Squint assessment

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  • Both eyes should be monitored simultaneously. Of particular interest are differences in the way each eye moves as they approach the limits of their field of fixation. These limits are explored when the fixation target is moved to the extremities of the ‘H’ pattern.
  • Squint assessment

    1. 1. ASSESSMENT OF A SQUINT PATIENT Siraj Safi Lecturer in Optometry PICO, HMC , Peshawar
    2. 2. Assessment Steps 1. 2. 3. 4. 5. 6. History Visual Acuity Ocular Deviation Ocular Movement Binocular Function Refraction
    3. 3. 1.History
    4. 4. 1.History Patient with ocular motility disorder present for one or more of the following reason:  Manifest strabismus  Defective ocular movement  Nystagmus  AHP  Defective vision  Subjective symptoms 
    5. 5. 1.History continue….    The reason for attendance must first be established. In children greater emphasis is placed on obstetric history and developmental miles stone. Where as the medical history can be of paramount importance in adult.
    6. 6. 1.History continue…. a. Medical history:     The child general development Recent illness and treatment Any trauma to the head and face Any systemic disease b. Obstetric history    The mothers health during pregnancy Delivery The child birth weight c. Family history    Parental consanguinity Strabismus Refractive error
    7. 7. 1.History continue…. e. Strabismus in children:       The Direction of strabismus The age at which it was first noticed Who noticed it Whether the onset was gradual or sudden Frequency of deviation (constant or intermittent) Previous treatment, if any, and the type and results of such treatment f. Strabismus in Adults:   Cosmetic Subjective symptoms
    8. 8. 2.Visual Acuity
    9. 9. 2.Visual Acuity   Easy in adults or older children Very difficult in infants. But even than can be assessed by various techniques
    10. 10. Normal visual development   From Alec. M Ansons and Helen Davis The development of VA from birth to age three year Age New Born I months Visual Acuity 6/240 6/180 - 6/90 4 - 6 months 6/18 - 6/6 3 years 6/6 with single optotypes
    11. 11. Normal visual development  Age related VA estimated by test method From Kenneth W. Wright Technique Birth 2 months 4 months 6 months OKN 20/400 20/800 20/200 20/100 20/60 20-30 months 20/800 20/200 20/150 20/50 18-24 months 20/40 20/20 6-12 months FPL 20/400 VEP 20/800 20/150 20/60 1 year Age for 20/20
    12. 12. Age Indication For VA Tests  Age 0-6/12: VEP ,FCPL, OKN, CSM, Objection to occlusion, Catford Drum etc.  6/12 to 2 years: 100s & 1000s, Stycar balls, FCPL, Cardiff cards…  2 to 3 years: Kay pictures, Illiterate E, Lea Symbol.........  3+ years: Sheridan Gardener, Landolt C, Snellen , LogMar…….
    13. 13. CSM     The ability of each eye to fixate Centrally, steadily, and Maintain fixation. Centrally means foveal fixation Steady means no nystagmoid movement Maintain mean the ability of one eye to maintain fixation when viewing is converted from a monocular condition to a binocular condition.
    14. 14. 3.Ocular deviation
    15. 15. 3.Ocular deviation  Detection of Strabismus can be made through: Observation of the patient appearance  Observation of the corneal reflex  The cover test 
    16. 16. 3.Ocular deviation cont…  The cover test It is an objective test which is the core stone of investigation of strabismus. Requires:  Pin torch  Occluder  Target for 33cm and 6m
    17. 17. 3.Ocular deviation cont… The cover test can be used in two ways: 1) The cover /uncover in which one eye is covered and the observer notes: a) The movement of the uncovered eye to take up fixation. b) The position and movement of the covered eye as cover is removed. 
    18. 18. 3.Ocular deviation cont… 2) Alternate cover test in which both eyes are covers alternatively the movement of the covered eye is noted as the cover is changed from one eye to the other. It is more dissociative than cover/uncover test
    19. 19. 3.Ocular deviation cont…  Information provided by the cover test:  Direction of deviation The difference in angle from near to distance The effect of accommodation Comitance and incometance Estimation of VA The speed of recovery in latent strabismus Constant ,intermittent, unilateral or alternating Latent nystagmus or latent component in manifest nystagmus DVD A/V Pattern         
    20. 20. 3.Ocular deviation cont… Confirmation and measurement of strabismus: 1. Hirschberg 2. Krimsky 3. Prism cover test 4. Simultaneous PCT 5. Maddox rod 6. Double Maddox rod 7. Maddox wing 8. Major amblyoscope 9. Diagnostic occlusion
    21. 21. 1.Hirschberg Used as an initial screen for strabismus How it works: At 33cm front of child with penlight shining at eyes Light reflection will be at the same point in each eye Normal Exotropia Esotropia
    22. 22. 3.Ocular deviation cont… 1. Hirschberg
    23. 23. 2.Krimsky Test This test is used to centralize the corneal reflection in the squinting eye with compared to the fixing eye.
    24. 24. 3.Prism Cover Test Measure squint/misalignment  Single prism/prism bar  Primary position or in all positions of gaze  For near and distance 
    25. 25. 4. SIULTANEOUS PCT     The prism is placed in front of the deviating eye and a cover simultaneously introduced in front of the fixing eye. The aim is to neutralize the movement of the squinting eye as the fixing eye is covered. The test is performed with the same way by increasing the strength of the prism until the squinting eye did not move under the prism. It grieves the estimation of tropia only.
    26. 26. 5.MADDOX ROD   Use of the Maddox rod provides entirely subjective method of measuring horizontal, vertical and torsional deviation . (Phoria) Dissociation of the eye is achieved by presenting a spot light to one eye and a line image to the other eye.
    27. 27. 6.Double MADDOX ROD     Torsional deviations: Torsional deviation can be measured with double Maddox rod. The Maddox rod can be placed parallel in front of both eyes better if have different color. The patient is asked wither the both lines are exactly align when placed parallel Maddox rod in front of both eyes or vertical prism can be introduced to separate the lines and than ask
    28. 28. 7.MADDOX WING   The Maddox wing dissociates the eyes by means of two septa, so that the horizontal and vertical measurement scales are visible to the left eye and the right eye sees the two arrows , one vertical to indicate the horizontal measurement and the other horizontal indicating the vertical measurement for 33cm with correction. Measurements are recorded in prism dioptres
    29. 29. 8. Synoptophore  Uses:     Angle of deviation Assessment of retinal correspondence Fusional amplitude Stereopsis
    30. 30. 9.DIAGNOSTIC OCCLUSSION Diagnostic occlusion can be used to induce full dissociation when it is thought that the maximum angle of deviation has not been revealed. Used in:  Intermittent exotropia.  To diagnose whether symptoms are due to hetrophoria.  To differentiate between real or apparent limitation of abduction in children. 
    31. 31. 4.Ocular Movement
    32. 32. 4.Ocular Movement A. B. C. D. E. Clinical assessment and recording of ocular movements 3- step test Hess test FDT FGT
    33. 33. Muscle Length of active muscle (mm) Origin Anatomic insetion Direction innervation of pull Medial Rectus 40 Annulus Of zinn 5.5 mm from Medical limbus 90o Lower CN III Lateral Rectus 40 Annulus Of ainn 6.9 mm from Lateral limbus 90o CN VI Superior Rectus 40 Annulus Of ainn 7.7 mm from Superior limbus 23o Upper CN III Inferior Rectus 40 Annulus Of ainn 6.5 mm from Inferior limbus 23o Lower CN III Superior Oblique 32 Orbital apex Posterior to above Equator in annulus of Superotemporal zinn Quadrant 51o CN IV Inferior Oblique 37 Behind lacrimal fossa 51o Lower CN III Muscular area near Macula
    34. 34. A way to remember     All obliques Abduct All vertical Recti Adduct All superior muscles Intort  All inferior muscles Extort
    35. 35. ocular movements      The ocular movements are of four types:  Ductions Versions Vergences Supra nuclear movements
    36. 36. Ocular movements (terms)     Agonist muscle Antagonist muscle Yoke Muscles Synergist Laws of ocular motility   Sherrington law of reciprocal innervations Hering Law of equal innervations
    37. 37. Full muscle sequelae will include     Primary paresis of the muscle Over action of contralateral synergist Contracture (O/A) of ipsilateral antagonist Under action of contralateral antagonist (2ndry inhibitional palsy)
    38. 38. Nine Position Of Gaze
    39. 39. The Diagnostic Positions of Gaze RSR LIO RIO LSR R RLR LMR RIR LSO L RMR LLR RSO LIR
    40. 40. H-PATTERN TEST Instruction to the Px should be: “We are now going to assess how well your eye muscles work together. I would like you to follow the target with your eyes while keeping your head still. Let me know if you feel any pain on eye movement or if you detect double vision at any time in the test.” RSR LSR LIO RIO RLR LMR LLR RMR RIR LIR LSO RSO
    41. 41. Recording of Ocular Movements Grid form Rt. Gaze Lt. Gaze RT .SR LT .IO RT .IO LT .SR RT .IR LT .SO RT .SO LT .IR
    42. 42. Recording of Ocular Movements Grid form Rt. Gaze Lt. Gaze Rt+/ Lt- Rt-- / Lt++ E.g. RT SO Palsy
    43. 43. Recording of Ocular Movements  Diagrammatic form Rt. eye Lt. Eye
    44. 44. Recording of Ocular Movements      Descriptive form: e.g.. Rt. Medial rectus is under acting -2 or Rt. MR u/a -2 Rt. MR u/a --
    45. 45. Three – Step Test
    46. 46. Three – Step Test    Superior oblique palsies are often diagnosed using the three-step test. There are eight cyclovertically acting muscles; four work as depressor of the eye and four work as elevators of the eye. Four in each eye.
    47. 47. Step-1 Determine which eye is hypertropic by using the cover test. Step-1 narrows the number of possibly under acting muscles from eight to four  e.g. Rt hypertropia: This means that either the depressors of the Rt eye are weak (RIR,RSO) or the elevators of the Lt eye are weak (LIO,LIR). Draw an oval around them
    48. 48. R Hypertropia Elevators of L eye RSR RIO LIO LSR RSO LIR RIR RSO Depressors of R eye LSO
    49. 49. Step-2  Determine whether the vertical deviation is greater in Rt gaze or in Lt gaze.  e.g. in Lt gaze. This implicates one of the four vertical acting muscles used in left gaze, the two possible muscles at this point are either both intortors or both extortors. Draw an oval around the four vertically acting muscles that are used in Lt gaze. It may be either the RSO or LSR. These are the only muscles  circles twice.
    50. 50. R Hypertropia RSR RIO LSR LIO RSO RIR RSO RSO LIR LSO Left Gaze
    51. 51. Step-3    This step is also known as Bielschowsky head tilting test, it involves tilting the head to the Right then to the Left. Head tilt to the Right stimulate intorsion of the Rt eye (RSR,RSO) and extorsion 0f the L eye (LIR,LIO) and vice versa. e.g. in the same case suppose that the vertical deviation increases to the Rt tilt. This implicates the four muscles that act vertically in the R tilt position. Draw an oval around these muscles. Note that the RSO is the only muscles that is surrounded by three ovals.
    52. 52. RIO LSR LIO LIO RSR RSO RIR Tilt to R side RSO RSO Rt. SO Palsy LIR LSO Left Gaze
    53. 53. Hess test
    54. 54. Principle of test 1. Dissociation of the eyes by either:   Red and Green goggles in case of Hess. The mirror in case of Lees Screen. 2. Foveal projection in the presence of normal retinal correspondence. 3. Herring’s and Sherrington’s Law: Explain the development of muscle sequelae.
    55. 55. Uses of Hess Test 1. Diagnosis of  Underaction or Overaction of EOM.  Mechanical or Neurogenic palsy.  A or V pattern 2. Planning of surgery and post-op effects of surgery 3. Monitoring of condition.
    56. 56. How to interpret
    57. 57. How to interpret
    58. 58. 4.Ocular Movement  FDT force duction test: The purpose of the force duction test is to assess passive movement of the globe in case in which active ocular movements are limited either neurologically or mechanically.
    59. 59. 4.Ocular Movement  FGT force generation test: The force generation test assesses the active muscle force which enables eye movement to take place. The aim of the test is to calculate the potential force in an apparently paralised muscle.
    60. 60. 5.Binocular Function
    61. 61. Investigation of BSV       It can be done through: Bagolini Glasses Worth 4 lights Prism reflex test 4 ∆ Prism test Stereo acuity tests
    62. 62. Bagolini glasses   Apparatus consists of a pair of plano- glasses marked with fine parallel striation of 45o & 135o on the other. Line image is formed at 90o of striation.
    63. 63. Bagolini glasses Test distance  Can be used at 6m & 33cm Position of Gaze   Can be used in any desired gaze Upward and downward gaze especially in “A” &“V” pattern
    64. 64. Worth 4 light test It consists of four circular lights  Two green lights  One red light  One white light.
    65. 65. Worth 4 light test Test’s Phenomenon    Red light is seen through red filter. Green light is seen through green filter. White light is seen by both eyes.
    66. 66. Worth 4 light test Results 1. 4 lights indicates BSV either normal or less usually abnormal. 2. 2 lights are seen if left suppression is present. 3. 3lights are seen if there is right suppression. 4. 5 lights are seen if diplopia is present.
    67. 67. Prism reflex test    The prism is used to assess the motor system of the patient. A 15∆ to 20∆ is placed in front of one eye and response of the other eye is seen. A response should be obtained in infants aged 6 months and up ward.
    68. 68. Prism reflex test Results    If all three movements are seen motor fusion is present, however Asymmetry of movement should be noted. If the eye behind the prism fails to adduct then there is a scotoma present in that eye. If the other eye fails to recover then it indicates that suppression prevented the recovery or lack of motor fusion.
    69. 69. 4 ∆ Prism test  The main aim of the test is to prove the presence of normal binocular single vision.
    70. 70. 4∆ Prism test A 4∆ prism is placed in front of one eye and the recovery is noted. The strength of image moves the image a little bit in the foveal area, if the recovery and movement is seen then there is no scotoma present. Prism can be used B.I, B.O, B.U & B.D.
    71. 71. Stereo acuity       Include : Lang two pencil test Titmus Fly Test The Frisby Stereo-test TNO test The Lang Stereo-test
    72. 72. Tests for Stereopsis (Qualitative Tests) Lang 2 pencil test Method: Pt places the pencils tip on the tip of the examiner’s pencil. Result: It is a test mainly used for the detection of gross stereopsis. 1.
    73. 73. Titmus Fly Test – Polaroid Vectograph
    74. 74. Titmus Fly Test – Polaroid Vectograph This test uses crossed Polaroid filters to present slightly different aspects of the same object to each eye. The test comprises of three sections: • The Housefly - which shows large disparities and should be seen in depth by most subjects. • Circle Patterns – this section consists of patterns containing four circles. One of the circles in the pattern contains a graded disparity (crossed), so that when it is viewed binocularly it is seen to float in front of the others. The disparities of the circles range from 800 to 40 secs of arc. • Animals – there are 3 rows of animals, one animal in each row having a crossed disparity which ranges from 400 – 100 secs of arc.
    75. 75. The Frisby Stereo-test
    76. 76. The Frisby Stereo-test This is the only clinical test based on actual depth, where random shapes are printed on three clear plastic plates of different thickness. The test does not require any form of dissociation. Each plate has 4 squares of curved random shapes, and one square contains a hidden circle that is printed on the opposite surface. Disparities range from 600 to 15 secs of arc. Care should be taken that neither the plates nor the Px’s head move significantly during the testing procedure, as this may provide monocular cues. If the first plate is recognised successfully then the thinner plates, which give smaller disparities, are presented in a similar fashion.
    77. 77. The TNO Test
    78. 78. TNO Each test plate consists of a stereogram in which the images presented to each eye have been superimposed and printed in complimentary colours. The stereograms are viewed through a pair of red and green filters. The random dot stereograms have the advantage that they completely eliminate monocular cues, the patient is required to describe the shape which can only be seen stereoscopically.
    79. 79. The TNO test has 7 plates. The first four plates are for screening purposes, the disparities are large and ungraded. Plate I 2 butterflies are present, one can be seen monocularly, the other is only seen in stereopsis. Plate II 4 discs, 2 are seen monocularly two require stereopsis. Plate III four hidden shapes (O, , ∆, ) are arranged around a centrally placed cross Plate IV This is a suppression test. There are 3 discs, one seen by the right eye, one by the left, and one is seen binocularly. Plate V-VII Here the test items (Pac-man Shapes) are presented at 6 different disparities ranging from 15 – 480 secs of arc.
    80. 80. Plate V Plate VI Plate VII 480 120 30 240 60 15
    81. 81. The Lang Stereo-test
    82. 82. Lang The test consists of vertical sections that are seen alternately by each eye as they are seen through in-built cylindrical lens elements. Displacement of the random dots creates the disparity which ranges from 1200 to 550 secs of arc. The cards are held at the subject’s reading distance and he or she is asked to name or point to the pictures.
    83. 83. 6.Refraction
    84. 84. Cycloplegia and retinoscopy    Accurate refraction in children usually requires full cycloplegia. Adequate cycloplegia for retinoscopy may be obtained in 60 minutes following the instillation of cyclopentolate 1% eye drops. Below the age of three months mydriatics are used in lower concentration to reduce the risk of toxicity. 
    85. 85. Refraction   The routine use of atropine for diagnostic cycloplegia or mydriasis is unnecessary and may cause harmful side-effects. However, in patients with darkly pigmented irides cyclopentolate may prove insufficient for full cycloplegia and it may be necessary to use atropine eye drops or ointment.
    86. 86. Correction of refractive error Hypermetropia :    In all forms of esotropia, full correction of hypermetropia is the treatment of choice. In practice, a reasonable lower limit for spectacle correction is + 1.50 dioptres (+ 3.00 ret. @ 2/3 metre). When prescribing, 'full correction' means that only the working distance is allowed for with no subtraction for cycloplegia. 
    87. 87. Refraction Hypermetropia :    In esophoria full correction In exophoria or tropia under correction In children without strabismus the precise indication for treatment of spherical errors is ill defined and will depend on the age of the child symptoms and the magnitude of the error. 
    88. 88. Refraction      Myopia In esophoria or tropia under correction In exophoria or tropia full correction or even over correction High myopia (-6.00 D or more) may require correction in infancy and moderate myopia (4.00 D or more) in two year olds and older children. Lesser degrees of myopia do not usually cause problems in small children and prescription can be based on subjective refraction over the age of six years.

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