Typically bilateral inferior lens subluxations of the lens is seen in:
Correct Answer: Homocystinuria
Description: B i.e. Homocystinuria Uniocular diplopia together with finding of shining golden crescent on oblique and dark black crescent line on coaxial illuminationQ (both b/o edge of subluxated lens) suggest a diagnosis of subluxated ectopia lentis. Congenital rubella presents with deafness, cardiac malformation and cataract Q. Other defects include glucoma, salt pepper retinopathy, microcephalus, cerebral palsy, intrauterine growth retardation, hepatosplenomegaly, mental & motor retardation. (but not ectopia lentis or lens dislocation.) Q Ectopia lentis (or displacement of lens) may be seen in Marfan's syndrome (bilateral supero-temporal)Q, homocystinuria (bilateral infero-nasal or infero temporal)Q and sulfite oxidase deficiencyQ. Ectopia Lentis (Displaced Lens) - It refers to displacement of lens from its normal position (in patellar fossa. Paial displacement of lens (i.e. still remaining in pupillary area) is called subluxation whereas, completely dislocated lens rendering the pupil aphakia is k/a dislocation (luxated). - It is usually a bilateral conditionQ caused by extensive zonular malformation. The lens is displaced in the opposite direction to the weak zonules (usually superomedially)Q i.e. mostly upwards and bilateral. - Ectopia lentis may be congenital or acquired. The condition is often hereditary (congenital)Q and usually presents in childhood or young adulthood. - The clinical features of subluxated lens include poor vision, uniocular diplopia, glare, myopia, astigmatism, reduced amplitude of accomodation and sudden loss of visionQ. Signs include an obvious lens displacement, however, this may not be visible through an undilated pupil. The lens is small but the edge and zonules are generally invisible until the pupil is dilated. So the pupil should be dilated to assess the extent of displacement and intactness of zonules. Fluctuating anterior chamber depth and vision, iridodinesis/ iridodonesis (i.e. tremulous iris) and phacodinesis/ phacodonesis (i.e. tremulous or a visibly mobile lens) accentuated by eye movements. The lens may displace completely into anterior chamber or vitreous or become cataractous. Vitreous may herniate forward into anterior chamber. Pupillary block glucoma commonly occurs d/t anterior herniated vitreous or subluxated lens. Posterior displacement of lens into vitreous may cause lens induced uveitis. - In Marfan's syndrome because of frequently intact zonules, the accomodation in retained. Whereas, in homocystinuria the zonules containing high levels of cysteine, disintigrate so the accomodation is often lost.
Category:
Ophthalmology
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