capsular fibrosis  Results Surgical complications 12 6 1 Fig. 6 Retraction of scarcely overlapping PPCCC rim from optic rim due to fibrosis emerging from ACCC larger than optic allows for delayed vitreous herniation  Table 1 Complications Results First 150 cases:  • vitreous presenting in AC during surgery: none  • vitreous entrapment detected postoperatively   • minor: four eyes   • major: two eyes (→ translimbal AVE in one eye)  • CME / RD: none Cases # 151 to >1000:  • oversized PPCCC with incomplete diaphragm: four eyes   • secondary desenclavation : two cases   • delayed vitreous herniation: two cases (→ single-port ppVE)  • retinal detachement: one eye   • highly myopic 58 yr-old male, AL>26.5 mm, 4 months postop: Cryo+gas  • CME: none  • endophthalmitis: none After-cataract preventive effect 7 right 8 8 left 8 right 9 10 Fig. 7 Right Left  Fig. 8 Right left  Fig. 9 Posterior capsule sandwiched between anterior capsule and optic precludes direct contact which catalyses anterior LEC transdifferentiation leading to fibrosis. Residual fibrosis essentially confined to haptic–optic junction  Fig. 10 Schematic close-up view highlighting capsule–IOL interplay at haptic junction. Undercrossing of PPCCC edge allows for localized anterior capsule contact with optic, resulting in fibrosis adjacent to haptic junction which may spread out along rhexis rim  Detailed risk profile 21 20 22 23 Discussion The advantages, possible downsides, and specific features of the technique are addressed in the following: 2 3 8 10 8 1 Eradication of residual fibrosis and ongrowth with additional polishing. Additional polishing of the anterior capsule specifically avoids fibrosis or ongrowth inside the haptic-optic junction, and fully excludes residual fibrosis in the areas where both capsules overlap. 10 11 11 12 Immediate stability of capsular diaphragm and implant. Due to the lack of forward movement of the optic as seen after in-the bag fixation due to the loss of haptic memory and the distension of the capsule diaphragm as the capsules seal and fibrose, no myopic refractive shift occurs. While delayed by up to 4 weeks after bag-fixation depending upon the haptic design and material, final refraction is thus instantly attained, allowing prescription of final glasses 1 week after surgery, when the patient is seen by the referring ophthalmologist. Posterior positioning of the IOL optic by about 1 mm compared to bag-fixation significantly increases the interspace between the iris and optic. This avoids chronic iris chafing when a sulcus-fixated add-on IOL is secondarily implanted in order to correct for an erroneous IOL power selection, or to add astigmatic correction or multifocality. Fig. 11 decentration  Fig. 12 undersizing  independent of the optic edge design 16 independent of the optic material renaissance of the round-edged optics As opposed to PPCCC with bag-fixation of the optic, POBH creates a stable and watertight diaphragm. Vitreous prolapse or entanglement will not occur should the anterior chamber flatten after retracting the aspiration–infusion tip following removal of residual OVD from the anterior chamber. The POBH technique as such is safe and highly effective with regard to after-cataract prevention. It is not only feasible, but highly recommended to perform it under topical anesthesia in order to guarantee bright and stable retroillumination when performing the PPCCC. No special or extra instruments or implants are required. Interestingly, no case of endophthalmitis occurred in the whole series, despite the fact that no intracameral or postoperative antibiotic prophylaxis had been performed. Though this series is not large enough to draw a meaningful conclusion, it may be attributed to the fact that buttonholing avoids seclusion of bacteria within the retrolental space. Other than with bag-fixation, the optic and capsule surface are fully exposed to the aqueous humor circulation from both sides. In case of an endophthalmitis, the vitreous cavity may be easily accessed for translimbal tapping and bimanual vitrectomy after temporary desenclavation of the IOL optic. Sizing of the ACCC 13 right Viscodissection of the central hyaloid-capsular interspace (Berger´s space and Wieger´s ligament) 14 Sizing and centration of the PPCCC The posterior capsule being extremely stretchable and elastic, buttoning-in will also be feasible when a PPCCC turns out to be smaller than 4 mm. Also, the forces of the haptics will center the optic unto the anatomical axis within a suboptimally centered PPCCC. Therefore, though a 5 mm diameter and perfect centration should always be aimed at, deviation from this target will be tolerated. However, with a too large PPCCC that evades the optic rim, even when only along part of optic circumference, the IOL must be buttonholed through the ACCC with the loops either placed in the sulcus or capsular bag equator in order to avoid delayed vitreous prolapse. Therefore, the ACCC should be well-centered and no larger than 5–6 mm in diameter, to preserve the option of anterior rhexis fixation of the optic. Apart from providing an alternative for safe IOL fixation, an appropriately dimensioned ACCC also serves as a ruler for adequate sizing of the PPCCC. 9 Viscodissection of the peripheral hyaloid-capsular interspace (Girard´s space) Before implanting the IOL, the peripheral interspace between posterior capsule and anterior hyaloid must be circumferentially dissected with OVD in preparation of optic buttonholing. If not appropriately performed, the hyaloid surface may be shoveled up and damaged by the rim of the optic. Selection of IOL design 12 15 Fig. 13 left right green circle  Fig. 14 Schematic depicting interrelationship between posterior capsule and anterior hyaloid (Courtesy of Dr. T. Miyoshi). In practice, Wieger´s ligament may be completely detached; conversely, hyaloid may be closely adhering to capsule over extended areas  Fig. 15 Continuous haptic-optic transitions allow PPCCC rim to smoothly slide along IOL circumference as optic is buttoned-in and centered within PPCCC by loops residing in capsular bag fornix  7 26 CME is provoked by the dissipation of cytokines released in the anterior segment, and by vitreous traction exerted by the anterior displacement of the vitreous body following exchange of the natural lens volume by a thin artificial lens. In these regards, POBH has certain advantages over standard in-the-bag IOL implantation. Firstly, as opposed to a sole PPCCC, optic buttoning-in creates a watertight diaphragm blocking the posterior dissipation of cytokines. In addition, viscodissection of the posterior capsule and anterior hyaloid creates a contiguous cushion of OVD behind the capsule–IOL diaphragm including the zonular region which precludes access of cytokines to the posterior segment until it is eventually resorbed. The more posterior positioning of the buttonholed optic together with the OVD cushion behind it, and the lack of subsequent anterior movement of the optic, prevent both immediate and delayed anterior displacement of the vitreous body. Severing the attachments between the posterior capsule and the hyaloid, namely Wieger´s ligament, may help to avoid traction on the vitreous when the chamber happens to flatten during OVD aspiration, or thereafter. 18 22 4 bottom pseudoexfoliation syndrome high myopia peripheral retinal pathologies requiring controls and treatment 16 14 17 17 Fig. 16 Rhexis-fixation precludes postoperative IOL rotation in an oversized bag and delayed optic rotation by haptic compression arising from capsular bag shrinkage  Fig. 17 open square  2 Table 2 Indications Summary of indications Pediatric cataracts PEX-Syndroma High myopia Peripheral retinal disease Multifocal IOLs Toric IOLs Accommodative lens system In conclusion, primary posterior capsulorhexis combined with posterior optic buttonholing is a well-controlled, safe, and highly effective procedure with a steep learning curve, thus carrying the potential of becoming a routine alternative to standard in-the-bag implantation of intraocular lenses. As opposed to standard in-the-bag placement, its effectiveness is completely independent of optic material and optic edge design. This technique is meant for the skilled and dedicated surgeon, and must be carefully approached. It should be reserved to large pupil eyes. Should the pupil come down during the surgery, one may switch to standard in-the-bag surgery, optionally combined with a small PPCCC. Thorough viscodissection of anterior hyaloid and posterior capsule is crucial. Additional anterior capsule polishing is highly recommended, as it abolishes any residual fibrosis without any risks or downsides. Though long-term results in children's eyes support sustained efficacy and lack of complications, 5-year results should be awaited until the technique may be considered or recommended as a routine alternative to standard in-the-bag fixation of the IOL. For the time being, it is recommended with pseudoexfoliation syndrome, high axial myopia, peripheral retinal disease, multifocal IOLs, and toric IOLs when made available.