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Strabismus Research

Caloroso EE. “A sequential strategy for achieving functional binocularity in strabismus.” J Amer Optom Assoc, 59:378, 1988. Abstract: The clinical approach to achieving functional binocularity for constant strabismus includes a series of sequential steps utilizing several therapy options. Passive therapy included lenses, prisms, filters, occlusion, medications, and strabismus surgery. Active therapy adds visual exercises and/or self-monitoring systems such as biofeedback. Consideration of commonly used options and an overall sequential strategy is presented as a practical guide to the successful management of strabismic patients.


Chryssanthou G. “Orthoptic management of intermittent exotropia.” Am Orthoptic J, 24:69-72, 1974. This study reviewed the cases of 27 patients with intermittent exotropia (ages 5 to 33 years ) who received orthoptic treatment. A total of 89% of patients showed definite improvement, with 66.6% graded excellent or good 6 months to 2 ½ years after termination of orthoptic treatment.


Coffey B, Wick B, et al. “Treatment options in intermittent exotropia: a critical appraisal.” Optom Vis Sci, 69:386-1404, 1992. Abstract: This paper reviews the clinical literature related to five different treatment modalities used for intermittant exotropia (IXT): overminus lens therapy, prism therapy, occlusion therapy, extra-ocular muscle surgery, and orthoptic vision therapy. Based upon review of 59 studies of treatment of IXT, and using each author’s stated criteria for success, the following pooled success rates were revealed: overminus lens therapy (N=215), 28%; prism therapy (N=201), 28%; occlusion therapy (N=170), 37%; extra-ocular muscle surgery (N=2530), 46%; and orthoptic vision therapy (N=740), 59%. Success rates for IXT surgery differed depending upon whether a functional (43%) or cosmetic (61%) criterion was used to evaluate treatment success. These pooled success rates must be viewed carefully because nearly all the studies suffer from serious scientific flaws such as small sample sizes, selection bias, inadequately defined treatment and success criteria, absence of statistical analysis, and results reported in a manner that makes interpretation difficult.


Cooper J, Medow N. “Intermittent exotropia basic and divergence excess type.” Binocular Vis & Eye Muscle Surg, 8:185-216, 1993. Abstract: Intermittent exotropia is a unique strabismus with a specific set of sensory motor findings. This paper provides a comprehensive review of nomenclature, epidemiology, sensory motor findings, theories of etiology, and treatment of intermittent exotropia, of both basic and divergence excess types.


Cooper J. “Review of Computerized Orthoptics with Specific Regard to Convergence Insufficiency.” Am. J. of Optom. and Phys. Optics. 65(6): 455-463, 1988. Abstract: Tradition vision therapy has used line targets to improve vergence function. Manipulation of these targets is slow and arduous. Automated therapy using Randot targets is good for patient motivation, reliability and standardization.


Cooper J. “Orthoptic treatment of vertical deviations.” J Amer Optom Assoc, 59:463-8, 1988. Abstract: Four patients with large vertical deviations were treated with a combination of prismatic glasses and orthoptics. The lease amount of prism which eliminated diplopia, followed by horizontal fusional range extension, was prescribed. After vergences were normalized, the prism was further reduced by two prism diopters and horizontal fusional range extension was repeated. This process was repeated until either a plateau was achieved or the prism was eliminated. All four patients completed therapy with almost total alleviation of symptoms and elimination of full-time prismatic correction.


Duckman RH. “Management of binocular anomalies: efficacy of vision therapy, exotropia.” Am J Optom Physiol Opt, 64:421-9, 1987. Abstract: This paper presents a survey of the literature on management of the various forms of exotropia. Criteria for success of treatment are examined. A table summarizing the results of 11 studies is given. The data support the premise that vision therapy is successful in the treatment of exotropia. Over 61% of patients achieved a status of good or better.


Flax, N. “A comparison of functional results in intermittent divergent strabismus treated surgically and optometrically.” J Opt Vis Devel, 17:18-9, 1986. Abstract: The literature was reviewed to determine functional outcomes when intermittent exotropia is treated surgically. Twenty-two credible papers were located and these were analyzed in terms of binocular function. The results achieved surgically are compared and contrasted with published results when strabismus


Flax N, Duckman RH. “Orthoptic treatment of strabismus.” J Amer Optom Assoc, 49:1353-61, 1978. Abstract: This paper examined the effectiveness of orthoptics as a viable treatment modality for strabismus. A review of pertinent literature and an analysis of the data was presented. The results of several studies show a combined functional cure rate of 72.4%.


Gallaway M, Vaxmonsky T, Scheiman M. “Management of intermittent exotropia using a combination of vision therapy and surgery.” J Amer Optom Assoc, 60:428, 1989. Abstract: Vision therapy has been shown to provide higher success rates than surgery in the treatment of intermittent exotropia, but vision therapy is not successful in all cases. A case of intermittent exotropia is presented that illustrates the use of vision therapy in combination with surgery. Issues that should be considered when selecting this treatment option are discussed.


Goldrich SG. “Optometric therapy of divergence excess strabismus.” Am J Optom Physiol Opt, 57:7-14, 1980. Abstract: A review and analysis of the vision training procedures were carried out over a period of 2 years at State University of New York (SUNY), University Optometric Center. Training included motility, accommodative rock, fusion, anti-suppression, and stereoscopic skills by a variety of techniques and devices. Patients who exhibited smaller pre-training angles of deviation, increased maturity, and greater motivation responded most successfully to treatment. The results achieved in this study compare favorably with those obtained by traditional orthoptic procedures.


Kran BS, Duckman R. “Divergence excess exotropia.” J Amer Optom Assoc, 58(11): 921-930, 1987 This paper presents a summary of information regarding divergence excess exotropia. This paper deals with the description (i.e. definition, onset, natural history, prevalence, sexual distribution, symptomatology, and the differential diagnosis of the two (subtypes) of this entity and reviews the various treatment options (surgery, lens therapy, prism therapy, and vision training) currently available with emphasis on vision training/orthoptics. It was concluded that divergence excess exotropia is effectively managed at least as well as by vision training/orthoptics as it is by surgery.

Kushner B. “Recently acquired diplopia in adults with long-standing strabismus. Arch Ophthalmol. 2001;119:1795-1801. Background: The evaluation and management of recentonset diplopia in an adult with a history of long-standing strabismus can be perplexing and challenging. No guidelines exist, to my knowledge, for the examination of suchpatients. Design: A retrospective medical record review. Subjects: Patients seen in my practice with a history of recently acquired diplopia and a history of strabismus dating back to childhood. Results: One hundred fifty-two patients who met the enrollment criteria were identified. Using the treatment approach outlined herein, 132 patients were relieved of their symptoms of diplopia. In most cases, the onset of the diplopia could be correlated with a change in the patients ocular alignment, refractive needs, or refractive management. Returning patients to their motor status before the onset of symptoms or addressing the change in refractive needs or management usually resulted in relief of symptoms. Conclusion: In most cases, adult patients with a history of long-standing strabismus and a recent onset of diplopia can be effectively treated.

Loy, O.D., J. The Success of Vision Therapy in the Treatment of a Perseverant Intermittent Exotrope. Optometry – Journal of the American Optometric Association June 2006 (Vol. 77, Issue 6, Pages 272-273).

Background: Intermittent exotropia affects about 2% of the U.S. population. Patients often are concerned about their appearance and complain of diplopia, headaches, photophobia, reading difficulties and blurred vision. The social and psychological implications of this condition on the patient have lead to a great deal of research on the best treatment strategies to reduce the frequency of the eye turn and enhance the fusional process. Often patients and clinicians may make the assumption that surgery may be necessary to correct large intermittent exotropic deviations. However, evidence-based studies have shown that vision therapy has a 60% success rate pooled across 17 studies. This is statistically more successful than all other treatment modalities for functional success.

Case Report: LJ is a healthy 14-year-old boy who was brought to us with a 50 prism diopter AX(T) at distance and near. His large deviation revealed a guarded but favorable visual prognosis. His sensory characteristics revealed normal visual acuity in both eyes, normal correspondence, tertiary fusion, and mild suppression. His parents wanted to explore all nonsurgical means of treatment. Efficient binocular vision was achieved in open space within 3 months of vision therapy to improve monocular visual functioning, normal peripheral, central and foveal fusion. LJ has a less than 1% frequency in his eye turn; obtained clear, comfortable vision at all distance; and has normal stereopsis and fusional ranges that meet Floms criteria for functional success. With home maintenance therapy, subsequent followups with LJ have not shown regression in his progress.

Conclusion: This demonstrates that a motivated, perseverant intermittent exotrope who understands his or her visual problem can have success with vision therapy.


O’Shea RP, McDonald AA, Cumming A, Peart D, Sanderson G, and Molteno AC. “Interocular transfer of the movement aftereffect in central and peripheral vision of people with strabismus.” Invest. Ophthalmol. Vis. Sci. 1994 35: 313-317. Abstract. To compare binocularity in central and peripheral vision of people with early-onset strabismus and people with normal binocular vision. METHODS. Ten subjects with early-onset strabismus, and nine subjects with normal binocular vision were tested. To assess binocularity, interocular transfer (IOT) of a rotary movement aftereffect (MAE) was measured. The MAE stimuli were either confined to the central 2.8 degrees of the visual field or were presented 10 degrees into peripheral vision.

Results. In peripheral vision, there was no significant difference in IOT for the two groups of subjects. In central vision, there was a significant decrease of IOT in subjects with early-onset strabismus. Their IOT was, however, significantly greater than zero.

Conclusions. Early-onset strabismus appears to spare binocularity in peripheral vision but reduces it in central vision. It does not abolish binocularity assessed by IOT of MAE, suggesting that some binocular connections survive early-onset strabismus, even in central vision.


Pritchard C, Ellis GS. “Management of intermittent exotropia: For non-surgical therapy.” Am Orthoptic J, 48: 21-24, 1998. Abstract: This article reviews the nonsurgical treatment for intermittent exotropia. Intermittent exotropia is a condition involving both sensory and motor defects. To enhance results of surgical treatment of the motor defect, nonsurgical techniques can be applied to treat the sensory defect. The available nonsurgical techniques (orthoptics) are numerous, as are the applications. The techniques can be applied when surgery is not indicated or when surgery is delayed. They can also be applied pre- or postoperatively to improve surgical success rate.


Sanfilippo S, Clahane A. “The effectiveness of orthoptics alone in selected cases of exodeviation: The immediate results and several years later.” Am Orthoptic J 20: 104-117, 1970. This study reviewed the effectiveness of basic orthoptic procedures in the treatment of exodeviation in 31 patients. Orthoptic sessions ranged from 5 to 22 with most patients being seen seven to eight times. Before therapy 80.6% were graded as poor and 19.4% were graded fair on the basis of specific criteria. The orthoptic therapy resulted in the attainment of excellent binocular status in 64.5% of the patients. The long-term follow-up revealed 51.7% classified as excellent and 32.3% improved from the initial examination.


Wick B. “Accommodative esotropia: efficacy of therapy.” J Amer Optom Assoc, 58:562-6, 1987. Abstract: Retrospective examination was performed on the records of 54 patients who had undergone treatment of accommodative esotropia. The patients were classified based on the Duane classification as having either convergence excess (n=11) or equal esodeviations (n=43). Over 90% of the patients achieved total restoration of normal binocular function with treatment. The results and implications of this study are discussed.


Wick B, Cook. “Management of anomalous correspondence: efficacy of therapy.” Am J Optom Physiol Opt, 64:405-10, 1987. Abstract: Recently reported success rates for treatment of anomalous correspondence were reviewed and an estimate of the prognosis for successful binocular re-education of patients with esotropia and anomalous correspondence was presented. Based on current therapy techniques reported in the literature, with careful aggressive therapy, 50% of esotropic patients with anomalous correspondence should be expected to achieve binocular vision provided sufficient time (up to 12 months) can be devoted to binocular re-education.


Ziegler D, Huff D, Rouse MW. Success in strabismus therapy: A literature review. J Amer Optom Assoc, 53(12): 979-9883, 1982. Abstract: The purpose of this study was to review the literature pertaining to non-surgical cure rates for strabismus published since 1958 and compare it to Flom’s prognostic model. From the studies which specified Flom’s functional cure or its equivalent, it was determined that strabismic cure rates using vision therapy could be broken down as follows:

Constant esotropia – 29%

Intermittent esotropia – 73%

Constant exotropia – 53%

Intermittent exotropia – 62%