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tournal ofNeurology, Neurosurgery, and Psychiatry 1996;60:275-280 275 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.60.3.275 on 1 March 1996. Downloaded from NEUROLOGICAL INVESTIGATIONS

Investigation of visual loss: neuro- from a neurologist's perspective

Christian J Lueck

A large proportion of the human nervous visual fields are performed carefully. system is devoted to receiving and processing visual information.' This means that the Optic nerveldisc potential for CNS disease to produce visual Although the classic pattern of loss disturbance of one sort or another is is a central , optic disease can enormous. The great advantage to the give rise to various field defects including arcu- clinician dealing with a visual disturbance is ate scotoma, centrocaecal scotoma, paracen- that the visual pathways are organised very tral scotoma, and altitudinal field defects. The precisely, with preservation of topographic pattern of monocular visual field loss is of lim- relation from through optic , ited utility in distinguishing one disease from chiasm, tracts, geniculate nuclei, radiations, another.6 Swelling of the head may and on into the .2 Hence, careful give rise to an enlarged . attention to visual field disturbance is likely to give a fairly precise clue as to what part of the is being affected. Compression of the central chiasm typically Because certain diseases are more likely to gives rise to a bitemporal hemianopia. There affect some parts of the visual system than oth- are, however, considerable variations on this, ers, it is often possible to narrow down a dif- including bitemporal partial field defects ferential diagnosis simply on the basis of site of (which may be considerably asymmetric), and lesion. This process of restricting the differen- junctional scotomata. It is important to exam- tial is further enhanced by knowing the time ine the upper temporal visual field of the course over which visual disturbance has "good eye" in a patient presenting with appar- developed. These two considerations make the ent unilateral visual loss. A binasal visual field

investigation of such disturbances much more defect has been reported to occur with side- http://jnnp.bmj.com/ straightforward. ways compression of the chiasm (in theory picking out the uncrossed fibres of each side), but this is rare.7 Damage to the whole optic Differential diagnosis ofvisual loss chiasm will, of course, give rise to total bilat- Visual loss has a wide differential diagnosis eral visual field loss. (table 1). Visual loss secondary to trauma, or longstanding, non-progressive visual loss (for Retrochiasmal lesions example, ),3 is not considered Congruity of homonymous defects tends to on September 30, 2021 by guest. Protected copyright. further here; nor is visual loss secondary to increase as the lesion becomes more posterior, diseases of the eye itself, to visible disturbance but this is by no means an absolute rule. of the retina, or secondary to psychogenic Lateral geniculate lesions tend to give rise to causes.4 "wedge hemianopias". Lesions in the can give rise to homonymous upper VISUAL FIELD LOSS or lower quadrantanopias. Assessment requires accurate visual fields.' lesions typically produce congruous hemi- anopias which may or may not be macular Retinaloptic disc sparing. If the lesion in the occipital lobe is Ophthalmoscopically visible lesions of the very posterior, it may spare the cortical repre- retina or are likely to produce focal sentation of the far lateral visual field, thereby scotomatous field loss. Patterns of visual field producing sparing of the temporal crescent of loss likely to be encountered by a neurologist the contralateral eye. and referable to disorders of the retina or include central visual field loss (macular TIME COURSE Department of Clinical lesion), concentric visual field loss, sectoral The temporal evolution of visual loss may be Neuroscience, Western visual field loss, altitudinal field loss, and arcu- divided into four groups: transient (reversible), General Hospitals ate scotomata. Bilateral macular sparing irreversible onset over seconds/minutes, Trust, Crewe Road, Edinburgh EH4 2XU, homonymous hemianopias may masquerade progressive onset over hours/days, or progres- UK as bilateral concentric field reduction. There is sive onset over days to months or longer. C J Lueck usually a small step at the vertical meridian if It may be difficult to be confident in allocat- 276 Lueck J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.60.3.275 on 1 March 1996. Downloaded from Table 1 Differential diagnosis ofvisual loss based on site and timing oflesion Site oflesion Transient Seconds to minutes Hours to days Days to months + Retinal : CRAO/BRAO "Phlebitis" Macular degenerations Thromboembolic CRVO/BRVO Ischaemia Hereditary retinal disease: Benign (young) pigmentosa Retinal Cone/rod dystrophies Photostress (ischaemia) Storage disorders (dystrophies) Neurodegenerative conditions Angle closure glaumoma Uveomeningeal syndromes Carcinoma associated Optic nerve/ AION (vasculitic) Abnormal fundus: Typical ON Compressive: optic disc Obscurations AION: Atypical ON: (papilloedema) Vasculitic Immune Thyroid Non-vasculitic Infective Aneurysm Leber's HON Leber's HON Granuloma Disc haemorrhage Neuroretinitis Paget's disease Paraneoplastic Infective/inflammatory: Big blind stop syndrome Toxic Neuroretinitis HTLV 1 (TSP) Optic nerve head Tuberculosis Normal fundus: Orbital/paranasal sinus infection PION (compressive lesion) Leber's HON Infiltrative Toxic/nutritional (B12) Hereditary neuropathy Chronic papilloedema Post irradiation AVM Optic disc dysplasia Optic chiasm Cystic tumours Pituitary tumour Compressive: Craniopharyngioma Ruptured AVM (pregnancy) Neoplasm Mucocele Pituitary abscess Sphenoidal mucocele Sphenoidal abscess Dilated IlIrd ventricle Demyelination Granuloma (sarcoid, TB) Adenohypophysitis Aneurysm Primary hypothyroidism Thalassaemia Postradiation damage Subacute/chronic meningitis Septo-optic dysplasia Empty sella syndrome Retrochiasmal TIA CVA: Demyelination Tumour: pathways Migraine Thromboembolic Cerebral abscess Intrinsic Haemorrhage Tumour Extrinsic Trauma (children) (tumour) Poisoning AVM Spasm (angiography) Meningitis Creutzfeldt-Jakob Migraine Encephalitis Pelizaeus-Merzbacher Impaired cerebral perfusion Metachromatic leukodystrophy Progressive multifocal leukoencephalopathy Subacute sclerosing panencephalitis Schilder's disease AION = anterior ischaemic ; AVM = arteriovenous malformation; BRAO = branch retinal artery occlusion; BRVO = branch retinal vein occlu- sion; CRAO = central retinal artery occlusion; CRVO = central retinal vein occlusion; CVA = cerebrovascular accident; HON = hereditary optic neuropathy; HTLV 1 = human T lymphocytic virus, type I; ON = optic ; PION = posterior ischaemic optic neuropathy; TB = tuberculosis; TIA = transient ischaemic attack; TSP = tropical spastic paraparesis. http://jnnp.bmj.com/

ing the patient's symptoms to one specific attack, would the whole face be normal or group, and more than one differential diagnos- would one half of it be affected? tic category may therefore have to be consid- Whether or not the transient visual field loss ered. A typical example of this would be when was referable to the eye or to the occipital cor- a patient awoke with visual loss in one eye- tex, preliminary investigations are similar,

this could have arisen suddenly over seconds looking for causes of transient ischaemic on September 30, 2021 by guest. Protected copyright. to minutes during the night, or, alternatively, attack.89 Such tests include haematological have developed over several hours. All possible (full blood count, erythrocyte sedimentation diagnoses in both groups would then have to rate, clotting) and biochemical (glucose, urea, be considered. and electrolytes, cholesterol) blood tests, chest radiography, ECG, and cranial CT. Depending on circumstances, other more spe- Investigation of visual loss cific tests may be indicated.89 TRANSIENT VISUAL LOSS IN ONE EYE Carotid ultrasound (Doppler or duplex) By definition, the visual fields will be normal examination is appropriate if the visual loss in relation to a transient attack. It is therefore affected one eye, if the patient would entertain crucial to try to determine the nature of the the idea of an endarterectomy. The degree of visual field disturbance on the basis of the his- stenosis must be more firmly established with tory. Patients are notoriously unable to tell the further imaging, such as selective carotid difference between visual disturbance in one angiography, but some centres are increasingly visual hemifield versus that in one eye (amaurosis using MR angiography.9 fugax), and it can be very difficult to sort this Amaurosis fugax may occasionally be the out. Apart from asking the patient whether harbinger of irreversible visual loss in patients alternate eye closure was attempted, it is often with .10 If there is any sugges- helpful to ask them what their vision was like tion of , jaw claudication, or general during the attack: I usually ask them if, were malaise, an erythrocyte sedimentation rate they to look directly at my face during an should be performed as an emergency. If it is Investigation ofvisual loss: neuro-ophthalmology from a neurologist's perspective 277 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.60.3.275 on 1 March 1996. Downloaded from not raised, but the story is suggestive, strong possibility of posterior ischaemic optic neu- consideration should be given to temporal ropathy should be considered, although this artery biopsy because up to 17% of cases are condition is rare.2 not associated with raised erythrocyte sedi- Usually, however, shows mentation rate.'0 changes which suggest a diagnosis, provided In young people, recurrent monocular the patient is seen within 24 hours of visual visual loss is often a benign condition, unasso- loss. Such diagnoses include retinal arterial ciated with an increased risk of . It is , venous occlusion, optic nerve head probably due to vascular spasm, and may be infarction (anterior ischaemic optic neuropa- pathogenetically related to migraine." It is thy), haemorrhage, or acute disc swelling. The usually regarded as a diagnosis of exclusion, last may be associated with sudden visual loss and only applicable after the above investiga- in acute papilloedema, or Leber's hereditary tions and imaging of the optic nerve or visual optic neuropathy. Visual disturbance with field pathways have come back negative."I 12 loss usually confined to an enlarged blind spot Obscurations are transient disturbances of can also be seen in diabetic papillopathy,'7 18 or vision which occur in association with papil- the big blind spot syndrome,219 although these loedema secondary to raised intracranial pres- conditions more commonly present with mini- sure of whatever cause. This usually results in mal visual symptoms. Table 2 lists the various bilateral visual symptoms, but if the papil- ophthalmoscopic findings seen in each of the loedema is unilateral, monocular symptoms above diagnoses. can result. Typically patients do not lose vision Table 2 also lists appropriate investigations. entirely (vision does not go "black"), but com- Certain points are amplified below. plain of greying of vision, often in association (1) If there are no abnormalities in the retina, with change in posture. In this situation, it is posterior ischaemic optic neuropathy is a pos- obviously mandatory to image the head (MRI sibility, but imaging the would be or CT13) to look for a cause of raised pressure. required to exclude a compressive lesion. If imaging shows no space occupying lesion, Other investigations would be similar to those lumbar puncture is indicated. There are many for anterior ischaemic optic neuropathy causes of a raised CSF pressure in the absence (AION).2 of a space occupying lesion (pseudotumour (2) The investigation of central retinal artery cerebri),3 but one important condition is sagit- occlusion is similar to that for amaurosis tal sinus thrombosis. Nowadays, this can often fugax,89 although local retinal causes such as be detected by MR angiography, but formal radiation retinopathy28 may contribute to its angiography may still be required, depending aetiology. on local facilities. This condition and its man- (3) In central retinal vein occlusion, search for agement have been dealt with in a recent edit- anticardiolipin antibodies is probably not orial in this Journal.'4 worthwhile unless the patient has other fea- There are a few unusual causes. Ocular tures of systemic erythematosus.2930 ischaemia can present with transient visual (4) Anterior ischaemic optic neuropathy may loss provoked by exposure to bright light (pho- be arteritic or non-arteritic. An erythrocyte

tostress). There are usually ophthalmoscopic sedimentation rate is required as an emer- http://jnnp.bmj.com/ changes to suggest the diagnosis, including gency, and, if any other feature suggests tem- peripheral exudates and haemorrhages, micro- poral arteritis, a temporal artery biopsy should aneurysms, and new vessels. A photostress be performed, even if the sedimentation rate is test3 is useful in this circumstance, and further normal (see above). The role of ophthalmic investigation will include carotid ultrasound colour Doppler is as yet undetermined, but it with tests as for amaurosis fugax. Transient may be of use in differentiating arteritic from visual disturbance provoked by changes in non-arteritic AION."32 In the absence of clini- ambient lighting can also be produced by reti- cal features of temporal arteritis or a raised on September 30, 2021 by guest. Protected copyright. nal diseases such as cone dystrophies, and erythrocyte sedimentation rate, biopsy is diagnosis can be aided by the use of elec- unlikely to be positive, and is therefore unnec- troretinography.51' Finally, if the diagnosis essarily invasive. The exception to this is in remains obscure, an attempt should be made bilateral simultaneous AION in which a large to measure during an proportion of patients have evidence of sys- attack as acute closed angle can temic connective tissue disease.2 In younger rarely present with transient visual loss.16 patients or those with bilateral disease, investi- gation for coagulation abnormalities is appro- SUDDEN, IRREVERSIBLE VISUAL LOSS IN ONE priate.24 The history may point to one of the EYE rarely-encountered associations between Conditions referable to primary ocular struc- AION and other diseases,2 but routine investi- tures such as acute angle closure glaucoma or gation beyond that indicated in table 2 is prob- vitreous haemorrhage will not be discussed ably not worthwhile unless it does. here. Nevertheless, it is likely that there will be (5) Neuroretinitis is generally thought of as a abnormalities on ophthalmoscopy to aid diag- relatively benign condition in which central nosis, especially if the patient is seen within a visual loss occurs over hours and is associated day or so of the acute event. If possible, with a central scotoma and a macular star on dilatation should be performed as failure to ophthalmoscopy.25 33 However, it may present perform this often results in missing ophthal- acutely, and have a poor prognosis.26 In this moscopic clues to diagnosis. If ophthal- situation, investigation should include tests for moscopy is completely normal, then the vasculitic and infective diseases (particularly 278 Lueck J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.60.3.275 on 1 March 1996. Downloaded from Table 2 Ophthalmoscopicfindings and investigations in acute monocular visual loss Condition Ophthalmoscopicfindings Appropriate investigations Central retinal Opacification of nerve fibre layer ESR artery occlusion Cherry spot Fluorescein angiography (Cholesterol) embolus/microemboli (as for amaurosis fugax) Attenuation of arterial tree Carotid ultrasound/angiography Central retinal Retinal venous dilatation FBC, ESR, fibrinogen, glucose vein occlusion20 21 Scattered retinal haemorrhages (several Lipid profile disc diameters from optic disc) (fluorescein angiography) (BP, intraocular pressure) AION Sectoral/complete optic disc swelling ESR, ? temporal artery biopsy Disc haemorrhages Fluorescein angiography Exudates/macular star FBC, fibrinogen, glucose (Small optic discs22) Protein electrophoresis (Buried drusen23) Lipid profile (coagulopathy screen24) Neuroretinitis25 26 Disc swelling, peripapillary exudates (As for AION) Macular star formation VDRL, ANA, serum angiotensin converting enzyme Possibly vitreous cells25 Viral titres, Lyme serology Leber's hereditary Circumpapillary telangiectatic Fluorescein angiography optic neuropathy microangiopathy Mitochondrial DNA (Non-oedematous) elevation of optic disc Infiltrative optic Optic disc swelling B mode ultrasonography neuropathy Haemorrhages/exudates MRI/CT, lumbar puncture; chest radiography Bence-Jones protein Serum angiotensin converting enzyme Bone marrow, abdominal CT Diabetic Disc swelling, usually bilateral Glucose, haemoglobin Al c papillopathy'7 18 Haemorrhages/exudates Fluorescein angiography Big blind spot Swollen optic disc (?absent) MRI/CT, lumbar puncture syndrome2 19 Venous overfilling, occasional haemorrhage Fluorescein angiography Multiple evanescent white dots27 ESR = erythrocyte sedimentation rate; AION = anterior ischaemic optic neuropathy; FBC = full blood count; VDRL = venereal disease research laboratory test; ANA = antinuclear antibody.

cat scratch fever) as well as those tests listed gested that the prognosis for going on to for AION, but in most cases investigation is develop is much less ifMRI is negative.26 otherwise normal than if it shows multiple (6) In Leber's hereditary optic neuropathy, lesions.40 For these reasons, it has been advo- fluorescein angiography shows peripapillary cated that all cases of typical telangiectasia and an apparently swollen disc should have MRI,4' but this remains contro- which paradoxically does not leak,34 although versial. There is no role for visual evoked these findings are not always present.35 This potentials, CT, or lumbar puncture in the finding should be followed by mitochondrial clinical management of typical isolated optic DNA analysis.35 Interestingly, there may be neuritis. surprisingly little by way of relative afferent If any of the features of typical optic neuritis

pupillary defect.36 is missing, both optic nerves are affected, there http://jnnp.bmj.com/ (7) Occasionally optic nerve head drusen can is no evidence of recovery after four weeks, or present as , often with inferior there are additional features, then further nasal field defect.23 This diagnosis is generally investigation is warranted. In the first instance, taken to be a diagnosis of exclusion after full it is appropriate to image the orbits, paranasal investigation in the form of CT/MRI, lumbar sinuses, sphenoid, and pituitary fossa to detect puncture, and investigations as for AION. The compressive lesions (which may have acutely drusen themselves may be more specifically decompensated) or infective processes such as detected by CT, MRI, fluorescein angiogra- paranasal sinus disease. As a first line investi- on September 30, 2021 by guest. Protected copyright. phy, or ocular ultrasound. 13 37 gation, enhanced orbital CT is proba- bly still the investigation of choice,'342 but OPTIC NERVE DEVELOPING OVER intrinsic and inflammatory optic nerve lesions HOURS TO DAYS are better shown on MRI,43 and both may be If a patient presents with the typical history required. Skull radiography is not useful in the and signs of optic neuritis, standard wisdom investigation of visual loss.44 Lumbar puncture has been that there is no need to image the is indicated if imaging does not yield a diagno- patient, provided there are no clinical features S1S. to suggest a diagnosis of multiple sclerosis.3 Previous or concurrent symptoms of infec- Recently, however, this view has been changed tive illness raise the possibility of viral, paravi- somewhat by two developments. Firstly, the ral, or postviral syndromes, or active bacterial recent optic neuritis trial suggested that or fungal infection. It is thus worth consider- patients with typical optic neuritis should be ing screening blood and CSF for viruses, bac- treated with intravenous methyl prednisolone terial infections, and fungal infections as (whatever the severity) as this significantly appropriate to the clinical picture. Optic neu- reduced the likelihood of progressing to diag- ritis has been reported in systemic lupus ery- nosable multiple sclerosis at two years38 thematosus, and other immune mediated (although the most recent report from the conditions such as Sjogren's syndrome and optic neuritis study group suggests that the ulcerative colitis.'2 If the optic neuritis is atypi- two year benefit is not maintained at three cal in any way, antinuclear antigen and anti- years39). Secondly, recent studies have sug- dsDNA antibodies, along with extractable Investigation ofvisual loss: neuro-ophthalmology from a neurologist's perspective 279 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.60.3.275 on 1 March 1996. Downloaded from nuclear antigen should be checked. possibly with the help of a toxicology screen. Perhaps the most common "lookalike" of If visual field testing suggests a lesion of the optic neuritis is sarcoidosis affecting the optic optic nerve and there is disc swelling on fun- nerve. Suspicion should be raised by failure of doscopy, further thought is required. the visual loss to improve, or any evidence of Papilloedema (disc swelling due to raised past or present iritis or . Initial investi- ) does not typically cause gation in the form of a chest radiograph, central visual field loss. Therefore, if there is serum angiotensin converting enzyme, and raised intracranial pressure, this must be due lumbar puncture is appropriate. Unfortu- to a structural cause which is associated with nately, Kveim testing is no longer available as a optic nerve disease/compression, but imaging diagnostic test. In the absence of any other should already have detected such a cause. If clinical features, my experience has been that imaging is normal and the discs are swollen, further tests such as pulmonary function tests the next test should be a lumbar puncture. In or gallium scans are unlikely to be rewarding, this circumstance, raised pressure should not but could be considered. be regarded as the cause of the visual loss. An About 20% of simultaneous bilateral optic alternative cause in the form of inflammatory neuritis in adults turns out to be due to disease such as sarcoidosis must be considered Leber's hereditary optic neuropathy, even in and investigated as above. Failing this, carci- the absence of affected relatives,45 and in this nomatous meningitis or direct optic disc infil- circumstance, mitochondrial DNA analysis tration by haematological malignancy should should be performed. A further 20% turn out be considered, and investigated appropriately. to be due to multiple sclerosis.45 Other possi- Hereditary optic neuropathies may be diag- bilities include toxic neuropathy. This could nosed on the basis of a positive family history, be due to medication the patient is taking, or but occasionally one can be surprised by the possibly to an external agent such as lead. way Leber's hereditary optic neuropathy pre- Serum lead, B 12, and a toxicology screen sents, and searching for the known mitochon- should be added to the above tests, along with drial DNA mutations is worthwhile at this careful questioning of the patient regarding point.35 drugs, diet, and work exposure. Two other reasons for progressive anterior pathway visual failure may have to be consid- OPTIC NERVE PATHOLOGY DEVELOPING OVER ered. Dysplasia of the optic disc may be associ- DAYS OR MONTHS ated with visual field disturbance. This is often In this situation, imaging is mandatory, and longstanding, but occasionally comes to the should include good views of the optic nerves attention of the patient and requires explana- (intraorbital, intracanalicular, and intracra- tion. Typical examples include tilted optic nial) including the pituitary fossa region. As discs, which are usually associated with super- mentioned, there is some debate as to whether otemporal field loss,2 or optic nerve head high quality enhanced orbital CT, or gadolin- drusen (hyaline bodies).48 Diagnosis of the ium enhanced MRI is superior as a first line second is suggested by anomalous optic disc investigation,'34243 but it is not uncommon for vasculature, and can be difficult, particularly if

both to be required eventually. Practically, it the drusen are buried. Help may be required http://jnnp.bmj.com/ depends on local facilities. Most lesions large in the form of fluorescein angiography (look- enough to cause visual loss by optic nerve ing for autofluorescence), or B mode ultra- compression will be visible, but it is not sonography.'3 37 Occasionally calcification of uncommon for optic nerve sheath menin- the optic nerve head can be seen on unen- giomas to be missed: repeated scans may be hanced CT. 13 37 necessary, and are especially indicated if there Finally, it is not unheard of for a neurologist is evidence of optic disc swelling or optociliary or neuro-ophthalmologist to be referred a on September 30, 2021 by guest. Protected copyright. shunt vessels on fundoscopy.46 patient who actually has an ophthalmological Further investigation of any lesion found diagnosis, even if the source of referral is an will, of course, depend on the nature of the ophthalmologist. The most common situation lesion. Imaging in the form of angiography in which this arises is that of a may be necessary, or it might be appropriate to being misdiagnosed as possible optic nerve proceed to biopsy. Likewise, thyroid function disease. It is always worth re-examining the tests may be appropriate, but these are often ocular fundus in the case of monocular visual normal in thyroid eye disease; the use of a disturbance, particularly if there is no associ- TRH test considerably improves the diagnos- ated relative afferent pupillary defect, so as not tic yield.47 to be led into inappropriate investigations. If imaging of the optic nerve fails to show a reason for the visual loss, infective and inflam- matory causes should be screened for with 1 Zeki S. A vision of the . Oxford: Blackwell, 1993. VDRL, HTLV I titres, serum angiotensin con- 2 Miller NR. Walsh and Hoyt's clinical neuro-ophthalmology. 4th ed. Vol 1. Baltimore: Williams and Wilkins, 1982. verting enzyme, and screen, and 3 Glaser JS. Clinical neuro-ophthalmology. 2nd ed. consideration should be given to an HIV test. Philadelphia: JB Lippincott, 1991. 4 Miller NR. Walsh and Hoyt's clinical neuro-ophthalmology Nutritional optic neuropathy can be screened 4th ed. Vol 5, part 2. Baltimore: Williams and Wilkins, for by checking folate and B12, in combina- 1985:4541-63. 5 Acheson JF, Sanders MD. Vision. J Neurol Neurosurg tion with a careful dietary history. Smoking, Psychiatty 1995;59:4-15. alcohol, drugs (prescribed, "recreational", or 6 Keltner JC, Johnson CA, Spurr JO, Beck RW, Optic Neuritis Study Group. Baseline visual field profile of otherwise-for example, ) are causes optic neuritis. The experience of the optic neuritis treat- of toxic amblyopia and must be looked for, ment trial. Arch Ophthalmol 1993;111:231-4. 280 Lueck J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.60.3.275 on 1 March 1996. Downloaded from

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