Crystalline lens subluxation

Crystalline lens subluxation: Description, Causes and Risk Factors:Crystalline lens subluxationThe crystalline lens of the eye is designed to refract the light entering the iris and project/focus it onto the retina. The lens itself contains no vasculature, nerves, or connective tissue. It sits behind the iris and the front of the lens is in contact with the aqueous fluid of the anterior chamber while the posterior surface of the lens is in contact with the vitreous. The lens is held in place by zonular fibers, otherwise known as suspensory ligaments. These fibers connect to the cilliary body around the circumference of the lens.Subluxation implies displacement. Luxation refers to a lens that is totally dislocated. The term ectopia lentis has been used interchangeably with subluxation. However,this should be a term reserved for bilateral cases. Subluxation of the crystalline lens has been described as being either acquired or congenital. Better terminology would be that subluxation of the lens can be either acquired (such as from trauma) or due to congenital systemic causes. Rarely are infants born with displaced lenses; instead the phenomenon develops during life due to a predisposing systemic condition. Traumatic subluxation is slightly more common than lens displacement associated with underlying systemic disorders.Traumatic mechanical stretching of the zonules is the main cause of the subluxation. This occurs as the eye is compressed in an anteroposterior direction (such as with impact by a fist or other projectile) and the subsequent distention of the globe in the mediolateral plane ruptures the zonular fibers. Spontaneous lens subluxation associated with congenital conditions varies in pathophysiologic mechanism depending upon the condition. The direction of displacement in each case is characteristic but by no means completely diagnostic. Marfan's syndrome is the most commonly encountered underlying condition inpatients with crystalline lens subluxation. More than 70% of patients with Marfan's syndrome have displacement of the crystalline lens. In Marfan's syndrome, the lens tends to be displaced superotemporally. This results from a predominance of abnormally constructed collagen vascular tissue and faulty lens zonules and istypically non-progressive. Further, as the zonules are still attached to the lens, some degree of accommodation exists.The main concern with lens subluxation is the development of secondary angle-closure glaucoma. Any time the crystalline lens displaces, the possibility exists that the lens cancome into firm apposition with the back surface of the iris. When the pupil is obstructed, there is pupil block, iris bomb

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