Ординатура / Офтальмология / Английские материалы / Clinical Ophthalmology A Systematic Approach 7th Edition_Kanski, Bowling_2011

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•A less dense cataract, although still visually significant, will allow visualization of the retinal vasculature with the indirect but not with the direct ophthalmoscope. Other features of visually significant cataract are central or posterior opacities over

3 mm in diameter.

•A visually insignificant opacity will allow clear visualization of the retinal vasculature with both the indirect and direct ophthalmoscope. Other features of visually insignificant cataract are central opacities less than 3 mm in diameter and peripheral, anterior or punctate opacities with intervening clear zones.

2Morphology of the opacity can give important clues to aetiology (see above).

3Associated ocular pathology may involve the anterior segment (corneal clouding, microphthalmos, glaucoma, persistent fetal vasculature) or the posterior segment (chorioretinitis, Leber amaurosis, rubella retinopathy, foveal or optic nerve hypoplasia).

4Other indicators of severe visual impairment include absence of central fixation, nystagmus and strabismus.

5Special tests such as forced choice preferential looking and visually evoked potentials also provide helpful information but should not be relied exclusively upon since they may be misleading.

Systemic investigations

Unless there is an established hereditary basis for the cataracts, the investigation of the infant with bilateral cataracts should include the following:

1Serology for intrauterine infections.

2Urine. Urinalysis for reducing substance after drinking milk (galactosaemia) and chromatography for amino acids (Lowe syndrome).

3Other investigations include fasting blood glucose, serum calcium and phosphorus, red blood cell GPUT and galactokinase levels. Children who have calcium and phosphorus anomalies severe enough to cause cataracts are unwell.

4Referral to a paediatrician may be warranted for dysmorphic features or suspicion of other systemic diseases. Chromosome analysis may be useful in this context.

Treatment

Timing is crucial and the main considerations are as follows:

1Bilateral dense cataracts require early surgery when the child is 4–6 weeks of age to prevent the development of stimulus deprivation amblyopia. If the severity is asymmetrical, the eye with the denser cataract should be addressed first.

2Bilateral partial cataracts may not require surgery until later if at all. In cases of doubt it may be prudent to defer surgery, monitor lens opacities and visual function and intervene later if vision deteriorates.

3Unilateral dense cataract merits urgent surgery (possibly within days) followed by aggressive anti-amblyopia therapy, despite which the results are often poor. The timing of intervention should be balanced by the suggestion that early intervention (<4 weeks) may result in an increased risk of subsequent secondary glaucoma. If the cataract is detected after 16 weeks of age then the visual prognosis is particularly poor.

4Partial unilateral cataract can usually be observed or treated non-surgically with pupillary dilatation and possibly part time contralateral occlusion to prevent amblyopia.

5Surgery involves anterior capsulorhexis, aspiration of lens matter, capsulorhexis of the posterior capsule, limited anterior vitrectomy and IOL implantation, if appropriate. It is important to correct associated refractive errors.

Postoperative complications

Cataract surgery in children carries a higher incidence of complications than in adults.

1Posterior capsular opacification is nearly universal if the posterior capsule is retained in a child under the age of 6 years. It is also of more significance in young children because of its amblyogenic effect. The incidence of opacification is reduced when posterior capsulorhexis is combined with vitrectomy.

2Secondary membranes may form across the pupil, particularly in microphthalmic eyes or those with associated chronic uveitis. A fibrinous postoperative uveitis in an otherwise normal eye, unless vigorously treated, may also result in membrane formation.

3Proliferation of lens epithelium is universal but usually visually inconsequential, since it does not involve the visual axis. It becomes encapsulated within the remnants of the anterior and posterior capsules and is referred to as a Soemmerring ring.

4Glaucoma eventually develops in about 20% of eyes.

•Closed-angle glaucoma may occur in the immediate postoperative period in microphthalmic eyes secondary to pupillary block.

•Secondary open-angle glaucoma may develop years after the initial surgery; it is therefore important to monitor the intraocular pressure long-term.

5Retinal detachment is an uncommon and usually late complication.

Visual rehabilitation

Although the technical difficulties of performing cataract surgery in infants and young children have mostly been resolved, visual results are hampered by amblyopia. With regard to optical correction for the aphakic child, the two main considerations are age and laterality of aphakia.

1Spectacles are useful for older children with bilateral aphakia.

2Contact lenses provide a superior optical solution for both unilateral and bilateral aphakia. Tolerance is usually reasonable until the age of about 2 years, although after this period problems with compliance may develop as the child becomes more active and independent.

3IOL implantation is increasingly being performed in younger children and appears to be effective and safe in selected cases. Awareness of the rate of myopic shift which occurs in the developing eye, combined with accurate biometry, allows the calculation of an IOL power targeted at initial hypermetropia (correctable with spectacles) which will ideally decay towards emmetropia later in life. However, final refraction is variable and emmetropia in adulthood cannot be guaranteed.

4 Occlusion to treat or prevent amblyopia is essential. Atropine penalization may also be considered.

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Ectopia lentis

Ectopia lentis refers to a displacement of the lens from its normal position. The lens may be completely dislocated, rendering the pupil aphakic (luxated), or partially displaced, still remaining in the pupillary area (subluxated). Ectopia lentis may be hereditary or acquired. Acquired causes include trauma, a large eye (e.g. high myopia, buphthalmos), anterior uveal tumours and hypermature cataract. Only hereditary causes are discussed below.

Without systemic associations

1Familial ectopia lentis is an AD condition characterized by bilateral symmetrical superotemporal displacement. It may manifest congenitally or later in life.

2Ectopia lentis et pupillae is a rare, congenital, bilateral, AR disorder characterized by displacement of the pupil and the lens in opposite directions. The pupils are small, slit-like and dilate poorly (Fig. 9.28A). Other findings include iris transillumination, large corneal diameter, glaucoma, cataract and microspherophakia.

3Aniridia is occasionally associated with ectopia lentis (Fig. 9.28B).

Fig. 9.28 Ectopia lentis without systemic associations. (A) Ectopia lentis et pupillae; (B) inferior subluxation in aniridia

(Courtesy of J Schuman, V Christopoulos, D Dhaliwal, M Kahook and R Noecker, from Lens and Glaucoma, in Rapid Diagnosis in Ophthalmology, Mosby 2008 – fig. A; U Raina –fig.B)

With systemic associations

Marfan syndrome

1Pathogenesis. There is mutation of the fibrillin-1 gene (FBN1) on chromosome 15q21.

2 Inheritance is AD with variable expressivity; a minority of patients manifest only ocular signs.

3Musculoskeletal features

•Tall, thin stature with disproportionately long limbs compared with the trunk (arm span > height – Fig.

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9.29A).

•Kyphoscoliosis, sternal prominence (pectus carinatum) or depression (pectus excavatum).

•Long spider-like fingers and toes (arachnodactyly – Fig. 9.29B) and mild joint laxity.

•A narrow high-arched (‘gothic’) palate (Fig. 9.29C).

•A long-shaped head, malar hypoplasia, enophthalmos and downslanting palpebral fissures.

•Flat feet, cutaneous striae and easy bruising.

•Muscular underdevelopment and predisposition to hernias.

4Cardiovascular lesions include dilatation of the aortic root, mitral valve prolapse and aortic aneurysm formation.

5Ectopia lentis which is bilateral and symmetrical is present in 80% of cases. Subluxation is most frequently supero-temporal, but may be in any meridian. Because the zonule is frequently intact (Fig. 9.29D), accommodation is retained, although rarely the lens may dislocate into the anterior chamber or vitreous (Fig. 9.29E). The lens may also be microspherophakic.

6Other ocular features include angle anomaly which may result in glaucoma, retinal detachment associated with lattice degeneration, hypoplasia of the dilator pupillae, peripheral iris transillumination defects, cornea plana and strabismus.

Fig. 9.29 Marfan syndrome. (A) Long limbs compared with the trunk; (B) arachnodactyly; (C) high-arched palate; (D) superotemporal subluxation with intact zonule;

(E) dislocation into the vitreous is rare

Weill–Marchesani syndrome

Weill–Marchesani syndrome is a rare systemic connective tissue disease, conceptually the converse of Marfan syndrome.

1Inheritance is AR or AD; the former maps to 19p13.3-p13.2 and the latter to FBN1, the same as Marfan syndrome.

2Systemic features include short stature, brachydactyly characterized by short, stubby fingers (Fig. 9.30A) and toes, stiff joints and mental handicap.

3Ectopia lentis which is inferior occurs in 50% of cases during late childhood or early adult life. Microspherophakia is common so that subluxation occurs anteriorly to cause pupil block or occasionally into the anterior chamber (Fig. 9.30B).

4 Other ocular features include angle anomalies, asymmetrical axial lengths and presenile vitreous liquefaction.

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Fig. 9.30 Weill–Marchesani syndrome. (A) Bradydactyly; (B) dislocation of microspheric lens into the anterior chamber

(Courtesy of R Curtis – fig. B)

Homocystinuria

1Pathogenesis. Inborn error of metabolism in which decreased hepatic activity of cystathionine beta-synthase results in systemic accumulation of homocysteine and methionine.

2Inheritance is AR with the gene locus on chromosome 21q.22.3.

3Systemic features

•Coarse blond hair, blue irides, malar flush (Fig. 9.31A), Marfanoid habitus but infrequent arachnodactyly.

•Neurodevelopmental delay, mental handicap, psychiatric disturbance and osteoporosis.

•Thromboses in any vessel and at any age, particularly postoperatively or postpartum.

•Treatment involves oral pyridoxine, folic acid and vitamin B12 to reduce plasma homocysteine and methionine levels.

4Ectopia lentis, typically inferonasal (Fig. 9.31B), is almost universal by the age of 25 years in untreated cases. The zonule, which normally contains high levels of cysteine (deficient in homocystinuria), disintegrates (Fig. 9.31C) so that accommodation is often lost. Secondary angle-closure may occur as a result of pupil block caused by lens incarceration in the pupil, or a total dislocation into the anterior chamber.

5 Other ocular features include iris atrophy, optic atrophy, cataract, corneal opacity, myopia and retinal detachment.

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Fig. 9.31 Homocystinuria. (A) Coarse blond hair; (B) inferior subluxation with zonular disintegration; (C) histology shows matted zonular fibres lying over the ciliary epithelium

(Courtesy of J Schuman, V Christopoulos, D Dhaliwal, M Kahook and R Noecker, from Lens and Glaucoma, in Rapid Diagnosis in Ophthalmology, Mosby 2008 – fig. B; J Harry and G Misson, from Clinical Ophthalmic Pathology, Butterworth-Heinemann 2001 – fig. C)

Other systemic associations

1Sulphite oxidase deficiency is an AR inborn error of sulphur metabolism characterized by progressive psychomotor deterioration, progressive muscular rigidity, decerebrate posture and demise usually before the age of 5 years. Ectopia lentis is universal.

2Hyperlysinaemia is a very rare, AR inborn error of metabolism caused by a deficiency in lysine alpha-ketoglutarate reductase. Systemic features include lax ligaments, hypotonic muscles, seizures and mental handicap. It is occasionally associated with ectopia lentis.

3Stickler syndrome is occasionally associated with ectopia lentis, retinal detachment being the most common problem.

4Ehlers–Danlos syndrome is occasionally associated with ectopia lentis, scleral fragility, keratoconus and myopia being more common.

Management

The main complications of ectopia lentis are (a) refractive error (lenticular myopia), (b) optical distortion due to astigmatism and/or lens edge effect, (c) glaucoma (see Ch. 10) and, rarely, (d) lens-induced uveitis.

1Spectacle correction may correct astigmatism induced by lens tilt or edge effect in eyes with mild subluxation. Aphakic correction may also afford good visual results if a significant portion of the visual axis is aphakic in the undilated state.

2Surgical removal of the lens, using closed intraocular microsurgical techniques, is indicated for intractable ametropia, meridional amblyopia, cataract, lens-induced glaucoma, uveitis or endothelial touch.

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Abnormalities of shape

Anterior lenticonus

1Signs

•Bilateral axial projection of the anterior surface of the lens into the anterior chamber (Fig. 9.32A).

•In early cases the red reflex shows an ‘oil-droplet’ (Fig. 9.32B).

2Alport syndrome is present in the vast majority of patients. It is an AD or X-LR condition characterized by progressive sensorineural deafness and renal disease associated with abnormal glomerular basement membrane. Haematuria usually begins in childhood, whereas renal failure occurs later.

3Other ocular features include fleck retinopathy (see Fig. 15.17) and posterior polymorphous corneal dystrophy (see Fig. 6.59).

Fig. 9.32 (A) Anterior lenticonus; (B) red reflex shows an ‘oil-droplet’ sign

Posterior lenticonus

1Inheritance. Most cases are unilateral, sporadic and not associated with systemic abnormalities. Rarely bilateral cases may be familial.

2Signs

•A round or conical bulge of the posterior axial zone of the lens into the vitreous (Fig. 9.33A) associated with local thinning or absence of the capsule.

•Opacification of the posterior capsule (Fig. 9.33B) is common.

•With age, the bulge progressively increases in size and the lens cortex may opacify. Progression of cataract is variable, but many cases present with an acutely opacified white lens in infancy or early childhood.

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Fig. 9.33 (A) Posterior lenticonus; (B) red reflex shows opacification of the posterior capsule

Lentiglobus

Lentiglobus is a very rare, usually unilateral, generalized hemispherical deformity of the lens which may be associated with posterior polar lens opacity.

Microspherophakia

1Signs. The lens is small and spherical (Fig. 9.34).

2Causes include familial (dominant) microspherophakia which is not associated with systemic defects, Marfan syndrome, Weill –Marchesani syndrome, hyperlysinaemia and congenital rubella.

3Ocular associations include Peters anomaly and familial ectopia lentis et pupillae.

4 Complications include lenticular myopia, subluxation and total dislocation into the anterior chamber (see Fig. 9.30B).

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Fig. 9.34 Microspherophakia

(Courtesy of R Bates)

Microphakia

1Sign. A lens with a smaller than normal diameter (Fig. 9.35).

2Association. Lowe syndrome (see above), in which the lens is not only small but also disc-like.

Fig. 9.35 Microphakia

Coloboma

A coloboma is characterized by notching (segmental agenesis) at the inferior equator (Fig. 9.36) with corresponding absence of zonular fibres. It is not a true coloboma as there is no focal absence of a tissue layer due to failure of closure of the optic fissure. Occasionally a lens coloboma may be associated with a coloboma of the iris or fundus.

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Fig. 9.36 Lens coloboma

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