Subluxation and Dislocation of the Lens
Subluxation or dislocation of the lens, also called ectopia lentis, refers to a partial or complete displacement of the crystalline lens from its normal position due to the weakening or rupture of zonular fibers.
- Subluxation: The lens is partially displaced but remains within the pupillary area.
- Dislocation (Luxation): The lens is completely displaced out of the pupillary area, either into the anterior chamber or the vitreous cavity.
Causes of Lens Subluxation/Dislocation
A. Traumatic Causes
- Blunt trauma (e.g., sports injury, road traffic accident)
- Penetrating trauma (e.g., sharp object injury, gunshot wounds)
B. Non-Traumatic Causes
1. Congenital/Hereditary Causes
- Marfan syndrome - Lens subluxation is usually superotemporal.
- Homocystinuria - Lens dislocation is inferonasal.
- Ehlers-Danlos syndrome - Can cause lens instability.
- Weill-Marchesani syndrome - Lens dislocation often inferior.
2. Acquired Causes
- Pseudophakia (complication of cataract surgery)
- High myopia
- Hyper mature cataract
- Syphilis, Uveitis, Pseudoexfoliation syndrome
Types of Lens Displacement
- Partial Subluxation: Lens remains partially attached to the zonules.
- Complete Dislocation:
- Anterior dislocation - Can cause acute angle-closure glaucoma.
- Posterior dislocation - Can lead to vitreous inflammation and retinal detachment.
Clinical Features
- Decreased vision
- Monocular diplopia
- Iris tremulousness (iridodonesis)
- Lens shimmering (phacodonesis)
- Acute pain and redness (if glaucoma develops)
Diagnosis
A. Slit-Lamp Examination- Detects iridodonesis and phacodonesis.
B. Gonioscopy
- Checks for angle closure in anterior dislocation.
C. Retinal Examination
- Indirect ophthalmoscopy to rule out retinal detachment.
D. Investigations
- Ultrasound B-scan (for posterior dislocation)
- OCT (for zonular assessment)
- Genetic Testing (for syndromic cases)
- Homocysteine levels (if homocystinuria is suspected)
Management
A. Conservative Management (For mild subluxation)
- Spectacles or contact lenses (for refractive correction)
- Mydriatics (e.g., Atropine 1%) (to relieve pupillary block)
- Regular monitoring (if no complications)
B. Surgical Management
1. Anterior Dislocation
- Emergency lens removal (ICCE or Pars Plana Lensectomy)
- Intraocular Lens (IOL) implantation
- Scleral-fixated IOL (SFIOL)
- Anterior Chamber IOL (ACIOL)
2. Posterior Dislocation
- Pars Plana Vitrectomy with Lensectomy
- IOL implantation if needed
3. Management of Complications
- Glaucoma → IOP-lowering medications, surgery
- Retinal Detachment → Vitrectomy with repair
Key Points for Exams
- Most common cause: Trauma
- Superotemporal dislocation: Marfan syndrome
- Inferonasal dislocation: Homocystinuria
- Most serious complication: Secondary glaucoma
- Treatment of choice for posterior dislocation: Pars plana vitrectomy with lensectomy