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Isolated ectopia lentis
Isolated ectopia lentis (IEL) is a rare, clinically variable, eye disorder characterized by dislocation of the lens, often causing significant reduction in visual acuity.
The prevalence of IEL is not known. About 90 cases have been reported to date, primarily in Europeans.
Patients with IEL are found to have dislocation of the lens, which may present at any age, but may be present from birth. Dislocation of the lens can be very mild leading to late diagnosis. In more severe cases, the anomaly is generally detected earlier with a greater impact on visual acuity. Lens dislocation may be progressive. Some patients are also found to have displacement of the pupils, usually in the opposite direction to lens displacement (known as ectopia lentis et pupillae). Other findings include congenital abnormalities of the iris, spherophakia, enlarged iris processes leading to abnormal iridocorneal angle, iridodonesis, lens coloboma, refractive errors (hyperopia, myopia, astigmatism), and early-onset cataract. They may develop amblyopia. Increased intraocular pressure (20%-25% of cases), retinal detachment and glaucoma may also befound. Ocular findings vary widely within families, and between the eyes in an affected individual. Visual acuity is variable depending on the severity of ocular anomalies and complications, ranging from light perception to 20/20 vision. IEL does not involve systemic abnormalities.
Dislocation of the lens is the result of a loss of zonular fibers. Recessive mutations in the ADAMTSL4 (1q21.2) gene and dominant mutations in FBN1 gene (15q21.1) have been reported to cause IEL. Mutations in the former are thought to be the most important cause of this condition in Europeans. The exact function of these genes has not been clearly established. ADAMTSL4 mutations appear to manifest as a more severe, earlier onset condition than FBN1 mutations.
Diagnosis is based on typical ocular findings through ophthalmologic examination and can be confirmed by molecular genetic testing of the causative genes.
Patients with IEL by definition do not have associated systemic abnormalities, although cardiac and skeletal examinations should be performed to help exclude Marfan syndrome (diagnosed according to the Ghent criteria) (see this term). Ectopia lentis is also a feature of homocystinuria, sulfite oxidase deficiency, Weill-Marchesani syndrome, aniridia, and Knobloch syndrome (see these terms), as well as pseudoexfoliation.
Prenatal diagnosis for pregnancies at increased risk is possible if the disease-causing mutations in the family have been identified.
ADAMTSL4-related IEL is inherited in an autosomal recessive manner. FBN1-related IEL follows an autosomal dominant pattern of inheritance.
Management and treatment
Visual acuity, refractive error, and intraocular pressure should be monitored regularly in affected patients. The primary aim of treatment in children is to prevent amblyopia through early correction of refractive errors. Surgical intervention may be considered by experienced ophthalmic surgeons. Lensectomy may be considered in patients with cataracts, in cases where the ectopic lens affects vision significantly. Treatment of the resulting aphakia may be with contact lenses. Alternatively, an intraocular lens (IOL) may be inserted in the anterior chamber, and sutured or glued into the posterior chamber or into the capsule, if it has been preserved during surgery. Complications include loss of accommodation, secondary glaucoma, and retinal detachment. A standard approach should be adopted in cases of retinal detachment. All patients found to have mutations in FBN1 should have regular cardiac examinations.
Visual prognosis depends on the degree of lens dislocation, the age of onset, age of treatment and complications.
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