Causes of Zonulopathy

• Zonulopathy is a state in which there is a deficiency of zonular support for the lenticular capsule

• Zonulopathy may include malposition of the lens (subluxation or dislocation), though in many cases no malposition may be present

Etiology for zonulopathy include: 

1. Pseudoexfoliation syndrome

2. Traumatic zonulysis

3. Iatrogenic zonulysis (Cataract extraction, pars plana vitrectomy, repeat intravitreal injections)

4. Ultra-brunescent cataracts

5. Retinitis pigmentosa

6. Aniridia

7. Advanced age

8. Intraocular neoplasm

9. Systemic syndromes including Marfan syndrome, homocystinuria, Weill-Marchesani syndrome and Ehlers-Danlos syndrome

• The zonular fibers, also known as the zonular apparatus or zonule of Zinn, originate from the basal laminae of the nonpigmented epithelium of the ciliary body, and insert into the lens capsule at the equatorial region

• The fibers insert 1.5mm anterior to the equator and 1.25 mm posterior, and are 5-30 um in diameter

• Approximately 140 fiber bundles make up the zonular apparatus, with a key component of the fibers being fibrillin, a connective tissue glycoprotein that provides strength and elasticity to the fibers

• Fibrillin is coded by the FBN1 gene, which is anomalous in Marfan syndrome resulting in poor zonular stability and lens subluxation

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Image from Rajan Eye Care Hospital

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