Prevention of posterior capsule opacification with the CO2 laser

BACKGROUND AND OBJECTIVE: Posterior capsule opacification (PCO) is a common complication after cataract extraction, despite the modern surgical techniques and lenses being used for this procedure. Its prevention challenged many investigators, because the current treatment of choice, capsulotomy with Nd:YAG laser, is associated with sight-threatening complications. In the present study, the authors investigated two approaches of preventing PCO using the CO2 laser. MATERIALS AND METHODS: A 15-W CO2 laser with a 17- or 18-gauge hollow probe was used on 20 sheep eyes and 14 rabbit eyes. Lens extraction was done by phacoemulsification. In the equatorial treatment study, the anterior chamber was filled with either air or a viscoelastic substance, and laser burns were applied to the equator of the lens capsule and to the peripheral anterior capsule to destroy the epithelial cells. In the capsulotomy study, a primary posterior capsulotomy was created by delivering 1 to 3 laser shots to the capsule behind an implanted intraocular lens (IOL). RESULTS: The CO2 laser was satisfactory in sheep eyes after filling the anterior chamber with air. In rabbit eyes, however, it was technically impractical to work with air. Using a viscoelastic material to maintain the anterior chamber, the hollow probe of the CO2 laser becomes plugged up and therefore is unable to affect the ocular tissue. However, by combining viscoelastic and air pumping, both the destruction of the lens epithelial cells and the creation of a central posterior opening behind a capsular-fixated IOL was repeatedly achieved. CONCLUSION: Using the CO2 laser for destruction of lens epithelial cells and the creation of controlled posterior capsulotomy is feasible and practical. A different design of the probe (closed gauge) is required to enable it to operate clinically in a fluid or viscoelastic environment.     

Degenerated lens epithelial cells in rabbit and human eyes after intraocular lens implantation

PURPOSE: To evaluate the role of lens epithelial cells (LECs) in posterior capsule opacification. SETTING: Departments of Ophthalmology and Pathology, Wakayama Medical College, Department of Anatomy, Kansai Shinkyu College, and Department of Ophthalmology, Kobe Kaisei Hospital, Japan. METHODS: We examined the presence of degenerated LECs on the capsules of the eyes of rabbits and a patient after intraocular lens (IOL) implantation. Phacoextraction of a crystalline lens and IOL implantation were done in 5 albino rabbits under general anesthesia. The animals were killed after 2 months. Lens capsules were removed and fixed. During vitreous surgery, a lens capsule with an IOL was removed from a patient. Ultrathin sections of specimens were studied by transmission electron microscopy. RESULTS: Presumed LECs proliferated between the posterior capsule and the IOL in association with collagenous matrix. Debris from the degenerated cells and destroyed intracellular organelles was also seen. CONCLUSION: Lens epithelial cells proliferating on the posterior capsule cannot survive indefinitely.     

Phacoemulsification versus extracapsular cataract extraction: a comparative study of cell survival and growth on the human capsular bag in vitro

AIMS/BACKGROUND: Phacoemulsification is rapidly replacing conventional extracapsular cataract extraction (ECCE) as the method of choice for cataract surgery in the Western world. However, posterior capsule opacification (PCO) still remains the major postoperative complication, affecting 20-50% of patients, and results from persistent cell growth of epithelial cells remaining after surgery. This study aimed to compare cell survival and growth on capsular bags following ECCE and phacoemulsification surgery using an established human capsular bag culture system. METHODS: Sham ECCE and phacoemulsification cataract operations were performed on pairs of human donor eyes. Capsular bags were dissected free, pinned flat on a petri dish, and incubated with Eagle's minimum essential medium (EMEM) alone or EMEM supplemented with 10% fetal calf serum (FCS). Ongoing observations were made using phase contrast microscopy. RESULTS: Cell growth was observed across the posterior capsule of all preparations studied. It was found that there was no significant difference in the rate of cell growth on the posterior capsule with the two extraction methods, such that 50% confluency was achieved in 7.0 (SD 1.8) (n = 7) days for ECCE and 7.43 (2.1) (n = 7) days for phacoemulsification surgery. The physical changes to the capsule as a result of cell growth, such as wrinkling and capsular tensioning, were also seen in both groups. CONCLUSIONS: Cell survival and growth is dependent on the donor, rather than the surgical technique performed. There is no significant difference between phacoemulsification and ECCE surgery on the rate and nature of cell growth on the posterior capsule in vitro.     

Lens epithelial cell proliferation, migration, and metaplasia following capsulorhexis

AIM: To study the behaviour of residual lens epithelial cells after capsulorhexis and expression of material from the isolated lens. METHODS: Human and bovine lens capsules were isolated, sterile non-toxic silicone rings inserted, and the preparations placed in organ culture for up to 12 weeks. Cell coverage of the posterior lens capsule was recorded and the capsules were examined, both pre- and post-coverage, for (a) proliferative activity and (b) cytoskeletal components. RESULTS: After a lag period outgrowth was observed across the posterior capsule. The rate of cell coverage was dependent upon both species and the presence or absence of serum. The proliferative activity of the cells was greatest at or near the leading edge and decreased once covered. Wrinkles became visible in the posterior capsule during the late stages of precoverage and increased in both number and complexity. All cells on both the human and bovine posterior capsules contained F-actin and vimentin and the majority were immunolabelled for alpha-smooth muscle actin (alpha-SMA). CONCLUSIONS: This model exhibits many of the in vivo characteristics of the lens capsule after extracapsular surgery and may prove useful in further elucidating the cellular mechanisms of posterior capsule opacification.     

Combined pars plana vitrectomy, lens removal and intraocular lens implantation for complications of diabetic retinopathy. Surgical results in 120 cases

We performed combined vitrectomy, lens removal and posterior chamber intraocular lens implantation for proliferative diabetic retinopathy in 120 eyes of 101 patients. Follow-up periods ranged from 3 to 63 months, with a mean of 17 months. Three lens removal methods were used: extracapsular cataract extraction (14 eyes), phacoemulsification and aspiration (49 eyes), and pars plana phacoemulsification (57 eyes). Preoperative rubeosis iridis or neovascular glaucoma was found in 21 eyes. Gas or temporary silicone oil tamponade was employed in 32 eyes. Surgical results were good, and the postoperative vision was finger counts or below only in 13 eyes. Thus the combined surgery proved to have no serious problems. Our results indicate two important points. (1) It is best to chose either of the following two methods for the lens surgery: phacoemulsification with continuous circular capsulorhexis, self sealing sclerocorneal incision, and in-the-bag fixation of the posterior chamber lens, or pars plana phacoemulsification leaving the anterior capsule, rub off and aspirating the lens epithelial cells, continuous circular capsulorhexis, and posterior chamber lens implantation in front of the anterior capsule from a self-sealing sclerocorneal wound. (2) It is mandatory to do complete vitrectomy and cut out the vitreous gels incarcerated in the sclerotomy site.     

Light and scanning electron microscopy of rabbit lens capsules with intraocular lenses

PURPOSE: To examine postoperative changes in the lens capsules of rabbit eyes after phacoemulsification and aspiration of the crystalline lens and implantation of posterior chamber intraocular lenses (IOLs) using light and scanning electron microscopy. SETTING: Research Laboratory, Department of Ophthalmology, Wakayama Medical College, Japan. METHODS: The crystalline lens was emulsified and aspirated and an IOL implanted in the capsular bag or ciliary sulcus of each eye in adult albino rabbits under general anesthesia. Animals were killed after 4 weeks, and the lens capsules were removed. The specimens were observed under phase-contrast microscopy and processed for light and scanning electron microscopy. RESULTS: Phase-contrast microscopy revealed presumed lens epithelial cells (LECs) on the central posterior capsules in association with regenerating lenticular fibers and Elschnig pearls in the peripheral capsules. Scanning electron microscopy showed the accumulation of fibrous extracellular matrix on the surface of the posterior capsule in eyes in which the IOL was implanted in the ciliary sulcus. Deposition of packed material attached to the surface of IOLs and of Soemmering's ring were observed in eyes with in-the-bag IOL fixation. At a higher magnification, a parallel arrangement of lenticular fibers was seen in the regenerated lens structure on posterior capsules. An identical structure was observed under light microscopy. Outgrowth of presumed LECs from residual anterior lens capsules and adhesion of macrophages and giant cells were observed on the IOL surface. CONCLUSION: Two types of postoperative changes were observed in lens capsules after implantation of IOLs: accumulation of fibrous extracellular matrix and newly formed lenticular fibers. These changes are attributed to the proliferation of LECs and can induce posterior capsule opacification after IOL implantation.     

Cell proliferation on the outer anterior capsule surface after extracapsular lens extraction in rabbits

PURPOSE: To use light microscopy to evaluate the presence and distribution of cells that proliferate on the outer surface of the anterior capsule after experimental lens extraction in rabbit eyes. SETTING: Research Laboratory, Department of Ophthalmology, Wakayama Medical College, Wakayama, Japan. METHODS: Extracapsular lens extraction, with or without implantation of a poly(methyl methacrylate) intraocular lens, was performed in 10 adult albino rabbits under general anesthesia. Animals were killed 1 month postoperatively. Each eye was embedded in paraffin and examined by light microscopy. RESULTS: A capsular bag composed of the anterior and posterior capsules was observed. Mononuclear cells, presumed to be lens epithelial cells (LECs), had proliferated in the space between the capsules as well as on the outer surface of the anterior capsules, in association with an accumulation of extracellular matrix. CONCLUSION: After lens extraction, LECs migrated to and proliferated on the anterior surface of the anterior capsule.     

Extracellular matrix of opacified anterior capsule after endocapsular cataract surgery

BACKGROUND: We determined the types and distribution of glycosaminoglycans (GAGs) and collagens, in anterior capsular opacification after endocapsular phacoemulsification and aspiration (ECPEA) and intraocular lens implantation. METHODS: Opacified anterior capsules were removed from human eyes after ECPEA. Immunohistochemical staining was performed to determine GAGs with monoclonal antibodies to chondroitin, chondroitin-4-sulfate (C4S), chondroitin-6-sulfate (C6S), dermatan sulfate (DS), and keratan sulfate (KS); collagens with monoclonal antibodies to types I, II, and III collagens; and cellular characteristics with monoclonal antibodies to vimentin, desmin, alpha-smooth muscle actin, and cytokeratin. Decorin mRNA and type I collagen mRNA were detected by in situ hybridization. RESULTS: In the capsules, the C6S, DS, KS, and types I and III collagens were similar to the chemical components found at the adhesion site of the anterior and posterior capsules after extracapsular cataract extraction, and cellular components contained vimentin, desmin, alpha-smooth muscle actin, cytokeratin, decorin mRNA, and type I collagen mRNA. CONCLUSIONS: The GAGs and collagens in opacified anterior capsule after ECPEA were similar to those found during wound healing, although KS is present in normal anterior segment tissue during development and only in the cornea postnatally. These chemical components may be produced by myofibroblast-like cells presumably transformed from lens epithelial cells.     

Porcine interferon-gamma inhibits the growth of Legionella pneumophila in WiREF cells in vitro

In the present study eight human eyeballs were specifically prepared for scanning-electron-microscopic observation of the zonule. The zonule consisted of two main layers of radial fibres, an anterior and a posterior one, that inserted on the anterior and the posterior lens capsules, respectively. Some fibres inserted on the equator of the lens. Posterior zonular fibres originated at the pars plana, entered the dorsal part of the ciliary valleys and then changed their direction towards the posterior face of the lens. Posterior fibres inserted on the posterior capsule of the lens by branched endings 1 mm behind the equator of the lens. Anterior zonular fibres originated mainly at the pars plana and occasionally at the ciliary valleys. After running completely through the ciliary valleys in close contact with the lateral walls of the ciliary processes, they changed their direction at the anterior endings of the pars plicata and reached the anterior lens capsule. Anterior zonular insertions were achieved by webbed endings that diffused into the anterior capsule 2 mm in front of the lens equator. The extraordinary distension capacity of the zonular fibres was demonstrated by pulling the anterior lens capsule after hydrodissection. As a consequence, the anterior fibres were stretched up to four times their original length without breaking or disinserting.     

Expression of the beta 4 integrin subunit in the mouse heart during embryonic development: retinoic acid advances beta 4 expression

Dye transfer between lens fiber cells and between lens epithelial cells and underlying fiber cells was studied using a wide dynamic range-cooled CCD camera, H2O immersion objectives and image analysis techniques. Each lens was decapsulated by a new technique which leaves the epithelial cells adherent to the lens fiber mass. Lucifer Yellow CH was injected into either single epithelial cells or single fiber cells using the standard whole cell configuration of the patch voltage clamp technique. The results demonstrate extensive dye communication between fiber cells at the lens posterior surface, anterior surface, and equatorial surface. Dye transfer between deep fiber cells was also observed. Dye transfer between approximately 10% of epithelial cells and their underlying fiber cells was apparent when care was taken to yield wide dynamic range images. This was required because the relatively high concentration of dye in the epithelial cell masks the presence of much lower dye concentrations in the underlying fiber cell. A mathematical model which includes dye concentration, time, and spatial spread suggests that those epithelial cells that are coupled to an underlying fiber cell are about as well dye coupled as the epithelial cells themselves. The relatively low dye concentration in a fiber cell is due to its larger volume and diffusion of the dye along the axis of the fiber away from the fiber/epithelial junction.     

Effect of postoperative mydriatics on the iris

PURPOSE: To assess the role postoperative mydriatics play after extracapsular cataract extraction (ECCE) and posterior chamber intraocular lens (IOL) implantation in causing iris modifications and in controlling inflammation. SETTING: Outpatients Department, Ninewells Hospital, Dundee, Scotland. METHODS: The prospective study comprised 136 patients who had standardized ECCE. Half the patients used a mydriatic for 2 weeks postoperatively. Anterior chamber activity, pain, and eye redness were evaluated at 2 weeks postoperatively; pupil shape, peripheral anterior synechias, IOL position, and iris adhesions, at 6 weeks. RESULTS: Iris-lens adhesions were significantly more common in the group using a mydriatic. There was no difference between the two groups in postoperative inflammation. CONCLUSION: Mydriatics should not be used routinely after ECCE with posterior chamber IOL implantation.     

Inhibition of migrating lens epithelial cells at the capsular bend created by the rectangular optic edge of a posterior chamber intraocular lens

BACKGROUND AND OBJECTIVE: To study the mechanism of the reportedly low incidence of posterior capsule opacification (PCO) in eyes treated with a posterior chamber intraocular lens (PC IOL). MATERIALS AND METHODS: Various IOL designs, including the PC IOL, were studied using scanning electron microscopy. Rabbit lens capsules were studied histopathologically 2, 3, and 4 weeks after implantation of a PC IOL in one eye and a biconvex polymethylmethacrylate (PMMA) IOL in the contralateral eye as a control. RESULTS: The optic edge of the PC IOL was sharp and rectangular, whereas that of the biconvex PMMA or silicone IOLs from various manufacturers had been smoothed and rounded by polishing. PCO was significantly reduced in the eye with a PC IOL in all rabbits. The lens capsule wrapped tightly around the optic edge of the PC IOL so that it conformed to the same shape and thereby created a distinct rectangular bend in the capsule or a rectangle between the optic edge and the posterior capsule. Migrating lens epithelial cells (LECs) were obviously inhibited at that site. CONCLUSIONS: A discontinuous capsular bend or rectangle created by the sharp, square optic edge of the PC IOL may have induced contact inhibition to migrating LECs and reduced PCO. How, whether, and to what extent this design-dependent effect is influenced by features of the IOL material needs to be clarified by comparison with results achieved with an IOL made from the same material in a different design and vice versa.     

Conversion from phacoemulsification to extracapsular cataract extraction: incidence, risk factors, and visual outcome

PURPOSE: To evaluate the incidence, risk factors, and visual outcome in cases converted from phacoemulsification to routine extracapsular cataract extraction (ECCE). SETTING: Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India. METHODS: A retrospective study was performed in 540 eyes that had clear corneal phacoemulsification performed by an experienced phacoemulsification surgeon. The cases in which phacoemulsification was initiated and then converted to ECCE were studied. The main parameters evaluated were the factors responsible for the conversion, corneal endothelial cell loss, and visual outcome. RESULTS: Twenty eyes (3.7%) required conversion to ECCE during phacoemulsification. Pupillary miosis (6 cases), posterior capsule rupture (5 cases), prolonged phaco time (4 cases), posterior extension of the capsulorhexis (2 cases), corneal thermal burn (1 case), subluxation of the lens (1 case), and malfunctioning of the ultrasonic handpiece (1 case) were the reasons for the conversion. The mean percentage of endothelial cell loss was 11.06% +/- 2.3 (SD); 18 cases (90.0%) achieved a visual acuity of 20/40 or better at 6 weeks. CONCLUSIONS: Intraoperative pupillary miosis, posterior capsule rupture, and very hard nuclear cataract causing prolonged phacoemulsification were the major risk factors for conversion to ECCE. Optimal preoperative preparation and prompt recognition of complications during phacoemulsification can lead to timely conversion to ECCE to achieve a good visual outcome.     

Mice deficient for the secreted glycoprotein SPARC/osteonectin/BM40 develop normally but show severe age-onset cataract formation and disruption of the lens

SPARC (secreted protein acidic and rich in cysteine, also known as osteonectin/BM40) is a secreted Ca2+-binding glycoprotein that interacts with a range of extracellular matrix molecules, including collagen IV. It is widely expressed during embryogenesis, and in vitro studies have suggested roles in the regulation of cell adhesion and proliferation, and in the modulation of cytokine activity. In order to analyse the function of this protein in vivo, the endogenous Sparc locus was disrupted by homologous recombination in murine embryonic stem cells. SPARC-deficient mice (Sparctm1Cam) appear normal and fertile until around 6 months of age, when they develop severe eye pathology characterized by cataract formation and rupture of the lens capsule. The first sign of lens pathology occurs in the equatorial bow region where vacuoles gradually form within differentiating epithelial cells and fibre cells. The lens capsule, however, shows no qualitative changes in the major basal lamina proteins laminin, collagen IV, perlecan or entactin. These mice are an excellent resource for further studies on how SPARC affects cell behaviour in vivo.     

Siderosis of the lens (author's transl)

Incipient siderosis of the lens is reflected by an extremely fine granular, almost homogenous closely subcapsular brown discoloration between the anterior capsule of the lens and the epithelium. Advanced siderosis of the lens leads to subcapsular "rust spots" of varying size, especially in the region below the pupil; to increasing permeability cataract with protein breakdown and also to brown discoloration of the developing hollow spaces and clefts containing protein. In extensive siderosis of the lens, there was the following histological evidence of iron infiltration colour reactions: Between epithelium and capsule: (fusiformly) changed epithelia, intercellular substance formed by metaplasia of epithelia with connective tissue fibrillae (birefractive capsular cataract), in large, balloon-like epithelial cells freely occurring in the liquefied capsule, by decomposition of these cells in all fluid cavities containing protein (water clefts, etc.). On the other hand, there were no siderous granulations of protein: in normal epithelial cells of the lens, in unchanged fibres of the lens, in Wedl's cells and in Morgagni's or myelin droplets.     

Left ventricular function of the heart regressed by nifedipine in spontaneously hypertensive rats

The clinical course of lens opacity and the morphological changes in lens epithelial cells after intravitreal silicone oil injection were observed for 3 months in 21 normal adult albino rabbits. After the simple vitrectomy in both eyes of each rabbit, silicone oil was injected into the vitreous in one eye and the other eye was kept as the control. By photoslit-lamp microscopy, 8 of the 14 examined eyes showed early posterior subcapsular lens opacity one month after silicone oil injection. By transmission electron microscopy, intracellular vesicles near the interdigitation of the lens epithelial cells were observed in all of the 7 eyes examined histologically 2 weeks after the procedure. These changes were not observed in the 7 fellow control eyes. As a result, it is surmised that cataract formation after intravitreal silicone oil injection may be associated with morphological changes in the lens epithelial cells.     

Echo color Doppler imaging of carotid vessels in hemodialysis patients: evidence of high levels of atherosclerotic lesions

BACKGROUND: Although a variety of approaches to manage cataracts in children have been studied, no consensus exists on the optimum approach. The authors, therefore, conducted a prospective, nonrandomized, consecutive study to evaluate three most commonly adopted methods of management of pediatric cataracts. METHODS: Lensectomy anterior vitrectomy (LAV), extracapsular cataract extraction with intraocular lens implantation (ECCE + IOL) and ECCE, primary posterior capsulotomy, anterior vitrectomy with IOL (ECCE + PPC + AV + IOL) were the surgical procedures performed. Aphakia in the LAV group was corrected with spectacles or contact lenses. Intraoperative and postoperative results were analyzed. Discrete variables among the three groups were compared using chi square test. RESULTS: One hundred ninety-two eyes were included in the study. There was no statistically significant difference in the intraoperative complications in the three groups. During a mean follow-up period of 11.3 months, postoperative obscuration of the visual axis was seen in 43.7% of eyes in the ECCE + IOL group and in 3.65% of eyes in the ECCE + PC + AV + IOL (p < 0.001). Two of the seven patients in the LAV group in whom contact lenses were prescribed developed corneal infiltrates. Severe postoperative anterior uveitis occurred in 15.9% and 13.8% of eyes in the ECCE + PPC + AV + IOL and ECCE + IOL groups, respectively. None of the eyes that underwent LAV developed this complication (P < 0.001). There was no statistically significant difference in the incidence of retinal detachment, endophthalmitis, or glaucoma in the three groups. CONCLUSION: Of the three approaches, ECCE + PPC + AV + IOL was conducive to at least short-term maintenance of a clear visual axis, provided optimum refractive correction, and was not associated with increased risk of short-term complications. Continued follow-up of these eyes is necessary to conclude on the long term results of this technique.     

A novel ALL-L3 cell line, BALM-16, lacking expression of immunoglobulin chains derived from a patient with hypercalcemia

OBJECTIVE: The purpose of the study is to evaluate whether a posterior capsulectomy combined with anterior vitrectomy is a necessity in pediatric cataract. DESIGN: The incidence of posterior capsule opacification, the need for additional surgical interventions, and the influence of a primary posterior capsulectomy after cataract surgery in children were evaluated. The analysis was carried out by studying patients' records retrospectively or after prospective follow-up. PARTICIPANTS: In 94 eyes (69 aphakic and 25 pseudophakic), the medical records were studied retrospectively. Twenty-eight eyes (18 aphakic and 10 pseudophakic) were observed prospectively during 1 year after surgery. In 20 eyes (6 aphakic and 14 pseudophakic) of 10 patients with bilateral cataract, a prospective comparison between the 2 eyes of the same patient also was carried out. INTERVENTION: Cataract surgery through the limbus with or without a primary posterior capsulectomy was performed in 114 eyes (43 of these received a posterior chamber intraocular lens [IOL] and 71 remained aphakic). In 28 eyes, the surgery was carried out by way of the pars plana (6 eyes received an anterior chamber IOL and 22 remained aphakic). MAIN OUTCOME MEASURES: Incidence of posterior capsule opacification, the need for secondary surgical intervention, and visual acuity were measured. RESULTS: Opacification of the posterior capsule is observed in all children's eyes when a primary posterior capsulectomy (combined with an anterior vitrectomy) was not carried out. Earlier secondary cataract formation is associated with a younger age and with implantation of an IOL. Eyes undergoing a primary opening of the posterior capsule during the initial surgery of children with bilateral cataract achieved, in most cases, a better visual acuity than did their fellow eyes. CONCLUSION: Although possibly a choice in older children, a primary posterior capsulectomy combined with anterior vitrectomy is a must in younger children and particularly when implantation of an IOL is planned.     

High-resolution digital retroillumination imaging of the posterior -004 capsule after cataract surgery

PURPOSE: To develop a system for high-resolution imaging of the posterior lens capsule after intraocular lens surgery for objective assessment of posterior capsule opacification (PCO). SETTING: Department of Cataract and Refractive Surgery, St. Thomas' Hospital, London, United Kingdom. METHODS: A system was developed that uses coaxial illumination and imaging based on Zeiss components with a digital camera directly linked to a computer for online image verification and image analysis. RESULTS: The system produced high-resolution digital images with even background illumination of sufficient quality to demonstrate progressive lens epithelial cell changes that are amenable to computer image analysis. CONCLUSION: This system produced excellent images for objective documentation and quantitative measurement of PCO.     

Spontaneous disappearance of Elschnig pearls after neodymium:YAG laser posterior capsulotomy

Posterior capsule opacification (PCO) from Elschnig pearl formation is a common complication of extracapsular cataract extraction. After PCO treatment by neodymium:YAG (Nd:YAG) laser posterior capsulotomy, Elschnig pearls may undergo hyperproliferation at the edge of the capsulotomy, which may close it. We have seen six eyes in five patients who presented with spontaneous disappearance of Elschnig pearls, resulting in a perfectly clear posterior capsule several years after an Nd:YAG posterior capsulotomy. Possible causes include (1) falling of pearls into the vitreous through the capsulotomy; (2) phagocytosis of pearls by macrophages; (3) cell death by apoptosis.