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What Is Microphakia?

Microphakia is a congenital lens anomaly in which the crystalline lens has a smaller than normal equatorial diameter. The lens often has altered curvature and can contribute to significant refractive error, usually lenticular myopia. Because the lens is small and zonular support may be weak, it can be prone to subluxation or dislocation. A crowded anterior segment increases the chance of pupillary block and angle closure glaucoma. Microphakia may occur alone or as part of systemic syndromes.

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What Is Microphakia?

Microphakia is a congenital lens anomaly in which the crystalline lens has a smaller than normal equatorial diameter. The lens often has altered curvature and can contribute to significant refractive error, usually lenticular myopia. Because the lens is small and zonular support may be weak, it can be prone to subluxation or dislocation. A crowded anterior segment increases the chance of pupillary block and angle closure glaucoma. Microphakia may occur alone or as part of systemic syndromes.

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Causes and Associated Conditions

Microphakia arises from abnormal development of the lens and its suspensory zonules during embryogenesis. It is seen in association with conditions such as Weill Marchesani syndrome and sometimes with homocystinuria or other connective tissue disorders. In some patients, no systemic cause is found and the anomaly is isolated. Shallow anterior chambers and narrow angles are common anatomic features. Zonular weakness increases the risk of lens instability over time.

Clinical Features and Visual Effects

Patients with microphakia often present with high myopia, blurred distance vision, or anisometropia in childhood or young adulthood. On slit lamp exam, the lens appears small, and in a well dilated pupil, the equator may be visible. The anterior chamber is usually shallow, and gonioscopy reveals narrow angles. Subluxation can cause irregular astigmatism, monocular diplopia, or sudden shifts in vision. Episodes of pupillary block can lead to painful rises in intraocular pressure if not recognized.

How Is Microphakia Diagnosed?

Diagnosis combines clinical examination with imaging. The eye care professional assesses lens size and position at the slit lamp, measures anterior chamber depth, and performs gonioscopy. Ultrasound biomicroscopy or anterior segment optical coherence tomography can quantify lens size and its relation to the iris and angle. Refraction documents the degree of lenticular myopia and astigmatism. Systemic evaluation and genetic consultation are considered when features suggest an underlying syndrome.

How Is Microphakia Managed?

Management aims to correct refractive error and prevent or treat complications such as glaucoma and lens dislocation. Glasses or contact lenses are used for myopia and astigmatism, and amblyopia therapy is started early in children when needed. Prophylactic laser peripheral iridotomy can relieve or prevent pupillary block in eyes with very narrow angles. When lens subluxation or uncontrolled glaucoma threatens vision, lens extraction with or without intraocular lens implantation and, sometimes, glaucoma surgery are considered. Lifelong monitoring is important due to ongoing risk.

FAQs About Microphakia

Is microphakia the same as microspherophakia?

No. Microphakia refers to a small lens diameter, while microspherophakia describes a lens that is both small and abnormally spherical. The two can overlap but are not identical.

Why does microphakia increase glaucoma risk?

The small lens and shallow anterior chamber can block aqueous flow at the pupil, leading to pupillary block and angle closure if untreated.

Can microphakia be treated without surgery?

Refractive error often responds to glasses or contacts, and laser iridotomy can help prevent angle closure. Surgery is reserved for significant lens instability or glaucoma that cannot be controlled.

What systemic diseases are linked to microphakia?

Weill Marchesani syndrome and some connective tissue disorders are classic associations. A thorough medical evaluation helps identify related conditions.

References

National Center for Biotechnology Information (NCBI) MedGen. ?Microphakia (Concept Id: C0266541).? https://www.ncbi.nlm.nih.gov/medgen/78609

Orphanet. ?Isolated microspherophakia.? https://www.orpha.net/en/disease/detail/519396

EyeWiki (American Academy of Ophthalmology). ?Microspherophakia.? https://eyewiki.org/Microspherophakia

NCBI Bookshelf (StatPearls). ?Microspherophakia.? https://www.ncbi.nlm.nih.gov/books/NBK576395/

American Academy of Ophthalmology (AAO) EyeNet. ?Microspherophakia: Genetics, Diagnosis, and Management.? https://www.aao.org/eyenet/article/microspherophakia-genetics-diagnosis-management