The four inspection methods are the covering method、Hirschberg Test 、Single visual target inspection method(The image of the retina in both eyes is a scene of the same object)Dual visual target examination method(Look at two different visual targets with both eyes)。

--occlusion--

The patient\'s eyeballs must have movement function in order to use the occlusion method to check eye position，If the patient\'s eye movement is severely impaired，Even unable to exercise，It is not suitable to use the covering method to check eye position。Another one，The patient must have the ability to gaze in both eyes，Concentration，Can cooperate。

There are four forms of covering method：Alternate cover test 、cover-cover-uncover test 、Prism alternating covering method and prism covering uncovered method。

(1)Alternate cover test ：Commonly used for patients with esotropia and intermittent strabismus。

Operation method：If you cover one eye，The contralateral eye is still focused on the front visual target without any movement，Then move the eye shield to the opposite eye，Observe the direction of movement of the previously covered eye，If from outside to inside，Indicating the possible presence of exotropia or exotropia during the examination，If moving from inside out，Indicating that the subject may have esotropia or esotropia。Repeat and alternate covering a few times like this，Observe the direction of movement of one eye after removing the cover，Further confirm the initial examination results。If vertical movement of the eyeball is observed，This indicates that the subject may have vertical strabismus or vertical esotropia。

Some show strabismus during examination，Start to manifest as esotropia，Repeatedly covering both eyes alternately，Only then did he show strabismus，For example, intermittent exotropia，At the beginning of the examination, it was exotropia，After alternating covering，Only manifested as exotropia。If the eyes are repeatedly covered alternately，Can fully display the maximum oblique viewing angle。

The inspection distance should be33cmand6mtwo kinds。

(2)Covering off the covering method：The main methods for distinguishing between esoteric and overt strabismus。

Like other covering methods，Patients only have the ability to focus on regulating visual targets，The inspection results are the feasible ones。

Operation method：Cover one eye，Carefully observe the direction of movement of the other eye，The direction of movement of the uncovered eyeball。If there is movement，Indicating the presence of significant strabismus in the patient，According to the direction of movement, which type of strabismus is it。If the uncovered eyes move from outside to inside，Indicating that the patient has exotropia;Moving from inside out，Indicating the presence of esotropia;If there is vertical motion，Indicating the presence of vertical strabismus，Either upward or downward strabismus。

If you don\'t cover your eyes, don\'t move，Cover the other eye in the same way，Observe the movement status of the non covered eye on the opposite side using the same method。The first covered eye is the slanted eye of a strabismus patient，The non covered eye on the opposite side naturally does not move，Because both before and after covering are non covering eye gaze;If it covers the gaze of a strabismus patient，Deviation of the eyes leads to movement。So to cover up the inspection, both eyes must be covered first in order to obtain the correct result。

The method of covering and removing covers can also observe hidden strabismus。for example，Cover the patient\'s right eye，The left eye remains focused on the target ahead without any movement。Open the patient\'s right eye，If the left eye still doesn\'t move，Movement in the right eye，Based on the direction of movement, it is possible to determine whether the patient has an implicit inclination or an implicit inclination。If the right eye moves from inside out，It indicates the presence of esoteric strabismus;Movement from outside to inside，Indicating the presence of exotropia。

(3)Alternating prism covering method：Used to measure the total degree of both hidden and visible skewness。however，Cannot express the degree of strabismus separately for the two parts。This method is often used before correcting strabismus surgery，Provide maximum degree of eye deviation for surgical design。These two parts combined，Reflects the maximum degree of natural deviation of the eyeball caused by the imbalance of extraocular muscles，Excluding the impact of fusion functionality。

Operation method：The blindfold should move quickly from one eye to the other，To prevent fusion from occurring，Cannot expose a large oblique angle of view。After several alternating covers，The maximum separation state can only occur in the eye position。Handheld prism，Place the prism in front of one eye according to the direction of the strabismus，During esotropia，Prism with bottom facing outward;During exotropia，The bottom of the prism faces inward;When squinting upwards，Prism bottom downwards;When looking downwards，The bottom of the prism faces upwards。Continue to cover both eyes alternately，Continuously adjust the power of the prism，Until there is no more eye movement when alternately covering。Complete neutralization of skewness often requires the simultaneous application of horizontal and vertical prisms。 The alternating prism covering method uses the refractive power of a prism to completely neutralize the deviation of the eye position，At this point, the prism power is the degree of strabismus in the eye position。

The alternating prism covering method is often used for concomitant strabismus，otherwise，Alternating covering always leads to eye movement。

(4)Prism masking method：This method is applicable for measuring the degree of strabismus，Not only applicable to concomitant strabismus，Also suitable for non common strabismus。

Operation method：During inspection，Cover the staring eye with a blindfold，A prism placed in front of a tilted eye，Repeatedly covering the staring eye，Continuously adjust the power of the prism，Until covering the gaze，Oblique eyes no longer exhibit eye movements。At this point, the prism power is the degree at which the patient shows strabismus。Replace the gaze and repeat the above examination。

The use of masking to remove masking or alternating masking may result in missed diagnosis of the following strabismus：Minor esotropia(<5o);Minor strabismus(microtropia)Small degree esotropia。

The above examination methods are not suitable for rotational strabismus。

--Hirschberg Test --

If the patient has poor fixation in one or both eyes，Unable to steadily and continuously focus on the visual target directly in front，Or poor eye movement function，Or there may be serious limiting factors，Make the eyes unable to move，or，The patient is young and has poor attention, making it difficult for them to cooperate，All of the above situations are suitable for corneal reflection examination of eye position。This method can only roughly estimate the oblique viewing angle，Far less accurate than the prism covering method。And when estimating strabismus，We can\'t do it yetKappaExcluding corners。

Corneal reflection method is divided into four types：The first type isHirschbergThe first report，callHirschgergInspection method。The second type isKrimskyImproved corneal reflection method。The third method is the homography corneal reflection method。The fourth method is the visual arch corneal reflection method。

(1)HirschbergHirschberg Test

Place the light directly in front of the patient，Horizontal with the patient\'s eyeball，Located on the median plane of the patient。At this point, observe the reflection point on the patient\'s cornea。The focal point of the gaze is located in the center of the pupil，The reflection point on the deviated cornea is located in a non central area。Corneal reflection spot deviates from the center of the pupil1mm，Equivalent to visual axis deviation7o(15△)。If the corneal reflection point is located at the pupil edge，Visual axis deviation of approximately2mm，equivalent to15o(30△);The corneal reflection point is located between the pupil edge and the corneal edge，Approximately skewed4mm,equivalent to30o(60△);The reflection point located at the corneal edge is equivalent to45o(90~100△)。

(2)KrimskyHirschberg Test

Place the point light source directly in front of the patient，The same location as described in the above method。Let the patient\'s eyes with good vision focus on the light，Place the prism in front of your gaze，The direction of a prism is determined based on the type of oblique view，Continuously increasing the power of the prism，Gradually move the corneal reflection point of the deviated eye from the eccentric position to the center of the pupil。At this moment，The degree of a prism added to the gaze in front of the eye is similar to the degree of strabismus in slanted eyes。

Someone placed a prism in front of skewed eyes，Observing corneal reflection points through a prism，Continuously adjust the power of the prism，Until the corneal reflection point moves and deviates from the center of the eye pupil。At this moment，The prism power added to the deviated eye is approximately equal to the strabismus power of the deviated eye。

(3)Corneal reflection method using the same camera

Ask the patient to focus on the visual target inside the tube，Gaze at the visual target inside the lens，If the other eye deviates，Adjust the position of the lens barrel of the synchronous machine，Move the position of the refracted corneal reflection point to the center of the pupil，At this moment，The degree pointed by the pointer on the dial is the degree of deviation。

(4)Visual arch corneal reflection method

Like checking the surrounding field of view，Let the patient sit down，Place the chin on the chin rest，Head pressed against the curved frame，Look at the circular hole in the center of the visual field with one eye，Place the point light source at the upper edge of the field of view bow，Shine on the patient\'s cornea，Gradually move the position of the light source，Gradually move the corneal reflection point of the deviated eye to the central part of the pupil。At this moment，The position of the point light source on the visual arch is the degree of strabismus of the slanted eye。

--Single visual target inspection method--

Observing a visual target with both eyes simultaneously，Causing patients to develop diplopia，Judging eye position based on changes in the position of the diplopia image。It mainly includes three methods：Red filter method，Single Markovnikov inspection method and double Markovnikov inspection method。Suitable for paralytic strabismus。

(1)Red filter method：

The position of the point light source is the same as the above inspection method。Place the red filter in front of your right eye，The patient sees a point light source as two point light sources, red and white，Generate diplopia。Add a prism in front of the patient\'s eyes(Horizontal or vertical)Overlap two object images，At this moment，The degree of the prism added in front of the patient is the degree of strabismus。

(2)Single Markov Rod Inspection Method：

The Mahalanobis rod is composed of a series of parallel cylindrical mirrors，By using a Markov pole, a point light source can be turned into a line。Due to the optical properties of the Markovian rod, the direction of this light ray is perpendicular to the cylindrical mirror that makes up the Markovian rod。The Mahalanobis rod changed the shape of the visual target，Thus, it disrupted the fusion，So the detected strabismus includes two parts: hidden and visible strabismus。

When the patient focuses on the point light source ahead，Place the Mahalanobis pole horizontally in front of the right eye，Make the patient see the point light source as a vertical beam of light，When viewed with the left eye, the color changing light source appears。If the vertical light point light source，Explain the patient\'s binocular alignment;If the point light source。If a vertical light passes through a point light source，Explain the patient\'s binocular alignment;If the point light source is on the left side of the vertical ray(Ipsilateral diplopia)，Indicating that the patient has exotropia，If the point light source is located to the right of the vertical ray(crossed diplopia)，Indicating that the patient has exotropia。The method for detecting vertical strabismus is similar to the method for detecting horizontal strabismus，First, rotate the Markov rod90o。When measuring oblique angle of view，Place prisms of different degrees，Until the light passes through the point light source。At this moment，The degree of the prism added in front of the eyes is the degree of strabismus。

Advantages and disadvantages of the Mahalanobis bar inspection method：During the horizontal strabismus examination，Cannot control regulatory set，The examination results may not completely match the strabismus in daily life。The advantage is that it is suitable for strabismus，Micro strabismus and low degree esotropia。

(3)Double immediate inspection method：

Used for measuring rotational strabismus。Using two red and white martensitic poles，In front of both eyes respectively。Ma\'s pole frame is often installed on a tripod，Sometimes placed on the audition stand。The direction of the Mahalanobis pole mirror is horizontal，So the patient sees two perpendicular rays of light。Let the patient adjust the direction of the Mahalanobis pole mirror by themselves，Until the two rays of light seen by each eye are parallel。At this moment，The direction of the Mahalanobis pole mirrors in front of both eyes is no longer parallel，The angle is the degree of rotational strabismus。

If you look at the direction of the Mahalanobis pole mirror in front of you and keep it horizontal，Only rotating and numbing the Mahalanobis pole in front of the eyes，At this point, the direction of rotation of the Mahalanobis rod is the direction of oblique rotation。

--Dual visual target examination method--

This examination method is suitable for paralytic strabismus，When checking the strabismus angle for patients，First, check the first oblique perspective，Check the second oblique perspective again。This type of examination requires patients to have normal retinal correspondence。

The dual visual target examination method refers to the patient\'s two eyes focusing on their respective visual targets，And they use their respective concave centers to gaze at the visual target。like this，Subjective oblique angles are detected at various diagnostic eye positions，It is also an objective oblique perspective，Because they are the same。

There are multiple methods for this type of inspection，The commonly used ones are Lancasterscreen、HessScreen and video camera。

(1)Lancasterscreen：

The patient wears red and green glasses，The red and green lenses can alternate left and right for inspection, and the instrument includes：A red strip light projector、A green strip light projector and a screen。Divide the screen equally into side lengths by black lines7cmThe small square，Check the distance2m，At this distance, each perspective is2o。During the examination, the patient\'s head remains stable。According to convention，Wear a red lens in the right eye when starting the examination，The inspector uses a projector to project a red light strip upwards，Ask the patient to project a green strip of light onto the screen using their own projector，And require the patient to subjectively overlap the two lights together。Record the relative position of the two-color light strip，Repeat the examination at each diagnostic eye position in this way，Then exchange red and green glasses lenses between the left and right eyes，Repeat the check again，Determine the eye position when both eyes are gazing separately。This examination separates two eyes，Can only be used for patients with normal retina correspondence。

(2)Hessscreen：

The patient wears green glasses during the examination，Keep your head upright and remain still。Check the distance50cm。HessOn the screen, they are arranged in sequence25A small red light，Central section9individual，The horizontal or vertical distance between adjacent lights15o，Usually only used in the center9A lamp。If the paralysis of the extraocular muscles is mild，Can be expanded to the surrounding area，Light up the surrounding areas separately16A lamp。

After a small red light on the screen lights up，Ask the patient to project a green light spot onto the screen，When the patient believes that the green light spot overlaps with the small red light，Record the position of the green light spot，Repeat the checks in sequence like this，Take the center9Small red lights are lit up separately，Connect the positions of the green light spots with straight lines。

After the patient\'s red and green glasses were exchanged between the left and right eyes，Recheck again。

HessDuring screen inspection，The color of the green glasses complements the traffic light on them，so，Eyes with red lenses can only seeHessThe red light on the screen，It\'s staring at the eyes;Eyes wearing green lenses can only see the projector or flashlight shining on themHessGreen light spot on the screen。When the patient subjectively feels that the red light and green light spots overlap，The centers of the macula in both eyes of the patient are focused on two visual targets。Because the visual direction of the concave centers of both eyes is the same。This isHessThe difference between screen inspection and diplopia inspection。During diplopia examination，The visual target falls on the retina outside the fovea centralis of the slanted eye macula，Generate diplopia。HessThe inspection result of the screen is actually the oblique angle of view of each diagnostic eye position when the two eyes are separated。analysisHessScreen inspection results，In fact, it is to analyze the functional status of the extraocular muscles in paralytic strabismus based on the oblique perspective of each diagnostic eye position。

(3)Visual inspection method：

Ask the patient to overlap two completely different images, such as a tractor and a house，The tractor enters the house。If the patient has normal retinal correspondence，On the dial of the same camera, the patient\'s level can be directly measured、Vertical and rotational strabismus，At this point, the measured strabismus is the main oblique angle，It is also an objective oblique perspective。If the patient has monocular suppression or abnormal retinal correspondence，Two sheets1You can\'t find the overlapping point of the macular fovea in a high-quality picture。At this point, the patient can be instructed to look at each picture separately，Simultaneously adjust the position of both arms of the same camera，Alternate the lights on both sides，Until there is no more gaze movement in both eyes，The measured oblique angle at this time is the objective oblique angle。

Pseudo strabismus andKappaThe appearance of angles often giving people a squint，Make inexperienced individuals make incorrect judgments。Most patients with pseudostrabismus have a widened nasal bridge，And often accompanied by epicanthic folds。Due to the epicanthus covering the sclera，It seems that the eyeball is in internal rotation，Thus mistakenly believing that the eye position is skewed。The covering method can prove the correct position of both eyes。

KappaAngle is the angle between the visual axis and the optical axis of the eyeball。If the macular fovea is located on the temporal side of the optical axis，The corneal reflection point is located in the center of the pupil and leans towards the nasal side，This is called positivityKappahorn，The appearance appears to be strabismus。If the position of the macular fovea is on the nasal side of the optical axis，The corneal spot is located on the temporal side of the central cornea，This is called negativeKappahorn，Appearance resembling esotropia。

Although we often use point light sources as visual markers to check the eye position of children，Actually, the most ideal way is to adjust the visual target。Replace point light source visual targets with adjustable visual targets，It can be observed that regulatory factors have an impact on eye position，This is of great significance for diagnosing and adjusting the degree of glasses。

After the first glance，You have identified the patient\'s main problem，For example, the right eye is in an esotropia oblique position。Then the second step should be to determine whether the patient can alternate their gaze，By covering the left eye, one can focus on the eye，Skewed eyes force the right eye to turn outward in order to focus on the target。If the patient can maintain the gaze position with their right eye，Even after opening the cover on the left eye, one can still gaze with the right eye，At this point, you can draw a conclusion，The patient has alternating esotropia，The visual acuity of both eyes is basically equal。If the patient cannot maintain the gaze position with their right eye，Patients are not allowed to alternate their gaze，There may be a certain degree of amblyopia in the right eye。

When checking eye position or measuring oblique angle of view，Patients should be allowed to see from a distance(6m)Look closely(33cm)Conduct separate inspections。When wearing corrective glasses，You should also check the eye position when wearing glasses，Measure the oblique angle of view when wearing glasses。 A──VThe characteristics of the syndrome should be noted，esotropiaAFind its maximum oblique viewing angle directly above the eye position，exotropiaAThe maximum oblique viewing angle is located directly below the eye position;esotropiaVThe maximum oblique viewing angle of the sign is located directly below the eye position，Externally inclinedVgo on a journey，The maximum oblique viewing angle is at the eye position directly above。At the same time, the patient should be carefully observed for compensatory head position，Is the chin raised or retracted。