DISLOCATED LENS (Ectopia Lentis)

Partial or complete lens dislocation (Figure 8-11) may be hereditary or may result from trauma.

Hereditary Lens Dislocation

Hereditary lens dislocation is usually bilateral and is commonly associated with homocystinuria and Marfan's syndrome (Chapter 15). The vision is blurred, particularly if the lens is dislocated out of the line of vision. If dislocation is partial, the edge of the lens and the zonular fibers holding it in place can be seen in the pupil. If the lens is completely dislocated into the vitreous, it can be seen with the ophthalmoscope.

A partially dislocated lens is often complicated by cataract formation. If that is the case, the cataract may have to be removed, but this procedure should be delayed as long as possible because vitreous loss, predisposing to subsequent retinal detachment, is likely during surgery. If the lens is free in the vitreous, it may lead in later life to the development of glaucoma of a type that responds poorly to treatment. If dislocation is partial and the lens is clear, the visual prognosis is good.

Traumatic Lens Dislocation

Partial or complete traumatic lens dislocation may occur following a contusion injury such as a blow to the eye with a fist. If the dislocation is partial, there may be no symptoms; but if the lens is floating in the vitreous, the patient has blurred vision and usually a red eye. Iridodonesis, a quivering of the iris when the patient moves the eye, is a common sign of lens dislocation and is due to the lack of lens support. This is present both in partially and in completely dislocated lenses but is more marked in the latter.

Uveitis and glaucoma are common complications of dislocated lens, particularly if dislocation is complete. If there are no complications, dislocated lenses are best left untreated. If uveitis or uncontrollable glaucoma occurs, lens extraction must be done despite the poor results possible from this operation. The technique of choice is limbal or pars plana lensectomy using a motor-driven lens and vitreous cutter.

10.1036/1535-8860.ch8

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