Lentis

BASICS


DESCRIPTION


• Displacement of the lens.


• This may be divided into subluxed lens, which is partially displaced, and luxated or dislocated lens, which is completely displaced.


• May be an isolated anomaly, or associated with various systemic diseases or trauma.


EPIDEMIOLOGY


Incidence


• Marfan disease 4–6/100,000 births (1) and approximately 60–75% have ectopia lentis.


• Homocystinuria 1/200,000 births (1) and approximately 80–85% have ectopia lentis.


Prevalence


Unknown.


RISK FACTORS


• Trauma.


• Family history.


• Marfan syndrome


• Type 1 Ehlers–Danlos.


• Weill–Marchesani


• Homocystinuria.


• Hyperlysinemia.


• Sulfite oxidase deficiency.


• Molybdenum cofactor deficiency.


• Infantile glaucoma with buphthalmos.


• Persistent ocular fetal vasculature.


• Coloboma of ciliary body.


Genetics


• Isolated ectopia lentis can be autosomal dominant due to mutations in the fibrillin 1 gene (FBN1,15q21), the same gene involved in Marfan syndrome (1).


• An autosomal recessive form of isolated ectopia lentis is associated with mutation in ADAMTSL4 gene (1q21) (2).


• Ectopia lentis et pupillae is autosomal recessive (3), gene unknown.


• Weill–Marchesani may be autosomal dominant due to mutation in FBN1 or autosomal recessive due to mutations in ADAMTS10 (19p13.3) or ADAMTS17 (15q24) (4).


• Type 1 Ehlers Danlos is due to mutations in collagens COL5A1, COL5A2, or COL1A1.


• Homocystinuria is autosomal recessive and linked to the gene coding cystathionine beta-synthase (21q22.3) (1). Other less common disorders of cysteine metabolism may also be associated with ectopia lentis.


• Mutation in the sulfite oxidase gene (SUOX, 12q13.13) cause autosomal recessive sulfite oxidase deficiency (5).


• Hyperlysinemia is caused by mutation in the alpha-aminoadipic semialdehyde synthase gene (AASS, 7q31.3) (6).


• Virtually any form of glaucoma resulting in buphthalmus may rarely be a cause of ectopia lentis. The genetics of the underlying disorder determine the inheritance pattern. The same holds true for other rare syndromic causes of ectopia lentis and coloboma.


• Persistent ocular fetal vascular is usually not genetic (see chapter).


GENERAL PREVENTION


• Genetic counseling.


• Some recommend restricted activity or protective polycarbonate lens in patients with systemic conditions associated with ectopia lentis.


• Some forms of homocystinuria may respond to vitamin B6, methionine-restricted diet, betaine, or supplementary cysteine (1).


– This treatment has been shown to reduce the incidence of lens dislocation.


PATHOPHYSIOLOGY


Weakening or stretching of the zonular attachments lens (1).


ETIOLOGY


• Traumatic rupture of zonules.


• Congenital zonular deficiency (e.g., ciliary body coloboma).


• Defective zonules that results in weakening.


– Marfan—defect in fibrillin.


– Ehlers–Danlos—defect in type V collagen.


– Homocystinuria—zonules deficient in cysteine.


COMMONLY ASSOCIATED CONDITIONS


• Marfan syndrome: Aortic root dilation, Marfanoid habitus, pectus excavatum/carinatum, and other features.


• Ehlers–Danlos: joint laxity, “cigarette paper” scars of skin and other features.


• Weill–Marchesani: short stature, cardiac abnormalities, abnormal hands


• Homocystinuria: Developmental delay (50%), Marfanoid habitus, premature grey hair, hypercoagulability and other features.


• Hyperlysinemia: Severe developmental delay.


• Sulfite oxidase deficiency: Severe developmental delay.


DIAGNOSIS


HISTORY


• Family history of ectopia lentis or any of the above-mentioned associated conditions.


• History of ocular trauma.


PHYSICAL EXAM


• Full ocular examination including slit lamp examination pre- and post-dilation.


• Pupil position (e.g., corectopia).


• Assess if zonules absent, broken, or stretched.


• Assess if lens edge flat, round, crenulated.


• Measurement of intraocular pressure.


• Cycloplegic refraction and assessment of vision: Can refract through aphakic (with or without pharmacologic mydriasis) or phakic visual axis for best vision.


• Full physical exam for systemic associations.


DIAGNOSTIC TESTS & INTERPRETATION


Lab


Initial lab tests

• None if history of ocular trauma (ectopia always unilateral).


• All patients without clear family history or diagnosis and no trauma should have urine/blood homocysteine levels as risk of stroke/death under general anesthesia.


Follow-up & special considerations

• Genetic consult for further work up and evaluation if warranted.


– Consider cardiology consultation.


Imaging


Initial approach

Consider echocardiogram if considering Marfan syndrome or Weill–Marchesani.


Follow-up & special considerations

• Follow for increased movement of lens, change in vision/refraction, and amblyopia.


– Weill–Marchesani follow for progressive shallowing of anterior chamber and secondary closed angle glaucoma.


– Glaucoma risk also in other forms of ectopia lentis (Marfan, persistent ocular fetal circulation, trauma).


Diagnostic Procedures/Other


Molecular genetic testing as indicated.


Pathological Findings


• Fibrillinopathy: Loss of periodicity in zonules with fibrillin staining.


– Homocystinuria and related disorders: PAS positive zonular material on lens edge and ciliary body.


– Weill–Marchesani: Peripheral anterior synechia.


DIFFERENTIAL DIAGNOSIS


Microspherophakia.


TREATMENT


MEDICATION


• Homocystinuria (see earlier).


• If lens dislocated into anterior chamber consider glaucoma treatment including mannitol to shrink vitreous, topical steroids to reduce inflammation, and short acting mydriatics with patient in supine position. After lens floats back behind pupil, then pilocarpine.


• Weill–Marchesani: Aggressive cycloplegia (e.g., atropine) may deepen anterior chamber as short-term treatment.


ADDITIONAL TREATMENT


General Measures


• Correction of refractive error (1).


– Treatment of amblyopia if present.


Issues for Referral


• Genetic consultation.


– Cardiology as indicated.


– Metabolics consultation as indicated.


Additional Therapies


Massage of cornea may be needed to release lens dislocated into anterior chamber.


COMPLEMENTARY & ALTERNATIVE THERAPIES


None.


SURGERY/OTHER PROCEDURES


• Lensectomy and anterior vitrectomy.


– Typically poor zonule support prevents lens implantation in children (1).


– Contact lens or spectacles are then used for aphakic correction.


– Weill–Marchesani: Early lensectomy advised if anterior chamber deepening.


– Use of argon laser iridoplasty or YAG laser lysis of zonules has been reported.


IN-PATIENT CONSIDERATIONS


Initial Stabilization

• As needed for associated systemic diseases.


– If lens in anterior chamber maintain supine position.


Admission Criteria


• As indicated by systemic disease.


– Admit all patients with homocystinuria undergoing surgery night before and after surgery.


IV Fluids


Homocystinuria 1.5 × maintenance starting night before surgery and continuing through 1 night after.


Nursing


Maintain supine position and strict bed rest as long as lens in anterior chamber.


Discharge Criteria


If lens is not returned to retropupillary position by medical means, lensectomy before discharge.


ONGOING CARE


FOLLOW-UP RECOMMENDATIONS


Routine ophthalmic examination depending on degree of dislocation and presence of other pathology including amblyopia.


Patient Monitoring


• Cardiology, metabolics, developmental services as needed.


– Visual acuity, intraocular pressure.


DIET


Methionine-restricted diet in patients with homocystinuria.


PATIENT EDUCATION


• Genetic counseling.


www.marfan.ca/ and www.marfan.org/marfan/.


www.mdjunction.com/homocystinuria.


PROGNOSIS


• Good visual prognosis with early intervention and routine follow-up.


• Even in patients requiring lensectomy most achieve vision of 20/40 or better (1).


– If not complicated by untreated amblyopia.


COMPLICATIONS


Amblyopia, glaucoma, retinal detachment (particularly in patients with Marfan disease), lens dislocation.



REFERENCES


1. Neely DE, Plager DA. Management of ectopia lentis in children. Ophthalmol Clin North America 2001;14(3):493–497.


2. Ahram D, Sato TS, Kohilan A, et al. A homozygous mutation in ADAMTSL4 causes autosomal-recessive isolated ectopia lentis. Am J Hum Genet 2009;84:274–278.


3. Colley A, Lloyd IC, et al. Ectopia lentis et pupillae: The genetic aspects and differential diagnosis. J Med Genet 1991;Nov 28(11):791–794.


4. Faivre L, Dollfus H, Lyonnet S, et al. Clinical homogeneity and genetic heterogeneity in Weill-Marchesani syndrome. Am J Med Genet 2003;123A:204–207.


5. Kisker C, Schindelin H, Pacheco A, et al. Molecular basis of sulfite oxidase deficiency from the structure of sulfite oxidase. Cell 1997;91:973–983.


6. Sacksteder KA, Biery BJ, Morrell JC, et al. Identification of the alpha-aminoadipic semialdehyde synthase gene, which is defective in familial hyperlysinemia. Am J Hum Genet 2000;66:1736–1743.

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Nov 9, 2016 | Posted by in OPHTHALMOLOGY | Comments Off on Lentis
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