Clinical examination of squint

strabismus

1. Pr esenter : Dr. Reshma Clinical Evaluation of Squint

2. 1.HISTORY TAKING 2.VISUAL ACUITY &REFRACTION 3.EVALUATION OF MOTOR STATUS Inspection of eyes and Head posture Motor cooperation of eye- Extraocular movements in 9 gaze positions Ocular deviation – Cover, Uncover,Alternate Cover,Prism Bar Cover Tests Corneal reflection Tests- Hirschberg’s,Krimsky,Bruckner test Maddox rod , Maddox Wing, Double Maddox Rod Diagnostic Occlusion Diplopia Charting,HESS Screen Test Synaptophore ,Major Amblyoscope Head tilt test Convergence,AC /A ratio Forced Duction test, Forced Generation test

3. EVALUATION OF SENSORY STATUS Suppression - Worth 4 Dot Test 4prism Dioptre Base Out Test Bagolinis Filter test,Maddox Rod test,After Image test Binocular perimetry,Haploscopy Retinal Correspondance - Afterimage test Striated Glasses of Bagolini,Major Amblyoscope , Projection devices Diplopia Test Foveo foveal test of Cuppers Stereopsis Titmus fly test Random Dot test, TNO test LANG stereotest 1 & 2 , LANG 2 Pencil Test Synaptophore

4. HISTORY TAKING

5. Related to fatigue or illness ? More obvious in distance or near fixation ? H/O defective vision Ass w/ Nystagmus or Diplopia In case of Diplopia uniocular /binocular Duration Type of diplopia- horizontal / cyclovertical Direction of gaze in which it occurs Whether more marked in distance or near vision

6. In ACUTE CASES Precipitating factors like trauma, convulsions ,febrile episode before onset of squint. H/O neurological symptoms like loss of consciousness, motor weakness,slurring of speech,giddiness,hemiparesis,tremors H/o of previous surgery for squint, occlusion therapy, atropine penalization h/o Fever ( viral meningitis ) h/o Long standing early morning headache with nausea and vomiting ( raised ICT ) h/o Hearing loss, tinnitus, vertigo Tingling and numbness ( multiple sclerosis )

7. Birth and medical history • Significant antenatal history • Maternal infection , any drugs taken during pregnancy • Any untoward event during delivery • Length of labour , Birth trauma, forceps, birth asphyxia Gestational age • Birth weight of the child • Developmental milestones , both physical and mental • Other associated neurological problems like cerebral palsy, epilepsy, mental retardation,craniofacial anomalies, behavioural anomalies, handedness

8. VISUAL ACUITY

9. INFANTS AND PREVERBAL CHILDREN (Birth – 14 months) 1.FIXATION PREFERENTIAL TEST(CSM METHOD) Central , S teady and M aintained fixation? Central foveal fixation Steady no nystagmoid movement Maintained ability to maintain fixation when converted from monocular to binocular viewing Does he follow target? Does he get upset when 1 eye is closed? 2. OPTOKINETIC NYSTAGMUS Nystagmus elicited by passing a succession of black and white stripes in field of vision Uses the minimum separable as a measure of visual acuity

10. 3.FORCED CHOICE PREFERENTIAL LOOKING TEST attention more attracted by patterned stimulus than homogenous surface 4.VISUAL EVOKED POTENTIAL Light stimulus to retina (checkerboard/stripes/ unpatterned flash) Recorded by surface electrodes on occiput Changes in cortical electrical pattern

11. T oddlers (14 m to 2 and half years) HUNDRED &THOUSAND SWEET TEST CARDIFF ACUITY TEST DOTT VISUAL ACUITY TEST STYCAR BALLS

12. Preschoolers (2 and half to 5 years) LEA Symbols Allen Picture Card Broken Wheel Test Tumbling E Chart Landolt C Chart Sjogren Hand Test HOTV test Isolated hand figure test Sheridan –Gardiner HOTV test Pictorial vision charts (crowded KAY picture) 11. Bork candy bead test

13. School going children (5 to 15 years) Tumbling E Chart Landolt C Chart Sjogren hand chart Snellen’s Chart LogMAR chart

14. REFRACTION

15. Under full cycloplegia (paralysis of ciliary muscles) esp in children neutralize effect of accommodation which masks ref error Adequate cycloplegia - 1% cyclopentolate in 60 min In darkly pigminted irides or high hypermetropia – Atropine may be required <12 m 0.5% atropine >12 m1% atropine Ass with hypermetropia (commonest) , astigmatism , anisometropia , myopia

16. HYPERMETROPIA In a child with esotropia,esophoria Full cycloplegic correction even <2 years In a child with exotropia . exophoria Under correction ASTIGMATISM > 1.5 D  correction given especially after 18 months

17. MYOPIA In a child with esotropia,esophoria Under correction In a child with exotropia . exophoria Full cycloplegic correction

18. GOALS OF STRABISMUS EXAMINATION 1.Establishing a cause for strabismus 2. Diagnosing amblyopia 3.Measuring the deviation 4.Assessing binocular sensory status

19. HEAD POSTURE Face turn to right /left  horizontal deviation Head tilt to right or left shoulder  torsional deviation Chin elevation or depression  vertical deviation To compensate for deviation To permit BSV To eliminate diplopia and place eyes in most comfortable position Patient position head to reduce need for affected muscle to contract

20. Head placed in field of action of involved muscle ;eye moves out of field of action In some , head placed in opposite field to increase separation between diplopic images Head tilt to counteract torsional and vertical diplopia Chin elevation for weakness of vertically acting muscles SO palsy  Ocular torticollis IN RSO, Chin depression Face turn to left H ead tilt to left shoulder

21. rule out pseudoptosis -on fixating with affected lid, lids will open to normal width rule out jaw winking Marcus Gunn Phenomenon –whether lid fissure width changes when jaw is moved or patient chews or speaks rule out retraction syndrome - lid fissure changes when patient moves eyes to left or right rule out pseudostrabismus -epicanthus (semilunar fold of skin running downwards at side of nose with concavity directed towards inner canthus)

22. PSEUDOTRABISMUS False appearance of squint in the absence of any deviation Even when visual axes are parallel, eyes seem to have a squint

23. VISUAL AXIS (line of sight) Line passing from fovea to point of fixation PUPILLARY AXIS Line passing through centre of apparent pupil perpendicular to cornea and meets retina on nasal side of fovea ANGLE KAPPA Formed at the intersection of these 2 axes at centre of pupil

24. When 1 eye is pointing in (towards the nose)  Positive Angle Kappa When an eye is pointing out (away from the nose )  Negative Angle Kappa Normal fovea lies just temporal to anatomical axis light shown in centre of cornea cause reflex on visual axis just nasal to centre of cornea (+angle kappa =5 degrees)

25. Large +angle Kappa (in hypermetropia )  pseudoexotropia Large - angle Kappa (in myopia)  pseudoesotropia

26. INTERPUPILLARY DISTANCE Note ocular deviation by measuring Interpupillary Distance 1.Ordinary mm scale 2.Pulzone –Hardy rule 3.Synaptophore

27. Evaluation of motor status

28. Types of Eye Movements Uniocular Eye Movements Ductions 2.Binocular Eye Movements Version : (Binocular Conjugate Eye Movements) Vergence : ( Binocular Disjugate eye movements)

29. Uniocular movements Ductions – only one eye is open, the other covered/closed tested by asking the patient to follow a target in each direction of gaze. Types of ductions :-

30. Binocular movements Versions :- Binocular ,simultaneous, conjugate movements in same direction. both eyes open, attempting to fixate a target &moving in same direction . Abduction of one eye accompanied by adduction of other eye is called conjugate movements .

31. Types of versions :- Dextroversion & laevo version Elevation & depression Dextro elevation & dextro depression Laevo elevation & laevo depression

32. Vergences : binocular,simultaneous,disjugate /disjunctive movements ( opp.direction ) Convergence – simultaneous adduction Divergence – outward movement from convergent position

33. 9 Positions of GAZE

34. Abduction is normal when Temporal limbus touches lateral canthus Adduction is normal when Nasal 1/3 rd cornea crosses nasal punctum Inferior Obliques On Lateral version, Upwards deviation from horizontal line passing through centre of pupil Superior Obliques On Lateral version, Downwards deviation from horizontal line passing through centre of pupil Abduction /adduction/ infraduction should have at least 10mm of rotation Supraduction of 5-7mm

35. In paresis normal ductions observed due to extra innervation called in to compensate for the paresis In versions this is picked up as extra innervation going to yoke muscle which overacts 1.Primary underaction of involved muscle 2. Sec contracture of unopposed I/L antagonist 3.Sec contracture of yoke muscle 4. sec inhibitional palsy of C/L antagonist

36. Hering’s law of motor correspondence states that when eyes move into a gaze direction, simultaneous innervation leads to yoke muscles having equal force Sherrington ‘s law of reciprocal innervation states that increased innervation and contraction force of a given EOM is accompanied by reciprocal decrease in innervation and contraction force against its antagonist

37. In RSO palsy If patient is looking up and left(in direction of I/L antagonist-RIO) RIO receives reduced innervation  as it does not have to overcome the normal antagonistic action of RSO (SH LAW) But less innervation to C/l yoke of RIO LSR, giving false impression that LSR is paretic ( HER LAW) Inhibitional palsy of contralateral antagonist 2. if looking down and right …more innervation required to move right eye to abduction, C/L Yoke more innervated  over acting LIR

38. MEASUREMENT OF DEVIATIONS

39. HIRSCHBERG TEST Initial screening for strabismus Uses 1 st purkinje image Gives rough estimate of angle of a manifest squint Useful in young uncooperative patients When fixation in deviating eye is poor Procedure 1.Patient asked to fixate at point light 33cm away 2. Deviation of corneal light reflex from centre of pupil noted Each mm deviation = 7 degree (1 degree = 2 prism diopter approx )

40. KRIMSKY TEST Based on Herring Law of equal innervation for quick evaluation of angle of strabismus Used to centralize corneal reflection in squinting eye as compared to reflex in fixing eye Results expressed in Prism Dioptres PROCEDURE: 1.Patient asked to fixate on a point light 2. Prisms of increasing power (with apex towards direction of manifest squint ) placed in front of Non Fixating eye till corneal light reflex centred in squinting eye 3. Power of the prism required to centre light reflex = amount of squint in PD

41. BRUCKNER TEST Performed using direct ophthalmoscope To obtain red reflex simultaneously in both eyes Deviated eye has a brighter and lighter reflex than fixing eye Helps in diagnosing media opacities, strabismus, refractive errors

42. PREREQUISITES FOR COVER UNCOVER TEST Ability to fixate target Have central fixation in BE No gross /severe mobility defects Vision >6/60 in both eyes Simplest method to Distinguish between phoria and tropia

43. COVER TEST Detects and confirms tropia (manifest) Procedure: 1.Patient asked to fixate on a point light Normal looking/fixating eye covered with occluder Look for movement of uncovered eye Test to be performed for near (33cm ) and distance (6m)fixation To be done in all gaze fixations

44. Covering one eye of patient with normal BSV interrupts fusion In presence of squint , uncovered eye moves in opposite direction to take fixation In Apparent squint , no movement When eye is uncovered It will establish fixation

45. COVER UNCOVER TEST Detects and confirms phoria (latent) Observe covered eye as cover is removed In heterophoria covered eye will deviate towards heterophoric position Eg eye will move outward in presence of esophoria

46. ALTERNATE COVER TEST Identify TOTAL squint ( tropia + phoria ) More dissociative than cover uncover test Procedure : 1.Hold occluder over 1 eye for several seconds (which dissociates BSV) 2.Rapidly move occluder to other eye 3.Observe refixation shift of unoccluded eye, speed and smoothness of recovery 4. Occluder is shifted back and forth several times Both eyes are covered alternatively Movement of covered eye noted as cover is changed from 1 eye to other

47. PRISM COVER TEST Single prism /prism bar used Measures amount of deviation in near or distance fixation in all gaze positions in prism diopters Measures both heteroptropia and heterophoria Combines alternate cover tests with prisms PROCEDURE: 1.Prisms of increasing strength with apex towards deviation placed in front of 1 eye BASE OUT – EsO BASE IN ---- ExO 2. Patient asked to fixate with other eye 3.Cover –Uncover test performed till there is no recovery movement of eye under cover

48. MADDOX WING Based on principle of dissociation by dissimilar objects Measures heterophoria for near (33 cm) in PD Through 2 slits, RE sees vertical white arrow and horizontal red arrow LE sees vertical and horizontal line of numbers

49. PROCEDURE: 1. patient asked to tell number on horizontal line which vertical arrow points (gives amount of Horizontal phoria ) Number on vertical line at which red arrow is pointing (vertical phoria measurement) 2.Cyclophoria measures by asking patient to align red arrow with horizontal line

50. MADDOX ROD Consists of multiple cylindrical high plus lenses of red colour set together in a metallic disc which converts appearance of white spot of light into a red streak Measures horizontal and vertical deviations Dissociative –blocks fusion (measures phoria )

51. PROCEDURE: 1.Patient asked to fix on a point of light in centre of Maddox tangent scale at distance of 6m 2.Maddox rod is placed in front of 1 eye Maddox rod converts point light image into a line Thus patient sees a point light with 1 eye and a red line with other Due to dissimilar images of 2 eyes, fusion is broken and heterophoria becomes manifest The no: on Maddox tangent scale where red line falls will be amount of heterophoria in degrees Dissociation b/w point light and redline can be measured by superimposition of 2 images by prisms in front of 1 eye with apex towards phoria

52. DOUBLE MADDOX ROD TEST Measures Tortional deviations Used in cyclodeviations PROCEDURE: Maddox rod is placed in front of each eye (one red, one white). Vertically aligned cylinders produce 2 horizontal lines Patient asked whether the 2 lines align exactly with each other The colour of the tilted line is identified by the patient. The corresponding Maddox rod is rotated until the patient reports that it is vertical. The rotation required indicates the size of torsion. The two lines will fuse if there is no residual non-torsional deviation.

53. SYNAPTOPHORE Measures angle of deviation Assesses retinal correspondance Checks for and measures fusion Assesses and measures Stereopsis Measures ocular alignment subjectively or with cover testing When dissimilar targets are presented to each eye,patient is asked to superimpose them If patient has NRC, horizontal, vertical, and torsional deviations can be read directly fom the calibrated scale.

54. PARK ‘S 3 STEP TEST IN SO PALSY (4 TH NERVE)

55. Determine which eye is hypertropic 4 possible underacting muscles isolated Eg , IN STEP 1 if Right hypertropic means either 1. RE Depressors(RSO, RIR) are weak or 2. LE Elevators (LIO ,LIR)

56. In STEP 2 , determine if vertical deviation greater in Ror L gaze Eg if its more in Left gaze, draw an oval around the 4 vertically acting muscles used in left gaze Thus it might be either RSO or LSR

57. STEP 3 involves tilting head to right and then to left Head tilt to right stimulates R intorters (RSR, RSO) L extorters (LIR,LIO) and vice versa If Vertical deviation increases to Right tilt implicates 4 muscles that act vertically in right tilt around which oval is drawn RIGHT SUP OBLIQUE is the only muscle with 3 circles Around it

58. DIPLOPIA CHARTING Patient asked to wear Red and green diplopia charting glasses Red glass in front of right eye and green in front of left In a semi dark room, he is shown a linear light from a distance of 4 feet and asked to comment on the images in primary position and in other positions of gaze Patient tells about the position , Brightness and separation of the 2 images in different fields

59. Maximum separation in the field of action of paralytic muscle If 2 images are joined together No diplopia If images are separatedconfirms diplopia Maximum separation in the quadrant in which muscle is restricted Image is displaced towards field of action of paralysed muscle HOR separation with uncrossed images Esodeviation HOR separation with crossed images Exodeviation VERT separation with uncrossed images Obliques involved VERT separation with crossed imagesVertical recti

60. HESS SCREEN TEST Principles 1. Dissociation of eyes by Red and green goggles 2. Foveal projection in the presence of normal retinal correspondence Hering ‘s and Sherrington’s Law explain the development of muscle sequelae Uses 1. Diagnosis of underaction / overaction 2. Mechanical or neurogenic palsy 3.Planning of surgery & post op effects of surgery 4.Monitoring of condition

61. Electronic Hess screen contains a tangent pattern (2D projection of a spherical surface )printed onto a dark grey background Red lights that can be individually illuminated by a control panel indicate cardinal positions of gaze within a central field (15 degree from primary position) and a peripheral field (30 degree of ocular rotation ) Inner square of 8 dots and outer square of 16 dots

62. PROCEDURE: 1.Patient is seated 50 cm from the screen and wears red Green goggle(red in front of right eye) & has a green pointer 2 . The examiner illuminates each point which is used as point of fixation 3 .This can be seen only with RE ,which becomes fixating eye 4 .Patient is asked to superimpose their green light on red light, so plotting the relative position of the left eye 5 . All points are plotted in turn In Orthophoria, 2 lights should be more or less superimposed in all 9 positions of gaze 6.Goggles are then reversed (red filter in front of left eye) and procedure is repeated 7.The relative positions are marked by the examiner on Hess chart and connected with a straight line

63. LEES SCREEN Is a modification of HESS screen Uses different method of dissociation Red and green complementary colour dissociation is replaced with double sided mirror Mirror prevents both eyes viewing same screen simultaneously although patient perceives both images seen by fovea of each eye as if they are projected straight ahead

64. INTERPRETATION: 1.2 charts are compared 2. Smaller chart  eye with paretic muscle(RE) 3. Larger chart eye with overacting yoke muscle (LE) 4.Smaller chart will show it greatest restriction in main direction of action of paretic muscle (R LR) 5.Larger chart will show its greatest expansion In main direction of action of yoke muscel (L MR) 6. Degree of disparity b/w plotted point and template in any position of gaze gives an estimate of angle of deviation

65. Forced duction test (FDT) (traction test) Simple and most useful method for diagnosing presence of mechanical restriction of ocular motility To assess passive movement of the globe To differentiate b/w incomitant squint due to EOM paralysis and that due to mechanical restriction of ocular movements FDT + ve (resistance encountered during passive rotation)  incomitant squint due to mechanical restriction FDT – ve  EOM palsy

66. PROCEDURE 1.4% LIDOCAINE 2.Supine position 3.Lids retracted 4. Patient asked to look in the direction of muscle being tested- the paretic muscle (to relax antagonist ) If RLR possible paretic muscle ,patient asked to look to right 5.Eye held with toothed forceps applied to conjunctiva near the limbus near insertion of possible mechanically restricted muscle (on opp side of possibly paretic muscle ) Eg -If LR paresis, apply forceps near MR insertion 6.Eye is moved in the direction of action of muscle ( opp to that in which mechanical restriction is suspected) Eg -if LR was possible paretic muscle, eye grasped at medial limbus and an abduction rotation movement attempted If eye can be rotated with forceps past voluntary moved limit presence of paretic muscle If moves freely  Negative RestrictedPositive

67. To distinguish b/w lateral rectus paralysis & mechanical restriction involving the medial aspect of the globe, apply the forceps at 6 and 12 o clock position and move the eye passively into abduction NO RESISTANCE  paralysis of lateral rectus muscle RESISTANCE mechanical restrictions do exist medially and contracture of MR , conjunctica , tenon’s or MR myositis to be considered

68. Forced generation test ( FGT ) Performed to differentiate b/w palsy vs Paresis in restrictive pathology To calculate potential force in apparently paralysed muscle To assess active muscle force which enables eye movement to take place Patient is asked to move in a given direction while the observer grasps eye with an instrument If the muscle is paretic, examiner feels less than normal tension

69. DIAGNOSTIC OCCLUSION Used to induce full dissociation when its thought that maximum angle of deviation has not been revealed Used in Intermittent exotropia To diagnose whether symptoms are due to heterophoria To differentiate b/w real or apparent limitation of abduction in children

70. CONVERGENCE Place fixation object at 40 cm in midsagittal plane of patient ‘s head Move the object towards the patient till 1 eye loses fixation and turns out This point is Near point of convergence (Normal 8-10 cm or less) Dominant eye  eye that maintains fixation

71. ACCOMMODATIVE CONVERGENCE/ ACCOMODATION RATIO Amount of convergence (in Prism Dioptres )per unit change in Accomodation (in Dioptres ) GRADIENT METHOD Dividing change in deviation (in PD)by change in lens power An accommodative target must be used and working distance held constant (33cm or 6m) Plus or minus lens used to vary accommodative requirement HETEROPHORIA METHOD Distance and near deviations and IPD used If more exotropic or less eso at near fixation  less convergence or low AC/A ratio If more esotropic or less exo at near fixation high AC/A In Accomodative eso a diff in eso of 10 PD or more b/w near and distance fixation high AC/A

72. Evaluation of sensory status

73. EVALUATION OF SENSORY STATUS Suppression - Worth 4 Dot Test 4prism Dioptre Base Out Test Bagolinis Filter test,Maddox Rod test,After Image test Binocular perimetry Stereopsis Titmus fly test Random Dot test, TNO test LANG stereotest 1 & 2 , LANG 2 Pencil Test Synaptophore Retinal Correspondance - Afterimage test Striated Glasses of Bagolini Major Amblyoscope Diplopia Test Foveo foveal test of Cuppers

74. WORTH 4 DOT TEST D issociation test which can be used for both distance and near fixation Differentiates b/w BSV, ARC, Suppression PROCEDURE: 1.Patient wears red green goggles with red lens in front of right eye 2.Patient is seated in a dark room 3.He views an illuminated box with 4 circular lights- 2 green lights 1 red light 1 white light 4. Testing distance can be varied to identify size of suppression scotoma 5.Red light seen through red filter;Green through green filter;white light by both eyes White light is only binocular fusion target

75. 4 dots  Normal Retinal Correspondance In ARC, with Manifest Squint 5 dotsEsODEVIATION-Uncrossed (red on right) ExODEVIATION -Crossed (red on left) 3 green dotsSuppression of Right eye 2 red dots Suppression of left eye

76. 4 D PRISM TEST Main aim- to prove the presence of normal BSV Test done to detect a small central suppression scotoma (or foveal suppression). In patients who have decreased stereopsis but are orthophoric on cover testing . In small to intermediate angle deviations The level of dissociation is mild

77. Procedure Instruct the patient to look at a distance target. A 4-BO prism is quickly placed over RE with base out and the examiner observes the movement of LE. A sudden displacement of the image onto the parafovea will cause re-fixation if the image is falling on corresponding points on a normal retina. The test is repeated on LE and the examiner observes the movement of the RE. Strength of prism moves image a little bit in foveal area leading to recovery movement in other eye no movement will occur if the image has been shifted within a nonfunctioning ( scotomatous ) area

78. Interpretations When the test is negative, the patient is considered to be bifoveal . When the prism is over the right eye, the left eye moves out and in. When the prism is over the left eye the right eye goes out and in. There are two responses when there is a scotoma ( microtropia ). There is a scotoma on the right eye if the prism is over the right eye and there is no response bilaterally vice versa for the fellow eye

79. BAGOLINI STRIATED GLASSES It detects BSV or suppression Evaluation of near and distance retinal corrrespondance with minimal dissociations Each lens of Bagolini Glasses have fine parallel striations which convert point source of light into a line PROCEDURE: 1.2 lenses placed at 45 and 135 degrees in front of each eye respectively 2. Patient asked to fixate a small light source Testing distance at 6m and 33 cm 3.Each eye perceives an oblique line of light perpendicular to that perceived by fellow eye 4. Can be used in any desired gaze

80. RESULTS: 2 streaks intersect at their centres in form of oblique cross  BSV or ARC of harmonious type 2 lines but not forming cross Incomitant squint with NRC Only 1 streak no simultaneous perception and suppression of other eye Small gap in one of the streakCentral suppression Scotoma

81. TEST FOR FIXATION  Visuoscope or Fixation Star of Ophthalmoscope Patient asked to cover 1 eye and fix the star with other eye Fixation may be CENTRIC normal on the fovea ECCENTRIC unsteady Parafoveal Macular Paramacular peripheral

82. SYNAPTOPHORE Consists of 2 tubes, having a right angled bend, mounted on a base Each tube has a light source for illumination and a slide carrier at outer end and a reflecting mirror at right angled bend and eyepiece of +6.5 D at inner end USES to diagnose anomalies of binocular vision with targets that are presented to each eye To assess deviation and quantify binocular vision(Precise measurement of angle alpha, Objective and subjective angle of deviation, Vertical and tortional deviations) To detect and quantify area and density of suppression To detect ARC To measure fusional amplitudes,Stereopsis

83. PROCEDURE: The patient is instructed to place chin on the chin rest . Chin rest and IPD adjusted accordingly. The examiner uses the toggle switches to show the patient the slide illuminated to right and left eye. As the examiner switches the toggle from the right eye to the left eye it is representative of cover testing. The eye that is illuminated is the eye that is fixating. The examiner should be able to see the eye movements and be able to neutralize a horizontal deviation by using the arms at the side of the machine.

84. There is a scale near the arms to note the size of deviation . Neutralizing a vertical deviation requires the use of the R/L Hyper knobs. Cyclo deviations are also neutralized using the appropriate knobs Near deviations can be neutralized by placing a -3.00 sphere trial lenses in the lens holder in front of the eyepiece. This way, the patient has to exert 3 D of accommodation to make the objects clear.

85. The goal of the examiner is to have the patient fuse the fusion targets Worth’s Grade 1 slides( red slides)  simultaneous perception slides - test subjective and motor angles. Grade 2 slides (green) - test motor and sensory fusion. Grade 3 slides (yellow) stereoscopic vision slides and -test the presence of third grade binocularity

86. Examination of simultaneous perception  determination of angle of strabismus and retinal correspondence assessment Fusion amplitude evaluated with use of nearly same pictures, differing in only small details Stereoscopy examined with use of slightly decentred special pictures, which are projected on disport retinal point, within Pannum ‘s area, giving the impression of depth and stereoscopy

87. Measurement of Angle of Anomaly:  denotes the degree of shift in visual direction. determined by calculating the difference between the objective and subjective angles of deviation . Procedure : 1.The arms of the synaptophore are set at zero . 2. Both the arms of the instrument are moved by the examiner while alternately flashing the light behind each slide until there is no further fixation movement of the patient’s eye (alternate cover test). 3.The reading of both the arms is noted at this moment and the sum total of the reading of both the arms gives the objective angle of anomaly(MOTOR ANGLE ) 4.The subjective angle of anomaly (SENSORY ANGLE )is the angle at which the visual targets are superimposed, there is no shift and the deviation is neutralized . Angle of Anomaly = Objective Angle – Subjective Angle

88. The interpretation of this test is as follows- If Subjective Angle = Objective Angle → NRC If Subjective Angle < Objective Angle → ARC If Angle of Anomaly = Objective Angle →Harmonious ARC (full sensory adaptation) If Angle of Anomaly < Objective Angle →Unharmonious ARC

89. AFTER IMAGE TEST In patients who can fixate with foveal area To determine ARC and dense suppression Highly dissociating orthoptic test PROCEDURE: 1.In dark room occlude non dominant eye 2. Dominant eye to be stimulated in direction of strabismus Horizontal beam for horizontal strabismus and vertical beam for vertical strabismus 3. Non dominant eye getting opposite beam 4. Patient fixates on lighted beam for 10 sec so that fovea is stimulated 5.Patient instructed to close eyes and observe white lines( POSITIVE AFTER IMAGE) asked to draw position 6.After lights on patient instructed to see blank wall to see black line ( NEGATIVE AFTER IMAGE)

90. If Retinal correspondence is Normal  draws a cross In case of suppression draws 1 line Esotropic with ARC  draws vertical image to left of horizontal Exotropic with ARC draws vertical image to right of horizontal

91. FOVEO FOVEAL TEST OF CUPPERS In patients with eccentric fixation An asterisk placed on fovea of deviated eye (under visuoscopic guidance) Other eye fixates the light on a Maddox cross or tangent screen If one breaks through suppression scotoma of deviated eye, patient can report position of images In NRC  Fixation target superimposed on central fixation light of Maddox crossfovea have common visual direction In ARCThe asterisk superimposed on one of the numbers on the horizontal bar of Maddox scale, number indicating angle of anomaly in degrees

92. FIELD OF BINOCULAR VISION Tested in patients with paralytic squint with some field of single vision Performed on the perimeter using a central chin rest

93. NEUTRAL DENSITY FILTER TEST Visual Acuity is measured without and with neutral density filter placed in front of the eye In functional Amblyopia  Visual Acuity slightly improves In organic amblyopia VA markedly reduced when seen through the filter

94. stereopsis

95. TESTS FOR STEREOPSIS Based on 2 principles 1.Using targets in 2 planes ,constructed so that they stimulate disparate retinal elements , giving a 3D effect Eg - Concentric rings, Titmus fly test, TNO test, Random Dot Stereograms, Polaroid Test, Langs stereo test, Stereoscopic targets presented haploscopically in Major Amblyposcope 2.Using 3 D targets Eg - Lang ‘s 2 pencil test

96. QUALITATIVE TESTS FOR STEREOPSIS Lang’s 2 pencil test Synaptophore QUANTITATIVE TESTS FOR STEREOPSIS Random Dot test TNO test Lang’s stereo test METHODS USING POLARIZATION Targets provided as vectographs and images seen by 1 eye is polarized at 90 degree using polarized glasses Titmus Fly test Polaroid test Random dot stereograms TNO test

97. VECTOGRAPHS Consists of polaroid material on which 2 targets imprinted so that they are polarized at 90 degrees with respect to each other Patient provided with Polaroid Spectacles so that each target is seen separately with 2 eyes TITMUS STEREO TESTS: 3D polaroid vectograph made of 2 plates in form of a booklet 3 PARTS-1.FLY TEST 2.ANIMAL TEST 3.CIRCLE TEST

98. 1.FLY TEST Right side of booklet – large housefly To test gross stereopsis Threshold 3000 sec of arc Useful in young children If subject asked to pick up one of the wings of fly and subject sees stereoscopically he will reach above the plate In absence of gross stereopsis fly appears as flat photograph

99. 2.ANIMAL TEST If gross stereopsis present Test consists of 3 rows of 5 animals each,1 animal from each row imaged disparately (threshold 10,200, 400 sec of arc respectively) In each row , 1 of the animals correspondingly imaged in 2 eyes printed heavily black (misleading clue) Subject asked which animal stands out subject with stereopsis will name the disparately imaged animal subject without stereopsis will name the animal printed black

100. 3 .CIRCLE TEST Consists of 9 squares, each containing 4circles arranged in form of lozenge Only 1 circle in each square is disparately images at random threshold ( 800 to 40 sec of arc) If subject has passed other 2 tests , he is asked to PUSH DOWN the circle that stands out When he finds no circle to push or makes a mistake limit of his stereopsis presumably reached Circle no 5 equivalent to 1 sec of arclowest limit of fine central stereoacuity

101. RANDOM DOT STEREOGRAM TEST Devoid of monocular clues Patients cannot guess what stereo figure is and where it is located Provides truer measurement of stereopsis than Titmus test

102. TNO TEST Each test plate consists of a stereogram in which images presented to each eye have been superimposed and printed in complimentary colours Stereograms are viewed through a pair of red and green filters Random dot Stereograms have the advantage that they completely eliminate monocular cues, the patient is required to describe the shape which can be only seen stereoscopically

103. TNO Test has 7 plates 1 st 4 plates are for screening purposes,the disparities are large and ungraded PLATE I  2 Butterflies of which 1can be seen monocularly , other only in stereopsis PLATE II  4 discs, 2 seen monocularly , 2 need stereopsis PLATE III  4 hidden shapes arranged around centrally placed cross PLATEIV  S uppression test.There are 3 discs,1 seen by right eye,1 by left , 1 seen binocularly PLATE V-VII  test shapes (PAC man Shapes )presented at 6 different disparities ranging from 15-480 secs of arc

104. LANG ‘S STEREO TEST Cards are held at the subject’s reading distance and he or she is asked to name or point to the pictures Displacement of random dots creates the disparity which ranges from 1200 to 550 secs of arc

105. FRISBY STEREO TEST Only clinical test based on actual depth , where random shapes are printed on 3 clear plastic plates of different thickness Doesn’t require any form of dissociation Each plate has 4 squares of curved random shapes 1 square contains a hidden circle that is printed on the opposite surface Disparities range from 600 to 15 secs of arc Care taken that neither the plates nor the patient ‘s head move during testing as this may provide monocular cues If the 1 st plate is recognized successfully , then thinner plates, which give smaller disparities, are presented in a similar fashion

106. SIMPLE MOTOR TASK TEST 2 PENCIL TEST: Detect presence or absence of gross stereopsis (threshold value 3000-5000 sec of arc) PROCEDURE: Examiner holds pencil vertically in front of the patient Ask patient to touch its upper tip with the tip of the pencil in his hand with 1 swift movement from above Patient having stereopsis passes the test with both eyes open

107. ANTERIOR & POSTERIOR SEGMENTS

108. Examination of A ssociated l id problems Ptosis Media opacities Examination of pupillary reflexes U nderlying optic nerve or retinal pathologies Examination of fundus in Excluding macular pathology macular scarring optic disc hypoplasia retinoblastoma O bjectively observing torsion of eye

109. REFERENCES Binocular Vision and ocular motility by GUNTER K. VON NOORDEN Pediatric ophthalmology and Strabismus AA0 section 06 Practical Orthoptics by T. Keith Lyle Strabismus Simplified by Pradeep Sharma Kanski Clinical Ophthalmology