Microspherophakia: Characteristics and Genetics
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Questions and Answers

What is the characteristic of the crystalline lens in Microspherophakia?

  • No change in the shape of the lens
  • Increased anteroposterior diameter and reduced equatorial diameter (correct)
  • Increased equatorial diameter and reduced anteroposterior diameter
  • Complete absence of the lens

    • Which gene is associated with Weill-Marchesani syndrome?

  • Fibrillins
  • ADAMTS10 (correct)
  • ADAMTS17
  • LTBPs

    • What is the pattern of inheritance in familial microspherophakia?

  • X-linked dominant
  • Both autosomal dominant and autosomal recessive (correct)
  • Autosomal dominant
  • Autosomal recessive

    • What is the classic triad of signs in Microspherophakia?

    <p>Angle closure glaucoma, shallow anterior chamber, and refractive myopia</p> Signup and view all the answers

    What diagnostic procedure may be useful in the diagnosis of Microspherophakia?

    <p>Ultrasound biomicroscopy (UBM)</p> Signup and view all the answers

    What type of imaging technology is used to produce two-dimensional cross-sectional images of the anterior segment?

    <p>Ultrasound biomicroscopy</p> Signup and view all the answers

    What is the most common sight-threatening complication of microspherophakia?

    <p>Secondary angle closure glaucoma</p> Signup and view all the answers

    What is the treatment of choice for managing complications in microspherophakia?

    <p>Cycloplegics</p> Signup and view all the answers

    What is a common indication for clear lens extraction in patients with microspherophakia?

    <p>Lens dislocation or subluxation</p> Signup and view all the answers

    What is a potential intraoperative complication of clear lens extraction in patients with microspherophakia?

    <p>Difficulty in performing capsulorhexis and implanting IOL</p> Signup and view all the answers

    Study Notes

    Microspherophakia (MSP)

    • Characterized by increased anteroposterior diameter and reduced equatorial diameter of the crystalline lens
    • Rare condition, usually bilateral

    Genetics

    • Mutations in genes include:
      • LTBPs (family of proteins with structural homologies with fibrillins)
      • ADAMTS17 (part of the same family of metalloproteinases as ADAMTS10, associated with Weill-Marchesani syndrome)

    Associations

    • May occur as an isolated defect, or be associated with systemic/local anomalies
    • Entities associated with microspherophakia include:
      • Weill-Marchesani syndrome
      • Homocysteinuria
    • Familial microspherophakia is not associated with systemic abnormalities and has an autosomal recessive pattern of inheritance, but can also be autosomal dominant

    General Pathology

    • Zonular fibers may be abnormally long and somewhat rudimentary
    • Abnormal development and distribution of secondary lens fibers
    • Hyaloid degenerations occur due to changes in shape of lens affecting the lens fibers

    Pathophysiology

    • Mechanisms suggested include:
      • Zonular instability leading to lens dislocation/subluxation or secondary angle closure glaucoma

    Diagnosis

    • Thorough family history and history of systemic anomalies is required
    • Symptoms:
      • Diminution of vision
      • Acute eye pain
    • Signs:
      • Triad of angle closure glaucoma, shallow anterior chamber, and refractive myopia
      • Other findings include:
        • Lens dislocation/subluxation
        • Zonular instability
    • Diagnostic procedures:
      • UBM (ultrasound biomicroscopy) for morphological details of anterior chamber angle, iris, ciliary body, zonules, and lens
      • Screening tests for associated systemic conditions (e.g. serum homocysteine levels, urine screening test for homocysteinuria)

    Complications

    • Glaucoma is common in microspherophakia (up to 51% of patients)
    • Secondary angle closure glaucoma is the most common sight-threatening complication
    • Progressive microspherophakia leads to severe and progressive lenticular myopia
    • Zonular instability can lead to lens dislocation or subluxation

    Management

    • Medical and surgical management of complications can be difficult
    • Cycloplegics are the treatment of choice
    • Miotics may lead to pupillary block glaucoma
    • Stepwise protocol for treatment of glaucoma in microspherophakia:
      • Medications
      • Laser trabeculoplasty
      • Trabeculectomy
    • Indications for clear lens extraction in patients with microspherophakia:
      • Uncontrolled glaucoma
      • Progressive myopia
      • Zonular instability
    • Intraoperative complications associated with clear lens extraction in these patients include:
      • Difficulty in performing capsulorhexis
      • Difficulty in implanting IOL due to smaller bag size

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    Description

    Microspherophakia is a rare bilateral condition characterized by increased anteroposterior diameter and reduced equatorial diameter of the crystalline lens. It involves genetic mutations in specific proteins, affecting the eye.

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