Published on March 14, 2014
Posterior capsular opacification (Secondary cataract, after cataract) Definition: Opacification of the posterior capsule due to partially absorbed traumatic cataract or following ECCE or phaco. PCO is actually misnomer bcz its not the capsule which opacifies…rather an opaque membrane develops over the PC.
Incidence: PCO is the most common complication of cataract surg. PCO is a major problem in paediatric cataract surgery where the incidence approaches 100%. PCO incidence has been reported to occur in 36%-97% of patients 2-4 years after ECCE. The corresponding incidence within 1 year after phaco was 2%-15 % & within 3 years it was found to range between 2% and 63%.
RISK FACTORS Nonmodifiable Age: younger individuals are at a higher risk. Diabetes: diabetics had significantly severe PCO after cataract surgery when compared with nondiabetics. The incidence of PCO is high in eyes with uveitis. In these eyes, hydrophobic acrylic IOLs provide a better visual outcome & lower incidence of PCO than silicone, PMMA or heparin- coated PMMA IOLs. Patients with myotonic dystrophy & retinitis pigmentosa showed a significantly higher incidence & density of PCO. In traumatic cataracts, the incidence of PCO is significantly higher and has been quoted to be as high as 92% at the 3-year follow-up.
Modifiable Surgical Techniques Continuous Curvilinear Capsulorhexis. Delays the development of central visual obscuration by facilitating fusion between the edge of the CCC to the PC, forming a ring which provides a closed environment restricting LECs migration toward the central PC. Facilitates in-the-bag fixation of the IOL which enhances the IOL optic barrier effect, reducing the incidence of central PCO. There is an increased Incidence of fibrosis-type PCO in cases of ciliary sulcus fixation.
with a capsulorhexis smaller than the IOL optic, the adhesion between the anterior capsule & the IOL optic keeps the anterior lens epithelium away from the posterior capsule the incidence of migration of the anterior LECs behind the IOL optic. Modifiable Surgical Techniques Anterior Capsule Overlap of IOL Optic.
The hydraulic force exerted by hydrodissection causes a cleavage between the lens capsule & the cortex, which could cleave mitotically active LECs from the capsule. Modifiable Surgical Techniques Cortical Cleaving Hydrodissection. The edge of the anterior capsule is slightly tented up by the tip of the cannula, while injecting the fluid.
Cortical cleavage hydrodissection. The cannula is placed immediately under the anterior capsule. It is one of the most important maneuvers to reduce the incidence of PCO.
Modifiable Surgical Techniques Cortical Clean Up. Thorough removal of residual cortical fibers number of mitotically active cells that have the potential to proliferate and migrate across the central visual axis.
Modifiable Surgical Techniques Polishing (Scraping) the Anterior Capsule. Polishing of the anterior capsule has been effective in reducing fibrotic opacification but ineffective in reducing regeneratory opacification.
Modifiable Surgical Techniques IOL Factors IOL Design Plate-haptic versus Loop-haptic IOLs. A high rate of ACO as well PCO (up to 65%) has been reported with the plate haptic design IOLs, due to incomplete fusion of the anterior & posterior capsule leaves along the plate haptic axis the lack of capsule bending at the optic edge. This allows LECs to migrate centrally onto the posterior capsule various forms of LEC fibrosis.
Modifiable Surgical Techniques IOL Factors IOL optic Design Lenses with a plano convex optic (plano posterior) appear to have a lower rate of PCO than biconvex lenses due to mechanical or barrier effect of the IOL, which prevents LEC proliferation & central migration, explains the high incidence of regeneratory PCO reported with IOL designs that hold the posterior capsule away from the lens optic. “No space, No cells”
Modifiable Surgical Techniques IOL Factors Optic Edge Design The discontinuous sharp bend created by the sharp optic edges of the IOL appeared to induce contact inhibition (mechanical barrier) of migrating LECs. Therefore, the sharp optic edge design was found to be more effective in the prevention of PCO formation compared with IOLs with round optic edges.
Blocking of LEC migration at posterior sharp optic edge due to bending of the capsule (left) compared to round edge IOL (right).
Modifiable Surgical Techniques IOL Factors Haptic Designs & Angulation Haptic angulation reduces the incidence of PCO by maximizing the barrier effect to migrating LECs at the posterior optic edge by pushing the IOL backward against the posterior capsule.
Fusion of capsule at haptic-optic junction for different haptic designs. Acrysof multipiece with nearly complete fusion. Acrysof single-piece with incomplete fusion which may serve as one entry site (arrows) for regenerating LECs & no sharp edge at junction.
Modifiable Surgical Techniques IOL Factors Accommodating IOLs These IOLs have in common a hinge-like junction of haptics to optic that should allow the shifting of the optic when the haptics are compressed. This design leads to significant PCO with most patients needing YAG capsulotomies within the 1st 2 years after surgery early PCO due to missing barrier along broad haptic-optic junctions Infolding of haptics due to cap. constriction
Modifiable Surgical Techniques IOL Factors IOL material Hydrophilic acrylic lenses are more prone to develop PCO than hydrophobic acrylic lenses or silicone lenses. This may be due to the high water content being more “inviting” to lens epithelial cells (LEC) ingrowth or the fact that the optic edge of IOLs in this group is never as sharp as with the hydrophobic materials. IOL materials: hydrophobic & hydrophilic.
Modifiable Surgical Techniques IOL Factors IOL material Biocompatibility. Capsular biocompatibility is defined as the reaction of LECs and the capsule to the IOL material and design. This encompasses LEC ongrowth, ACO & PCO. AcrySof has the lowest rate of fibrosis of the anterior capsule with no membrane growth (i.e. more biocompatible)
Bioadhesive IOL Materials. Bioactive materials allow a single LEC to bond both to the IOL & the posterior capsule producing a sandwich pattern including the IOL, the cell monolayer and the posterior capsule. This sealed sandwich prevents further epithelial ingrowth prevent PCO. Therefore, a bioactive material such as hydrophobic acrylic would prevent PCO more than PMMA & silicone IOLs, which are biocompatible but also bioinert. Hydrophobic acrylic material binds more firmly to fibronectin, a plasma protein that is also secreted by LECs, compared with PMMA, silicone & hydrophilic acrylic materials. Therefore, it has been established that hydrophobic acrylic materials bind more firmly with the capsule.
Pathogenesis Viable LECs
Lens capsule is a transparent covering that surrounds the lens. Histologically it is a basement membrane composed of type IV collagen fibers & sulphated glycosaminoglycans. The capsule is produced anteriorly by the lens epithelium & posteriorly by the elongating fiber cells. Though it has no elastic tissue, it is highly elastic in nature because of lamellar or fibrillar arrangement of fibers. This property of the lens gradually decreases with age. Lens capsule is thickest near equator and thinnest at posterior pole. Thickness of anterior lens capsule with age, whereas thickness of posterior capsule remains constant or changes slightly.
In the normal crystalline lens, the LECs can be divided into 2 different biological zones: A. The ant. epithelial cells ("A" cells) consists of a monolayer of flat cuboidal, epithelial cells with minimal mitotic activity. In response to a variety of stimuli, they proliferate & undergo fibrous metaplasia. B. The second zone is the equatorial lens bow ("E" cells), in which cell mitoses, division & multiplication are quite active. New lens fibres are continuously produced in this zone throughout life. It’s
The development of PCO is a very dynamic process. It involves three basic phenomena: proliferation, migration, & differentiation of residual LECs. Clinically, two different components of PCO can be differentiated, namely a regeneratory and a fibrotic component. The residual LECs themselves secrete various cytokines that control the development of PCO
•Regeneratory PCO is much more common; it is caused by posterior migration of the E cells along the posterior capsule large balloon like bladder cells, known as Wedl cells which are clinically termed as Elschnig pearls. Each pearl represents the failed attempt of an epithelial cell to differentiate into a new lens fiber.
•Fibrotic PCO is caused by differentiation of A cells into myofibroblasts which are spindle-shaped, fibroblast-like cells. They express smooth muscle actin filament & become highly contractile. These cells proliferate & migrate to the posterior capsule and form a layer by secreting extracellular ground substances & a basement membrane like material causing whitening and wrinkling of the capsule.
Mixture of Elschnig’s pearls and fibrosis on the posterior capsule
Types of PCO Elschnig pearls • Proliferation of lens epithelium • Occurs after 3-5 years • Usually occurs within 2-6 months • May involve remnants of anterior capsule and cause phimosis Fibrosis
Complications of extensive fibrotic reaction of capsule: Rhexis contraction IOL decentration bad visual outcome spacielly with multifocal IOLs. partial buttonholing With IOL tilt. Arrows indicate location where the rhexis has“slipped” behind the optic.
CLINICAL EVALUATION Decreased VA, Visually significant PCO is defined as BCVA by 2 snellan’s lines. Impaired contrast sensitivity. Glare disability. Hinders examination of the peripheral fundus.
Source: American Journal of Ophthalmology 2014; 157:171-179.e1 (DOI:10.1016/j.ajo.2013.08.016 ) Copyright © 2014 Elsevier Inc. Terms and Conditions no grade, PCO No grade, PCO absent or only affecting the peripheral capsule. PCOGrading
Grade 1 Grade 1: any PCO affecting an area 4 mm in diameter around the visual axis, but not obscuring the retina . Copyright © 2014 Elsevier Inc. Terms and Conditions Source: American Journal of Ophthalmology 2014; 157:171-179.e1 (DOI:10.1016/j.ajo.2013.08.016 ) PCOGrading
Grade 2 Grade 2, central PCO slightly obscuring the view of the macula, but permitting an assessment of the C/D ratio . Source: American Journal of Ophthalmology 2014; 157:171-179.e1 (DOI:10.1016/j.ajo.2013.08.016 ) Copyright © 2014 Elsevier Inc. Terms and Conditions PCOGrading
Source: American Journal of Ophthalmology 2014; 157:171-179.e1 (DOI:10.1016/j.ajo.2013.08.016 ) Copyright © 2014 Elsevier Inc. Terms and Conditions Grade 3 Grade 3: central PCO slightly obscuring the view of the macula, but permitting an assessment of the C/D ratio. PCOGrading
Source: American Journal of Ophthalmology 2014; 157:171-179.e1 (DOI:10.1016/j.ajo.2013.08.016 ) Copyright © 2014 Elsevier Inc. Terms and Conditions Grade 4 Grade 4, central PCO sufficiently obscuring the view of the entire fundus PCOGrading
Surgery-related factors to reduce PCO: A well-centered Capsulorrhexis edge overlapping the IOL optic edge around the entire circumference. Multiquadrant cortical cleaving hydrodissection enhances cortical clean up. Aspiration of LECs from the anterior capsule during cataract surgery How to Achieve a Low PCO Rate?
IOL-Related Factors to Reduce PCO How to Achieve a Low PCO Rate? •In the bag fixation enhances IOL optic barrier. •Bio compatible IOL. Acry sof IOL is the most biocompatible. •Sharp posterior optic edge (the most effective method to PCO). •Maximum IOL OPTIC -PC contact.
Experimental devices: Sealed capsule irrigation for PCO prevention Sealed capsule irrigation (SCI). This small, flexible, soft silicone device seals the capsulorhexis temporarily allowing the isolated safe delivery of irrigating solutions containing pharmacological or non-pharmacological agents into the capsular bag following cataract surgery without exposing surrounding IO structures to potentially toxic substances.
PCO is a major problem in paediatric cataract surgery where the incidence approaches 100%. This is thought to be due to the higher proliferative capacity of lens epithelial cells in the young compared with the old. Dense PCO & secondary membrane formation is particularly common following paediatric IOL implantation. A delay in diagnosis can cause irreversible amblyopia. PCO in Children
A heparin coated PMMA IOL reduces inflammation & the incidence of PCO . Low molecular weight heparin added to the irrigating fluid during cataract surgery has resulted in less fibrin and pigment deposits on the lens. The capsular tension ring (CTR) may be useful. When the CTR is in place inside the capsular bag it exerts a 360° tangential tension on the posterior capsule Primary posterior CCC & primary anterior vitrectomy may be necessary to prevent or eliminate the onset of central PCO. Surgical Prevention
In younger children, visual axis obscuration due to PCO can be treated with pars plana vitrectomy and membranectomy. In older children , Nd: Yag posterior capsulotomy. Treatment
Treatment of capsular opacification Nd:YAG laser capsulotomy • Accurate focusing is vital • Apply series of punctures in cruciate pattern • 3 mm opening is adequate • Indications BCVA bcz of hazy PC – Hazy PC causing inadequate fundus view – Monocular Diplopia or glare
Posterior capsule following a Nd:YAG laser posterior capsulotomy
Potential complications • Damage to implant • Cystoid macular oedema - uncommon • Retinal detachment - rare except in high myopes •Short-term increase in IOP •No improvement in the visualization of the peripheral retina •Increases the overall costs for cataract treatment •Not available in large parts of the developing world. •Difficult to perform in young children. •ocular inflammation Disadvantage
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