대한안신경의학회지 : 제 2 권제 2 호 ISSN: 2234-0971 REVIEW 시야장애와시야검사 박지윤 전주예수병원신경과 Visual Field Defect and Visual Field Test Ji-Yun Park, MD Department of Neurology, Presbyterian Medical Center, Jeonju, Korea The art of examining the visual fields is valuable ophthalmic technique that allows investigation of each and every part of visual sensory pathways. Perimetric techniques are variable such as static perimetry, kinetic perimetry and confrontation test. The defects that are found can be interpreted as being in one particular are of the area of the visual system. This article provide an overview of these structures, detail methods of veisual field testing, then describe a framework for the localization and diagnosis of disorders affecting the afferent visual pathways. Keywords: Visual field tests; Visual pathways; Hemianopsia 서론시야장애는망막 (retina) 에서부터후두엽까지시각경로를침범하는다양한원인에의해발생할수있다. 이러한시각경로는각위치에서일정한규칙성을가지며배열되기때문에특정부위의병변은특징적인시야장애를나타내게된다. 따라서, 대면검사법 (confrontation test), 동적시야측정 (kinetic perimetry), 정적시야측정 (static perimetry) 등을통해서시야장애의형태를측정한다면병변의위치, 범위등을유추할수있으므로임상적으로중요한의미를갖는다. 본고는시각계의해부학적지식과시각계의특정병변에따른시야장애및시야측정방법에대해살펴보고자한다. 시각계의신경해부학 (Neuroanatomy of the visual pathways) 외부에서들어온시각자극은망막 (retina) 의광수용체 (photoreceptor) 에서과분극되어전기자극으로변환된후신경절세포의축삭인시신경섬유를통해전달된다. 망막의신경절세포는시신경유두에가까이분포할수록시신경의중앙부위에위치하게분포하게되고위코쪽, 아래코쪽, 위관자쪽, 아래관자쪽망막에서받아들인자극은시각교차에도착할때까지망막에해당하는부위와같이위치에서진행하게된다. 예를들어아래관자쪽시각영역에서들어오는빛은위코쪽망막에들어와시신경의위코쪽으로진행하며시각교차에도착하게된다. 시신경섬유는시신경유두 (optic disc) 에서사판 (lamina cribrosa) 을통과하여희소돌기아교세포 (oligodendrocyte) 에둘러싸여안구밖으로나오며시신경을형성한다 (Fig. 1). 공막 (sclera) 이뇌수막 (meninges) 과연결되며지주막하강 (subarachnoid space) 에서시신경을둘러싸여있어뇌압이증가하면시신경유두에영향을미치며시신경우두부종 (papilledema) 이발생하게된다. 양쪽눈의코쪽망막에서나온신경섬유들은시각교차 (optic chiasm) 에서교차하여반대편관자쪽망막에서나온섬유와만나서한 Correspondence to: Ji-Yun Park, MD Department of Neurology, Presbyterian Medical Center, 365 Seowon-ro, Wansan-gu, Jeonju 560-750, Korea Tel: +82-63-230-1572; FAX: +82-63-230-1578; E-mail: truejy@jesushospital.com Received: Nov. 12, 2012 / Accepted: Nov. 12, 2012 Copyright 2012 The Korean Society of Neuro-Ophthalmology http://neuro-ophthalmology.co.kr 71
Park J-Y Visual Field Defect and Visual Field Test 쪽시각로 (optic tract) 를이룬다. 이러한이유로뇌하수체종양과같은 시각교차병변에의한시야결손은양관자쪽반맹 (bitemporal heminaopsia) 이관찰될수있다. 이때교차대비교차섬유는 53:47 로교차 하는섬유가더많다. 아래코쪽망막에서온배쪽 (ventral) 축삭은교 차후반대쪽시신경쪽으로약간굽어달린후뒤로향하게된다 (wilbrand s knee). 1 Wilbrand 무릎이손상되면편측단안시야결손과반대 쪽눈의위관자쪽사분맹이생길수있다 (junctional scotoma). 가쪽무릎체 (lateral geniculate body) 는시상베게 (pulvinar) 로부터돌 출된작은타원형의융기부이다. 가쪽무릎체는여섯개의세포층으 로구성되며시각로의축삭이이곳에서연접한다. 가쪽무릎체를구 성하는신경세포의축삭은시각부챗살 (optic radiation) 을형성한다. 시각부챗살은뒤로진행하여속섬유막 (internal capsule) 의렌즈핵 뒤부분 (retrolenticular part) 을통과하여시각겉질 (visual cortex, 영역 17) 에서끝난다. 시각겉질인새발톱피질 (calcarine cortex) 은대뇌반구 의안쪽면에위치하는새발톱고랑 (calcarine sulcus) 의윗입술과아랫 입술에위치한다. 시각겉질의뒷부분은황반부위의중심시야를담당 하고, 앞부분 8-10% 는반대측눈의측두쪽으로 60-90 에해당하는말 초부위의시각자극만을관여한다. 시각연합영역 ( 영역 18, 19) 은사물 과색깔인식에관여한다. Temporal 귀쪽 Fields of vision 시야 Nasal Nasal 코쪽코쪽 Temporal 귀쪽 시야검사 (Visual field testing) 시야검사는환자의주관적표현을바탕으로결과를얻게되므로검사를시작하기전, 환자가잘이해할수있도록검사방법을설명함으로써정확하게검사를수행할수있도록하는게중요하다. 대면검사 (confrontation test) 는환자와검사자가 50-100 cm의거리를두고마주본후환자는검사자의오른쪽눈을, 검사자는환자의왼쪽눈을주시한다 (Fig. 2). 2 두사람의중간지점에서검사자의손가락을주변에서중심으로점차이동시켜시표를두사람이동시에볼수있다면환자의주변시야는정상이다. 이검사법은검사자의시야가정상이라는전제아래환자의시야와비교하는것으로쉽게빨리측정할수있으나, 시야결핍을재는능력과검사의민감성은자동화된시야검사기구로표적과조명을표준화하고컴퓨터로가동되는프로그램에비해미흡하며, 만약대변검사로이상이발견되면시야계를사용해서검사해야한다. 3 각각의시야측정방법의장단점은 Table 1에기술되어있다. 1. 동적시야측정 (kinetic perimetry) 시야계반구의반지름은 330 mm가표준이고그원의중심에눈이오도록되어있다. 이를확인할수있는대표적인시야계로는골드만시야계로 (Fig. 3), 2 암실에서일정한조명하에검사한다. 환자는편하게앉아머리를고정하고한쪽눈을가린다음다른눈으로는정면의점을주시한다. 적당한시표를주변부에서중심부로움직여 (1초동안 5 Cerebral peduncle 대뇌다리 Macula 황반 Optic nerve 시각신경 Optic chiasma 시각교차 Optic tract 시각로 A C Lateral geniculate body 가쪽무릎체 Optic radiation 시각로부챗살 B Left visual cortex 왼쪽시각겉질 Fig. 1. Anatomy of the visual pathway. Visual cortex 시각겉질 Right visual cortex 오른쪽시각겉질 Fig. 2. Confrontation testing of the visual field (A) maintenance of fixation is essential (B) bimanual testing of the visual field: The examiner closes the eye that is directly opposite to the eye the patient has closed and uses the field of his or her open eye s monocular perception as a basis for comparison to the patient s visual field, while presenting visual stimuli in the opposing portion of the patient s visual field. (C) Counting of fingers held to either side of the vertical meridian tests the central visual field with relatively smaller test objects, as compared with the bimanual tests. 72 http://neuro-ophthalmology.co.kr
시야장애와시야검사 박지윤 Table 1. Advantages, disadvantages, and most appropriate neuro-ophthalmic uses of computerized threshold, Goldmann kinetic, and tangent screen kinetic perimetry Advantages Disadvantages Best neuro-ophthalmic uses Computerized threshold Reproducible More objective More standardized Less reliance on a technician Interechnician variability less important Lengthy Tedious Optic neuropathy Papilledema Chiasmal disorders Repeated follow-up Goldmann kinetic Short Driven by technician or doctor Skilled perimetrist or physician can focus attention on suspected defect areas More subjective Depends on the skills of the perimetrist Retrochiasmal disorders Neurologically impaired patients Patients who are unable to do a computerized field test Severe visual loss Functional vision loss Tangent screen kinetic Short Can be performed in the examination room Central 30 only Central field defects Functional visual loss a b c d e f A B A B Fig. 3. (A) Goldmann kinetic perimetry and (B) normal goldmann kinetic field of the right eye. 가량 ) 환자에게시표가보일때신호를하게한다. 시표의크기와밝기 를다르게하여반복측정한뒤검사용지에그린다. 비교적많은시간 이소요되며검사자의숙련도에따라검사결과에차이가많다는단 점이있다. Fig. 4. (A) Humphrey computerized perimeter and (B) normal Humphrey computerized visual field of the right eye. Note (a) the tabulation of the fixation losses and false-positive and -nagative errors; (b) the raw data, recording the luminance, given in decibels (db), of the dimmest stimulus the subjective saw at that position in the visual field; (c) the gray scale, containing a conversion of the raw data using the key at the bottom of the readout; (d) the total deviation; (e) the pattern deviation; and (f) the statistical analysis, including the mean deviation (MD). 2. 정적시야측정 (static perimetry) 다양한크기와밝기의시표를정해진위치에놓고비추어서시표가보이면환자에게누르게한다. 전산화된자동시야계는프로그램에정해진대로환자가예측하지못하는방향에서검사시표를자동적으로보여주고환자의반응결과를기록한다. 환자의반응에따라검사시표의밝기를자동적으로조절하여반복검사함으로써특정시야에서감도역치 (sensitivity threshold) 를찾아내어명암도나망막감도의역치로출력한다. 험프리 (Humphrey) (Fig. 4) 와옥토퍼스 (Octopus) 가대표적인자동시야계이다. 자동시야계검사는검사자의숙련도에크게의존하지않으며재현성 (reproducibility) 이뛰어나다. 검사결과가저장되어자동적으로다음검사결과와비교분석할수있다. 또동적시야검사에서놓치기쉬운국소암점을더잘찾아낼수있다. 시야검사결과협착 (contraction), 감도저하, 암점 (scotoma) 등으로인한시야결손이나타나면시야장애가있다고본다. 1) 협착협착은시야의주변부경계를이루는이솝터들이정상시야의것보다좁아져서중심쪽으로이동한경우로, 좁아져서보이지않게된시야결손부위에서는시표의색이나크기에관계없이보이지않는다. 협착은모든방향에서일어나동심원같이좁아진도심협착뿐만아니라반맹에서처럼부분협착의형태를보인다. 2) 감도저하시야장애의대부분이이에속하며, 정상시야의이솝터에해당하는시표는환자에게보이지않고이보다크거나강한시표라야보이게된다. 감도저하는전반적저하 (general depression) 와국소적저하 (local depression) 로나뉜다. 전반적저하는각막혼탁, 백내장, 유리체혼탁등눈의매체혼탁시에볼수있는시야장애로시력이중심부를포함한시야의모든곳에서감퇴되어모든이솝터가정상보다좁아져 http://neuro-ophthalmology.co.kr 73
Park J-Y Visual Field Defect and Visual Field Test Table 2. Visual fields defects Monocular field defects Fig. 5. Visual pathways: correlation of lesion site and field defect, view of underside of the brain. 있다. 국소적저하는시야장애의가장흔한형태이며, 주변시야의어 느한부분에서발생하면해당이솝터는찌그러진형태를취하고시 야범위내에서발생하면암점의형태를나타난다. 시각경로를따라발생한질환에의한협착이나감도저하를보이는 시야결손의형태는다양하다. 시야결손 (Visual field defect) 해부학적위치에따라반맹 (hemianopsia) 과협착, 사분맹 (quadrantanopsia), 수평반맹 (altitudinal defect), 중심옆 (paracentral) 암점, 중심 (central) 암점, 주시점맹점 (cecocentral), 활꼴 (arcuate) 암점등다양한 시야결손의형태가나타나게된다 (Fig. 5). 망막의손상으로인한시야 결손은대부분검안경검사상이상소견이동반되며, 대부분의시신 경이상은시력저하를동반한다. 따라서시력이보존되어있는시야장 애가관찰되면망막이상이나시신경이후의병변을의심해보아야한 다. 4 이러한시야결손은크게단안성 (monocular), 양안성 (binocular), 접합부 (junctional) 세가지로구분될수있다 (Table 2). 5 1. 단안성시야결손 (monocular visual field defect) 단안성시야결손은일측눈이나시신경의병변을의미하지만, 드물 게시신경교차초기병터나, 6 측두초승달증후군 (temporal crescent syndrome) 에서관찰될수있으므로주의가필요하다. 황반, 망막또는 Localized defects Wedge-shaped temporal field defect Arcuate and paracentral field defects Central scotoma or depression Enlarged physiologic blind spot Centrocecal scotoma or depression Equatorial annular scotoma or depression Altitudinal hemianopia Generalized defects Generalized depression or peripheral contraction Binocular field defects Homonymous Hemianopias Complete: macular splitting Incomplete congruous: horizontal sectoranopia Incomplete congruous: paramidline-sparing vertical hemianopia Incomplete: macular sparing Incomplete: two scotomas Incomplete: incomgruous Incomplete: unilateral sparing of temporal crescent Incomplete: unilateral defect of temporal crescent Bitemporal hemianopias Complete With central depression, scotomatous Binasal field defects Complete Incomplete Altitudinal field defects Noncongrous and monocular Congruous Quadrantanopias Superior homonymous, incomplete Inferior homonymous, complete Bilateral central fields defects Scotoma or depression Bilateral peripheral field defects Generalized depression or peripheral contraction Bilateral checkerboard scotomas Bilateral homonymous hemianopias Junctional field defects Complete monocular plus Bitemporal hemianopia plus 시신경의병터는암점 (scotoma) 이한시야주변까지확대되는시야장애를유발한다 (Fig. 6). 유두황반다발의손상은중심암점, 주시점맹점암점, 4 중심옆암점이발생할수있다. 활꼴암점, 코쪽결손 (nasal defect), 코쪽계단 (nasal step) 형암점은유두황반다발중활꼴섬유 (arcuate fiber) 의손상을의미하며측부쐐기결손 (temporal wedge defect) 형암점 74 http://neuro-ophthalmology.co.kr
시야장애와시야검사 박지윤 Fig. 6. Diagrammatic representation of the retinal layers, disposition of fibers in the nerve fiber layer and optic nerve, and visual field defects caused by retinal or optic nerve lesions. The vertical bars (a, b, c) represent partial (a) to complete (c) retinal lesions; the corresponding field defects are depicted underneath retinal lesions affecting the nerve fiber layer have an arcuate shape with the base located peripherally and, in temporal retinal lesions, in the horizontal meridian. 은코쪽방사섬유 (nasal radiating fiber) 의손상을의미한다. 수평반맹 은짧은후섬모체동맥 (short posterior ciliary artery) 의침범에의한허 혈성시신경병에서종종관찰되나시신경이상과관련된어떤시야결 손에서도같은양상으로발생할수있다. 7 2. 양안성시야결손 (binocular visual field defect) 양안성시야결손은임상적으로단일병변이라면시신경교차 (optic chiasm) 이후의병변을의미한다. 양측두반맹 (bitemporal hemianopia) 은시신경교차에서교차되는양측망막의코쪽절반에서유래된 시각섬유가압박을받으며발생한다. 시신경교차는뇌하수체바로위 에위치하고있기때문에뇌하수체종양, 빠르게진행하는수두증, 동 맥류 (suprasellar aneurysm), 두개인두종 (cranipharngioma), 안장결절 (tuberculum sellae) 의수막종등의압박에의해발생한다. 8 병터의위치 가앞쪽에위치한다면중심시야결손이동반될수있으며, 시각로를 포함한뒤쪽에위치한다면동측반맹이함께동반되어나타날수있 다. 아래코쪽망막 (inferior nasal retina) 에서기원하는시각신경섬유는 시각로에서교차할때반대쪽시각신경의전방으로향했다가다시뒤 로돌아간다 (wilbrand s knee). 1 따라서시각신경과시각신경교차가만 나는부위의병터에서는시각신경병터로인한같은쪽눈의중심암점 (central scotoma) 과함께반대쪽문의위관자쪽사분맹 (superior temporal quadrantanopia) 이동반될수있다 (junctional scotoma, 이음부암점 ). 동측반맹 (homonymous hemianopia) 은교차후방부시각경로의병터를시사하고, 반대족시각로 (optic tract), 가쪽무릎체 (lateral geniculate body), 시각로부챗살 (optic radiation), 후두엽의병변에의해발생한다. 양측눈의시야결손모양이정확히일치하지않는불일치시야결손 (incongruous field defect) 은양측시신경이최종적으로만나는후두엽병터에서비교적멀리있는시각로다는것을의미한다. 반면에양측눈의시야장애모양이동일하다면일치시야결손 (congruous field defect) 을의미하며새발톱피질 (calcarine cortex) 에비교적가까이위치한병변을시사한다. 가쪽무릎핵 (lateral geniculate nucleus) 은독특한혈관분포로인해특징적인시야장애가발생한다. 앞쪽맥락막동맥 (anterior choroidal artery) 의허혈이발생하는경우가쪽무릎핵의가쪽과안쪽말단 (lateral and medial tips) 의병변으로수평경선주위를제외한위, 아래시야의결손 (quadruple sectoranopia) 이발생하며 9 가쪽후맥락막동맥 (lateral posterior choroidal artery) 의허혈이발생하는경우가쪽무릎핵의문 (hilum) 과중간영역 (middle zone) 의병변으로수평경선을포함하는쐐기모양의시야결손 (wedge-shaped horizontal homonymous sector defect) 이발생한다. 10 측두엽이나새발톱고랑 (calcarine fissure) 의아래쪽에병변이있을때는상동측사분맹 (superior homonymous quadrantanopsia, pie-in-the-sky field defects) 이나타나며, 시각로부챗살의위쪽이나새발톱고랑의위쪽에병변이있을때는하동측사분맹 (inferior homonymous quadrantanopsia) 이나타난다. 정상적으로시야의중앙으로부터측두쪽으로 60-90 는동측측두쪽망막으로부터시각자극이들어오지않는단안영역 (monocular field) 으로측두초승달모양 (temporal crescent) 이라하는데, 줄무늬피질의전방부위가담당하고있는데이곳의병터가발생하는경우시신경교차 (optic chiasm) 이후병변중유일하게단안성시야결손을보이는측두초승달중후군 (temporal crescent syndrome) 이발생하게된다. 새발톱피질 (calcarine cortex) 이나후두엽병터인경우이론적으로일치시야결손 (congrunous field defect) 이발생하여야하나실제로시야결손이전적으로일치하는경우는드물다. 중심시야를담당하는후두부피질의뒷부분은비교적영역이넓고일부는중뇌동맥에서혈류를공급받으므로일측후두엽의병터의경우황반에해당하는시야가남아있는황반보존 (macular sparing) 이발생할수있다. 3. 이음부암점 (junctional field defects) 완전단안시야장애를동반한불완전시야장애 (complete monocular plus incomplete contralateral ocular field defects) 는양측눈이나시신경의이상, 시신경교차부위와일측시신경이음부병터에서관찰될수있으며, 동측반맹을동반한이음부암점은시각로와시신경교차 http://neuro-ophthalmology.co.kr 75
Park J-Y Visual Field Defect and Visual Field Test 이음부병터에서발생할수있다. 양귀쪽반맹을동반한이음부암점은시신경교차와시신경이음부병터에서발생할수있다. 아래코쪽망막 (inferior nasal retina) 에서기원하는시신경섬유는시신경교차부의앞쪽에서교차하는축삭이반대쪽시신경전방으로약간굴곡을이룬 (Wilbrand s knee) 후시각로로주행하는데이부위의시신경과시신경교차가만나는부위의병터에서는시신경병터로인한동측눈의중심암점 (central scotoma) 과함께반대쪽눈의상측두사분맹 (superior temporal quadrantanopia) 이동반되는이음부암점 (junctional scotoma) 으로나타난다. 결론시야장애가있더라도대부분은시력저하가동반되지않으므로환자가증상을호소하지않더라도문진시시야장애를묻고측정하는습관은중요하다. 시야장애는대면검사의경우쉽고빨리측정할수있으나, 시야결핍을재는능력과검사의민감성이떨어지므로의심되는경우시야검사기구를사용해야한다. 편리하게많이사용하는험프리같은정적시야측정의경우간편하고재현성이뛰어나지만, 30 정도의중심시야만측정할수있으므로말초시야의장애를놓칠수있어필요한경우골드만시야계같은동적시야측정을고려해보아야한다. REFERENCES 1. Horton JC. Wilbrand s knee of the primate optic chiasm is an artefact of monocular enucleation. Trans Am Ophthalmol Soc 1997;95:579-609. 2. Schiefer U, Wilhelm H, Hart W, Hoyt WF. Clinical Neuro-Ophthalmology: A Practical Guide: Springer, 2007. 3. Liu GT, Volpe NJ, Galetta SL. Neuro-Ophthalmology: Diagnosis and Management. Oxford: Elsevier Limited, 2010. 4. Frisén L. Clinical tests of vision. Raven Press, 1990. 5. Walsh T. Visual Fields: Examination and Interpretation. New York: Oxford University Press, 2010. 6. Hershenfeld SA, Sharpe JA. Monocular temporal hemianopia. Br J Ophthalmol 1993;77:424-427. 7. Hayreh SS, Zimmerman B. Visual field abnormalities in nonarteritic anterior ischemic optic neuropathy: their pattern and prevalence at initial examination. Arch Ophthalmol 2005;123:1554-1562. 8. Newman RP, Kinkel WR, Jacobs L. Altitudinal hemianopia caused by occipital infarctions. Clinical and computerized tomographic correlations. Arch Neurol 1984;41:413-418. 9. Helgason C, Caplan LR, Goodwin J, Hedges T 3rd. Anterior choroidal artery-territory infarction. Report of cases and review. Arch Neurol 1986; 43:681-686. 10. Luco C, Hoppe A, Schweitzer M, Vicuna X, Fantin A. Visual field defects in vascular lesions of the lateral geniculate body. J Neurol Neurosurg Psychiatry 1992;55:12-15. 76 http://neuro-ophthalmology.co.kr