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VISION THERAPY Vision Therapy is that part of optometric care which is devoted to developing , improving and enhancing visual performance of people. Nearly all humans are born with the potential for good eyesight ,but visionthe ability to identify, interpret and understand what is seen- is learned and developed, starting from birth. In learning to walk, a child begins by creeping , crawling, standing, walking with assistance and finally walking unaided. A similar process from gross to fine motor control takes place in the development of vision.One visual skill builds on another, step by step as we grow.Science indicates that we do not “see” with our eyes or our brain, rather , vision is the reception and processing of visual information by the total person. Since more than 70% of all information we receive is visual, it becomes clear that efficient visual skills are the critical part of learning ,working and even recreation. Developing Developing visual skills includes learning to use both eyes together effectively, having both eyes move, align, fixate and focus as a team. This enhances the ability to interpret and understand the potential visual information that is available to you. Any deficiency in any of the above visual abilities results in failure to co- ordinate vision with other senses and vision problem problem may occur, resulting resulting in confusing signals. Vision Therapy is , therefore, often requested for individuals with the following visual dysfunctionAccommodative Disorder- focusing problem. Amblyopia – lazy eye. Ocular Motility Dysfunction- eye movement disorder. Strabismus- misalignment of eyes. Treatment of learning disabilities- particularly reading disorder including attention deficiency, dyslexia, dyspraxia, or other reading problem. Vergence Dysfunction- inefficiency in using both eyes together. Visual rehabilitation after traumatic brain injury or stroke. There are broad range of vision v ision therapy techniques and methods among the practitioners, which makes the vision therapy practice difficult to standardize and evaluate. However, studies have shown that following vision therapy techniques have brought results for many CVS patients-
VISION THERAPY FOR ACCOMMODATION ACCOMMODATION FUNCTION There are several vision therapies which can be tried for accommodation excess, insufficiency, infacility, lag and poor stamina. Ideally the following steps should be followed in sequential order for the improvement of accommodation function. However , the clinician may wish to vary this sequence depending on the particular need of the patientAchieve sufficient accommodative amplitude amplitude monocularly, may be a range of + and – 2.50D, proceed from small step to large lens power, eg , + and – 0.50D to + and – 2.50D. Achieve 20 cycles per minute, monocularly, proceed from slow to fast. Accommodative facility of each eye should be nearly equal. Sometimes this may not be possible for pathological reason or incurable amblyopia. Introduce bi-ocular vision therapy and try to achieve the results as above. The following clinical vision therapies may be tried which should also be practiced in house to have good and fast results-
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Accommodative Tromboning Select a good book or some interesting reading material. material. Hold the book at arm’s length. Ask the patient to read for meaning while pulling it closer. The book is advanced to the binocular near point of accommodation and then slowly pushed away to arm’s length again. The process continues for a 10 minutes or so depending upon the patient’s ability. Initially ,the patient may have difficulty in comprehending comprehending the material because the focus f ocus of attention is on movement of the book , but with practice, the movement becomes a background activity and comprehension increases. This improves amplitude, accuracy, and stamina of accommodation in an entertaining entertaining manner. Jump Focus Rock :The most popular jump focus procedure for accommodative facility and amplitude is with the use of Hart Chart or Dynamic Fixation Test Chart. The task involves discriminating and identifying letters in sequence from two different charts –one at far,i.e, at 3 m and another at near,i.e, at 40 cms. The patient alternatively fixates the same letters in sequence on the chart as rapidly as possible. Speed of focusing is emphasized. The clinician standardized the length of one complete cycle and time taken for completing each cycle is recorded. The same therapy can be practiced by the patient in his house in the following mannerHold the thumb six inches from your nose. Focus on your thumb. Take one deep breath and exhale slowly. Then focus on an object 10 feet away .Take a deep breath and exhale slowly. Repeat this several times. Lens Rock:The patient is asked to look at the reading material material or the wrist watch at a near reading distance. distance. Use a range of flipper lens from + and – 0.50D to + & - 2.5 0Dsph flipper depending depending upon the patient’s skill level. The patient needs to flip the flipper flipper to read through + and then – lens and thus complete the cycle. The The number of cycle completed in 1 or 2 minute is recorded. The procedure is usually introduced monocularly with a goal to maximally increasing accommodative facility of each eye and then binocularly VISION THERAPY FOR OCULAR MOTILITY Some patients may have deficient control over their saccade eye movements and may benefit from vision therapy. Amblyopic patients are the most common example. Some unilateral strabismic patients who are nonamblyopic have poor saccade with the deviating eye.There eye.There are also children ,independent ,independent of learning disability, have poor saccades and eye hand coordination. All of these patients may benefit by participating in a vision therapy program. The program should be ideally started monocularly and after each eye is shown to perform equally well, proceed to binocular training. The general approach is as underEnsure good position maintenance ,i.e, steady fixation on a stationary target. Go from gross (saccade) to fine ( small saccade as in reading ). Go from slow to fast (timing of several cycles).
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Develop good eye-hand coordination during saccadic demand ,and then go without hand as support (eg, no finger reading). Train each eye until they have equal skills. Go from monocular ( duction ) to binocular ( version ) saccades. Eliminate any head movement. Develop auditory – visual visual integration into the saccade and ensure good left to right sequencing sequencing as in English reading. Develop reflexive saccade. The final step is th finishing process to eliminate any overshoots, undershoots, or regressions, if possible. The following clinical vision therapies may be tried which should also be practiced in house to have good and fast resultsFixating and picking up objectsUsing ordinary objects like toys, raisins, peanuts, cookies sprinkles, ask the patient to fixate an object, monocularly and steadily for several seconds. The clinician observes the patient’s eye whether fixation is there or not. The use of afterimage for the patient’s subjective feedback as to the accuracy of fixation can also be used. Peanuts can be widely dispersed on a table for gross saccadic training . With improved performance the peanuts can be placed more closely together for fine saccadic training. Next the patient is encouraged to look from one peanut to the next as quickly as possible The performance can be timed as the therapist closely watches the patient’s eye. In step 4, the goal is to ensure eye-hand coordination. The patient picks upeach peanut in turn as accurately and quickly as possible. The patient’s reward , of course, can be eating of peanuts. Next each eye is given training until there is equal ability. In step 6 , the patient views the peanuts with both eyes, repeating steps one through four. An afterimage tag gives important visual feedback to the patient and can be used at each s tep in this sequence. In step 7, the patient is instructed to eliminate head movement,may be an object balanced on the head, when looking at and picking up the peanuts. Now hand clapping can be used as the patient picks up peanuts in rhythm to the auditory stimulus. In step 9, the patient attempts to pick up the peanuts while trying to simultaneously answer the questions asked by the clinician. This is a cognitive loading procedure to develop reflexive saccade. Finally ,the clinician provides feedback to the patient as to any remaining inaccuracies inaccuracies in saccadic eye movement.. The vision therapy therapy for saccadic eye movement movement can be practiced practiced by the patient patient in his house in the following mannerDot-to –dot games can be developed and and the patient is asked to connect a series of dots by drawing drawing a continuous line from one dot to the next , which usually completes a picture that is eventually revealed once the sequence is completed.
Vision Therapy for Pursuit eye movementGeneral approach to improve pursuit eye movement are as under-
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In step 1, try and have adequate position maintenance of a stationary target. Establishing central steady fixation of each eye is the prerequisite to effective pursuit training and should be the primary step when evaluating any of the eye movement system. Step 2 is to proceed from voluntary to reflexive responses. responses. The concept of “ mental effort” is useful useful . The patient’s attention must be actively engaged in the particular pursuit task. Next the eye- hand coordination is trained. t rained. The patient should practice correctly pointing to the moving targets. In time, after good eye- hand coordination is achieved, pointing should be discontinued so that pursuits can be practiced without this support. Step 4 involves progressing from small to large excursions, as large as possible. Note that the progression in saccadic therapy is different; training proceeds from gross to fine movements, because larger saccades are easier to control than smallerone ,eg, reading saccades. Pursuit training begins within a range where success comes easily, then ends with larger excursions. Speed is emphasized in step 5. Fast pursuits are normally more difficult than slow pursuits. Therefore Therefore it is wise to start pursuit training at a slow speed within the patient’s ability to perform and progressively increase the target speed. Jerky to smooth movement. Head movement to no head movements. A book on the may be kept and when it falls off, the cause is head motion. If monocular training of each eye is effective up to this point, the pursuits skill of the right and left eyes should be roughly same. If not, further training for the deficient eye is indicated. On occasion, it is impossible to achieve equality. Cognitive demands are introduced , proceeding from simple to complex. Some adults can calculate numbers while maintaining fixation on a moving target. Pursuit eye movements need to be integrated with general body posture, movements and balance. The following clinical vision therapies may be tried which should also be practiced in house to have good and fast resultsAutomated rotating disks, e.g, Bernell Rotator can be used. The speed of the rotation can be changed from slow to fast ; direction can be switched from clockwise to counterclockwise ; and the size of excursions can be increased by having the patient move closer to the target. Swinging ball, e.g., Marsden ball is suspended from the ceiling and set in a swinging motion. The patient can look at the target at eye level for horizontal pursuit training or from below while lying supine for circular pursuits. In home pursuit can be tried with penlight, the helper, may be mother or sibling moves the penlight target in various direction and the patient attempts to follow it smoothly and accurately. VISION THERAPY THERAPY FOR VERGENCE DYSFUNCTION DYSFUNCTION :Vergences are disjugate, synchronous and symmetric movements of the two eyes in opposite direction. Vergences are tonic movements and are slower than version. Depending upon the direction of movements, vergence movements are of following typesConvergence: refers to the medial movement of the two eyes so that they both are directed toward the object as it is brought closer into view . Convergence Convergence excess is the condition in which an esophoria esophoria or esotropia is more marked marked for near vision than for far vision . Convergence Convergence insufficiency is the condition in which an exophoria or exotropia is more marked for near vision than for far vision .
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Divergence : It is outward rotation of both the eyes which results from co- contraction of the two lateral rectus muscles. Divergence Divergence excess is the condition in which an exophoria exophoria or exotropia is more marked for for far vision than for near vision .Divergence .Divergence insufficiency insufficiency is the condition in which an esophoria esophoria or esotropia is more marked for far vision than for near vision. Vertical vergences : These are disjugate vertical movements of the eyes. In non strabismic disorders, the eyes tend to turn, although this tendency is controlled at times. Non strabismic binocular dysfunctions include convergence insufficiency, insufficiency, convergence excess, divergence insufficiency, insufficiency, and divergence excess. The major consequence of any non strabismic anomaly of binocular vision is poor eye coordination which results in asthenopia, the subjective symptoms of ocular fatigue that include eyestrain, discomfort and headaches arising from use of the eyes . Before embarking upon the vergence vision therapy ,we must ensure the followingFull correction of any significant ametropia, particularly latent hyperopia. Amblyopia therapy if needed, to improve vision to 6/18 or 20/60 atleast. Training of basic ocular motility in each eye ; fixation, saccades, pursuits, and accommodation. Prescribe compensatory prism and added lens combination as needed. Antisuppression therapy to establish diplopia awareness. Development of good monocular and binocular efficiceny skills. Maintenance of home exercises and periodic progress check ups.
The following vision therapies can be triedBrock String This simple piece of apparatus which consists of a long string, usually 10 or 20 feet long, upon which different colour beads are strung. The subject holds one end of the string with his finger at the bridge of his nose while the other end is held by the trainer. The exercise is for the subject to quickly focus the bead of regard when it is moved in and out, as well as focusing quickly from one bead to another. Provided the two eyes are functioning, the string should appear double and converging in a 'V' to meet at the bead of regard in all positions of gaze, e.g , up and out, down and in, etc. Being able to move the string in all directions can pinpoint errors in the visual system that would otherwise escape detection. Equipment: 10 or 20 foot string with three different different colored beads on it. Purpose: To develop binocular coordination, specifically convergence with accommodation. Also, memory tasks. Procedure: 1. One end end of the string string to a door door knob or the the clinician clinician may may hold , and have the subject hold other end to his nose. 2. The patient may be seated or standing with the string at eye level. 3. Spread the beads beads out , with the first first one about 1 foot in front of the nose, nose, and each consecutive consecutive bead one foot from the next one. 4. Ask the patient to look at the first bead , and see the string crossing crossing right at the hole in the bead, with two string in front and two at the back, and forming a cross at the bead.
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5. Now proceed proceed to next bead bead ,and again ask him to see the same “X” pattern . When the patient patient is able to get the “X” pattern at each bead, start rhythmic shift from bead to bead, calling out the colour of the bead at each shift. Gradations: Increase the speed of shifting. Slowly bring the closer bead closer to the patients nose. Remove all the beads, and just slide the convergence up and down the string. Use one bead, slowly move it up and down the string, like a "bug on a string". Add more beads, like five, to increase precision of control. Skip from bead to bead randomly, instead of in order. Stand on balance board. Add rhythm. Call each bead a name, then shift from bead to bead, calling, and remembering remembering names. Increase accommodative demand demand by placing small dots or small s mall letters taped onto the beads. Peripheral call, shift: Patient calls color of next bead he/she observed in the periphery, then shift, then call next, then shift. This requires a great deal of control . Alphabet Pencil Equipment: Two pencils with the alphabet written on them . Purpose: To develop accommodative convergence, and awareness of physiological diplopia. Procedure: Hold one pencil out at arms length (or therapist holds it), along midline of body, and hold second pencil halfway between far pencil and nose. Look at far pencil, should see that one single and two near pencils on either side. Then shift focus to near pencil. With this pencil single, the far one should now be double. The exercise is to shift focus back and forth from near to far looking at each letter of the alphabet. The awareness of physiological diplopia should be maintained throughout the exercise. Gradation: While shifting back and forth, slowly move the closer pencil in closer, until the letters on the near pencil get blurry, then move it back out, and back in, etc. Increase the speed of shifting from letter to letter. Include a third point of focus in the far distance and include that point in the focus shift, e.g. "A" (near), "A" (far), Clock on far wall. Introduce balance tasks, e.g. walking around while shifting, being pushed around in a wheelchair, standing on a balance board, and being pushed in a slow circle in a wheelchair. Pencil Push Up Exercise Exercise Equipment- One sharpen sharpen pencil. Purpose- To treat convergence insufficiency. Procedure1. Hold the the pencil pencil vertically vertically at the arm’s length directly directly in front front of your face face and and slightly slightly below eye level. 2. Gradually bring the pencil closer and closer to your nose tip. 3. At some some point point you will see the two two pencil. pencil. In case double vision does does not occur occur until until the pencil is almost to the nose, you probably do not have convergence insufficiency problem. 4. But some people may see double at five or six inches from their nose. "If that's the case, relax your eyes by looking at something across the room, then look back at the tip of the pencil, which should still be near your nose, and try to be able to see just one. Then move it out to arm's length and bring it in again" . Repeat this for about 10 to 15 minutes.
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"Over several days or weeks, you should be able to gradually bring the pencil closer each time until it's almost to your nose before you see two images into one.
Management of Amblyopia 1. Basis for Treatment Untreated amblyopia is an important health hazard. The risk for blindness is considerably higher for the amblyopic patient than for the general population.57 Vision loss in the healthy eye is often due to trauma, but in cases of functional amblyopia, diseases that usually affect both eyes first attack the eye with less functional impairment. Normal vision in both eyes substantially decreases the lifetime risk for ocular injury and incapacitating vision loss, thus reducing the socioeconomic cost of legal blindness. The treatment of amblyopia is justified not only because it improves vision in the amblyopic eye and decreases the risk of blindness in the fellow eye, but also because it facilitates fusion in a high percentage of cases, which, in turn, helps maintain eye alignment.94 Normal binocular vision and visual acuity are required in a variety of visually demanding careers. Treatment Treatment should be directed toward the two primary etiologies of amblyopia: form deprivation and binocular inhibition. Amblyopia therapy effectively restores normal or near-normal visual function by eliminating eccentric fixation and/or developing more extensive synaptic input to the visual cortex.95-99 It improves monocular deficits of visual acuity, monocular fixation, accommodation, accommodation, and ocular motility. The final step in amblyopia therapy, if possible, is to develop normal binocular vision. The establishment of binocular vision eliminates or significantly reduces the underlying binocular inhibition in unilateral amblyopia, which increases the probability of maintaining visual acuity improvements improvements (See Appendix Figure 1 for an overview of patient management strategy). 2. Available Treatment Options a. Optical Correction The rationale for correcting the refractive anomaly with spectacles or contact lenses is to ensure that the retina of each eye receives a clear optical image. Full correction of the ametropia is effective in some patients, especially isoametropic and anisometropic anisometropic (< 2 D) patients who are binocular.25,100 The use of spectacles versus contact lenses for optical correction has been the subject of debate. Selection of the optical correction involves consideration of the relative advantages of each. Contact lenses appear to have certain advantages, including: • Reduction of aniseikonia in cases of refractive and axial anisometropia101-107 • Improved cosmesis, which encourages better compliance with wearing the optical correction • Elimination or reduction of prismatic imbalance, weight problems, tilt, peripheral distortions, distortions, and visual field restrictions experienced experienced by users of o f spectacle lenses. Spectacles have the advantages of: • Being more economical in most cases • Providing a level of safety against injury to the better seeing eye • Serving as a modality for other optical modifications (bifocal or prism) in the management of residual binocular anomalies. b. Occlusion Occlusion has been the cornerstone of treatment of amblyopia for over 200 years. The rationale for using occlusion is that occluding the better eye stimulates the amblyopic eye, decreasing inhibition by the better eye. Occlusion enables the amblyopic eye to enhance neural input to thevisual cortex. It is also important in eliminating eccentric fixation. fixation. Both convenient and economical, occlusion occlusion requires minimal in-office participation. Occlusion can be classified in several ways: • Type (direct, inverse, alternating)
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. Time (full-time, part-time, minimal) . Occluder (bandage, tie-on, spectacles, contact lenses, pharmacologically induced). Numerous reports in the literature document the successful use of direct occlusion in the treatment of deprivation amblyopia, strabismic amblyopia with eccentric fixation, and anisometropic amblyopia. However, noncompliance with occlusion represents a significant factor in occlusion failures, especially in patients over 8 years of age in whom up to 50 percent noncompliance is common. Potential side effects of occlusion include: . Occlusion amblyopia (amblyopia of the better eye) resulting from indiscriminate or poorly supervised occlusion20 • Precipitation of strabismus or an increase in the magnitude of strabismus • Precipitation of diplopia • Poor compliance due to reduced vision during school and workrelated visual tasks • Cosmetic concerns • Skin allergies and irritations with bandage-type occluders. c. Active Vision Therapy Optometric vision therapy or orthoptics is used to correct or improve specific dysfunctions of the vision system. Vision therapy refers to the total treatment program, which may include passive therapy options(e.g., spectacles, occlusion, pharmacologic pharmacologic agents) and active therapy. With such passive treatment options as optical correction and occlusion,the patient experiences experiences a change in visual stimulation without any conscious effort. Active therapy is designed to improve visual performance by the patient's conscious involvement in a sequence of specific, controlled visual tasks or procedures that provide feedback about the patient's performance. When a reflexive response is achieved, it is anticipated that improved performance will transfer to other noncontrolled visual tasks, ultimately changing the underlying visual processing mechanism. Active vision therapy for amblyopia is designed to remediate deficiencies in four specific areas: eye movements and fixation, spatial perception, perception, accommodative efficiency, and binocular function. The goal of vision therapy is remediation of these deficiencies, with subsequent equalization of monocular skills and, finally, integration of the amblyopic eye into binocular functioning. Active monocular and binocular amblyopia therapies, as opposed to passive management (e.g., occlusion), reduce the total treatment time needed to achieve the best visual acuity. Monocular therapy involves stimulation techniques that enhance amblyopic resolution and foster more normal eye movements, central fixation, and accommodation of the amblyopic eye. Because active binocular inhibition is one of the underlying etiologies of unilateral types of amblyopia, antisuppression procedures are performed under binocular conditions152 or in-instrument conditions simulating binocular conditions. d. Management of Deprivation Amblyopia When a significant physical obstruction (e.g., congenital cataract) is diagnosed early, the initial management should involve consultation with an ophthalmologist regarding removal of the obstruction within the first 2 months of life. In the case of bilateral physical obstruction, surgery on the second eye typically follows the operation on the first eye by 1-2 weeks to minimize the period of binocular inhibition. Any significant refractive anomaly should be corrected, preferably with contact lenses, within 1 w eek after surgery. Parttime occlusion (2 hours per day) combined with visual stimulation techniques may also be prescribed. It is recommended recommended the patient be followed at 2-4 week intervals for 1 year to monitor visual acuity and binocular development. development. If after 1 year the the practitioner is satisfied with the the optical correction correction corneal physiology physiology is normal, and visual acuity has improved and stabilized, the patient can then be monitored at 6 month intervals. In the patient over 12 months old who has a physical obstruction, there may be a question about whether the condition is congenital or was acquired within the first 4-6 months of life. In these cases the prognosis for any significant improvement in visual acuity is poor. Electrodiagnostic testing is recommended to establish the prognosis before initiating any treatment or surgical consultation. e. Management of Isoametropic Amblyopia
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Initial treatment of isoametropic amblyopia involves full correction of the refractive error with spectacles or contact lenses. Within 4-6 weeks the practitioner should re-evaluate the visual acuity and refractive status and, if necessary, modify the optical correction to maintain full correction of the ametropia. Thereafter, Thereafter, followup may be conducted every 4-6 months to monitor visual acuity improvement. The patient may not reach his or her best visual acuity for 1-2 years after the initial correction of the refractive anomaly. Whereas these patients often have a severe accompanying accommodative insufficiency, the optometrist may prescribe active monocular vision therapy or consult with an optometrist who has advanced training or clinical experience in vision therapy. Ten to fifteen office visits plus home vision therapy 15- 20 minutes daily may be sufficient to improve monocular vision function and establish stable binocular vision. More office visits may be necessary if home therapy is not possible. f. Management of Anisometropic Amblyopia The initial step in managing anisometropic amblyopia is full correction of the refractive error with spectacles or contact lenses. Contact lenses have been advocated as the optical treatment of choice in myopic anisometropic amblyopia. amblyopia. A few patients, especially adults, may need to begin with less than the full anisometropic prescription prescription to ensure acceptance of the prescription and avoid diplopia. Simply correcting the refractive error improves visual acuity in some cases. This response is expected more often in younger patients or patients in whom the degree of anisometropia is reasonably small (< 2 D). For children under the age of 6, the recommended initial treatment consists of having the patient wear the refractive correction for 4-6 weeks, then re-evaluating visual acuity before prescribing additional therapy.For older children, adults, and those younger children who do not respond to refractive correction alone, the practitioner may prescribe part-time direct occlusion and active vision therapy or consult with an optometrist who has advanced training or clinical experience in vision therapy.17,80 Part-time occlusion with an opaque or translucent occluder may be used 2-5 hours per day. Active vision therapy is recommended recommended because several studies have shown a significant reduction in treatment time when procedures to improve monocular visual function are added. Once visual acuity has improved to a shallow amblyopia level (20/40-20/60), residual binocular anomalies, especially suppression, should be re-evaluated and treated. Therapy involving involving optical correction and occlusion only may last from 6 to 11.5 months, with the maximum effect of occlusion reached in the first 3-4 months. The addition of active vision therapy may reduce occlusion therapy time by up to 50 percent. When all treatment options are combined, the estimated treatment time to attain best visual acuity and establish normal binocular function in nonstrabismic anisometropic anisometropic amblyopia is office visits. For amblyopic patients who have a combined strabismus and anisometropia, anisometropia, the estimated reatment time is greater. Additional steps would be needed to treat the strabismus and, if possible, establish binocular vision. g. Management of Strabismic Amblyopia If the patient with strabismic amblyopia has a poor prognosis for binocular vision, the practitioner should set a treatment goal of shallow amblyopia to avoid the possibility of producing diplopia. When the prognosis is questionable because amblyopia complicates the evaluation of important prognostic factors, the practitioner should also also set a goal of shallow amblyopia. Once this level level has been reached, the prognosis for binocular vision can be made. For the patient with a good prognosis for establishing binocular vision, the practitioner practitioner should set a goal of best possible visual acuity. The first step in managing strabismic amblyopia is full correction of the refractive error with either spectacles or contact lenses. In certain cases the full correction may need modification to address binocular vision considerations or patient acceptance. The refractive correction alone seldom results in improvement of visual acuity. Occlusion and active vision therapy or consultation with an optometrist who has advanced training or clinical experience in vision therapy may also be part of o f the initial management plan. Full-time occlusion is recommended for constant strabismus; part-time occlusion, for intermittent strabismus. When full-time occlusion is prescribed, performance issues need consideration. consideration. To allow all ow the patient to function at school, at work, or when good visual acuity is critical, inverse occlusion may be considered with direct occlusion prescribed during less critical seeing tasks. In children under age 5 who have either
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central or eccentric fixation, direct full-time occlusion, with adjustments for performance, is the treatment of choice. For patients age 5 and over, eccentric fixation is a significant complication that requires more aggressive treatment. For older patients with eccentric fixation that does not respond to a trial period of 4-6 weeks direct occlusion, active vision therapy should be considered. Active vision therapy may include procedures to improve monocular visual function, especially procedures that promote central fixation. Once visual acuity has improved to 20/40-20/60, the optometrist should re-evaluate and treat residual binocular anomalies, especially suppression and strabismus, if appropriate. The duration of therapy using only optical correction and occlusion ranges from 6 to 11.5 monthswith the maximum effect of occlusion reached in the first 3-4 months. The addition of active vision therapy can reduce therapy time by up to 50 percent. The estimated treatment using a combination of treatment options is office visits to attain best visual acuity and central fixation. In some cases improved visual acuity will result in improved fusion and eye alignment. For patients who have a residual strabismus, the estimated treatment time may be greater; additional steps would be needed to treat the strabismus and establish normal binocular vision. 3. Patient Education The patient and/or parent should be informed of the diagnosis, the positive and negative aspects of the prognosis, the treatment options and sequence, and the estimated treatment time The final management plan formulated in consultation with the patient and/or parents should be responsive to their expectations and preferences. The optometrist should discuss the risks of no treatment (including the impact on future occupational opportunities opportunities and the probability of harm to the good eye) and the importance of protective eye wear and regular monitoring of the patient's condition. 4. Prognosis The prognosis for recovery of visual acuity and improvement of monocular deficits depends on the interplay of several factors: • Patient compliance • Specific type of amblyopia • Monocular fixation status • Age at onset • Initial visual acuity • Age of the patient when treatment is initiated • Type of treatment prescribed. There is a sensitive or critical period early in life when w hen an impediment to the development of normal binocular vision (constant strabismus or anisometropia) will cause abnormal visual input (suppression and/or monocular form deprivation), frequently frequently resulting in amblyopia. In contrast, there is a period which extends much farther in years years where the physiological effects of abnormal abnormal visual experience can be reversed. reversed. Considerable plasticity of the visual system is possible in humans with functional amblyopia up to 60 years of age. Numerous clinical studies have reported marked improvement improvement in visual acuity in the amblyopic eyes of older patients. However, the rate, degree, and extent of recovery may be somewhat diminished in the older patient. Motivation, interest, dedication, and commitment to a rigorous treatment program are critical. Amblyopia is a syndrome of visual processing abnormalities. Although improvement of visual acuity has been the emphasis of most clinical studies, it should not be the s ingle measure of success in the treatment of amblyopia.There amblyopia.There is interest in developing broader measures of visual function more appropriate for evaluating the condition of amblyopia and its treatment. Unfortunately, Unfortunately, review of current literature shows the focus limited almost entirely to the prognosis for visual acuity improvement. improvement. a. Deprivation Amblyopia The prognosis for improvement to 20/50 or better is good for a patient with unilateral congenital cataract if it is treated within the first 2 months of life. Unfortunately, the prognosis for binocular function remains poor, emphasizing the need for frequent followup through the critical period to maintain visual acuity improvements. improvements.
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b. Isoametropic Amblyopia For patients with hyperopic isoametropic amblyopia the likelihood of improving visual acuity to between 20/20 and 20/30 is excellent. This prognosis appears independent of the magnitude of the hyperopia, the initial aided visual acuity, or the age at initial correction. The prevalence of strabismus in patients with uncorrected hyperopic hyperopic isoametropia is percent. Approximately 30 percent of the patients remain strabismic even with the optical correction. Therefore, it is important to identify all associated conditions. Although there are no published studies, the general clinical impression is that the prognosis for patients with isoametropic myopic amblyopia due to form deprivation is also good. The practitioner, however, needs to be careful to rule out structural or pathological causes of reduced vision in these cases. The patient with nonstrabismic isoametropic isoametropic amblyopia should be monitored on a 4-6 month schedule. Maximal visual acuity improvement improvement is expected within the first 2 years following correction. To speed improvement of visual acuity, active vision therapy may be prescribed following the initial correction of the refractive anomaly to improve accommodative156 and binocular function. c. Anisometropic Amblyopia In cases of hyperopic and astigmatic anisometropic amblyopia, the chances of improving visual acuity to 20/40 or better are considered good; reported success rates are 80-90 percent. The prognosis for myopic anisometropic amblyopia, once considered hopeless, hopeless, is now considered fair; reported success rates are 5580 percent. Post-treatment followup is critical to maintain treatment success. Estimates that 25-87 percent of patients experience some decrease in their visual acuity after treatment emphasize the importance of closely monitoring patients with amblyopia once they have been treated. Followups at 2, 4, 6, and 12 months are recommended recommended during the first year after treatment of amblyopia even when treatment is successful.Most recurrent amblyopia can be attributed to failure to establish normal binocular vision once normal visual acuity has been achieved and the patient's failure to continue wearing the optical correction. d. Strabismic Amblyopia The prognosis for the patient with strabismic amblyopia was, until recently, considered poorer than that of one with anisometropia. Recent studies have shown that treating compliant young patients has a success rate similar to that reported for treatment of anisometropic amblyopia.67,128 amblyopia.67,128 The key to successful treatment of strabismic amblyopia is good patient compliance with the recommended treatment. treatment. The length of treatment needed to achieve success is age-related; on average, less time is needed for treatment of younger children. The treatment is longer for older children because they o ften develop eccentric fixation, which lengthens the treatment time and reduces the prognosis for successful treatment of the amblyopia.31,92,176 A more favorable prognosis is typically associated with early diagnosis, early treatment, and central fixation. For the patient who remains strabismic, there is a strong chance that the amblyopia will recur. When the patient is over 5 years old, the possibility of creating an alternating strabismus to help maintain approximately equal visual acuity is significantly less.177 The best method of maintaining improved visual acuity is to establish normal binocular vision.94 However, the fact there is no guarantee that amblyopia will not recur17 emphasizes the importance of monitoring amblyopic patients closely once they have been treated. Even following successful treatment of amblyopia and strabismus, followups at 2, 4, 6, and 12 months are recommended. recommended.
