• 2 SECTIONDefects Developmental

Homocystinuria

Key Facts

•Autosomal recessive (1/200 000 in USA)

•Defect in cystathionine-β-synthetase

•Tall stature

•Mental retardation (50%)

•Coarse, fair hair

•Malar flush

•Skeletal abnormalities or osteoporosis

•Vascular thrombosis causes increased anesthesia risk via a yet unestablished platelet mechanism

Clinical Findings

•Progressive lenticular myopia or myopic astigmatism

•Blue irides

•Bilateral, inferonasal (57%) lens subluxation (90% incidence), lens dislocation

•Abnormal and broken zonules

•Possible pupillary block glaucoma

•Retinal vascular occlusions

Ancillary Testing

•Systemic work-up necessary

•Urine sodium nitroprusside spot test for homocystine for all children

Differential Diagnosis

•Hyperlysinemia

•Sulfate oxidase deficiency

•See differential diagnoses for Marfan syndrome (p. 10)

Treatment

•Mild or severe subluxation: optimize refractive correction

•Moderate subluxation: lensectomy may be necessary, because lens edge bisects pupillary axis

•Amblyopia therapy (patching in cases of anisometropia or strabismus)

•Consider Nd : YAG laser zonulysis to displace lens out of visual axis

•Consider laser pupilloplasty

•Consider optical iridectomy

•Lensectomy:

•only if all other methods inappropriate • anesthetic thrombotic risk • bilateral lensectomy may be warranted to avoid second anesthetic risk • endocapsular tension rings intraoperatively

•Systemic: low methionine and high cysteine diet with supplemental pyridoxine (vitamin B6) may prevent lens subluxation and mental retardation

Prognosis

•Intraoperative complications can be high, although this is improving with newer endocapsular techniques and perioperative measures to prevent thromboembolic events (diet therapy to increase cysteine and lower serum methionine and homocysteine levels, vitamin B6 supplementation, good hydration, avoidance of hypoglycemia, perioperative antiplatelet drugs)

•Good surgical results can be limited by amblyopia

• 2 SECTIONDefects Developmental

Ectopia Lentis

Key Facts

•Defined as displacement or malposition of the crystalline lens of the eye

•Dislocated (luxed) lens: the lens is in the anterior chamber or in the vitreous cavity

•Subluxed lens: the lens is displaced but contained within the normal lens space

•Caused by zonular laxity or disruption

•May be due to trauma (most common cause) or hereditary disorder

•Isolated ectopia lentis is autosomal dominant (chromosome 15)

•Ectopia lentis et pupillae involves displaced pupils in the opposite direction of lens subluxation and is autosomal recessive

Clinical Findings

•Poor vision

•Monocular diplopia

•Red painful eye when associated with trauma

•Abnormal red reflex or scissoring on retinoscopy

•Associated with Marfan syndrome, homocystinuria, Weill–Marchesani syndrome

•Glaucoma occurs secondary to:

•lens dislocation in to the anterior chamber, resulting in pupillary block angle closure glaucoma • angle recession (after trauma) • associated angle dysgenesis

Ancillary Testing

•Dilated fundus examination

•B-scan ultrasonography (searching for dislocated lens)

•Retinoscopy shows myopia with astigmatism

•Appropriate systemic work-up when suspected

Differential Diagnosis

•Marfan syndrome (Fig. 2.1)

•Homocystinuria

•Weill–Marchesani syndrome

•Sulfite oxidase deficiency

•Hyperlysinemia

•Trauma (Fig. 2.2)

Treatment

•Laser peripheral iridectomy when pupillary block is present

•Pilocarpine once lens is posterior to iris, if lens is able to dislocate into anterior chamber

•Lens extraction:

•often need pars plana approach if lens is luxed or significantly subluxed

•capsular stabilizing devices are helpful when doing surgery on subluxed lens

•sulcus or iris fixation of the intraocular lens is often indicated

•Topical hypotensive agents

•Evaluate and treat amblyopia

Prognosis

•Poor visual outcome if congenital with amblyopia

•Good prognosis with early detection or later manifestations