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Diagnostic Techniques for Strabismus

Tests of Ocular Alignment . . Cover tests. Corneal light reflex tests. Dissimilar image tests. Dissimilar target tests. . Tests of Ocular Alignment . Eye movement capability. Image formation and perception.Foveal fixation in each eye.Attention.Cooperation.. Cover Tests prerequisites. Cover-

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Diagnostic Techniques for Strabismus

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    1. Diagnostic Techniques for Strabismus Ramin Sahebghalam M.D Oculoplastic and Strabismus Fellowship 2011

    2. Tests of Ocular Alignment

    3. Cover tests. Corneal light reflex tests. Dissimilar image tests. Dissimilar target tests. Tests of Ocular Alignment

    4. Eye movement capability. Image formation and perception. Foveal fixation in each eye. Attention. Cooperation. Cover Tests prerequisites

    5. Cover-uncover test, Alternate cover test, Prism and cover test. Prism and cover–uncover test, Prism under cover test. Cover Tests

    6. Cover Uncover Test Prism and Cover Test

    7. An absence of movement of an eye when the other eye is covered occurring in both eyes, means that the patient does not have a heterotropia It does not differentiate between orthophoria and heterophoria. Cover-Uncover Test

    8. Alternate Cover Test Alternate Prism and Cover Test

    9. The patient's right eye is covered while fixating a series of distant accommodative targets. After 2 to 3seconds, the right eye is uncovered , cover rapidly is moved to the other side and left eye is covered. The patient whose eye moves on alternate cover has either a heterophoria or heterotropia. Differentiation between the two requires the cover–uncover test. Alternate Cover Test

    10. A temporal horizontal shift is esophoria or esotropia, A nasal shift is exophoria or exotropia, The movement of the eye downward is hyperphoria or hypertropia . If both eyes make movements downward, it is called dissociated vertical deviation. Alternate Cover test

    11. Is used to measure the size of DVD, Base down prism is place on the eye, Cover is place in front of prism, Prism power is increased until no movement of the eye can be seen after removing the cover. Prism Under Cover Test

    12. Hirschberg, Krimsky and Modified Krimsky, Bruckner, Major amblyoscope. Light Reflex Tests

    13. A light reflected in the deviated eye: Nearer the pupillary center than the margin: 5°, At pupillary margin : 15°, Midway between pupillary margin and limbus it is 25°, At the limbus it is 45° to 60°, and beyond the limbus it is 60° to 80°. Hirschberg Method

    14. Each 1-mm deviation of light reflex represents 7° or 15 ? of deviation. Brodie’s rule: 1 mm=21 ? (using flash photographs with millimeter rulers included for standardization, Brodie estimated a Hirschberg ratio of 21 prism diopters/mm, this angle correlates highly with that derived from alternate prism and cover testing). Hirschberg Method

    15. Hirschberg Method

    16. Traditional: center the displaced light reflex by putting appropriate prism over deviated eye. Modified: hold the prism over fixating eye (easier to read). Krimsky Method

    17. The Krimsky test is especially useful in: Younger patients, Patients unable to maintain concentration for prolonged prism and alternate cover testing, Patients with diminished central fixation in one or both eyes. Krimsky Test

    18. Krimsky Method

    19. Dissimilar image tests are based on the patient's response to diplopia created by 2 dissimilar images. Maddox rod test, Double Maddox rod test, Red glass test. Dissimilar Image Tests

    20. Are based on the patient's response to the dissimilar images created by each eye viewing a different target; the deviation is measured first with one eye fixating and then with the other. Lancaster red-green projection test, Hess screen test, Major amblyoscope test. Dissimilar Target Tests

    21. Torsional strabismus occurs when the eye is abnormally rotated about the visual axis. Malfunction of the vertical rectus and oblique muscles is responsible. Evaluation of torsion is mandatory in vertical strabismus, whether or not the patient complains of torsional diplopia. Evaluation of Ocular Torsion

    22. Evaluation of torsion is not possible with external landmarks. While the actual axis of rotation is close to visual axis, it is easier for most examiners to visualize the fovea moving relative to the optic nerve. Evaluation of Ocular Torsion

    23. Primary oblique muscle overaction (most common). Secondary oblique muscle overaction ( most common :S.O paralysis). Restrictive processes involving cyclovertical muscles: Thyroid ophthalmopathy Brown syndrome, Blowout fracture Local myotoxicity (retro or peribulbar injections) Orbital displacement (plagiocephaly) Evaluation of Ocular Torsion Etiology

    24. Plagiocephaly

    25. Anatomic (objective) torsion refers to anatomic rotation of eye. Subjective torsion refers to the patient’s perception of rotation. Comparison of anatomic and subjective torsion can help determine the time of onset of cyclovertical strabismus. Evaluation of Ocular Torsion

    26. Fundus Photography (most accurate), Blind spot mapping, Indirect Ophthalmoscopy (easiest). Measuring Objective Ocular Torsion

    27. Measuring Objective Torsion Indirect Ophthalmoscopy Grading system for estimating abnormal torsion

    28. Measuring Objective Ocular Torsion

    29. Easily performed Quick Quantitative Measuring Subjective Torsion Double maddox rod test

    30. Measuring Subjective Torsion Double maddox rod test

    31. Provides a diagrammatic representation of horizontal, vertical and torsional strabismus in 9 diagnostic positions of gaze. Measuring Subjective Torsion Lancaster red-green test

    32. Measuring Subjective Torsion Lancaster red-green test

    33. Method: Patient is seated 1 meter from screen with head straight, wearing anaglyphic goggles. Room darkened. Examiner projects the red streak obliquely on the center of scale ( primary position). Measuring Subjective Torsion Lancaster red-green test

    34. Method: The streak is rotated upon patients command to be seen vertical. The patient is asked to place the green streak in the same place as the red streak. The actual location of projected streaks is manually recorded. Measuring Subjective Torsion Lancaster red-green test

    35. Method: Test repeated in 9 diagnostic positions of gaze. Examiner and the patient change flashlights and repeat the test. Measuring subjective torsion Lancaster red-green test

    36. Interpretation: The Lancaster red-green test is interpreted as if the two streaks are direct projections from the foveas: Left side of the plot indicates the left gaze and the right , right gaze. If the red streak is rotated clockwise, the right eye is extorted, if the red streak is upper, the right eye is upper. If the red streak is on the right, there is exotropia and vice versa. Measuring subjective torsion Lancaster red-green test

    37. Measuring Subjective Torsion Lancaster red-green test

    38. Measuring Subjective Torsion Lancaster red-green test

    39. The examiner can read the amount of subjective deviation directly from the screen. If this degree is equal to formerly measured objective deviation (measured in cover-uncover test, then NRC is present. If the two amounts are not equal, ARC is present Superimposition of both targets on zero shows harmonious ARC. Measuring Subjective Torsion Lancaster red-green test

    40. Possible in children who can count to five. If the visual acuity can be determined, so can the Worth 4 dot response. The test is performed with ordinary room illumination to provide the usual peripheral vision clues. Results should be reported as suppression or fusion. Best at detection of suppression. Worth 4 Dot Test

    41. Distant Worth 4 dot test. Near Worth 4 dot test. Worth 4 Dot Test

    42. 3° macular scotoma : Far W4DT: no fusion @ 6 m fusion begins @ 2.5 m Near W4DT: no fusion @ 2m fusion begins @ 0.66 m Worth 4 Dot Test Monofixation syndrome

    43. When NRC: In both far and near tests: ET: Homonymous diplopia (5 dots) XT: Heteronymous diplopia (5 dots) Worth 4 Dot Test Strabismic patients who acquire deviation of 10? or more after having developed normal binocular vision reflexes

    44. When ARC: Sees 4 dots Test must be done @ near 5° suppression scotoma in ET (40 cm) >5 ° suppression scotoma in XT Worth 4 dot test Strabismic patients who acquire deviation of 10? or more after having developed normal binocular vision reflexes

    45. Forced ductions, Active force generation, Saccadic velocity. Special Motor Tests

    46. This test places obilque muscles on maximum stretch by simultaneously retroplacing, torting and rotating the globe. Forced duction of rectus muscle are best done by pulling the eye forward to put these muscles on maximum stretch. Exaggerated Traction Test forced duction for oblique muscles

    47. One handed exaggerated traction test for the superior oblique muscle right eye

    48. Intraoperative assessment of completeness of an oblique muscle weakening procedure is the most useful application of this test. The test must be done before and after oblique tenotomy and disinsertion. The test can confirm the diagnosis of oblique muscle overaction. Exaggerated Traction Test forced duction for oblique muscles Applications

    49. Deciding over tuck or recess in SO paresis. Differentiation of IO paresis and Brown. The test helps differentiate hyperdeviation causes: inferior oblique overaction, DVD, rectus contracture. Exaggerated Traction Test forced duction for oblique muscles Applications

    50. Is investigated in adult patients with constant starabismus.( a study on 424 patients by Kushner B.J, Archive of Ophthalmo,vol 120, Nov 2002) Prism Testing for Prediction of Postoperative Diplopia

    51. Patient wears appropriate correction. Patent fixes to an accommodative Snellen optotype near to his vision threshold in better eye. Neutralize the deviation by placing prisms over the deviating eye and ask the patient if he sees double. Then remove the first prism and introduce increasing rotary or bar prisms, begin with 0 and overcorrect the deviation by 5 to 10 . Prism Testing for Prediction of Postoperative Diplopia Method

    52. If the patient sees double in any of the former stages, then he/she is asked about type of diplopia: Cross or uncross ? Sharp, or shadowy ghost images? What is the distance between the two images? Prism Testing for Prediction of Postoperative Diplopia Method

    53. Does not see double in any test :no risk. A shadowy ghost image in far periphery :(ARC):very low risk of temporary or constant post- op diplopia. Intense and close together:a little risk. Unable to subjectively localize the second image (lost or confused localization): Prism Testing for Prediction of Postoperative Diplopia what the patient my see:

    54. 9% of all adult patient with constant strabismus undergoing surgery will develop post op diplopia. 0.8% of such patients will develop constant diplopia. Prism Testing for Prediction of Postoperative Diplopia

    55. 28% of patients with positive pre-op prism test will develop temporary post op diplopia. 2% of such patients will develop permanent post-op diplopia. Prism Testing for Prediction of Postoperative Diplopia

    56. Predictive Values of the Test

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