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Chapter 029. Disorders of the Eye (Part 19)

Myogenic Ptosis The causes of myogenic ptosis include myasthenia gravis (Chap. 381) and a number of rare myopathies that manifest with ptosis. The term chronic progressive external ophthalmoplegia refers to a spectrum of systemic diseases caused by mutations of mitochondrial DNA. As the name implies, the most prominent findings are symmetric, slowly progressive ptosis and limitation of eye movements. In general, diplopia is a late symptom because all eye movements are reduced equally. In the Kearns-Sayre variant, retinal pigmentary changes and abnormalities of cardiac conduction develop. Peripheral muscle biopsy shows characteristic "ragged-red fibers." Oculopharyngeal dystrophy is a distinct autosomal. | Chapter 029. Disorders of the Eye Part 19 Myogenic Ptosis The causes of myogenic ptosis include myasthenia gravis Chap. 381 and a number of rare myopathies that manifest with ptosis. The term chronic progressive external ophthalmoplegia refers to a spectrum of systemic diseases caused by mutations of mitochondrial DNA. As the name implies the most prominent findings are symmetric slowly progressive ptosis and limitation of eye movements. In general diplopia is a late symptom because all eye movements are reduced equally. In the Kearns-Sayre variant retinal pigmentary changes and abnormalities of cardiac conduction develop. Peripheral muscle biopsy shows characteristic ragged-red fibers. Oculopharyngeal dystrophy is a distinct autosomal dominant disease with onset in middle age characterized by ptosis limited eye movements and trouble swallowing. Myotonic dystrophy another autosomal dominant disorder causes ptosis ophthalmoparesis cataract and pigmentary retinopathy. Patients have muscle wasting myotonia frontal balding and cardiac abnormalities. Neurogenic Ptosis This results from a lesion affecting the innervation to either of the two muscles that open the eyelid Muller s muscle or the levator palpebrae superioris. Examination of the pupil helps to distinguish between these two possibilities. In Horner s syndrome the eye with ptosis has a smaller pupil and the eye movements are full. In an oculomotor nerve palsy the eye with the ptosis has a larger or a normal pupil. If the pupil is normal but there is limitation of adduction elevation and depression a pupil-sparing oculomotor nerve palsy is likely see next section . Rarely a lesion affecting the small central subnucleus of the oculomotor complex will cause bilateral ptosis with normal eye movements and pupils. Double Vision Diplopia The first point to clarify is whether diplopia persists in either eye after covering the opposite eye. If it does the diagnosis is monocular diplopia. The cause is usually intrinsic .