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Describe ectopia lentis with its causes and management.

Ophthalmology · 3rd Professional

Definitions and Causes

Ectopia lentis is displacement of the lens from its normal position.
subluxation is partial displacement with the lens still in the pupillary area and some zonules intact; dislocation (luxation) is complete displacement, into the anterior chamber or the vitreous.

Cause	Direction and features
MARFAN syndrome	The commonest hereditary cause. Displacement is upward and temporal (superotemporal). The zonules are stretched but intact, so accommodation is preserved. Autosomal dominant, FBN1 (fibrillin) mutation. Systemic: tall stature, arachnodactyly, arm span exceeding height, high arched palate, joint hypermobility, and — critically — aortic root dilatation and dissection, and mitral valve prolapse. Other ocular: axial myopia, retinal detachment, a flat cornea and a hypoplastic iris dilator with poor dilation
Homocystinuria	Displacement is downward and nasal (inferonasal). The zonules disintegrate, so accommodation is lost and the lens may dislocate into the anterior chamber. Autosomal recessive; cystathionine beta-synthase deficiency. Systemic: marfanoid habitus, intellectual disability, osteoporosis, and above all a strong tendency to thromboembolism — which makes general anaesthesia hazardous and requires specific precautions
WEILL-marchesani syndrome	The "reverse Marfan": short stature, brachydactyly, stubby fingers and stiff joints. The lens is microspherophakic — small and spherical — causing high lenticular myopia, and dislocates anteriorly, causing pupil block glaucoma. Critically, miotics worsen the pupil block by relaxing the zonules and moving the lens forward, and cycloplegics are used instead — the reverse of ordinary angle closure
Other systemic	Sulphite oxidase deficiency; hyperlysinaemia; Ehlers-Danlos syndrome
Ocular causes	Trauma, which is the commonest cause overall; pseudoexfoliation with zonular weakness; hypermature cataract; high myopia; buphthalmos; chronic uveitis; and previous surgery
Isolated and congenital	Simple ectopia lentis (dominant); and ectopia lentis ET pupillae, in which the lens and pupil are displaced in opposite directions

Clinical Features and Management

Symptoms — blurred vision from the refractive change; monocular diplopia where the lens edge crosses the pupil.
Signs — phacodonesis (tremulousness of the lens) and iridodonesis on eye movement, which are the cardinal signs and are best seen by asking the patient to move the eye quickly and then fixate; an unequal anterior chamber depth; the lens edge visible in the pupil after dilation; vitreous in the anterior chamber; and a marked refractive difference between the phakic and aphakic portions — high lenticular myopia and astigmatism through the lens, and +10 D of aphakic hypermetropia beside it
Complications — pupil block glaucoma, particularly with anterior dislocation; corneal endothelial decompensation where the lens rests against the cornea; uveitis; retinal detachment, which is common in these eyes; cataract; and amblyopia in children

Applied Aspects

Refer every suspected Marfan for echocardiography; the eye sign is how many are identified, and aortic dissection is what kills them
Warn the anaesthetist in homocystinuria; thromboembolism under general anaesthesia is a recognised cause of death and requires hydration, anticoagulation and specific planning
Never give a miotic in Weill-Marchesani; it worsens the pupil block by moving the lens forward, and a cycloplegic is used instead — the reverse of the usual rule

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