Posterior Capsular Opacification

Posterior capsular opacification (PCO) is opacification of the posterior lens capsule after extracapsular cataract surgery, due to proliferation and migration of residual lens epithelial cells.

• Types: fibrosis (wrinkling and fibrous metaplasia) and regeneration (Elschnig pearls and Soemmering ring, from the equator, with swollen bladder cells).
• Incidence about 10 to 40 percent by 2 to 5 years in adults; in children, near 100 percent without primary posterior capsulotomy.
• Risk factors: young age, diabetes, uveitis, retinitis pigmentosa, pseudoexfoliation, myotonic dystrophy, residual cortex, large capsulorhexis, silicone and hydrophilic lens material, and round edge intraocular lens designs. Sharp edged optic and in-the-bag placement reduce risk.

• Gradual onset of blurred or hazy vision, glare, reduced contrast, monocular diplopia, months to years after clear initial recovery.
• Slit lamp and retroillumination: grey fibrotic wrinkles, pearl like clusters or dense membrane behind the intraocular lens.
• Vision loss is out of proportion to ocular findings sometimes (pearls in the visual axis).
• In children: poor vision recognised late, amblyopia and strabismus.

• Visual acuity, glare testing, slit lamp with dilation and retroillumination photography.
• Exclude other causes of vision loss: macular oedema, epiretinal membrane, optic neuropathy, and dry eye (macular optical coherence tomography).
• Evaluate the capsule, haptic position and optic, and intraocular pressure; confirm that the patient is at least 3 months after surgery with quiet eye.

• Neodymium doped yttrium aluminium garnet (Nd:YAG) laser posterior capsulotomy:
  • Pretreat with apraclonidine 1 percent or brimonidine 0.2 percent drops 30 to 60 minutes before and immediately after to blunt pressure spikes.
  • Dilate the pupil (tropicamide 1 percent, phenylephrine 2.5 percent), use a capsulotomy contact lens (Abraham), pulse energy 0.8 to 2.0 mJ per pulse with the focus slightly behind the capsule, single shots in cruciate or circular pattern creating an opening about 3 to 4 mm wide, in the pupillary area, and avoid hitting the lens optic (pitting).
  • Total energy under about 80 mJ lowers risk.
• Post laser: topical steroid (prednisolone acetate 1 percent or loteprednol 0.5 percent four times daily for 5 to 7 days) and check pressure at 1 to 2 hours (treat with timolol 0.5 percent or acetazolamide 250 mg if over 25 mmHg).
• Complications: transient pressure rise (up to 10 to 15 percent), lens pitting, cystoid macular oedema, retinal detachment (about 1 to 2 percent, higher in high myopia and young patients), lens subluxation, endophthalmitis (rare, with a rupture of the anterior hyaloid face).
• Contraindications and caution: active uveitis, corneal opacity, vitreous haemorrhage, patients unable to cooperate (children may need general anaesthesia or surgical posterior capsulorhexis).
• Surgical alternatives: posterior capsulorhexis with or without optic capture and anterior vitrectomy in children under 6 to 8 years.
• Prevention: thorough cortical clean up, polishing of posterior capsule, in-the-bag lens with a square edge, a capsulorhexis slightly smaller than the optic, and hydrophobic acrylic lens material.