Ectopia lentis
Ectopia lentis is abnormal partial or complete displacement of the eye’s crystalline lens from its normal position. It may be inherited or acquired.
Zonular fibers: Fine suspensory fibers that connect the lens capsule to the ciliary body and hold the lens in position. Their weakness or rupture allows the lens to shift from its normal position.
Crystalline lens: The transparent, flexible structure behind the iris that focuses light onto the retina. Ectopia lentis is displacement of this normally centered structure.
Marfan syndrome: An inherited connective-tissue disorder caused by pathogenic variants in FBN1, often affecting the eyes, skeleton, and cardiovascular system. Its zonular weakness commonly displaces the lens upward and outward.
Slit-lamp examination: A clinical examination using a microscope and a narrow beam of light to inspect the front of the eye. It can show lens decentration, tilted position, and trembling.
Ciliary body: The ring-shaped tissue behind the iris that produces aqueous humor and changes lens shape through the zonular fibers. It anchors the fibers whose failure can displace the lens.
Lens capsule: The transparent basement membrane surrounding the crystalline lens. Zonular fibers attach to the capsule and transmit support to the lens.
Homocystinuria: An inherited metabolic disorder, usually caused by deficient cystathionine beta-synthase, that raises homocysteine levels. It can weaken zonular support and displace the lens, often downward and inward.
Retinoscopy: An objective method of estimating refractive error by observing light reflected from the retina. It helps measure the optical effects of a displaced lens.
Lens subluxation: Partial displacement of the crystalline lens, with some zonular attachment remaining. It is the incomplete form of lens displacement.
Accommodation (eye): The eye’s adjustment of lens shape to focus on objects at different distances. Disrupted lens support can impair the shape changes needed for focusing.