안구운동 장애에 대한 실험적 연구 : 수직 Saccade계의 특성

Abstract

[한글]

Saccade안구운동은 안운동신경원의 방출이 펄스-스텝으로 변화할 때 발생되며 방정중뇌교 망상체에서의 방출에 의해 일정한 시간적 간격으로 계속 연결된다.

Saccade운동의 특징은 안구가 새로운 위치로 도달하는 과정에 있어 감속을 동반하나 비교적 일정하고 빠른 가속운동을 하는데 있으며 이때의 최대속도는 빠른 가속운동을 정량적으로 표시하는데 있어 지표가 되어왔다. Saccade속도는 수의적으로 변화시킬 수 없기

때문에 정상보다 감소된 속도는 외안근의 운동장애를 의미하며 안구운동을 제어하는 신경기전을 침범하는 질환들의 임상소견이라고 할 수 있다.

지금까지의 안구운동 제어계와 관련되는 많은 연구의 대부분은 수평안구운동에 국한되어 왔다. 이는 수평안구운동시에는 보는 범위가 넓고 외안근의 독립적 작용으로 이에 대한 연구분석이 더 용이했기 때문이다. 수평 saccade계에 대한 연구는 국내외적으로 이미 많은 연구가 있었으나 수직 saccade계의 특성에 관한 연구는 이렇다할 보고가 없다.

본 연구는 인간에 있어 안구운동 장애가 수직 saccade계에 미치는 영향을 추구한 실험적 연구로 첫째, 수직 saccade계의 특성이 수평 saccade계의 특성과 동일 범주내에 있는가를 알기 위하여 정상수직 saccade의 특성을 측정하였으며 둘째로는 외안근마비가 올 수 있는 약물인 sodium secobarbital을 전신적으로 투여하였을 때 발생되는 수직saccade계의 변화를 측정하였다. 측정범위는 비교적 광범위한 각변위 10°와 20°로 정하였으며 안구운동의 형태 및 saccade최대속도에 중점을 두고 추구하였고 본 연구결과의 응용성과 전망에 대해서도 검토하였다.

안구운동을 측정하기 위하여 안구운동 모니터, 시표발생장치, 기록기, 기타 각종 고정장치와 부대장치로 측정시스템을 구성하고 4명의 건강한 한국성인을 피검자로 선정하여 1주 간격으로 2회씩 동일한 실험을 암실에서 실시하였다. 기록지에서 saccade의 위치, 최

대속도와 수정운동등을 면밀히 관찰하였고 데이터는 통계적으로 처리하였으며 t-검정을 거쳐 5%의 의미있는 값을 구하여 다음과 같은 실험결과를 얻었다.

1. 정상수직 saccade평균최대 속도값과 sodium secobarbital투여 후 수직 saccade평균최대속도변화는 각각 수평 saccade계 와 유사하다.

2. 정상수직 saccade평균최대속도는 각변위 10°에서 279.3±34.2deg/sec이고 20°에서 427.8±47.4deg/sec이며, 상하운동방향에 따른 차이는 없다.

3. Sodium secobarbital 투여시

1) 수직 saccade계는 장애를 받아 최대속도는 감소하고 빈번한 수정운동이 발생된다.

2) 수직 saccade평균최대속도는 시간경과에 따라 점점 감소하여 30∼60분에서의 감소율은 각변위간에 차이없이 정상값의 1/3정도다.

3) 각변위 20° 상하운동시 상방운동은 하방운동보다 느리다.

4. 본 연구의 방법과 결과는 안구운동 장애를 일으키는 질병의 진단과 예후에 유효하게 응용될 수 있다고 생각한다.

The Experimental Study of Oculomotor Dysfunction-The Properties of the Vertical

Saccadic System in Humans

Young Jae Hong, M.D.

Department of Medical Science, The Graduate School, Yonsei University

(Directed by Professor Ouk Choi)

Saccadic eye movements are the product of pulse-step changes of ocular motor

neuronal discharges and are time-linked to discharges in the paramedian pontine

reticular formation.

The saccade is characterized by a rapid acceleration to a relatively constant

high velocity followed by a less rapid deceleration to the new eye position. The

peak velocity is used as a quantitative index of a rapid acceleration.

Since saccade velocity cannot be voluntarily altered, any observed slowing

indicates extraocular motor dysfunction and substantiates the clinical sign of

disease involving the neuronal mechanisms controlling eye movements.

Most of the work which has been done on modeling the eye movement control system

has involved only the horizontal eye movement control system. The horizontal eye

movements seem easier to analyze because of the greater observable horizontal

ranges and the assumption of an independent extraocular muscle system for

horizontal eye movement.

Many investigators have reported the properties of horizontal saccades around the

world but any available reports about the vertical saccadic eye movements are few

until now.

The aim of this study is to investigate the effects of oculomotor dysfunction on

the human vertical saccadic system. To evaluate the properties of vertical saccadic

system, the author measured normal vertical saccadic eye movements and compared

them with normal horizontal saccadic eye movements. Then sodium secobarbital which

produces paralysis of extraocular muscle was systemically administered and the

changes in the vertical saccadic eye movements were measured. The measurement of

range of angular distance is 10 and 20 degrees for the vertical saccadic eye

movement. The results are discussed in terms of the type of eye movements and

saccadic peak velocity as well as of future prospects for clinical and research

tools.

The experimental apparatus consisted of Biometrics Eye Movement Monitor,

oscillographic recorder, target function generator and other fixation devices. All

4 experimental subjects were healthy Korean adults. All experiments were performed

in a darkened room twice at one week intervals under the same procedure. The eye

position signals were measured in terms of peak velocity and corrective movement.

The data were analyzed statistically for significant change with the use of

t-test at the 5 per cent level and the main results are as fellows:

1. The average vertical saccadic peak velocity in normal and in sodium

secobarbital administered group is similar to the average horizontal saccadic peak

velocity.

2. The average vertical saccadic peak velocity is 279.3± 34.2deg/sec in the

angular distance of 10 degrees and 427.8±47.4deg/sec in the angular distance of 20

degrees, and shows no difference between upward and downward eye movement in normal

subjects.

3. In the group administered with sodium secobarbital,

1) The vertical saccadic system is suppressed. The peak velocity is reduced and

abnormal corrective movements are frequently produced.

2) The vertical saccadic peak velocity decreases with the lapse of time; within

30∼60 minutes after sodium secobarbital administration, the peak velocity is

reduced to approximately 1/3 of the normal value regardless of the angular

distance.

3) The upward eye movement is slower than the downward movement in the angular

distance of 20 degrees.

4. The author feels that the methods and results of this study may be useful

tools in diagnosis and prognosis of the diseases involving oculomotor dysfunction.

[영문]

Saccadic eye movements are the product of pulse-step changes of ocular motor neuronal discharges and are time-linked to discharges in the paramedian pontine reticular formation.

The saccade is characterized by a rapid acceleration to a relatively constant high velocity followed by a less rapid deceleration to the new eye position. The peak velocity is used as a quantitative index of a rapid acceleration.

Since saccade velocity cannot be voluntarily altered, any observed slowing indicates extraocular motor dysfunction and substantiates the clinical sign of disease involving the neuronal mechanisms controlling eye movements.

Most of the work which has been done on modeling the eye movement control system has involved only the horizontal eye movement control system. The horizontal eye movements seem easier to analyze because of the greater observable horizontal

ranges and the assumption of an independent extraocular muscle system for horizontal eye movement.

Many investigators have reported the properties of horizontal saccades around the world but any available reports about the vertical saccadic eye movements are few until now.

The aim of this study is to investigate the effects of oculomotor dysfunction on the human vertical saccadic system. To evaluate the properties of vertical saccadic system, the author measured normal vertical saccadic eye movements and compared

them with normal horizontal saccadic eye movements. Then sodium secobarbital which produces paralysis of extraocular muscle was systemically administered and the changes in the vertical saccadic eye movements were measured. The measurement of range of angular distance is 10 and 20 degrees for the vertical saccadic eye movement. The results are discussed in terms of the type of eye movements and saccadic peak velocity as well as of future prospects for clinical and research tools.

The experimental apparatus consisted of Biometrics Eye Movement Monitor, oscillographic recorder, target function generator and other fixation devices. All 4 experimental subjects were healthy Korean adults. All experiments were performed in a darkened room twice at one week intervals under the same procedure. The eye

position signals were measured in terms of peak velocity and corrective movement.

The data were analyzed statistically for significant change with the use of t-test at the 5 per cent level and the main results are as fellows:

1. The average vertical saccadic peak velocity in normal and in sodium secobarbital administered group is similar to the average horizontal saccadic peak velocity.

2. The average vertical saccadic peak velocity is 279.3± 34.2deg/sec in the angular distance of 10 degrees and 427.8±47.4deg/sec in the angular distance of 20 degrees, and shows no difference between upward and downward eye movement in normal subjects.

3. In the group administered with sodium secobarbital,

1) The vertical saccadic system is suppressed. The peak velocity is reduced and abnormal corrective movements are frequently produced.

2) The vertical saccadic peak velocity decreases with the lapse of time; within 30∼60 minutes after sodium secobarbital administration, the peak velocity is reduced to approximately 1/3 of the normal value regardless of the angular distance.

3) The upward eye movement is slower than the downward movement in the angular distance of 20 degrees.

4. The author feels that the methods and results of this study may be useful tools in diagnosis and prognosis of the diseases involving oculomotor dysfunction.