Friday, June 23, 2017

Lens Dislocation

Introduction
Lens dislocation may result from blunt trauma to the globe. As the anterior surface of the eye is struck, there is compression in the anteroposterior dimension with resultant stretching of the globe along its equator in the medial-lateral plane. As this occurs, it stretches the zonule fibers, which suspend the lens in place, and they along with the lens capsule may become disrupted.



Lens Dislocation. Lens dislocation revealed during slit-lamp examination. Note the zonule fibers, which normally hold the lens in place.

Clinical Features
The patient may experience symptoms of monocular diplopia or gross blurring of images, depending
on the severity of the injury. Occasionally there can be dramatic visual fluctuations caused by the lens changing position with resultant phakic and aphakic vision. There is generally a lack of pain except if secondary angle closure glaucoma occurs from the lens causing pupillary block.



On slit-lamp examination, the displaced crystalline lens appears as a crescent shape along its edge against a backdrop of the red reflex from the fundus. The edge of the subluxed lens may be visible only with pupillary dilatation.

Use caution in dilating the pupil, as this may cause the lens to sublux into the anterior chamber, which occurs if all the zonule fibers are torn.

Chronically, the lens may lodge in either the anterior chamber or the vitreous.

Lens Dislocation. The edge of this dislocated lens is visible with the pupil dilated as an altered red reflex

Risk Factors: Marfan syndrome, tertiary syphilis, and homocystinuria may be present and should be considered in patients presenting with lens dislocation.

Management
A subluxed lens does not always require surgery; partial subluxations may require only a change in refraction. Surgery is required if anterior dislocation of the lens results in papillary block and angle closure glaucoma results.

Clinical Pearls
1. Patients may experience lens dislocation with seemingly trivial trauma if they have an underlying coloboma of the lens, Marfan syndrome, homocystinuria, or syphilis.
2. Iridodonesis is a trembling movement of the iris noted after rapid eye movements and is a sign of occult posterior lens dislocation.
3. Phacodonesis is a tremulousness of the lens itself caused by disruption of the zonule fibers.
4. Lens dislocation or subluxation is commonly associated with traumatic cataract formation.
5. Other associated injuries include hyphema, vitreous hemorrhage, and globe rupture.

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