Lens Dislocation

Lens dislocation (luxation) is complete displacement of the lens from the patellar fossa, either into the anterior chamber (anterior dislocation) or into the vitreous cavity (posterior dislocation), with total zonular failure.

• Causes: blunt trauma (the commonest cause, usually with rupture of the zonules over the whole circumference), spontaneous after hypermature cataract, pseudoexfoliation, Marfan syndrome, homocystinuria, Weill-Marchesani syndrome, uveitis, high myopia, and iatrogenic (dropped lens or nucleus during cataract surgery, in about 0.3 to 1 percent).
• Anterior dislocation causes pupillary block, angle closure glaucoma and corneal endothelial damage.
• Posterior dislocation can cause retinal detachment, vitritis and glaucoma, but may be tolerated.

• Sudden loss or reduction of vision, with pain, redness and headache if pressure rises.
• Anterior dislocation: lens (or crystal clear lens with golden edge) visible in the anterior chamber, corneal oedema, high intraocular pressure, shallow or deep chamber depending on position.
• Posterior dislocation: aphakic appearance, deep anterior chamber, iridodonesis, vitreous in the anterior chamber; lens visible mobile in the vitreous.
• High hypermetropic refraction in aphakic eye (about +10 to +12 dioptres, with loss of accommodation), monocular diplopia from the phakic and aphakic zones.
• Dropped nucleus: postoperative inflammation, vitritis, glaucoma, cystoid macular oedema.

• Slit lamp for position, lens clarity, and corneal and angle status; intraocular pressure.
• B-scan ultrasound for posterior dislocation, retinal detachment, vitreous haemorrhage and retained fragments; ultrasound biomicroscopy for zonule status and angle.
• Gonioscopy once the cornea clears; dilated fundus examination.
• Systemic workup for non-traumatic cases: echocardiogram for aortic root and valve disease, plasma total homocysteine and methionine, FBN1 sequencing, syphilis serology, and examination of the fellow eye and family members.

• Anterior dislocation is an emergency:
  • Lower intraocular pressure: acetazolamide 500 mg intravenously then 250 mg orally four times daily, timolol 0.5 percent, brimonidine 0.2 percent, and hyperosmotic agent (mannitol 20 percent 1 to 1.5 g/kg intravenously over 30 minutes) if needed.
  • Dilate the pupil (phenylephrine 2.5 percent, tropicamide 1 percent) and keep the patient supine to try to reposition the lens into the vitreous; if this fails, avoid miotics and proceed to surgery.
  • Urgent lens removal through a limbal incision (intracapsular extraction or phacoemulsification with viscoelastic to protect the endothelium), with anterior vitrectomy and intraocular lens options.
• Posterior dislocation:
  • Observe if the eye is quiet, the lens is clear or small and in the lower vitreous, with aphakic contact lens or spectacles.
  • Remove when there is inflammation, raised pressure, retinal detachment, large or hard fragments, or visual need: pars plana vitrectomy with lensectomy or fragmentation using ultrasonic fragmatome, perfluorocarbon liquid to float the lens, and intraocular lens support by scleral fixation.
• Dropped nucleus: vitrectomy within 1 to 2 weeks (earlier if pressure or inflammation is uncontrolled), topical prednisolone acetate 1 percent hourly and cycloplegia (cyclopentolate 1 percent three times daily) pending surgery; intravitreal injection of antibiotic if endophthalmitis is suspected (vancomycin 1 mg in 0.1 mL and ceftazidime 2.25 mg in 0.1 mL).
• Control inflammation and pressure with topical steroids, aqueous suppressants, and treat secondary glaucoma.
• Aphakic correction: scleral fixated or iris claw intraocular lens, anterior chamber lens, or contact lens.
• Follow up for retinal detachment (up to 5 to 10 percent), cystoid macular oedema, corneal decompensation and glaucoma.