Marfan syndrome is a heritable disorder with ocular, cardiac, and skeletal manifestations. Though usually inherited as an autosomal dominant trait, the disorder appears with no family history in approximately 15% of cases. Marfan syndrome is believed to result from an abnormality of fibrillin, a connective tissue component. Affected individuals are tall, with arachnodactyly (Fig 4-15A) and chest wall deformities. Associated cardiac abnormalities include dilated aortic root and mitral valve prolapse.
From 50% to 80% of patients with Marfan syndrome exhibit ectopia lentis (Fig 4-15B). The lens subluxation tends to be bilateral and symmetric (usually superior and temporal), but variations do occur. The zonular attachments commonly remain intact but become stretched and elongated. Ectopia lentis in Marfan syndrome is probably congenital in most cases. Progression of lens subluxation is observed in some patients over time, whereas in many patients the lens position remains stable.
Ocular abnormalities associated with Marfan syndrome include axial myopia and an increased risk of retinal detachment. Patients with Marfan syndrome may develop pupillary block glaucoma if the lens dislocates into the pupil or anterior chamber. Open-angle glaucoma may also occur. In addition, children with lens subluxation may develop amblyopia if their refractive error shows significant asymmetry or remains uncorrected in early childhood.
Spectacle or contact lens correction of the refractive error provides satisfactory visual acuity in most cases. Pupillary dilation is sometimes helpful. The clinician may refract both the phakic and the aphakic portions of the pupil to determine the optimum visual acuity. A reading add is often necessary because the subluxated lens lacks sufficient accommodation.
In some cases, adequate visual acuity cannot be obtained with spectacle or contact lens correction, and removal of the lens may be indicated. Lens extraction—either extracapsular or intracapsular—in patients with Marfan syndrome is associated with a high rate of complications such as vitreous loss and complex retinal detachment. (Intracapsular and extracapsular cataract extraction are discussed in detail in Chapter 8.) Improved results have been reported with lensectomy using vitrectomy instrumentation, although the long-term results are not yet known.