Posterior capsule opacification

Posterior capsular opacificationP.C.O

Posterior capsule opacificationThe most common complication of cataract surgery by means of ECCE or phacoemulsification is opacification of the intact posterior capsule

P.C.OCapsular opacification stems from the continued viability of lens epithelial cells remaining after removal of the nucleus and cortex.These cells proliferate in several patterns.

Soemmerring,s ringWhere the edges of the anterior capsule adhere to the posterior capsule,a closed space will be reestablished consisting of nucleated bladder cells (wedl cells)

Elschnig pearlsIf the epithelial cells migrate outward,which resemble fish eggs, are formed on the posterior capsule.

p.c.oThe lens epithelial cells are capable of undergoing metaplasia with conversion to myofibroblasts. A matrix of fibrous and basement membrane collagen can be produced by these cells , will cause wrinkls in the posterior capsule , with resultant distortion of vision and glare.

p.c.o preventionMeticulous hydrodissection and attention to complete cortical cleanup are important preventive measurement for reducing the likelihood of these events

Factors known to influence rate of P.C.O-The age of the patient -History of intraocular inflammation -Presence of exfoliation syndrome -Size of capsulorrhexis -Quality of cortical cleanup -Capsular fixation of the implant -Lens implant design (square-edge optic) -Lens surface modification -Presence of intraocular silicone oil

P.C.O rate-Overall about 28% at 5 years -Incidence at 3 years :PMMA 56% Silicone 40% Acrylic 10% -Prevalence of ND:YAG capsulotomy in a large postmortem review: 0.9% acrylic IOL 12%-21% various silicone IOLs27%-33%PMMA IOL

Capsular fibrosisThe introduction of continuous curvilinear capsulorrhexis has been accompanied in some cases by anterior capsule contraction and fibrosis that is associated with clouding of the anterior capsule.

Capsular phimosis

The postoperative contraction of the anterior capsular opening as a result of fibrosis,such that the rim of capsular tissue is also visible through the undilated pupil.may cause decentration of an IOLoptic. More frequently with smaller capsulorrhexis openings,in patients with underlying exfoliation syn , with abnormal or asymetric zonular support and plate haptic PC IOL.

Treatment of P.C.OUse of the Nd:YAG laser is now a standard procedure for treating secondary opacification of the posterior capsule or anterior capsule contraction,although a dicission knife can be used through an ab externo corneal incision to open an opacified capsule in special cases.

Nd : YAG laser capsulotomy indications:-Best corrected visual acuity decreased as a result of a hazy posterior capsule -A hazy posterior capsule preventing the clear view of the ocular fundus required for diagnosis or therapeutic purposes -Monocular diplopia or glare caused by posterior capsule wrinkling Contraction of anterior capsulotomy margins(phimosis)encroaching on the visual axis or altering the lens optic position,requiring relaxing incisions

Preoperative stepsAsses best-corrected visual acuity Rule out other causes of decreased vision(C.M.E,) Review potential risks of the procedureBe sure that patient is able to cooperate with the procedure

contraindications-Inadequate visualization of the posterior capsule -An uncooperative patient who is unable to remain still or hold fixation during the procedure

Nd:YAG laser dicission-Usually painless and is performed as an outpatient procedure -Adjust the oculars of the microscope-laser delivery system so that focal point of the helium-neon aiming beam is clearly brought into focus -The pulse energy threshold for puncture of the posterior capsule 0.8-2 mj

Nd:YAG laser-Emits radiation at a wavelenght of 1064nmCan be operated: -A continuous wave -Pulsed modes: -long-pulsed 0.1-1.0ms -Q-switched 5-30ns -Mode-locked 30-200ps Two latter modes are most commonly used

Nd:YAG laser-An undilated pupil can help the surgeon pinpoint the location of the visual axis-The center of the visual axis is the desired site of the opening Usually adequate at 3-4mm in diameterLonger diameter openings may be required for more complete visualization of the fundus

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