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

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Ocular ischaemic syndrome

Pathogenesis

Ocular ischaemic syndrome (OIS) is an uncommon condition which is the result of chronic ocular hypoperfusion secondary to severe ipsilateral atherosclerotic carotid stenosis of more than 90%, resulting in a 50% reduction of ipsilateral perfusion pressure. It typically affects patients during the 7th decade and may be associated with diabetes, hypertension, ischaemic heart disease and cerebrovascular disease. The male : female ratio is about 2 : 1. Five year mortality is in the order of 40%, most frequently from cardiac disease. Patients with ocular ischaemic syndrome may also give a history of amaurosis fugax due to retinal embolism.

Diagnosis

OIS is unilateral in 80% of cases. It affects both anterior and posterior segments. The signs are variable and may be subtle such that the condition is missed or misdiagnosed.

1Presentation is usually with gradual loss of vision over several weeks or months although occasionally visual loss may be sudden or fleeting (amaurosis fugax). Ocular and periocular pain may also be present (40%). Patients may notice unusually persistent afterimages, or worsening of vision with sudden exposure to bright light (‘bright light amaurosis fugax’), with slow adaptation. The prognosis for vision is often very poor, though patients with better acuity at presentation are more likely to retain this. About 25% will deteriorate to ‘light perception’ by the end of 1 year.

2Anterior segment

•Diffuse episcleral injection and corneal oedema.

•Aqueous flare with few if any cells (ischaemic pseudoiritis).

•Iris atrophy and a mid-dilated and poorly reacting pupil.

•Rubeosis iridis is common, developing in up to 90%, and often progresses to neovascular glaucoma; the IOP may remain low due to poor ocular perfusion.

•Cataract in advanced cases.

3Fundus

•Venous dilatation, arteriolar narrowing, and haemorrhages and occasionally disc oedema (Fig. 13.48A) and cotton wool spots.

•Proliferative retinopathy with NVD and occasionally NVE.

•Spontaneous arterial pulsation, most pronounced near the optic disc, is present in most cases or may be easily induced by exerting gentle pressure on the globe (digital ophthalmodynamometry).

•Macular oedema can occur.

•In diabetic patients retinopathy may be more severe ipsilateral to carotid stenosis.

4FA

•Early phase shows delayed choroidal filling and prolonged arteriovenous transit time (Fig. 13.48B and C).

•Late phase shows disc and perivascular hyperfluorescence, and leakage at the posterior pole (Fig. 13.48D).

5 Carotid imaging may involve duplex scanning, digital subtraction angiography, MR or CT angiography.

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Fig. 13.48 Ocular ischaemic syndrome. (A) Venous dilatation, arteriolar narrowing, a few scattered flame-shaped haemorrhages and hard exudates, and disc oedema; (Band C) FA early phase shows delayed choroidal filling and prolonged arteriovenous transit; (D) FA late phase shows disc and perivascular hyperfluorescence, and spotty hyperfluorescence at the posterior pole due to leakage

(Courtesy of Moorfields Eye Hospital)

Management

1 Anterior segment manifestations are treated with topical steroids and mydriatics.

2Neovascular glaucoma may be treated medically or surgically (see Ch. 10).

3Proliferative retinopathy can be treated with PRP although the outcome is considerably less certain than in proliferative diabetic retinopathy.

4Macular oedema may respond to intravitreal steroid or anti-VEGF agents, or to carotid surgery.

5Carotid surgery. Endarterectomy or stenting may be performed to reduce the risk of stroke, may be beneficial for proliferative retinopathy and neovascular glaucoma, and may help to stabilize vision. Endarterectomy cannot be performed where there is total obstruction; extracranial-intracranial arterial bypass surgery is sometimes carried out. It should be noted that an increase in ocular perfusion following surgery can sometimes be associated with both a rise in intraocular pressure and exacerbation of neovascularization.

6Investigation and management of cardiovascular risk factors in conjunction with the appropriate medical specialists is essential. OIS is occasionally the only manifestation of marked systemic vascular disease. Full investigation should be carried out, broadly similar to that for retinal arterial occlusion.

Differential diagnosis

1Non-ischaemic CRVO also exhibits unilateral retinal haemorrhages, venous dilatation and cotton wool spots. However, haemorrhages are more numerous and mainly flame-shaped, and disc oedema is often present. Ophthalmodynamometry may help in distinguishing OIS from CRVO, as the arterial pressure is normal or high in the latter.

2Diabetic retinopathy also features dot and blot retinal haemorrhages, venous tortuosity and proliferative retinopathy. However, it is usually bilateral and hard exudates are present.

3Hypertensive retinopathy is also characterized by arteriolar attenuation and focal constriction, haemorrhages and cotton wool spots. However, it is invariably bilateral and venous changes are absent.

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Hypertensive disease

Retinopathy

Retinopathy consists of a spectrum of retinal vascular changes that are pathologically related to both transient and persistent microvascular damage from elevated blood pressure. The primary response of the retinal arterioles to systemic hypertension is narrowing (vasoconstriction). However, the degree of narrowing is dependent on the amount of pre-existing replacement fibrosis (involutional sclerosis). For this reason, hypertensive narrowing is seen in its pure form only in young individuals. In older patients, rigidity of retinal arterioles due to involutional sclerosis prevents the same degree of narrowing seen in young individuals. In sustained hypertension the inner blood–retinal barrier is disrupted in localized areas, with increased vascular permeability.

Signs

1Arteriolar narrowing may be focal (Fig. 13.49A) or generalized (Fig. 13.49B). Ophthalmoscopic diagnosis of generalized narrowing is difficult, although the presence of focal narrowing makes it highly probable that blood pressure is raised. It appears that the presence of arteriolar narrowing is a risk factor for coronary disease in women.

2Cotton wool spots develop in severe hypertension (Fig. 13.50A).

3Vascular leakage leads to flame-shaped retinal haemorrhages and retinal oedema. Chronic retinal oedema may result in the deposition of hard exudates around the fovea in the layer of Henle with a macular star configuration (Fig. 13.50B). Swelling of the optic nerve head is the hallmark of malignant (accelerated) hypertension.

4Arteriolosclerosis involves thickening of the vessel wall characterized histologically by intimal hyalinization, medial hypertrophy and endothelial hyperplasia (Fig. 13.51A). The most important clinical sign is the presence of changes at arteriovenous crossings (AV nipping – Fig. 13.51B); although not necessarily indicative of the severity of hypertension, their presence makes it probable that hypertension has been present for many years. Mild changes at arteriovenous crossings are seen in patients with involutional sclerosis in the absence of hypertension. The presence of generalized retinal arteriolar narrowing and possibly arteriovenous nipping are related to previously elevated blood pressure, independent of current blood pressure level. The grading of arteriolosclerosis is shown as follows (Fig. 13.52):

Grade 1: subtle broadening of the arteriolar light reflex, mild generalized arteriolar attenuation, particularly of small branches, and vein concealment.

Grade 2: obvious broadening of the arteriolar light reflex and deflection of veins at arteriovenous crossings (Salus sign).

Grade 3:

•‘Copper-wiring’ of arterioles (Fig. 13.51C).

•Banking of veins distal to arteriovenous crossings (Bonnet sign).

•Tapering of veins on both sides of the crossings (Gunn sign) and right-angled deflection of veins.

Grade 4: ‘Silver-wiring’ of arterioles associated with grade 3 changes.

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Fig. 13.49 Hypertensive retinopathy. (A) Focal arteriolar attenuation; (B) generalized arteriolar attenuation

Fig. 13.50 Severe hypertensive retinopathy. (A) Cotton wool spots, a few flame-shaped haemorrhages and arteriolosclerosis; (B) cotton wool spots, macular star and mild disc swelling

(Courtesy of P Saine – fig. A)

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Fig. 13.51 Arteriolosclerosis. (A) Histology shows a thickened vessel wall and narrowing of the lumen; (B) arteriovenous nipping; (C) ‘copper-wiring’

(Courtesy of J Harry – fig. A).

Fig. 13.52 Grading of retinal arteriolosclerosis

Choroidopathy

Choroidopathy is rare but may occur as the result of an acute hypertensive crisis (accelerated hypertension) in young adults.

1Elschnig spots are small black spots surrounded by yellow halos (Fig. 13.53A) which represent focal choroidal infarcts.

2Siegrist streaks are flecks arranged linearly along choroidal vessels (Fig. 13.53B) indicative of fibrinoid necrosis associated with malignant hypertension (Fig. 13.53C).

3Exudative retinal detachment, sometimes bilateral, may occur in severe acute hypertension such as that associated with toxaemia of pregnancy.

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Fig. 13.53 Hypertensive choroidopathy. (A) Elschnig spots; (B) Siegrist lines; (C) fibrinoid necrosis in a choroidal arteriole in malignant hypertension

(Courtesy of J Harry – fig. C)

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Sickle-cell retinopathy

Sickling haemoglobinopathies

Sickling haemoglobinopathies are caused by one or more abnormal haemoglobins which induce the red blood cell to adopt an anomalous shape (Fig. 13.54) under conditions of hypoxia and acidosis. Because these deformed red blood cells are more rigid than healthy cells, they may become impacted in and obstruct small blood vessels. The sickling disorders in which the mutant haemoglobins S and C are inherited as alleles of normal haemoglobin A have important ocular manifestations. These abnormal haemoglobins may occur in combination with normal haemoglobin A or in association with each other as indicated below.

1SS (sickle-cell disease, sickle-cell anaemia) affects 0.4% of black Americans and is caused by a point mutation on the betaglobulin gene. The disease is characterized by severe chronic haemolytic anaemia and periodic potentially fatal, crises due to vasoocclusive disease involving most organs, resulting in liver necrosis, painful crises (largely bone marrow infarcts), abdominal pain, acute chest syndrome and CNS symptoms. Despite the severity of systemic manifestations ocular complications are usually mild and asymptomatic.

2AS (sickle-cell trait) is present in about 10% of black Americans. It is the mildest form and usually requires severe hypoxia or other abnormal conditions to produce sickling.

3SC (sickle-cell C disease) is present in 0.2% of black Americans. It is characterized by haemolytic anaemia and infarctive crises that are less severe than in SS disease but may be associated with severe retinopathy.

4SThal (sickle-cell thalassaemia) is characterized by mild anaemia but may be associated with severe retinopathy.

Fig. 13.54 Several sickle red cells and one nucleated red cell in a peripheral smear of a patient with homozygous (HbSS) sickle cell anaemia

(Courtesy of N Bienz)

Proliferative retinopathy

Diagnosis

The development of proliferative retinopathy is usually insidious, and patients remain asymptomatic unless vitreous haemorrhage or retinal detachment occurs.

Stage 1 shows peripheral arteriolar occlusion and ischaemia.

Stage 2 is characterized by peripheral arteriovenous anastomoses of dilated pre-existing capillary channels (Fig. 13.55A).

Stage 3

•Sprouting of new vessels from the anastomoses; these have a ‘sea-fan’ configuration and are usually fed by a single arteriole and drained by a single vein (Fig. 13.55B and see Fig. 13.56A).

•About 30–40% of sea-fans involute spontaneously as a result of auto-infarction and appear as greyish fibrovascular lesions (Fig. 13.55C). Involution most frequently occurs about 2 years after the development of retinopathy.

Stage 4. The neovascular tufts may continue to proliferate and bleed into the vitreous (Fig. 13.55D).

Stage 5 is characterized by extensive fibrovascular proliferation (Fig. 13.55E) and retinal detachment (Fig. 13.55F).

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Fig. 13.55 Progression of proliferative sickle-cell retinopathy. (A) Peripheral arteriovenous anastomosis; (B) ‘sea-fan’ neovascularization; (C) spontaneous involution of a neovascular tuft; (D) haemorrhage due to traction; (E) extensive fibrovascular proliferation; (F) peripheral retinal detachment

(Courtesy of K Nischal – fig. A; R Marsh – figs B–F)

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Fig. 13.56 (A) Proliferative sickle-cell retinopathy stage 3; (B) FA early phase shows filling of new vessels (sea-fans) and extensive peripheral retinal capillary nonperfusion; (C) late phase shows leakage fromnew vessels

FA in stage 3 shows filling of sea-fans and peripheral capillary non-perfusion (Fig. 13.56B) followed by extensive hyperfluorescence due to leakage from new vessels (Fig. 13.56C).

Treatment

Treatment is not required in most cases because new vessels tend to auto-infarct and involute spontaneously without treatment. PRP probably does not alter the natural history. Occasionally vitreoretinal surgery may be required for tractional retinal detachment and/or persistent vitreous haemorrhage.

Differential diagnosis of peripheral retinal neovascularization

1Vascular disease with ischaemia

•Proliferative diabetic retinopathy.

•Branch retinal vein occlusion.

•Ocular ischaemic syndrome.

•Sickling haemoglobinopathies.

•Retinopathy of prematurity.

•Familial exudative vitreoretinopathy.

•Chronic myeloid leukaemia.

•Encircling buckle.

2Inflammatory disease with possible ischaemia

•Sarcoidosis.

•Retinal vasculitis.

•Intermediate uveitis.

•Eales disease.

•Acute retinal necrosis.

3Miscellaneous

•Incontinentia pigmenti.

•Autosomal dominant vitreoretinochoroidopathy.

•Long-standing retinal detachment.

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Non-proliferative retinopathy

Asymptomatic lesions

1 Venous tortuosity is one of the first ocular signs of sickling and is due to peripheral arteriovenous shunts.

2‘Silver-wiring’ of arterioles in the peripheral retina which represents previously occluded vessels.

3‘Salmon patches’ are pink, preretinal (Fig. 13.57A) or superficial intraretinal haemorrhages at the equator, which lie adjacent to arterioles and usually resolve without sequelae.

4‘Black sunbursts’ are patches of peripheral RPE hyperplasia (Fig. 13.57B).

5Macular depression sign is an oval depression of the bright central macular reflex due to atrophy and thinning of the sensory retina.

6Peripheral retinal holes and areas of whitening similar to ‘white-without-pressure’ are occasionally seen (Fig. 13.57C).

Fig. 13.57 Non-proliferative sickle-cell retinopathy. (A) Preretinal haemorrhage (‘salmon patch’); (B) RPEhyperplasia (‘black sunburst’) and preretinal haemorrhages;

(C) retinal hole and an area of whitening superiorly; (D) FA shows macular ischaemia

(Courtesy of J Donald M Gass, from Stereoscopic Atlas of Macular Diseases, Mosby 1997 – fig. B)

Symptomatic lesions

1 Macular arteriolar occlusion occurs in about 30% of patients (Fig. 13.57D).

2 Acute CRAO is rare.

3 Retinal vein occlusion is uncommon.

4 Choroidal vascular occlusion may occasionally be seen, particularly in children. 5 Angioid streaks occur in a minority of patients.

Anterior segment features

1Conjunctival lesions are characterized by isolated dark red vascular anomalies shaped like commas or cork screws. They involve small calibre vessels and are most often located inferiorly.

2Iris lesions consist of circumscribed areas of ischaemic atrophy, usually at the pupillary edge and extending to the collarette. Rubeosis may occasionally be seen.

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