Subluxed or Dislocated Crystalline Lens

Symptoms

• decreased vision: often due to high astigmatism or the eye becoming "aphakic" (no lens)
• monocular diplopia: seeing double with one eye covered; caused by the lens edge splitting the pupil
• fluctuating vision: sight changes as the lens shifts with head position
• ocular pain: may indicate secondary glaucoma if the lens moves forward into the angle

Clinical Findings

Clinical signs

• phacodonesis: quivering of the lens during eye movement (the most sensitive early sign)
• iridodonesis: tremulousness of the iris because the lens is no longer supporting it
• lens edge: the equator of the lens or visible zonules seen through a dilated pupil
• asymmetric ac depth: the anterior chamber is deeper where the lens has recessed

Genetic localization

• superotemporal (up & out): classic for marfan syndrome (fibrillin-1 defect)
• inferonasal (down & in): classic for homocystinuria (cbs deficiency)
• anterior (into ac): suggests weill-marchesani syndrome (microspherophakia)

Pseudoexfoliation (PXF)

• target pattern: white, flaky material on the lens capsule; a major cause of zonular weakness

Etiology

Primary causes

• trauma: the #1 cause overall; look for vossius rings or angle recession
• pxf syndrome: the most common non-traumatic cause in elderly patients
• marfan syndrome: autosomal dominant; associated with life-threatening aortic root dilation
• homocystinuria: autosomal recessive; associated with high thromboembolism risk
• weill-marchesani: short stature and small spherical lenses (microspherophakia)

Red Flags

• marfan suspicion: mandates an immediate echocardiogram to rule out aortic dissection
• homocystinuria surgery: high risk of fatal clots under general anesthesia; requires hydration
• anterior dislocation: an ophthalmic emergency; can cause acute pupillary-block glaucoma
• posterior dislocation: if the lens falls into the vitreous, it requires a retina specialist (lensectomy)

Investigations

Ocular exam

• slit lamp: check for phacodonesis before dilation and pxf flakes after dilation
• gonioscopy: evaluate for angle recession (trauma) or sampaolesi line (pxf)

Systemic workup

• marfan: cardiology referral for aortic root measurement
• homocystinuria: plasma homocysteine and urine nitroprusside tests
• syphilis: rpr/fta-abs (historically associated with "luetic" lens subluxation)

Treatment

Non-surgical

• observation: if vision is stable and there is no inflammation or glaucoma
• optical: aphakic contact lenses or spectacles if the lens is completely out of the visual axis

Surgical

• lens extraction: required for symptomatic cataracts, uncorrectable diplopia, or glaucoma
• advanced tools: use of capsular tension rings (ctr) or segments to stabilize the new iol
• fixation: scleral-fixated or iris-sutured iols are used when zonular support is absent

Clinical Pearl

Superotemporal lens subluxation points to Marfan (zonules intact inferiorly); inferonasal to homocystinuria (zonules disrupted superiorly) — the direction localizes the genetic disease before blood tests return.

Differential Diagnosis

• • pseudoexfoliation syndrome (weak zonules but lens usually still central)
• • morgagnian cataract (heavy nucleus sinks within the capsular bag)
• • simple ectopia lentis (isolated ocular finding without systemic disease)

Related Lens Conditions

• Acquired Cataract
• Blue Dot Cataract (Cerulean Cataract)
• Developmental Anterior Segment and Lens Anomalies/Dysgenesis
• Pediatric Cataract
• Posterior Subcapsular Cataract (PSC)