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

kanski 7th

Schnyder central crystalline dystrophy

Crystalline dystrophy is a disorder of corneal lipid metabolism which is associated with raised serum cholesterol in approximately 50% of patients.

1Inheritance is AD with the gene locus at 1p36.

2 Histology shows deposits of phospholipids and cholesterol.

3Onset is in the 2nd decade with visual impairment and glare.

4Signs

•Central, oval, subepithelial ‘crystalline’ opacity (Fig. 6.50A).

•Diffuse corneal haze (Fig. 6.50B) and prominent corneal arcus develop by the 3rd decade.

5Treatment is by excimer laser keratectomy.

Fig. 6.50 Schnyder crystalline dystrophy. (A) Early lesion; (B) late diffuse haze.

(Courtesy of K Nischal – fig. A)

Stromal dystrophies

Lattice corneal dystrophy type I (LCD1, Biber–Haab–Dimmer)

1Inheritance is AD with the locus at 5q31 (gene TGFB1).

2Histology shows amyloid, staining with Congo red (Fig. 6.51A) and exhibiting characteristic green birefringence when viewed with a polarizing filter (Fig. 6.51B).

3Onset is at the end of the 1st decade with recurrent erosions which precede typical stromal changes.

4Signs in chronological order:

•Anterior stromal, glassy, refractile dots (Fig. 6.51C).

•Coalescence into fine lattice lines, best seen on retroillumination (Fig. 6.51D).

•Deep and outward spread sparing the periphery.

•Generalized stromal haze that progressively impairs vision and may obscure some of the lattice lines (Fig. 6.51E).

•Corneal sensation is reduced.

5 Treatment by penetrating or deep lamellar keratoplasty is frequently required. Recurrence in the graft may occur.

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Fig. 6.51 Lattice dystrophy type 1. (A) Histology shows amyloid staining with Congo red; (B) green birefringence of amyloid when viewed with polarized light; (C) glassy dots in the anterior stroma; (D) fine lattice lines; (E) stromal haze

(Courtesy of J Harry – fig. A; J Harry and G Misson, from Clinical Ophthalmic Pathology, Butterworth-Heinemann 2001 – fig. B; D Smerdon

– fig. D).

Lattice corneal dystrophy type II (LCD2, Finnish type amyloidosis, Meretoja syndrome, amyloid cranial neuropathy with lattice corneal dystrophy)

1Inheritance is AD with a gene locus at 9q34.

2 Histology shows amyloid deposits in the corneal stroma and other involved sites.

3Onset is in the 2nd decade; erosions are rare.

4Signs

•Randomly scattered, short, fine lattice lines which are sparse, more delicate, more radially orientated and more peripherally located than in LCD1.

•Corneal sensation is impaired.

5Treatment by keratoplasty may rarely be required in later life to improve vision.

6Systemic features include progressive bilateral cranial and peripheral neuropathy, dysarthria, dry and extremely lax itchy skin, a characteristic ‘mask-like’ facial expression due to bilateral facial palsy, protruding lips and pendulous ears. Amyloidosis may also involve the kidneys and heart.

Lattice corneal dystrophy type IIIA

Lattice type IIIA is characterized by thick rope-like bands of deposited amyloid (Fig. 6.52). The age of onset is late (70–90 years) and inheritance AD (gene TGFB1).

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Fig. 6.52 Lattice dystrophy type IIIa

Gelatinous drop-like dystrophy (Japanese type amyloid corneal dystrophy)

This is a rare disorder mainly affecting Japanese patients.

1Inheritance is autosomal recessive (AR) with the gene locus at 1p32.

2Histology shows subepithelial and anterior stromal accumulation of amyloid (Fig. 6.53A).

3Onset is within the 1st and 2nd decades with severe photophobia, watering and visual impairment.

4Signs in chronological order:

•Grey subepithelial nodules.

•Gradual confluence, stromal involvement and increase in size giving rise to a mulberry-like appearance (Fig. 6.53B).

5 Treatment is with repeated superficial keratectomy because of early recurrences on corneal grafts.

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Fig. 6.53 Gelatinous drop-like dystrophy; (A) Histology shows irregular anterior stromal amyloid deposits; (B) clinical appearance

(Courtesy of J Harry and G Misson, from Clinical Ophthalmic Pathology, Butterworth-Heinemann 2001 – fig. A; Krachmer, Mannis and Holland, from Cornea, Mosby 2005 – fig. B)

Granular corneal dystrophy type I (GCD1, Groenouw type I)

1Inheritance is AD with the gene locus at 5q31 (gene TGFB1).

2Histology shows amorphous hyaline deposits which stain bright red with Masson trichrome (Fig. 6.54A).

3 Onset is in the 1st decade but vision is usually not affected in the early stage of the disease. Recurrent erosions are uncommon.

4Signs in chronological order:

•Small, white, sharply demarcated deposits resembling crumbs, sugar granules, rings or snowflakes in the central anterior stroma (Fig. 6.54B).

•The overall pattern of deposition is radial or disc shaped, or may be in the form of a Christmas tree.

•Initially the stroma between the opacities is clear (Fig. 6.54C).

•Gradual increase in number and size of the deposits with deeper and outward spread but not reaching the limbus.

•Gradual confluence and diffuse haze of intervening stroma (Fig. 6.54D) causes visual impairment.

•Corneal sensation is impaired.

5Treatment by penetrating or deep lamellar keratoplasty is usually required by the 5th decade. Superficial recurrences may require repeated excimer laser keratectomy.

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Fig. 6.54 Granular dystrophy type 1. (A) Histology shows red-staining material with Masson trichrome; (B) sharply demarcated crumbs; (C) increase in number and outward spread; (D) confluence

(Courtesy of J Harry – fig. A)

Granular corneal dystrophy type II (GCD2, Avellino, combined granular-lattice dystrophy)

1Inheritance is AD with the gene locus at 5q31 (gene TGFB1).

2Histology shows both hyaline and amyloid in the stroma that stains with Masson trichrome and Congo red.

3Onset is in the 2nd decade. Recurrent erosions are rare, and if present, mild so that some patients may be unaware of their disease.

4Signs. Superficial, fine, opacities that resemble rings, discs, stars or snowflakes, most dense centrally (resembling those seen in granular dystrophy type I) associated with deeper linear opacities reminiscent of lattice dystrophy (Fig. 6.55).

5Treatment is usually not required.

Fig. 6.55 Granular dystrophy type 2 (Avellino)

(Courtesy of W Lisch)

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Macular dystrophy (Groenouw type II)

Macular dystrophy is the least common stromal dystrophy, in which a systemic inborn error of keratan sulphate metabolism seems to have only corneal manifestations. It has been divided into clinically indistinguishable types I, IA and II depending on the presence or absence of antigenic keratan sulphate in the serum and cornea; these have been shown to be due to mutations in the same sulfotransferase gene (CHST6).

1Inheritance is AR with the gene locus at 16q22.

2Histology shows abnormally close packing of collagen in the corneal lamellae and abnormal aggregations of glycosaminoglycans which stain with Prussian blue and colloidal iron (Fig. 6.56A).

3Onset is towards the end of the 1st decade with visual deterioration.

4Signs in chronological order:

•Anterior stromal haze, initially involving the central cornea.

•Greyish-white, dense, focal, poorly delineated spots in the anterior stroma centrally and posterior stroma in the periphery (Fig. 6.56B).

•Superficial deposits may produce an irregularity of the corneal surface, although recurrent erosions are unusual.

•Increase in size and stromal haze (Fig. 6.56C).

•Increasing opacification with eventual involvement of full-thickness stroma up to the limbus, associated with corneal thinning (Fig. 6.56D).

5Treatment by penetrating keratoplasty is generally successful but late recurrence on the graft may occur.

Fig. 6.56 Macular dystrophy. (A) Histology shows deposits of abnormal glycosaminoglycans that appear blue with colloidal iron stain; (B) poorly delineated deposits;

(C) increase in size and stromal haze; (D) extensive involvement

(Courtesy of R Ridgway – figs. B, C and D; J Harry and G Misson, from Clinical Ophthalmic Pathology, Butterworth-Heinemann, 2001 – fig. A)

François central cloudy dystrophy

1Inheritance is AD.

2Signs

•Polygonal, cloudy grey opacities separated by relatively clear spaces, in the posterior stroma most prominent centrally, creating a leather-like appearance (Fig. 6.57).

•The signs are similar to posterior crocodile shagreen but it is differentiated by its central, posterior location and mode of inheritance.

3 Treatment is not required.

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Fig. 6.57 François central cloudy dystrophy

(Courtesy of W Lisch)

Endothelial dystrophies

Fuchs endothelial dystrophy

Fuchs endothelial dystrophy (FED) is characterized by bilateral accelerated endothelial cell loss. It is more common in women and is associated with a slightly increased prevalence of open-angle glaucoma.

1Inheritance may occasionally be AD although the majority are sporadic.

2Onset of this slowly progressive disease is commonly in old age, although earlier onset can occur.

3Signs

•Cornea guttata refers to irregular warts or ‘excrescences’ of Descemet membrane secreted by abnormal endothelial cells (Fig. 6.58A).

•Specular reflection shows tiny dark spots caused by disruption of the regular endothelial mosaic (Fig. 6.58B).

•Progression occurs to a ‘beaten metal’ appearance which may be associated with melanin deposition (Fig. 6.58C).

•Endothelial decompensation gradually leads to central stromal oedema and blurred vision, worse in the morning and clearing later in the day.

•Epithelial oedema develops when stromal thickness has increased by about 30%.

•Persistent epithelial oedema results in the formation of microcysts and bullae (bullous keratopathy – Fig. 6.58D and E) which causes pain and discomfort on rupture, thought to be due to exposure of naked nerve endings.

4Treatment

aConservative options include topical sodium chloride 5% drops or ointment, reduction of intraocular pressure and using a hair dryer to speed corneal dehydration in the morning.

bBandage contact lenses provide comfort by protecting exposed nerve endings and flattening bullae.

c Penetrating or deep lamellar endothelial keratoplasty has a high success rate and should not be delayed.

dOther options in eyes with poor visual potential include conjunctival flaps and amniotic membrane transplants.

5Cataract surgery may accelerate endothelial cell loss and result in decompensation. A ‘triple procedure’ (cataract surgery, lens implantation and keratoplasty) should be considered in eyes with corneal epithelial oedema or when preoperative pachymetry measurement is greater than 640 µm. If corneal thickness is less than 640 µm, a good visual outcome is to be expected.

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Fig. 6.58 Fuchs endothelial dystrophy. (A) Histology of cornea guttata shows irregular excrescences of Descemet membrane – PAS stain; (B) cornea guttata seen on specular reflection; (C) ‘beaten-bronze’ endothelium; (D) bullous keratopathy; (E) histology shows severe epithelial oedema with surface bullae – PAS stain

(Courtesy of J Harry – figs A and E; W Lisch – fig. D)

Posterior polymorphous dystrophy

Posterior polymorphous corneal dystrophy (PPCD) is a rare, innocuous and asymptomatic condition in which corneal endothelial cells display characteristics similar to epithelium. There are three forms, PPCD1-3, each caused by mutations in different genes.

1Inheritance is usually AD.

2Onset is at birth or soon thereafter, although it is most frequently identified by chance in later life.

3Signs consist of subtle vesicular endothelial lesions (Fig. 6.59A) that may become confluent (Fig. 6.59B), band-like lesions (Fig. 6.59C) or diffuse opacities which may be asymmetrical.

4 Ocular associations include iris abnormalities, glaucoma and Alport syndrome. 5 Treatment is not required.

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Fig. 6.59 Posterior polymorphous dystrophy. (A) Vesicles; (B) confluent vesicles; (C) band-like lesions

(Courtesy of W Lisch – figs B and C)

Congenital hereditary endothelial dystrophy

Congenital hereditary endothelial dystrophy (CHED) is a rare dystrophy in which there is focal or generalized absence of corneal endothelium. There are two main forms, CHED1 and CHED2, the latter being more severe.

1 Inheritance of CHED1 is AD with the gene locus on 20p11.2-q11.2. CHED2 is AR with the gene locus on 20p13.

2Onset is perinatal (Fig. 6.60A).

3Signs

•Bilateral, symmetrical, diffuse corneal oedema resulting in a blue-grey, ground-glass appearance (Fig. 6.60B) to total opacification (Fig. 6.60C).

•Visual impairment is variable and visual acuity may surpass that expected from the corneal appearance.

4Treatment by penetrating keratoplasty has a reasonable chance of success when performed early but is risky and technically more difficult than in adults. Undue delay in surgical intervention carries the risk of dense amblyopia.

5Differential diagnosis includes other causes of neonatal corneal opacification such as congenital glaucoma, mucopolysaccharidoses, birth trauma, rubella keratitis and sclerocornea.

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Fig. 6.60 Congenital hereditary endothelial dystrophy. (A) Bilateral perinatal corneal opacification; (B) mild; (C) very severe

(Courtesy of K Nischal – figs A and C; Krachmer, Mannis and Holland, from Cornea, Mosby 2005 – fig. B)

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