When junior physicians encounter ophthalmoplegia or oblique muscle hyper or deficiency, they are often confused in determining the damaged muscle or its innervated nerve because they have had little contact with patients. Not knowing how to proceed. Through repeated study and combined with clinical experience, I summarize the following, hoping to help young physicians: Zhang Hongwen, Ophthalmology Department, Jixian People’s Hospital, Tianjin, China
Review of relevant knowledge
The six diagnostic eye positions of both eyes and the six pairs of spouse muscles: ① to the right: right external straight, left internal straight; ② to the left: left external straight, right internal straight; ③ to the right: right superior straight, left inferior oblique; ④ to the left: left superior straight, right inferior oblique; ⑤ to the right: right inferior straight, left superior oblique; ⑥ to the left: left inferior straight, right superior oblique. Only one of the six pairs of spousal muscles in both eyes can be identified as having a problem by the six diagnostic eye positions. It is necessary to identify the monocular-damaged eye to further find the damaged pair of muscles.
The six diagnostic eye positions of the monocular eye with the six extraocular muscles: ① Inward – ronchoschisis. (2) outward – external rectus; (3) supra-nasal – inferior oblique; (4) infra-nasal – superior oblique; (5) superior temporal – superior rectus; (6) inferior temporal – inferior rectus. These six diagnostic eye positions are both diagnostic eye positions for the six extraocular muscles and pathologic eye positions in the case of extraocular muscle damage, where diplopia symptoms or abnormal position of the eye are most evident.
There are two important eye positions and two extraocular muscles in monocular eyes: (1) supra-nasal-inferior oblique muscle; and (2) infra-nasal-supra oblique muscle.
The specific methods are as follows.
1. Determine the pathological eye position: identify the eye position with the most obvious functional impairment (or the direction of greatest deviation of the compound image from the gaze) among the nine eye positions (tic-tac-toe method), which is the pathological eye position.
2. Determine the damaged eye: Use the peripheral object method to determine. When a colored translucent film is placed in front of one eye, the objects of the two eyes can be distinguished, and the eye that sees a larger object in the upper, lower, left, or right side is the damaged eye.
The method used in the diagnosis of vertical strabismus to distinguish the superior oblique muscle in one eye from the superior rectus muscle paralysis in the opposite eye
The first step is to determine the high and low position of both eyes. If the right eye is high and the left eye is low, then the right eye has paralysis of the inferior rotator muscle (superior oblique or inferior rectus); or the left eye has paralysis of the superior rotator muscle (superior rectus or inferior oblique).
The second step is to determine which side has the greatest vertical deflection when gazing to the side. The direction of gaze on the side with the greatest deflection is the direction where the direction of force of the paralyzed muscle is at the smallest angle to the visual axis – the ipsilateral rectus muscle; the contralateral oblique muscle.
Examples.
(1) vertical deflection is greatest when gaze is directed toward the side of low eye position: ipsilateral superior rectus muscle; contralateral superior oblique muscle.
(1) If the vertical deflection is greatest when the right side is high and the left side is low, then the paralyzed muscle is the left (ipsilateral) superior rectus or the right (contralateral) superior oblique muscle.
(2) If the right side is low and the left side is high, and the vertical deflection is maximum when gazing to the right side, then the paralyzed muscle is the right (ipsilateral) superior rectus or the left (contralateral) superior oblique muscle.
2. Maximum vertical deflection when gazing to the side with high eye position: ipsilateral inferior rectus muscle; contralateral inferior oblique muscle. (1) Right high, left low, right high, left low.
(1) High right and low left, with maximum vertical deflection when gazing to the right side, suggesting that the paralyzed muscle is the right (ipsilateral) inferior rectus muscle or the left (contralateral) inferior oblique muscle.
(2) Low right and high left, with maximum vertical deflection when gazing to the left, suggesting that the paralyzed muscle is the left (ipsilateral) inferior rectus or the right (contralateral) inferior oblique muscle.
The third step is to do a head tilt test (Bielschowsky head tilt test) so that the head is tilted to the side of the higher eye, and the vertical deflection increases, which is a positive head tilt test, a key step in the identification of the superior oblique muscle and the superior rectus muscle of the opposite eye.
1. Positive – the paralyzed muscle is the ipsilateral supraocular oblique muscle
2. Negative – the paralyzed muscle is the contralateral rectus oculi muscle
3. Identify the damaged muscles: identify all the muscles that have a role (force-giving) in the pathological eye position. Then, identify the muscle from which the direction of force is at the smallest angle to the visual axis of the eye (that eye position is the diagnostic eye position for that extraocular muscle), and it is the damaged muscle.
In most cases, the damaged muscles that are not easily identified are the superior and inferior oblique muscles, and the four angular positions in the tic-tac-toe method are the most important. The role of the extraocular muscles varies with the angle to the visual axis as the eye leaves the first eye position.
There is a pair of mate muscles in both eyes, is it the oblique muscle of one eye or the rectus muscle of the other eye that is damaged? Regardless of the eye position, the traction of the rectus muscle is strong, so, by comparison, symptoms of paralysis or hyperactivity of the rectus muscle are going to be relatively more pronounced in more than one eye position; whereas symptoms of paralysis or hyperactivity of the oblique muscle tend to be most pronounced only in the eye position where its action is at the smallest angle to the eye axis (the diagnostic eye position).
For example: the superior oblique muscle – its primary action is internal rotation; its secondary action is inferior and external rotation. However, its diagnostic eye position is inferior to the nose. That is, the direction of force of the superior oblique muscle is smallest in relation to the angle of the visual axis only when the eye is turned to the lower part of the nose!
When turning the eye inferiorly to the nose, while the internal rectus and inferior rectus muscles pull the eye to turn inward and downward, only the superior oblique muscle then gives force to turn the eye inferiorly to the maximum position for optimal coordination.
Due to the synergy of both eyes, the contralateral eye turns outward and downward, at this time, the inferior rectus muscle has the smallest angle with the direction of the eye’s visual axis and is the best direction of force, therefore, the inferior rectus muscle of the contralateral eye is the main muscle. However, regardless of the eye position, the traction force of the rectus muscle is strong, therefore, in comparison, the symptoms of paralysis or hyperactivity of the rectus muscle should be manifested in several eye positions; while the symptoms of paralysis or hyperactivity of the oblique muscle tend to be manifested only in the eye position where the angle between its force and the eye’s visual axis is minimal (diagnostic eye position).
When the superior oblique muscle is paralyzed, the rotation of the affected eye to the lower part of the nose (diagnostic eye position) is limited, and the position of the affected eye is high in that eye position, while the opposite is true when the superior oblique muscle is hyperactive, and the position of the affected eye is low in that eye position.
As an example.
The first step is to determine the pathological eye position: the patient’s diplopia is most severe when gazing down to the right. In this case, the right eye is turned to the lower temporal area and the left eye is turned to the lower nasal area.
In the second step, the damaged eye is identified: a red glass slide is placed in front of the patient’s right eye and the red image (right eye) is found to be clear and the colorless image (left eye) is lower than the red image and faint. This indicates that the left eye cannot be turned to the best position in that direction of gaze – high eye position – low and vague object (non-central gaze) – the left eye is a peripheral object eye – damaged eye.
The third part, determine the damaged muscle: for the left eye, there are three muscles acting together: the internal rectus, the inferior rectus, and the superior oblique muscle in the eye position below the nose, and the superior oblique muscle has the smallest angle between the direction of force and the visual axis! Thus, the superior oblique muscle of the left eye is the damaged muscle.
It is important to note that there is significantly more extraocular muscle paralysis than extraocular muscle hyperactivity. The inferior nasal eye position is observed for the superior oblique muscle for a single eye. For the damaged eye is the left eye, this eye position, if higher than the right eye, indicates the presence of left superior oblique muscle or right superior rectus muscle paralysis; conversely, if the left eye is lower than the right eye, it indicates the presence of left superior oblique muscle or right superior rectus muscle hyperactivity.
Another example: the inferior oblique muscle – its primary role is external rotation; its secondary role is superior and external rotation. Its diagnostic eye position is above the nose. In other words, only when the eye is turned above the nose, the direction of the force of the inferior oblique muscle is at the smallest angle to the visual axis! At this time, the primary role of the inferior oblique muscle is upward rotation, and the external rotation role is almost zero.
When turning the eye to the top of the nose, only the lower oblique muscle can give force again when the inner rectus and upper rectus muscles are pulling the eye to turn inward and upward, in order to make the eye turn to the top of the nose to the maximum position and achieve the best coordination.
Due to the synergy of both eyes, the contralateral eye turns to the superior temporal, at this time, the superior rectus muscle has the smallest angle with the direction of the eye’s visual axis and is the best direction of force, therefore, the superior rectus muscle of the contralateral eye is the main muscle.
The same reason as the upper oblique muscle dysfunction: the traction force of the rectus muscle is strong regardless of the eye position, therefore, in comparison, the symptoms of paralysis or hyperactivity of the rectus muscle have to be expressed in several eye positions; while the symptoms of paralysis or hyperactivity of the oblique muscle tend to be expressed only in the eye position where its force is at the smallest angle to the eye axis (diagnostic eye position).
When the inferior oblique muscle is paralyzed, the rotation of the affected eye toward the upper nose (diagnostic eye position) is limited, and the position of the affected eye is lower than that of the contralateral eye in this eye position, while the opposite is true when the inferior oblique muscle is hyperactive, and the position of the affected eye is higher than that of the contralateral eye in this eye position.
As an example.
In the first step, determine the pathological eye position: the patient’s right upper gaze has the greatest separation of the diplopia image, when the right eye is turned to the superior temporal and the left eye to the superior nasal.
In the second step, the damaged eye is identified: a red glass slide is placed in front of the patient’s right eye, and the red image (right eye) is found to be clear, and the colorless image (left eye) is higher than the red image and falsely larger. This indicates that the left eye cannot be turned to the best position in that direction of gaze – low eye position – high and defocused object (non-central gaze) – the left eye is a peripheral object eye – damaged eye.
The third part, to determine the damaged muscle: for the left eye, there are three muscles acting together: the internal rectus muscle, the superior rectus muscle and the inferior oblique muscle in the eye position above the nose, and the direction of the force of the inferior oblique muscle is at the smallest angle to the visual axis! Thus, the inferior oblique muscle of the left eye is the damaged muscle.
It remains to be noted that there is significantly more extraocular muscle paralysis than extraocular muscle hyperactivity. The supranasal eye position is observed for the inferior oblique muscle for a single eye. At this point the right eye cornea is above the temporal and the left eye cornea is above the nasal. At this point, if the left eye is lower than the right eye, it means that there is paralysis of the left inferior oblique muscle or the right inferior rectus muscle; conversely, if the left eye is higher than the right eye, it means that there is hyperactivity of the left inferior oblique muscle or the right inferior rectus muscle.
Rough determination of the degree of oblique muscle paralysis and hyperactivity.
1. observation during diagnostic eye position: if inconsistency in the position of the inferior corneal limbus can be observed, it is noted as paralysis or hyperactivity (+), or if there is clearly a high or low, it is noted as paralysis or hyperactivity (++).
2. Observation during lateral gaze at the eye position: if a high or low inferior corneal edge can be observed, it is noted as paralysis or hyperacusis (++++).
If you want to quantify it, check the synoptic machine and measure the amount of binocular deviation in these two eye positions separately.
The method I propose does not conflict with the Parks three-step method, my method is actually also a three-step method, and whether there is a problem vertically or horizontally, it can be analyzed from a single eye only, especially if the binocular hypermetropia is not obvious, monocular analysis is easier to determine the pathological eye position and further identify the damaged muscle:.
Step 1 – Determine the pathological eye position: identify the eye position with the most obvious functional impairment (or the direction of gaze with the largest deviation of the diplopia) among the nine examined eye positions (tic-tac-toe method), which is the pathological eye position.
Step 2: Determine the damaged eye: Use the peripheral object method to determine. Place a colored light-transmitting film in front of one eye to distinguish between the two eyes, and any eye that sees a larger object in the upper, lower, left, or right side is the damaged eye.
Step 3: Determine the damaged muscles: find all the muscles that have a role (force-giving) in the pathological eye position of the damaged eye. Then, identify the muscle with the smallest angle between the direction of force and the visual axis of the eye (the eye position is the diagnostic eye position of the extraocular muscle), which is the damaged muscle.
With the Parks three-step method.
A method used in the diagnosis of vertical strabismus to identify whether it is the superior oblique muscle of one eye or the superior rectus muscle of the contralateral eye that is paralyzed. 3 steps is a progressive method of elimination. It is particularly applicable when the high and low position of both eyes is obvious.
In the first step, the high and low position of both eyes is determined first. For example, if the right is high and the left is low, it suggests paralysis of the inferior rotator muscle (superior oblique or inferior rectus) of the right eye; or paralysis of the superior rotator muscle (superior rectus or inferior oblique) of the left eye.
The second step is to determine which side has the greatest vertical deflection when gazing to the side. The direction of gaze on the side with the greatest deflection is the direction where the direction of force of the paralyzed muscle is at the smallest angle to the visual axis – the ipsilateral rectus muscle; the contralateral oblique muscle.
Examples.
(1) The vertical deflection is greatest to the side of gaze with low eye position: ipsilateral superior rectus muscle; contralateral superior oblique muscle.
(1) High right and low left, with maximum vertical deflection when gazing to the left, suggesting that the paralyzed muscle is the left (ipsilateral) superior rectus or the right (contralateral) superior oblique muscle.
(2) If the right side is low and the left side is high, and the vertical deflection is maximum when gazing to the right side, the paralyzed muscle is the right (ipsilateral) superior rectus muscle or the left (contralateral) superior oblique muscle.
2. Maximum vertical deflection when gazing to the side with high eye position: ipsilateral inferior rectus muscle; contralateral inferior oblique muscle. (1) Right high, left low, right high, left low.
(1) High right and low left, with maximum vertical deflection when gazing to the right side, suggesting that the paralyzed muscle is the right (ipsilateral) inferior rectus or the left (contralateral) inferior oblique muscle.
(2) Low right and high left, with maximum vertical deflection when gazing to the left, suggesting that the paralyzed muscle is the left (ipsilateral) inferior rectus or the right (contralateral) inferior oblique muscle.
The third step is to do a head tilt test (Bielschowsky head tilt test) so that the head is tilted to the side of the higher eye, and the vertical deflection increases, which is a positive head tilt test, a key step in the identification of the superior oblique muscle and the superior rectus muscle of the opposite eye.
1. Positive – the paralyzed muscle is the ipsilateral supraocular oblique muscle
2. Negative – the paralyzed muscle is the contralateral rectus oculi muscle