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

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•Dehydration may be significant, particularly in younger patients and in hot countries

Factors that appear to decrease the risk of venous occlusion include increased physical activity and moderate alcohol consumption.

Systemic assessment

All patients

1Blood pressure.

2 Erythrocyte sedimentation rate (ESR) or plasma viscosity (PV).

3Full blood count (FBC).

4Random blood glucose. Further assessment for diabetes if indicated.

5Random total and HDL cholesterol. Additional lipid testing may be considered.

6Plasma protein electrophoresis. To detect dysproteinaemias such as multiple myeloma.

7Urea, electrolytes and creatinine. Chronic renal failure is a rare cause of RVO, but renal disease may occur in association with hypertension.

8Thyroid function tests. Patients with RVO have a higher prevalence of thyroid disease than the general population. Thyroid dysfunction is also associated with dyslipidaemia.

9ECG. To detect left ventricular hypertrophy secondary to hypertension; required for the Framingham equation used in the calculation of cardiovascular risk.

Selected patients according to clinical indication

Patients in whom these might be considered are those under the age of 50, those with bilateral RVO, a history of previous thromboses or a family history of thrombosis, and possibly in other patients in whom investigation for the common associations is negative.

1 Chest X-ray. Sarcoidosis, tuberculosis, left ventricular hypertrophy in hypertension.

2C-reactive protein (CRP). Sensitive indicator of inflammation.

3'Thrombophilia screen’. By convention refers to heritable thrombophilias; might typically include thrombin time, prothrombin time and activated partial thromboplastin time, antithrombin functional assay, protein C, protein S, activated protein C resistance, factor V Leiden mutation, prothrombin G20210A mutation; anticardiolipin antibody (IgG and IgM), lupus anticoagulant.

4 Autoantibodies. Rheumatoid factor, anti-nuclear antibody, anti-DNA antibody.

5Serum angiotensin-converting enzyme (ACE). Sarcoidosis.

6Fasting plasma homocysteine level. To exclude hyperhomocysteinaemia.

7 Treponemal serology. Local testing preference should be discussed with the microbiology team.

8Carotid duplex imaging to exclude ocular ischaemic syndrome.

Branch retinal vein occlusion

Classification

1 Major branch retinal vein occlusion (BRVO) at the disc (Fig. 13.27A) and away from the disc (Fig. 13.27B).

2Macular BRVO involving only a macular branch (Fig. 13.27C).

3Peripheral BRVO not involving the macular circulation (Fig. 13.27 D-F).

Fig. 13.27 Classification of retinal branch vein occlusion according to site of blockage. (A) Major at the disc; (B) major away fromthe disc; (C) minor macular; (D–F) peripheral not involving the macula

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Diagnosis

1Presentation depends on the extent of macular circulation compromised by the occlusion. Patients with macular involvement often present with the sudden onset of blurred vision and metamorphopsia, or a relative visual field defect. Patients with peripheral occlusions may be asymptomatic.

2VA is very variable and is principally dependent on the extent of macular involvement.

3Fundus (Fig. 13.28A).

•Dilatation and tortuosity of the affected venous segment.

•The site of occlusion is often identifiable as an arteriovenous crossing point.

•Flame-shaped and dot/blot haemorrhages, retinal oedema, sometimes cotton wool spots affecting the sector of the retina drained by the obstructed vein.

4FA shows variable delayed venous filling, blockage by blood, staining of the vessel wall, hypofluorescence due to capillary nonperfusion and ‘pruning’ of vessels in the ischaemic areas (Fig. 13.28B).

5OCT demonstrates and allows quantification of the severity of macular oedema and is a useful way of monitoring its course or the response to treatment.

6Course. The acute features usually resolve within 6–12 months and may be replaced by the following:

•Exudates, venous sheathing and sclerosis peripheral to the site of obstruction, collaterals and variable residual haemorrhage (Fig. 13.29A).

•Collateral are characterized by slightly tortuous veins that develop locally or across the horizontal raphe between the inferior and superior vascular arcades and are best detected on FA (Fig. 13.29B).

•The severity of residual signs is highly variable and they may be only subtle.

Fig. 13.28 Major superior branch vein occlusion. (A) Flame-shaped and blot haemorrhage, a few cotton wool spots and venous tortuosity; (B) FA shows blockage by blood and areas of capillary non-perfusion

(Courtesy of C Barry)

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Fig. 13.29 Old major superior branch vein occlusion. (A) Venous sheathing, collaterals, exudates and residual haemorrhages; (B) FA shows capillary non-perfusion and tortuous collaterals extending across the horizontal raphe between the superior and inferior arcades

Prognosis

At 6 months about 50% of eyes achieve vision of 6/12 or better. Approximately 50% of untreated eyes with BRVO retain 6/12 or better whilst 25% will have vision of <6/60. The two main vision-threatening complications are:

1Chronic macular oedema is the most common cause of persistent poor visual acuity after BRVO. Patients with visual acuity of 6/12 or worse may benefit from laser photocoagulation, provided the macula is not significantly ischaemic.

2Neovascularization. Retinal neovascularization occurs in about 60% of eyes with more than 5 disc areas of non-perfusion (Fig. 13.30B) and a third with less than 4 disc areas – about 40% overall. NVE are considerably more common than NVD. NVE usually develops at the border of the triangular sector of ischaemic retina drained by the occluded vein. New vessels usually appear within 6 –12 months but may develop at any time; they can lead to recurrent vitreous and pre-retinal haemorrhage, and occasionally tractional retinal detachment.

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Fig. 13.30 Long-standing major superior branch vein occlusion. (A) Few residual haemorrhages and cotton wool spots; (B) FA shows extensive capillary nonperfusion that carries a high risk of neovascularization

Further management

Follow-up should be at about 3 months with FA, if vision is compromised, provided retinal haemorrhages have cleared sufficiently. Further management depends on visual acuity and angiographic findings.

•With good macular perfusion and improving visual acuity, no treatment is required.

•If macular oedema is associated with good macular perfusion and visual acuity continues to be 6/12 or worse after 3–6 months, laser photocoagulation should be considered. Patients with visual acuity of less than 6/60 or those with symptoms for over a year are unlikely to benefit from laser. Prior to treatment, the FA should be studied carefully to identify leaking areas.

•If macular non-perfusion is present and visual acuity is poor, particularly if FA shows an incomplete foveal avascular zone (FAZ), laser treatment is unlikely to improve vision.

•Subsequent follow-up: 3–6 monthly intervals for up to 2 years, dependent on clinical and FA findings, because of the risk of neovascularization.

Treatment of macular oedema

1Grid laser photocoagulation (50–100 µm, 0.1 second duration and spaced one burn width apart) to produce a gentle reaction in the area of leakage as identified on FA. The burns should extend no closer to the fovea than the edge of the FAZ and be no more peripheral than the major vascular arcades. Care should be taken to avoid treating over intraretinal haemorrhage. It is also very important to identify shunts/collaterals on FA, which do not leak fluorescein, because they must not be treated. Follow-up should take place after three months. If macular oedema persists, re-treatment may be considered although the results are frequently disappointing.

2Intravitreal triamcinolone (IVT) is as effective as laser in eyes with macular oedema, but may cause cataract and elevation of intraocular pressure. An average of 2 injections of 1 mg are given in the first year.

3Periocular steroid injection is less invasive, although probably less effective, than the intravitreal route.

4Intravitreal anti-VEGF agents. Bevacizumab (Avastin) 0.05 mL/1.25 mg) in a regimen of 2–3 injections over 5–6 months has shown promising effects on macular oedema and vision, including in patients resistant to laser.

5Arteriovenous sheathotomy. Some positive results have been reported both for sheathotomy and for vitrectomy alone; a randomized controlled trial showed similar benefit from IVT.

Treatment of neovascularization

Neovascularization is not normally treated unless vitreous haemorrhage occurs because early treatment does not appear to affect the visual prognosis. If appropriate, scatter laser photocoagulation (200–500 µm size, 0.05–0.1 s duration and spaced one burn width apart) is

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performed with sufficient energy to achieve a medium reaction covering the entire involved sector (Fig. 13.31) as defined by the colour photograph and FA. A quadrant usually requires 400–500 burns. Follow-up should be after 4–6 weeks. If neovascularization persists retreatment can be considered, and is usually effective in inducing regression.

Fig. 13.31 Laser photocoagulation for neovascularization following branch vein occlusion

(Courtesy of C Barry)

Impending central retinal vein occlusion

Impending (partial) CRVO is a relatively poorly-defined condition which may resolve or progress to complete obstruction.

1 Presentation is with mild blurring of vision which is characteristically worse on waking and improves during the day. 2 Signs. Mild venous dilatation and tortuosity with a few widely scattered flame-shaped haemorrhages (Fig. 13.32).

3FA shows increased retinal circulation time.

4OCT may facilitate a degree of objective monitoring of the macular course, if CMO is present.

5Treatment is aimed at preventing progression to complete occlusion by correcting any predisposing systemic conditions, avoiding dehydration, and lowering intraocular pressure (e.g. systemic carbonic anhydrase inhibitors) to improve perfusion. Antiplatelet agents may be of benefit, and in some circumstances such as monocularity in an otherwise healthy patient it may be appropriate to consider other options such as anticoagulants, fibrinolytics or haemodilution.

Fig. 13.32 Impending central retinal vein occlusion

Non-ischaemic central retinal vein occlusion

Non-ischaemic CRVO is the most common type, accounting for about 75%.

Diagnosis

1 Presentation is with sudden, unilateral blurred vision.

2VA is impaired to a moderate-severe degree.

3 Relative afferent pupillary defect (RAPD) is absent or mild (in contrast to ischaemic CRVO).

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4Fundus (Fig. 13.33A)

•Tortuosity and dilatation of all branches of the central retinal vein, dot/blot and flame-shaped haemorrhages, throughout all four quadrants and most numerous in the periphery.

•Cotton wool spots, optic disc and macular oedema are common.

5FA shows delayed arteriovenous transit time, blockage by haemorrhages, good retinal capillary perfusion and late leakage (Fig. 13.33B).

6OCT is useful in the assessment of CMO, as described for BRVO.

7Course. Most acute signs resolve over 6–12 months. Residual findings include disc collaterals (Fig. 13.34A), epiretinal gliosis and pigmentary changes at the macula. Conversion to ischaemic CRVO occurs in 15% of cases within 4 months and 34% within 3 years.

Fig. 13.33 Recent non-ischaemic central retinal vein occlusion. (A) Venous tortuosity and dilatation, and extensive flame-shaped haemorrhages; (B) FA late phase shows blockage by blood, staining of vessel wall but good capillary perfusion

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Fig. 13.34 Old non-ischaemic central retinal vein occlusion. (A) Disc collaterals and a few residual retinal haemorrhages; (B) FA late phase shows diffuse hyperfluorescence due to chronic macular oedema

(Courtesy of Moorfields Eye Hospital)

Follow-up

In a clearly non-ischaemic occlusion, initial follow-up should take place after 3 months. Defined arrangements for review of test results should be in place. The patient should be instructed to make contact if the vision deteriorates as this may indicate the development of significant ischaemia. Pain or redness (may indicate neovascular glaucoma and occasionally inflammation without rubeosis) should also be reported. Subsequent review is dependent on the clinical picture, with discharge from follow-up usually at 18–24 months.

Prognosis

In cases that do not subsequently become ischaemic, the prognosis is reasonably good with return of vision to normal or near normal in about 50%. The main cause for poor vision is chronic macular oedema (Fig. 13.34B), which may lead to secondary RPE changes. To a certain extent the prognosis is related to initial visual acuity as follows:

•6/18 or better, it is likely to remain so.

•6/24–6/60, the clinical course is variable, and vision may subsequently improve, remain the same, or worsen.

•Worse than 6/60, improvement is unlikely.

Treatment of macular oedema

Laser photocoagulation for macular oedema is not beneficial. Some of the following novel therapies have exhibited apparent significant benefit and may play an increasing role in management.

1Intravitreal steroid. The score study showed an improvement in the vision of 3 or more lines at one year in over 25% of patients treated with an average of 2 injections of 1 mg triamcinolone versus 7% of controls. A trial (GENEVA) of a 0.7 mg dexamethasone sustained-release biodegradeable intravitreal implant (Ozurdex®) showed substantial visual improvement over the first 2 months following a single implantation, though this declined to baseline by 6 months.

2Intravitreal anti-VEGF agents. Ranibizumab showed a significant visual benefit when used for CMO. Injections were given monthly for 6 months and subsequently less intensively. Several uncontrolled case series suggest that approximately 50% of patients improve 2 or more lines with intravitreal bevacizumab, with 90% of eyes achieving stabilization of vision by 12 months. Pegaptanib also shows promising results.

3Experimental treatments include chorioretinal anastomosis, vitrectomy with radial optic neurotomy or tissue plasminogen activator (rTPA) local infusion.

Ischaemic central retinal vein occlusion

Ischaemic CRVO is characterized by rapid onset venous obstruction resulting in decreased retinal perfusion, capillary closure and retinal

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hypoxia. This may lead to profound vascular leakage, rubeosis iridis and raised intraocular pressure. Neovascular glaucoma is one of the most common indications for enucleation in the Western world.

Diagnosis

1 Presentation is with sudden and severe visual impairment.

2 VA is usually CF or worse.

3RAPD is marked.

4Fundus (Fig. 13.35A)

•Severe tortuosity and engorgement of all branches of the central retinal vein, extensive deep blot and flame-shaped haemorrhages involving the peripheral retina and posterior pole, severe disc oedema and hyperaemia.

•Cotton wool spots are often prominent.

5FA shows marked delay in arteriovenous transit time, which is longer than 20 seconds, central masking by retinal haemorrhages, extensive areas of capillary nonperfusion and vessel wall staining (Fig. 13.34B). Greater than 10 disc areas of retinal capillary nonperfusion is associated with an increased risk of neovascularization.

6 OCT may be useful for monitoring the course of CMO, particularly for those cases when treatment is carried out.

7Electroretinogram (ERG) is depressed.

8Course. Most acute signs resolve over 9–12 months. Residual findings include disc collaterals and macular epiretinal gliosis and pigmentary changes. Rarely subretinal fibrosis resembling that associated with exudative age-related macular degeneration may develop.

Fig. 13.35 Recent ischaemic central retinal vein occlusion. (A) Extensive flame-shaped and deep blot haemorrhages; (B) FA shows extensive hypofluorescence due to capillary non-perfusion

Prognosis

The prognosis is extremely poor due to macular ischaemia. Rubeosis iridis develops in about 50% of eyes, usually between 2 and 4 months (100-day glaucoma), and there is a high risk of neovascular glaucoma. The development of opticociliary shunts (retinochoroidal collateral veins) may protect the eye from anterior segment neovascularization and probably indicates a dramatic reduction in risk. Retinal neovascularization occurs in about 5% of eyes and is therefore much less common than with BRVO.

Follow up

Where possible, patients with ischaemic CRVO should be seen monthly for 6 months to detect the onset of anterior segment neovascularization. Angle neovascularization (Fig. 13.36A), while not synonymous with progression to neovascular glaucoma, is the best clinical predictor of its development because it may occur in the absence of neovascularization at the pupillary margin (Fig. 13.36B). Routine gonioscopy of eyes at risk should therefore be performed and the pupillary margin should be examined prior to mydriasis. Prophylactic PRP

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is generally not recommended even with marked ischaemia unless iris new vessels develop, though may be considered in patients unlikely to attend scheduled review. Subsequent review should usually be for up to 2 years to detect significant ischaemia and macular oedema.

Fig. 13.36 (A) Neovascularization of an open angle; (B) rubeosis iridis at the pupillary border; (C) panretinal photocoagulation

(Courtesy of E Michael van Buskirk, from Clinical Atlas of Glaucoma, WB Saunders 1986 –fig. A)

Treatment of neovascularization

Laser PRP should be performed without delay in eyes with angle neovascularization or rubeosis iridis. This involves the application of 1500 –3000 burns (0.5–0.1 second, spaced one burn width apart), with sufficient energy to produce a moderate reaction in the periphery but avoiding areas of haemorrhage (Fig. 13.36C). Some cases require further treatment if rubeosis fails to regress or continues to progress. Intravitreal anti-VEGF injections may be used adjunctivally in selected cases.

Papillophlebitis

Papillophlebitis (optic disc vasculitis) is an uncommon condition which typically affects otherwise healthy individuals under the age of 50 years. It is thought that the underlying lesion is optic disc swelling with resultant secondary venous congestion rather than venous thrombosis occurring at the level of the lamina cribrosa, as occurs in older patients.

Diagnosis

1 Presentation is with mild blurring of vision typically worst on waking. 2 VA reduction is mild to moderate.

3RAPD is absent.

4Fundus (Fig. 13.37)

•Disc oedema, which may be associated with cotton wool spots, is the dominant finding.

•Also present are venous dilatation and tortuosity with variable amount of retinal haemorrhages, usually confined to the peripapillary area and posterior fundus.

5Blind spot is enlarged on perimetry.

6 FA shows mild delay in arteriovenous transit time, hyperfluorescence due to leakage and good capillary perfusion.

7OCT may show CMO.

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Fig. 13.37 Papillophlebitis

Prognosis

The prognosis is excellent despite the lack of treatment. Eighty per cent of cases achieve a final visual acuity of 6/12 or better. The remainder suffer significant and permanent visual impairment as a result of macular oedema.

Hemiretinal vein occlusion

Hemiretinal vein occlusion is generally regarded as a variant of CRVO and may be ischaemic or non-ischaemic. It is less common than both BRVO and CRVO and involves occlusion of the superior or inferior branch of the CRV. A hemispheric occlusion blocks a major branch of the CRV at or near the optic disc. A hemicentral occlusion, which is less common, involves one trunk of a dual-trunked CRV, which persists in the anterior part of the optic nerve head as a congenital variant.

1 Presentation is with a sudden onset altitudinal visual field defect.

2VA reduction is variable.

3 Fundus shows the features of BRVO, involving the superior or inferior hemisphere (Fig. 13.38A).

4FA shows masking by haemorrhages, hyperfluorescence due to leakage and variable capillary non-perfusion (Fig. 13.38B).

5Treatment depends on the severity of retinal ischaemia. Extensive retinal ischaemia carries the risk of neovascular glaucoma and should be managed in the same way as ischaemic CRVO. Macular oedema usually responds poorly to grid laser due to extensive foveal capillary shutdown; newer treatments may be effective in some cases.

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