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Ptosis /ˈtoʊsɪs/ (from Greek Ptosis or πτῶσις, to “fall“) is a drooping or falling of the upper or lower eyelid. The drooping may be worse after being awake longer, when the individual's muscles are tired. This condition is sometimes called “lazy eye“, but that term normally refers to amblyopia. If severe enough and left untreated, the drooping eyelid can cause other conditions, such as amblyopia or astigmatism. This is why it is especially important for this disorder to be treated in children at a young age, before it can interfere with vision development. Ptosis occurs when the muscles that raise the eyelid (levator and superior tarsal muscles) are not strong enough to do so properly. It can affect one eye or both eyes and is more common in the elderly, as muscles in the eyelids may begin to deteriorate. One can, however, be born with ptosis. Congenital ptosis is hereditary in three main forms. Causes of congenital ptosis remain unknown. Ptosis may be caused by damage/trauma to the muscle which raises the eyelid, damage to the superior cervical sympathetic ganglion or damage to the nerve (3rd cranial nerve (oculomotor nerve)) which controls this muscle. Such damage could be a sign or symptom of an underlying disease such as diabetes mellitus, a brain tumor, a pancoast tumor (apex of lung) and diseases which may cause weakness in muscles or nerve damage, such as myasthenia gravis. Exposure to the toxins in some snake venoms, such as that of the black mamba, may also cause this effect. Ptosis can be caused by the aponeurosis of the levator muscle, nerve abnormalities, trauma, inflammation or lesions of the lid or orbit. Dysfunctions of the levators may occur as a result of a lack of nerve communication being sent to the receptors due to antibodies needlessly attacking and eliminating the neurotransmitter. Ptosis may be due to a myogenic, neurogenic, aponeurotic, mechanical or traumatic cause and it usually occurs isolated, but may be associated with various other conditions, like immunological, degenerative, or hereditary disorders, tumors, or infections Acquired ptosis is most commonly caused by aponeurotic ptosis. This can occur as a result of senescence, dehiscence or disinsertion of the levator aponeurosis. Moreover, chronic inflammation or intraocular surgery can lead to the same effect. Also, wearing contact lenses for long periods of time is thought to have a certain impact on the development of this condition. Congenital neurogenic ptosis is believed to be caused by the Horner syndrome. In this case, a mild ptosis may be associated with ipsilateral ptosis, iris and areola hypopigmentation and anhidrosis due to the paresis of the Mueller muscle. Acquired Horner syndrome may result after trauma, neoplastic insult, or even vascular disease. Ptosis due to trauma can ensue after an eyelid laceration with transection of the upper eyelid elevators or disruption of the neural input. Other causes of ptosis include eyelid neoplasms, neurofibromas or the cicatrization after inflammation or surgery. Mild ptosis may occur with aging. As a precautionary action, a person who notices a drooping eyelid, uneven dilation of one pupil, or even minor changes, such as delayed movement of one eye, should contact a neurologist. A drooping eyelid can be one of the first signals of a third nerve palsy due to a cerebral aneurysm, that otherwise is asymptomatic and referred to as an oculomotor nerve palsy. A person experiencing this condition would be wise to seek a neurologist who would order a CT scan to rule out the possibility of a cranial aneurysm being present or in development. #geneExpression #nucleicAcids #phenotype #protein #Cancer #gene #GeneticsLecture #genetics #mitosis #genomics #molecularBiology #locus #GeneticsExamQuestionsSolutions #GeneticExamQuestionsSolutions #Genetics101 #DNA #mRNA #PaternityTest #Ptosis #HornerSyndrome #droopingEyelid
