Detail of suppression and AC
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This document discusses the treatment of suppression and arc. It defines suppression as a cortical phenomenon that eliminates visual confusion and diplopia in strabismus. There are various types and causes of suppression. The purpose of suppression is to avoid diplopia and confusion. Treatment aims to eliminate suppression and establish binocular vision through techniques like occlusion, prism adaptation, and use of instruments like the TV trainer and bar reader that break suppression by manipulating target parameters.
Detail of suppression and AC
- 1. TREATMENT OF SUPPRESSION AND ARC RAJU KAITI OPTOMETRIST Dhulikhel Hospital, Kathmandu University Hospital
- 2. Introduction • Is a cortical adaptive phenomenon occurring in strabismus, which eliminates the problems of visual confusion and strabismic diplopia. • Sensory anomaly in which image of one eye is not perceived under binocular viewing condition. • It is an active but unconscious & involuntary physiological inhibition of vision which is present only under binocular viewing conditions. • May also occur in heterophorias when there is disturbance in sensory processing (such as uncorrected anisometropia) or in motor processing (such as reduced convergence skills). • As long as suppression is present, binocular vision cannot be established.
- 3. • Clinical association of suppression – Strabismus – Anisometropia – Aniseikonia – De compensated heterophorias • What is the purpose of suppression ??? – get rid of • Diplopia • Confusion – Diplopia & confusion may be overcome by actively ignoring the visual appreciation of the affected eye by process of ocular neglect.
- 5. Types of suppression 1. Depending upon etiopathogenesis: Physiological suppression Pathological suppression • Facultative suppression • Obligatory suppression 2. Depending upon the retinal area where image is suppressed Peripheral-diameters greater then 5 degrees Central (macular)-diameters greater than 1 degree Foveal- diameter less than 1 degree
- 6. 3. Depending upon Frequency: Constant-no awareness of the suppressed information Intermittent-a slow on-off awareness of the suppressed information Flashing-a fast on-off awareness of the suppressed information 4. Depending upon Intensity: Shallow-Diplopia or sensory fusion occurs readily despite suppression Deep-Suppression without diplopia or sensory fusion 5. Depending upon laterality: Unilateral (monocular) suppression Alternating suppression
- 7. • Facultative suppression • Type of suppression which occurs in the squinting eye – only during the time when it is squinting – Disappears immediately when the squinting eye assumes fixation. • No permanent loss of vision • It occurs in cases of alternating strabismus. • Obligatory suppression • Type of suppression that occurs in the squinting eye – during the time when it is deviating & – which persists even during the enforced fixation of the squinting eye. • Occurs in cases of unilateral strabismus. • Occur as a sequel of facultative suppression.
- 8. Pathophysiology of suppression • Suppression- related to Retinal rivalry. • Retinal rivalry – When dissimilarly patterned targets are simultaneously presented to the eyes of patient with normal binocular vision, one element is suppressed or alternate suppression occurs. • In cases of strabismus or anisometropia binocular rivalry is lost & is replaced by suppression. • Reduction of pupillomotor responses. – Reduction increases as depth of suppression increases. • VEP reports suggests – Cerebral cortex responsible for suppression. – Reduction in amplitude as well as reduction of peak latency.
- 9. Summary
- 10. Clinical Detection of Suppression • Worth Four dot Test • Maddox Rod Test • Bagolini striated glasses • Binocular scotometry • 4▲Base-out Test • Vectographic tests • Polarizing glasses & vis-a-vis
- 12. Patient with Foveal suppression: Diplopia remains
- 13. Patient with Foveal and zero measure point suppression
- 14. Treatment Goals • Eliminate Suppression – Accurately assess correspondence and sensory skills – Provide some conditions under which sensory fusion can possibly be established • Stabilize sensory Fusion whenever suppression is absent • Obtain Diplopia when strabismic • Obtain visual confusion when strabismic – Serve as trigger mechanism for motor fusion to regain bifoveal fixation • Improve motor fusion skills in any procedure where suppression has been eliminated and sensory fusion has been stabilized.
- 15. Passive Therapy • Occlusion disrupts habitual binocular stimulation • Prisms or filters can be used in place of occlusion. – Not very successful in removing high frequency and deep intensity suppression – Most useful when the patient already has a baseline of sensory and motor fusion skills or when these methods are combined with an ongoing active therapy program.
- 16. Active Therapy • Change target parameters and select instruments in a planned progression – Use some form of optical system to allow seeing some portion of target by individual eye – Bifoveal fixation can be achieved only when deviation is controllable by fusional vergence – Eliminate in one therapy procedure may appear in other therapy or under free space viewing – Strengthen the sensory motor fusion skill, transitory will be the suppression
- 17. • Anti-suppression therapy has two phases of treatment 1. Biocular phase – Make aware of physiologic diplopia – Non corresponding physiologic points are stimulated by one or more objects to produce diplopia • Pencil push up with target fixing at particular distance and neither fixing the target • Patient becomes accustomed to diplopia • If suppression is shallow, therapy can be carried out in normal room illumination • Deeper suppression may necessitate darker room and filters
- 18. – One target training can be done by prism overcorrection and patient tries to maintain diplopia when the prism is decreased • Vertical prism is helpful to elicit diplopia • Two different targets stimulate non-corresponding points resulting in diplopia – Both image should be seen in base in and base out position – E.g. Brewster stereoscope, Wheatstone stereoscope
- 19. Binocular Phase • Includes superimposition, flat fusion and stereopsis training • Superimposition training can be skipped once NRC has been established in patients with ARC • Intense foveal anti-suppression therapy can be given if complete functional care is desired • The goal of treatment is – Stereopsis of 100”of arc at objective angle, or – No suppression with synaptophore second degree targets and Worth four Dot test • Patching is often necessary between training to prevent suppression from recurring unless the strabismus is present
- 20. Antisuppression Target sequence • Targets that result in the fewest suppression responses or even better in a sensory-fusion response are chosen at the beginning of therapy. • Peripheral sensory fusion is unstable or non-existence-select large peripheral target with a little detail • For peripheral fusion with central suppression – peripheral combined with central detail – Central with little detail • For Foveal Suppression – Central combined with Foveal detail – Foveal with little detail – Foveal with detail
- 21. Target selection for Foveal anti-suppression therapy • Select – Binocular fusionable contour – Critical accommodative detail – Foveal sized suppression target – Fine stereopsis stimulation • Select the target not likely to be suppressed but most likely to be sensorially fused • Add the suppression breakers to eliminate suppression response
- 23. Active Therapy
- 24. Instrument selection • All instruments that allows separate targets to be presented to each eye can be used • Present target at zero prism demand • Determine whether the targets are best presented at the objective angle or at the Orthoposition • If the motor demand exceeds the patient’s ability to make a compensatory vergence response, suppression will result. • Target vergence demand should be less than patients expected vergence response • Most target presents with target needing zero vergence demand thus only motor fusion is necessary before sensory fusion to take place • If motor skills are poor, suppression is more likely than sensory fusion. • Anaglyphic or polaroid methods with visible binocular contours are not appropriate for constant strabismic but are appropriate for intermittent strabismic having peripheral sensory motor fusion
- 25. Instrument selection Antisuppression Training Techniques • Bar reading (target placed at O, Orthoposition) • Beads and Strings ( Target placed at O) • Bernell mirror stereoscope (Target placed at O, ˂D, ˂S) • Brewster stereoscope (Target placed at O, ˂D, ˂S) • Centration Point activities (Target placed at ˂D) • Cheiroscope (Target placed at ˂S) • Colored filter activities (Target placed at O, ˂S, ˂D) • Major Amblyoscope (Target placed at O, ˂D, ˂S) • Mirror superimposition (Target placed at ˂D, ˂S) • Pola- Mirror training (Target placed at O) • TV trainer (Target placed at O) • Vectograms/Transglyphs (Target placed at O, ˂D, ˂S) • Single Oblique Mirror Stereoscope (SOMS) (Target placed at O, ˂D, ˂S)
- 26. Examples of Anaglyphic activity 1. Penlight fixation with red-green glasses in dark room with intermittent rapid occlusion of deviating eye 2. Same with red lens over fixating eye 3. Same with red lens over deviating eye 4. Same without intermittent occlusion 5. Same with pink lens over fixating eye 6. Same with pink lens over deviating eye 7. Same with no lenses 8. Step 1-7 in normal room illumination 9. Step 1-7 with fixation of room objects with and without intermittent or rapid occlusion
- 27. Suppression breakers • Antisuppression alterations are possible for all therapy procedures and are called suppression Breakers. • In any orthoptic instruments and with any target sets, we should know how to eliminate suppression if it occurs. • Techniques: – Awareness of correct response – Fast Flashing – Blinking by patient – Movement of the suppressed target – Prism addition and removal – Pointing, both single and double – Change in target parameters • Should repeat breakers 15-20 times
- 28. 1. Awareness of correct response – Normal eye is covered such that the suppressed target can be seen and identified – Patient is then instructed to consciously attend to keep the target present 2. Fast flashing – flashing one or both of the viewed target – Possibly due to break up of the latency period need for suppression – Fast alternate flashing is the most effective for alternate strabismus – The flash rate should be fast enough to make it difficult for patient to consciously process which eye is fixating. – Ask the patient to concentrate on missing visual information without consciously thinking about which eye is fixating
- 29. Translid Binocular Interaction (TBI) Trainer with Wheatstone Stereoscope
- 30. 3. Blinking by Patients – Consciously blinking the eyes has been found to be important in reestablishing alignment in intermittent exotropia – Suppression are lessened with blinking – Rapid for deep and occasional blink when suppression is shallow 4. Movement of suppressed target – Oscillating suppressed target within the suppression zone (Macular massage) – Reversing the laterality also works i.e. oscillating the normal’s eye target – Rate of movement should be slow to moderate because too rapid movement doesn’t break through suppression – Chasing-the therapist moves one target to different prism demands, and the strabismic patient with NC is asked to move the 2nd target to a position of superimposition
- 31. 5. Prism addition and removal – Added prism moves the suppressed information out of the suppression zone; this is followed by removal of the prism and direct stimulation within the zone; repetition leads to suppression break. – Vertical prism (6-10 pd) is used because vertical dimension of suppression zone is usually smaller – For the resistant suppressor • Move suppressed target out of suppression zone • Move target back to suppression zone • Make patient aware of suppression zone • Move the target back in suppression zone • Make the patient keep all the information present when prism is removed • Repeat 15-20 times
- 32. Prism addition and removal
- 33. 6. Pointing, both single and double – Uses kinesthetic feedback to break suppression – In single pointing, the patient points to the suppression check of the usually suppressed eye, while trying to keep both suppression checks visible all the times. – In double pointing, the patient uses two hands and points to both the suppression checks simultaneously – Effective for treating Foveal suppression
- 34. 7. Changes in target parameters – Changing from one parameter to another is time consuming and least successful – Least preferred method Points to be considered for breaking suppression: • Brightness: – Brighter the target, the easier it will be for the suppressing eye – So put the brighter target in front of suppressing eye – The deeper the suppression the larger is the difference in brightness between the two targets must be
- 35. • Target size: – First target used should be larger than the suppression scotoma – Target size progressively reduces in size as the scotoma shrinks – Progression slower considerably once foveal antisuppression begins • Contrast: – More contrast between background and foreground in the target, the less likely is the target suppressed – Suppression is more difficult to break in natural conditions • Color: – Color targets are more interesting to patients and harder to suppress than black and white target
- 36. Bar reader Equipment 1. Red/Green Bar reader 2. Red/Green glasses 3. VA appropriate word searches 4. Sheet protector 5. Flip lenses, flip prisms • The bar reader (with the bars oriented vertically) should be placed on top of the word search and both should be placed in a sheet protector. The patient should wear the red/green glasses. The therapist should show the patient what each eye sees individually by covering the right eye so the patient can see what the left eye sees and visa-versa.
- 37. • When using the red and green bar reader, the eye with the red filter will be able to see through the red bars while the green bars appear black. The eye with the green filter will be able to see through the green bars but not the red ones. For the patient to be able to read across the entire line of text, both eyes must be working (i.e. no suppression). • The patient should be asked if any of the bars appear black as they read the lines. The bars may look dark but the words are still visible. This is not suppression, it is an artifact of the decreased luminance on the text with the use of the filters. If the bars look black and the patient can not see the letters beneath the bars, then suppression is present. • Suppression may be counteracted by using one of the following: a. Allow the patient to use a close working distance b. Tap or wiggle the bar reader c. Rapidly cover and uncover the non-amblyopic eye d. Coach the patient to ―look hard‖ out of the amblyopic eye (this may be encouraged by tapping the patient’s temple by that eye or by wiggling fingers temporal to the amblyopic eye) e. Blur the non-amblyopic eye slightly with a low plus lens
- 38. TV Trainer • To decrease the intensity and frequency of suppression • TV trainer is a plastic sheet with one side all green and the other side all red. • Has two suction cups attached so that it can be easily attached to TV • This is attached to television and patient wears a red-green glass • Eye behind red filter sees through red side and the eye behind green filter sees through green side of TV trainer. • If suppression is present, one side of TV trainer will turn black
- 39. • Patient is encouraged to try to eliminate the suppression by blinking, trying to converge or diverge or by moving closer or farther away from the television. • Passive form of therapy • Patient is encouraged to try to see through both sides of the plastic. • Watching television becomes impossible if suppression occurs. • This calls attention to suppression and a need for the patient to do something to eliminate the suppression • To increase or decrease the level of difficulty of the task, lenses and prisms can be used or the working distance can be increased or decreased.
- 40. Red/Green Glasses and penlight • Patient is dissociated during this procedure, pathologic diplopia occurs- so shouldn’t be used in strabismics and patients with AC • Pt. wears red/green glasses and holds 6prism BD before dominant eye and views a penlight or transilluminator. • Best to perform in room with rheostat to control room illumination • Room illumination is turned down until the only visible target is the light of penlight • Ask the pt. how many lights and what color lights are seen
- 41. • If suppression is present in this condition also, the light can be moved from side to side, or rapidly move an occluder from one eye to the other • Once diplopia is maintained, the room illumination can be gradually increased until the pt. can maintain diplopia awareness with full room illumination • To make conditions more natural, red/green glasses are then removed, which may stimulate suppression again • If suppression occurs, room illumination is again reduced until diplopia occurs • Then room illumination is increased until the patient can finally appreciate diplopia with full illumination and without red/green filters
- 42. Vertical Prism Dissociation • To decrease patients tendency to suppress • For patients who have moderate to strong suppression-common in anisometropia and high degrees of heterophoria or intermittent strabismus • Select room illumination and best in room with rheostat to control illumination • Select the distance at which the patient can succeed and gradually move to the distance at which he experiences difficulty • Place 6 prism BD in front of dominant eye and ask to view the target • Maintain room illumination to the level the patient manitains diplopia
- 43. • The objective is for the pt. to be able to maintain diplopia as the room illumination changes from low to normal lighting • Can be combined with saccadic and pursuit procedures to increase the level of difficulty • Multiple targets can be used like with hart chart rock • Target can be placed in rotating device • Can also be used while working to develop the feeling of convergence and divergence
- 44. Mirror superimposition • Pt. holds a small mirror at a 45 degree angle in front of one eye and views a target through the mirror • With other eye he views another target • Now the pt. must try to superimpose one image on top of the other • The objective is for the pt. to maintain awareness of both images simultaneously • Variety of targets can be used to increase difficulty level, generally first and second degree targets are used • This procedure is only necessary when suppression is intense enough to interfere with binocular vision therapy procedures
- 45. Vis-à-vis Purpose: Elimination of monocular suppression at distance Equipment: 2 pairs of Polarized goggles Procedure: 1. The patient and the therapist both wear a pair of polarized spectacles and stand facing each other. The patient and therapist should initially stand 2- 3 feet from one another. 2. If the patient is not suppressing an eye, she should be able to see both of the therapist’s eyes through the therapist’s polarized glasses. If she is suppressing her right eye, the therapist’s left eye will not be visible. If the patient is suppressing her left eye, the therapist’s right eye will not be visible. This should be demonstrated to the patient by having the patient cover an eye while looking at the therapist.
- 46. 3. Once the patient understands that when the therapist’s right eye looks dark, she is suppression her left eye and when the therapist’s left eye looks dark, she is suppression her right eye, then have the patient observe the therapist’s eyes for signs that she is suppressing. If suppression is noticed, the therapist should coach the patient to think hard about looking out of the suppressing eye and make it come back on 4. Once the patient is able to keep both eyes from suppressing at a distance of 2-3 feet, the distance should be increased. Increasing distance makes it more difficult to prevent suppression. 5. To check the patient’s attentiveness, the therapist may close an eye and ask the patient if he can tell which of his eyes are closed. To correctly answer, the patient must be able to see both of the therapist’s eyes (have no suppression). 6. Once the patient has demonstrated fairly good control of suppression, the therapist may challenge the patient by having the patient control suppression while balancing on one foot and/or by doing simple math problems or spelling short words backwards.
- 47. Key to Anti-Suppression Techniques Repetition on various instruments Ultimately transfer to open space viewing Can take 4 – 6 months to eliminate suppression & obtain normal sensory fusion response Peripheral to central to foveal fusion can take 2 - 4 months for each step Suppression is removed at same time normal sensory fusion is established Treatment of suppression is also a integrated part of treating other sensory anomalies
- 48. Anomalous retinal correspondence • Sensory anomaly where the fovea of the fixating eye and a non- foveal site of the deviating eye have a common visual direction • In which two fovea do not give rise to a common cortical visual directionalization • AC is a cortical phenomenon. The deviating eye has new “quasi” foveal site called the associated point, Point “a” • Not a retinal phenomenon, so , ARC is a misnomer • Only present with binocular viewing – Presence of crude binocularity
- 49. Angles for knowing ARC Objective angle(D): Angle by which the visual axis of the deviating eye fails to intersect the target of regard Subjective angle(S): Angle between the zero measure point of the deviating eye and point in that eye corresponding to the fovea of the other eye Angle of anomaly:(A) Angular separation between the fovea of one eye and point at that eye which corresponds to the fovea of the other eye (NC,A=0) A= ˂D - ˂S
- 50. Types AC • Normal retinal Correspondence (NC): – <D=<S; <A=0 • Anomalous Retinal Correspondence (ARC): – <D does not equal to <S – Types: Harmonius (HAC): <S=0; <A=<D Unharmonius (UHAC): <D greater than <S; <D greater than <A Paradoxical (PAC): <A or <S greater than <D; After strabismus surgery – PAC 1: <A greater than <D; <S smaller than 0 – PAC 2: <S greater than <D; <A smaller than 0
- 51. Types of ARC • Harmonious ARC; – Angle of anomaly(A)= objective angle (D) – (S)=0 – fig
- 52. • Unharmonious ARC – Subjective angle(S) is less than Objective angle but greater than zero. – Angle of anomaly not equal to the objective angle
- 53. Tests for ARC • Bagolini striated glass test • Vectographic slides • Major Amblyoscope • Hering-Bielschowsky after image test • Cupper’s test for determination of retinal correspondence • Prism bar and red filter test
- 54. Theories of Etiology • Adaptive Theory: – An adaptation to the sensory problems of strabismus to decrease the diplopia caused by the strabismus • Motor Theory: – In registered eye movement, eye moves and brain is told to allow for the movement that is, eye world doesn’t move when eye is moved • Corollary discharge: muscle as well as brain receive a signal to move • Reafferent discharge muscles move sending a signal to move and originate from spindle fibers
- 55. ARC: Prognosis Consideration • Small angle strabismus, good cosmesis, deep suppression and asymptomatic patients simply don’t need treatment • Strabismus direction: – AC in exotropia seldom prevent successful treatment – AC in esotropia has guarded prognosis, but not untreatable – Vertical AC questionable prognosis • Strabismus Frequency – Intermittent strabismus: covariation exists- leads to significant improvement in prognosis – Constant strabismus: Exhibit AC under all viewing conditions – So, plan is to change a constant to an intermittent strabismus whenever possible to produce covariation – Convergence can be stimulated or improved in exotropes so they can covary
- 56. • Anomalous Correspondence type: – HAC and UHAC are easiest to treat – PAC is most difficult; PAC 2 is the most difficult one • Stereopsis: – Reduced stereopsis in strabismics with AC- mostly; but some exhibit good stereopsis – Distinguish between stereopsis and monocular clue – Random dot stereo test is more promising – Lateral contour stereopsis leaves the prognosis in doubt
- 57. • Strabismus size: – Small angle esotropes with small angle of anomaly is most difficult to treat – Micro exotropes also difficult – As long as convergence can be stimulated, large exotropes are not difficult to treat – For esotropes angle of anomaly is of more value than strabismus size; smaller <A, more difficult • Prior surgeries: – AC treatment success lowers as number of surgeries increase – AC in consecutive strabismus is more difficult to treat than postsurgical strabismus – Postsurgical cases without objective and subjective symptoms are best to left untreated – Goal is to attain HAC or suppressing the deviating eye
- 58. Treatment Goals and Plans • Primary visual goal is to establish Normal Correspondence • AC in exotropia and esotropia is usually treated by one of the two conventional orthoptic plans, either by motor or sensory stimulation techniques • Treatment plan for vertical AC depends upon the associated horizontal deviation • Each strabismic patient starts AC treatment sequence and moves sequentially through its stages as the correct responses are achieved. • After the completion of AC therapy, the patient then progresses to the next phases of therapy, which treat the strabismus.
- 59. For Exotropia • Most exotropia with AC responds readily to motor stimulation and follow the following convergence improvement plan. 1. Initial treatment • Lens correction – Ammetropia correction – Minus overcorrection to control exotropia or to stimulate convergence • Occlusion – Part time for intermittents – If convergence could not be stimulated in constant exotropes, full time occlusion is indicated until motor control of deviation become possible
- 60. 2. Motor Stimulation – Convergence is taught to a constant or intermittent exotrope with AC by using active therapy – Covariation can be achieved with convergence and angle of anomaly will be reduced as Orthoposition is approached – Covariation occurs with exotropes of all sizes and types of AC – Active therapy should be performed with targets viewed at a zero prism demand which necessitates full convergence control of the exo to bifoveally fixates and sensorially fuse the targets. – In all cases of constant exotropias, gross convergence activities are performed to obtain voluntary convergence responses – Foveal tags (afterimages and Haidinger’s brushes) are then added to visual activities, so that correspondence can be monitored as the eye converge from exo to ortho alignment.
- 61. Preferred active therapy for Exotropia with AC 1. Gross convergence activities 1. Obtain convergence through accommodation 2. Teach voluntary control of convergence 2. Quoits vectogram and HB afterimage 1. Reinforce voluntary convergence 2. Obtain sensory fusion of targets at “O” pd demand 3. Determine correspondence when patient is bi fixating 3. Major Amblyoscope and foveal tag 1. Set the target at “O” pd demand 2. Reinforce voluntary convergence 3. Obtain sensory fusion of target at “O” pd demand 4. Determine correspondence when patient is bifixating targets Motor stimulation Therapy
- 62. Alternative Therapies for Exotropia • Are selected if motor stimulation plan doesn’t work • Sensory Stimulation - presenting flashing foveally centered targets at the objective angle, so that NC can be obtained with the eyes in the deviated position - Disadvantage Is the long period of intensive stimulation to eliminate AC (i.e. 4-6 months) - Full time occlusion of one eye during therapy is important to avoid any anomalous habitual viewing - So, intensive stimulation of normally corresponding retinal sites during therapy combined with elimination of anomalous habitual viewing with occlusion is important aspect - When exotropes maintain sensory fusion at deviation angle convergence is stimulated - Surgery - some exotropes , adults with longstanding constant , may show limitation in convergence skills - Want surgery for cosmesis - Controversial; normalization of AC in 1/5th of patients after surgery.
- 63. Management of AC in Esotropia • Esotropia with AC is difficullt but not untreatable • Covariation does occur as in exotropia but difficult to obtain fusional divergence to control the esodeviation • Treatment with motor stimulation (divergence)is limited • Although active therapy is preferred, passive prism therapy provides a workable alternative and is necessary for those who are unable to participate in orthoptic program • AC patients in esotropia are divided into 3 groups. – esotropia larger than 15 pd and angle of anomaly larger than 15 pd – esotropia less than 15 pd – esotropia larger than 15 pd and angle of anomaly smaller than 15 pd • Initial treatment with lenses and occlusion are same for the 3 groups but the subsequent active treatment has some differences.
- 64. Management of AC in Esotropia
- 65. • Initial treatment (common to all patients): – Lenses (in some cases bifocal) correct ametropia and reduce the angle – Occlusion for esotropia minimization – Compliance with both lens wear and occlusion therapy is mandatory for successful AC treatment • Esotropia larger than 15 pd and angle of anomaly larger than 15 pd – Sensory Stimulation (details on table next slide) – An intermediate stage between AC and NC shall occur in the therapy. In this stage both NC and AC operate on a conscious level for the deviating eye. This visual response is called “binocular triplopia” as normal eye sees one target and the deviating eye sees two targets in two different positions in visual space. – Alternative orthoptic procedures like kinetic biretinal stimulation – Centration therapy
- 66. Preferred active therapy for esotropia larger than 15 pd and angle of anomaly larger than 15 pd 1. Major Amblyoscope with first ,second and third degree peripheral targets Fast flash at the objective angle kinetic biretinal stimulation Comparison of eye movement and visual direction 10 -20 pd convergence demand Alternation of fixation 2. Centration activities Flashing light ,lens or prism rock ,push backs Physiological Diplopia Stereo fusion targets Sensory stimulation therapy
- 67. • For esotropia less than 15 pd and angle of anomaly of any size – Small angle esotropes frequently have HAC or UHAC, so <A is equal to or smaller than deviation – Some has PAC1 and in this <A is larger than the strabismic angle – Intermittent esotropes can exhibit covariation – Because the deviation falls within limit of normal divergence (10-15pd), the preferred technique for small angle esotropes is MOTOR STIMULATION – An orthoptic technique of eliminating AC by stimulating divergence is called Flom’s “swing technique. – SENSORY STIMULATION – For those who don’t respond to divergence procedures, sensory stimulation at objective angle should be tried – Crucial to use foveal and small central target rather than large central or peripheral targets – Care to be taken-anomalous sensory fusion can occur, and AC reinforced rather than eliminated
- 68. Preferred active therapy for esotropias less than 15 pd and angle of anomaly of any size 1. Major Amblyoscope or mirror-stereoscope with second and third degree peripheral /central targets Obtain anomalous sensory fusion at <S Improve divergence from <S Obtain sensory fusion with targets at “O” pd demand Evaluate correspondence under associated condition 2. Quoits vectogram and HBAIT Obtain anomalous sensory fusion at <S Improve divergence at ,S Obtain sensory fusion with targets at “O” pd demand Evaluate correspondence with fusion at “O” pd demand Change Quoits to central/foveal vectogram :repeat Motor stimulation Therapy
- 69. 3. Brewster stereoscope with 2nd and 3rd degree peripheral/central targets Obtain anomalous sensory fusion at <S Improve divergence by tromboning the card from to near Change the foveal-sized target 4. Bangerter’s binocular bifoveal stimulation The binocular phase of Bangerter’s pleoptic technique can be used to stimulate both foveas simultaneously. Provides a very sensitive way to monitor a small <A Repeatition of bifoveal stimulation (which the therapist is directly monitoring) will stimulate NC Bifoveal stimulation performed in cases with larger <A, but is most useful with small <A, which are difficult to detect in other procedures.
- 70. Esotropia Greater than 15 pd and an angle of anomaly less than 15pd • Moderate to large esotropia most commonly have <A larger than 15pd but exception occurs and for these exceptions, combined sensorimotor therapy is used. • Divergence control of deviation is difficult in these esotropes so sensory stimulation techniques are preferred. However, the effects of this stimulation may be negated, due to the small <A. • These patients make anomalous vergence movements, aligning the target with point ‘a’ rather than fovea, which reinforces AC. • Modification- select targets for which the radius is less than the size of <A which means to present a foveal sized target. • Such targets difficult to obtain and slow sensory response, so, divergence techniques are added
- 71. Preferred Active Therapy for Esotropia Greater than 15 pd and an angle of anomaly less than 15pd 1. Sensory stimulation with first ,second ,third degree peripheral/ central targets at <D 2. Motor stimulation with second and third degree central /foveal target at <S 3. Sensor motor stimulation with second degree foveal targets Combined vision therapy
- 72. Prism Therapy • Prism therapy, designed to break up or disrupt AC can be considered passive treatment. • Sometimes, prism therapy is combined with active therapy for maximum effectiveness, but, often, it is used in isolation • Corrective Prisms – prisms equaling the objective angle prescribed for full time wear • Inverse Prisms – Placing BI prism, in esotropia, before patient’s fixating eye – Encourages divergence and bifixation – Analogous to motor stimulation in amblyoscope; teach patient to covary – Logical but fusional divergence seldom occurs simultaneously
- 73. • Overcorrecting Prisms – BO prism in esotropia will appear to neutralize the deviation but within few minutes, days or weeks, the patients can adapt the corrective prism and so deviation will be developed again. This is due to Anomalous Fusional Movement (AFM) in patients with AC, esp. in esotropia • Strength of AFM can be measured by Progressive Prism Adaptation Test (PPAT) . Strength of prism is increased until the patient can no longer motor fuse the target. In this point, exotropia and crossed diplopia are produced • So, for AC treatment with overcorrecting prism, PPAT should be done and find the prism power that the patient can no longer anonymously motor fuse. • Prescribe until AFM decreases and correspondence changes to normal • Reduced VA and contrast through prism-reduced compliance
- 74. Additional Active Vision Therapy • Lid luster: – the diffuse light source is placed against the close lid of deviating eye while the normal eye fixates a target. The diffuse light seen by deviating eye is then projected into visual space . When centered on target , NC is present and when separated from the target, AC is assumed. • Binocular luster: – red-green glass worn by patient and views contourless white field. If he sees a yellowish sheen or luster, NC is present. A patient with AC will often report a split field, half red and half is green. The NC luster response, considered to be an NC fusion response, was then targeted as an initial therapy method to obtain an NC response. • Contourless fusion fields: – A field completely free of contours is felt to be optimal for achieving NC. Viewing of a flashing blank field in major amblyoscope is another procedure. • Translid binocular interaction trainer: – Effective for breaking both suppression and AC by preventing inhibitory interactions through an alternating asynchronous neural stimulation from the fast alternate intermittent flashing. Can be done both with eyes open, but more often, the flashing lamps are held against the closed lids.