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

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Fig. 14.62 (A) Cystoid macular oedema; (B) red-free image; (C) FA late phase shows a ‘flower-petal’ pattern of hyperfluorescence; (D) OCTshows hyporeflective spaces within the retina, macular thickening and loss of the foveal depression

(Courtesy of J Donald M Gass, from Stereoscopic Atlas of Macular Diseases, Mosby 1997 – fig. A; P Gili – fig. B; C Barry – fig. D)

Causes

1Ocular surgery and laser

•Clinically significant CMO occurs in probably 1–2% of eyes following phacoemulsification (see Ch. 9) but is higher following extracapsular extraction, particularly if associated with complications.

•Nd:YAG laser capsulotomy may cause CMO but the risk can be reduced if capsulotomy is delayed for 6 months or more after cataract surgery.

•Panretinal photocoagulation, if aggressive, may occasionally cause CMO.

•Other procedures such as retinal detachment surgery, glaucoma filtration surgery and corneal transplantation are sometimes followed by the development of CMO.

2Retinal vascular disease such as diabetic retinopathy, retinal vein occlusion, hypertensive retinopathy, idiopathic retinal telangiectasis, retinal artery macroaneurysm and radiation retinopathy.

3Inflammation such as intermediate uveitis, sarcoidosis, scleritis, birdshot retinochoroidopathy, multifocal choroiditis with panuveitis, toxoplasmosis, cytomegalovirus retinitis and Behçet syndrome.

4 Drug-induced due to topical prostaglandin derivatives and topical adrenaline derivatives in aphakic eyes.

5Retinal dystrophies including retinitis pigmentosa, gyrate atrophy and dominant CMO.

6Conditions involving vitreomacular traction such as epimacular membrane and vitreomacular traction syndrome (VMT).

7CNV.

8Fundus tumours such as retinal capillary haemangioma and choroidal haemangioma even when located well away from the macula.

9Systemic disease such as multiple myeloma, leukaemia and chronic renal failure.

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Epimacular membrane

Pathogenesis

An epimacular membrane (EMM), also known as a macular epiretinal membrane, cellophane maculopathy and macular pucker, is a sheetlike fibrocellular structure which develops on or above the surface of the retina. Proliferation of the cellular component and contraction of the membrane leads to visual symptoms, primarily due to retinal wrinkling, obstruction and localized elevation with or without CMO.

Classification

1Idiopathic

•No apparent cause such as previous retinal detachment, surgery, trauma or inflammation.

•About 10% are bilateral.

•Predominant cellular constituent is glial cells, probably derived from the indigenous posterior hyaloid membrane (PHM) cell population (‘laminocytes’); these may be stimulated by the process of posterior vitreous detachment (PVD).

•Tend to be milder than secondary.

2Secondary

•Occur following retinal detachment surgery (most frequent cause of secondary EMM), retinal break, panretinal photocoagulation, retinal cryotherapy, retinal vascular disease, inflammation and trauma.

•Binocularity dependent on whether both eyes affected by causative factors.

•Cell type more varied; pigment cells are prominent – thought to be derived from the RPE.

•Tend to be more severe than idiopathic EMM.

Diagnosis

1Presentation is with blurring and metamorphopsia although mild cases are often asymptomatic.

2Signs

•VA is highly variable, depending on severity, but 6/9 is typical.

•An irregular translucent sheen is present at the macula in early EMM, often best detected using ‘red-free’ light (Fig. 14.63A).

•As the membrane thickens and contracts it becomes more obvious and typically causes mild distortion of blood vessels (Fig. 14.63B).

•Advanced EMM may give severe distortion of blood vessels, marked retinal wrinkling and striae and may obscure underlying structures (Fig. 14.63C).

•Associated findings may include macular pseudohole (Fig. 14.63D), CMO and small haemorrhages.

4 Amsler grid testing typically shows distortion.

5OCT shows a highly reflective (red) surface layer associated with retinal thickening (Fig. 14.63E). OCT is useful in the exclusion of VMT, especially if CMO is present.

6FA has been superseded by OCT for routine assessment of EMM, but highlights vascular tortuosity (Fig. 14.63F) and demonstrates any leakage.

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Fig. 14.63 Epimacular membrane. (A) Translucent membrane seen with red-free light; (B) more obvious membrane with mild vascular distortion; (C) advanced membrane; (D) macular pseudohole seen with red-free light; (E) OCTshows high reflectivity and retinal thickening; (F) FA early venous phase highlights the vascular tortuosity

(Courtesy of L Merin – fig. A; C Barry – figs B, E and F; P Gili – fig. D)

Management

1Observation if the membrane is mild and non-progressive. Spontaneous resolution of visual symptoms sometimes occurs, typically due to separation of the EMM from the retina.

2Surgical removal of the membrane by vitrectomy to facilitate peeling usually improves or eliminates distortion (the main benefit), with an improvement in visual acuity of at least two lines in around 75% or more; in about a quarter VA is unchanged, and around 2% get worse.

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Degenerative myopia

Pathogenesis

Myopia is the result of complex hereditary and environmental factors. A refractive error of more than −6 dioptres constitutes high myopia, in which axial length is usually greater than 26 mm. ‘Pathological’ or degenerative myopia is characterized by progressive anteroposterior elongation of the scleral envelope associated with a range of secondary ocular changes, principally thought to relate to mechanical stretching of the involved tissues. It is a major cause of legal blindness, with maculopathy the most common cause of visual loss.

Diagnosis

1A pale tessellated (‘tigroid’) appearance is due to diffuse attenuation of the RPE with visibility of large choroidal vessels (Fig. 14.64A).

2Focal chorioretinal atrophy is characterized by visibility of the larger choroidal vessels and eventually the sclera (Fig. 14.64B).

3Anomalous optic nerve head which may appear unusually small, large or anomalous with a ‘tilted’ conformation (Fig. 14.64B). Peripapillary chorioretinal atrophy is very common, and in milder cases taking the form of a temporal crescent of thinned or absent RPE exposing the choroid and/or sclera.

4‘Lacquer cracks’ are ruptures in the RPE-Bruch membrane-choriocapillaris complex characterized clinically by fine, irregular, yellow lines, often branching and criss-crossing at the posterior pole (Fig. 14.64C). They are present in around 5% of highly myopic eyes and can precede the development of CNV, retinal haemorrhages without CNV, and geographic atrophy. It is thought that the flaw in the RPE barrier constituted by the cracks provides a route through which choriocapillaris tissue can grow.

5 Lattice degeneration (see Ch. 16).

6Subretinal ‘coin’ haemorrhages, which may be intermittent, may develop from lacquer cracks in the absence of CNV (Fig. 14.64D).

7A Fuchs spot is a raised, circular, pigmented lesion at the macula developing after a subretinal haemorrhage has absorbed (Fig. 14.64E).

8A staphyloma is an ectasia or bulging of the posterior sclera due to focal expansion and thinning (Fig. 14.64F). It occurs in about a third of eyes with pathological myopia, and is virtually always peripapillary or involves the macula. Staphyloma development can be associated with macular hole formation.

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Fig. 14.64 High myopia. (A) Tessellated fundus; (B) focal chorioretinal atrophy and tilted disc; (C) lacquer cracks; (D) Fuchs spot; (E) ‘coin’ haemorrhage; (F) axial CTshows a left posterior staphyloma

Complications

1Rhegmatogenous retinal detachment (RD) is much more common in high myopia, the pathogenesis including increased frequency of posterior vitreous detachment, lattice degeneration, asymptomatic atrophic holes, macular holes (Fig. 14.65A) and occasionally giant retinal tears. The prevalence of retinal detachment appears to be related to the severity of myopia.

2CNV (Fig. 14.65B)

aIncidence 5–10% of highly myopic eyes develop CNV which may occur de novo, or more commonly in association with lacquer cracks or chorioretinal atrophy (see Fig. 14.64B and C).

bThe visual prognosis is influenced by age, older patients tending to have a poorer outcome; the involved area tends to be smaller and shallower in younger patients with myopia-related CNV than in AMD.

cTreatment

•PDT has been the mainstay of therapy for subfoveal lesions, although with disappointing long-term results.

•Anti-VEGF therapy shows very promising results, with significant visual benefit; a lower injection frequency may be needed than for AMD but RD risk may be higher.

•Combination therapy with PDT is under investigation.

3Foveal retinoschisis and macular retinal detachment without macular hole formation may occur in highly myopic eyes with posterior staphyloma, probably as a result of vitreous traction. Retinoschisis may be mistaken clinically for CMO, and is better characterized by OCT than biomicroscopy.

4Macular hole may occur spontaneously or after relatively mild trauma, and is associated with the development of retinal detachment very much more commonly than age-related idiopathic macular hole. As with foveoschisis, macular staphyloma may predispose; it is possible that myopic foveoschisis and myopic macular hole may be part of the same pathological process. Vitrectomy may be effective for both, but the best surgical technique remains undefined.

5Peripapillary detachment is an asymptomatic, innocuous, yellow-orange, elevation of the RPE and sensory retina at the inferior border of the myopic conus (anomalous optic nerve head complex).

6Cataract, which may be either posterior subcapsular or early onset nuclear sclerotic.

7 Glaucoma. There is an increased prevalence of primary open-angle glaucoma, pigmentary glaucoma and steroid responsiveness. 8 Amblyopia is uncommon but may develop when there is a significant difference in myopia between the two eyes.

9Dislocation of the lens (natural or artificial) is a rare but well-recognized risk.

Table 14.4 -- Systemic associations of high myopia

•Down syndrome

•Stickler syndrome

•Marfan syndrome

•Prematurity

•Noonan syndrome

•Ehlers–Danlos syndrome

•Pierre–Robin syndrome

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Fig. 14.65 (A) shallow retinal detachment confined to the posterior pole, caused by a macular hole; (B) subretinal haemorrhage associated with CNV

(Courtesy of M Khairallah – fig. A)

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Angioid streaks

Ocular considerations

Histology

Angioid streaks are crack-like dehiscences in brittle thickened and calcified Bruch membrane, associated with atrophy of the overlying RPE (Fig. 14.66A).

Fig. 14.66 Angioid streaks. (A) Histology shows a break in thickened Bruch membrane; (B) ‘peau d’orange’ and subtle angioid streaks; (C) advanced angioid streaks; (D) FA arteriovenous phase shows hypofluorescence of angioid streaks and three foci or CNV (arrows); (E) angioid streaks and optic disc drusen; (F) subretinal haemorrhage caused by a traumatic choroidal rupture

(Courtesy of J Harry and G Misson, from Clinical Ophthalmic Pathology, Butterworth-Heinemann 2001 – fig. A; P Saine – fig. C; S Milewski

– fig. D)

Diagnosis

1Signs

•‘Peau d’orange’ (orange skin) mottled retinal pigmentation is common, and subtle associated angioid streaks may be overlooked (Fig. 14.66B).

•Grey or dark-red linear lesions with irregular serrated edges that lie beneath the normal retinal blood vessels that intercommunicate in a ring-like fashion around the optic disc and then radiate outwards from the peripapillary area, sometimes giving a ‘spider's web’ appearance (Fig. 14.66C).

•The streaks tend to increase in width and extent slowly over time.

2FA shows hyperfluorescent window defects due to RPE atrophy overlying the streaks, associated with variable associated hypofluorescence corresponding to RPE hyperplasia. FA is generally only indicated if CNV is suspected (Fig. 14.66D). The streaks can sometimes exhibit autofluorescence.

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3 ICGA demonstrates the streaks as hyperfluorescent bands with brighter hyperfluorescent ‘pinpoints’ distributed within these.

4Optic disc drusen are common (Fig. 14.66E).

Complications

Though angioid streaks are typically asymptomatic at first, the prognosis is guarded because visual impairment occurs in over 70% of patients as a result of one or more of the following:

1CNV is by far the most common cause of visual loss (see Fig. 14.66D). Conventional thermal laser photocoagulation may be successful in extrafoveal lesions although there is a high risk of aggressive recurrence. Intravitreal injection of anti-VEGF agents stabilizes vision but CNV commonly recurs or develops at a new site, and studies are ongoing.

2Choroidal rupture, which may occur following relatively trivial ocular trauma and result in a subretinal haemorrhage (Fig. 14.66F). Because eyes with angioid streaks are very fragile, patients should be warned against participating in contact sports and advised to use protective spectacles when appropriate.

3Foveal involvement by a streak.

Systemic associations

Approximately 50% of patients with angioid streaks have one of the following conditions:

Pseudoxanthoma elasticum

Pseudoxanthoma elasticum (PXE) is by far the most common association of angioid streaks. Approximately 85% of patients develop ocular involvement, usually after the second decade of life. PXE is a hereditary disorder of connective tissue in which there is progressive calcification, fragmentation and degeneration of elastic fibres in the skin (Fig. 14.67A), eye and cardiovascular system. In almost all cases it is caused by homozygosity or compound heterozygosity for mutations of the ABCC6 gene, encoding for cellular transport protein; it is therefore an AR condition in which ocular manifestations are common but of variable severity. The signs are as follows.

•‘Plucked chicken’ appearance of the skin resulting from small, yellowish macules, papules or plaques most commonly on the neck (Fig. 14.67B), axillae (Fig. 14.67C), antecubital fossae, groins and paraumbilical area, usually develops in children.

•Involved skin becomes progressively loose, thin and delicate.

•Calcification of elastic media and intima of arteries and heart valves, resulting in renal artery stenosis, intermittent claudication and mitral valve prolapse.

•Gastrointestinal haemorrhage, usually gastric in origin, is due to bleeding from fragile calcified submucosal vessels.

•Occasional bleeding from the urinary tract or cerebrovascular system.

•Severe angioid streaks (Grönblad–Strandberg syndrome).

Fig. 14.67 Pseudoxanthoma elasticum. (A) Histology shows thickened fragmented fibres in the dermis; (B) ‘chicken skin’ papules on the neck; (C) loose axillary skin

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

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Occasional associations

1Paget disease is a chronic, progressive metabolic bone disease characterized by excessive and disorganized resorption and formation of bone. Angioid streaks occur in only about 2%; it is thought that calcium binds to the elastin of Bruch membrane.

2Haemoglobinopathies occasionally associated with angioid streaks are: homozygous sickle-cell disease (HbSS), sickle-cell trait (HbAS), sickle-cell thalassaemia (HbS thalassaemia), sickle-cell haemoglobin C disease (HbSC), haemoglobin H disease (HbH), homozygous beta-thalassaemia major, beta-thalassaemia intermedia and beta-thalassaemia minor. In these the reason for the abnormally brittle Bruch membrane is thought to be iron deposition.

3Miscellaneous associations include familial hyperphosphataemia, idiopathic thrombocytopenic purpura, lead poisoning, haemochromatosis, Marfan syndrome and Ehlers–Danlos syndrome.

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Choroidal folds

Pathogenesis

Choroidal folds are parallel grooves or striae involving the inner choroid, Bruch membrane, the RPE and sometimes the retina (chorioretinal folds). They are likely to develop in association with any process that induces sufficient compressive stress within the choroid, Bruch membrane, and retina. Primary mechanisms include choroidal congestion and scleral compression, and occasionally tissue contraction. Choroidal folds should be distinguished from retinal folds, which have a different pathogenesis (usually epimacular membrane).

Causes

1Idiopathic (‘congenital’) folds may be present in healthy, often hypermetropic, individuals in whom visual acuity is typically unaffected. The folds are usually bilateral. A syndrome of idiopathic acquired hypermetropia with choroidal folds has been described

– in these patients elevated intracranial pressure should always be excluded even without evident papilloedema (see below) although a constricted scleral canal causing optic disc congestion has been proposed as an alternative mechanism in some patients.

2Papilloedema. Choroidal folds may occur in patients with chronically elevated intracranial pressure such as idiopathic intracranial hypertension, and may be associated with reduced visual acuity which can occasionally be permanent.

3Orbital disease such as retrobulbar tumours and thyroid ophthalmopathy may cause choroidal folds associated with impaired visual acuity.

4Ocular disease such as choroidal tumours, posterior scleritis, scleral buckling for retinal detachment, in association with hypotony maculopathy, and as an early sign of underlying CNV.

Diagnosis

1Presentation. The effect on vision is variable and dependent on the cause; many patients are asymptomatic, but some develop irreversible secondary degenerative retinal changes.

2Signs

•Parallel lines, grooves or striae typically located at the posterior pole. The folds are usually horizontally orientated (Fig. 14.68A).

•The crest (elevated portion) of a fold is yellow and less pigmented as a result of stretching and thinning of the RPE and the trough is darker due to compression of the RPE.

•Clinical examination should be directed towards the exclusion of optic disc swelling, as well as other ocular or orbital pathology.

3 OCT allows differentiation between choroidal, chorioretinal and retinal folds.

4FA shows hyperfluorescent crests as a result of increased background choroidal fluorescence showing through the stretched and thinned RPE and hypofluorescent troughs due to blockage of choroidal fluorescence by the compressed and thickened RPE (Fig. 14.68B); this facilitates distinction from retinal folds.

5Additional imaging. Ultrasound, CT or MR scanning of the orbits or brain may be indicated. In elevated intracranial pressure or acquired hypermetropia with choroidal folds, an enlarged perineural space may be noted on B-scanning and MR of the optic nerves.

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