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There are three keys to understanding how the new way of classifying and treating intermittent exotropia (IXT) differs from Burian's classic classification. First, the assumption that lateral rectus surgery selectively affects the distance deviation, recess/resect procedures affect the distance and near equally, and that medial rectus surgery selectively affects the near deviation, are false assumptions. Second, AC/A ratios in IXT can be calculated in all the usual manners, provided that any near measurement used in the calculation be made after prolonged monocular occlusion to eliminate the contaminating effect of the Scobee phenomenon. Third, the use of +3 diopter (D) lenses at near and prolonged monocular occlusion are not interchangeable and work on different mechanisms, the former on accommodative convergence and the latter on fusional convergence. All patients with IXT should have a measurement taken after prolonged monocular occlusion, as well as while fixating on a far distant outdoor target prior to surgery, which should target the largest angle measured.

To compare the effectiveness and safety of a novel binocular eye-tracking-based-home-treatment (CureSight) to patching.Prospective, multi-center, randomized, masked, controlled non-inferiority pivotal trial.A total of 103 children aged 4 to ≤9 years with anisometropic, small-angle strabismic, or mixed-mechanism amblyopia were enrolled at six clinical sites, randomized 1:1 to either CureSight treatment or patching.Binocular treatment group used the CureSight for 90 min/day, 5 days/week for 16 weeks (120 hours). The treatment combined anaglyph glasses and an eye tracker to induce dominant eye real-time blur around the fovea in dichoptic streamed video content. Patching group received 2-hour patching 7 days/week (224 hours). The pre-specified non-inferiority margin was 1 logMAR line.The primary outcome was the improvement in the amblyopic eye distance visual acuity (VA) from baseline at 16 weeks, modeled with a repeated measures ANCOVA. Secondary outcomes included stereoacuity, binocular VA, and treatment adherence rates, analyzed by a one-sample Wilcoxon-test within each group and a two-sample Wilcoxon-test comparing groups. Safety outcomes included the frequency and severity of study-related adverse events.Binocular treatment group VA improvement at 16 weeks was found to be not inferior to patching group improvement (0.28 logMAR (±0.13, p0.0001) and 0.23 logMAR (±0.14, p0.0001) in binocular treatment group and patching group (90% CI of difference [-0.008, 0.076]), respectively)), since the lower confidence bound of -0.008 falls within the non-inferiority margin of -0.1 logMAR. Stereoacuity improvement of 0.40 log-arcseconds (p0.0001) and improved binocular VA (0.13 logMAR, p0.0001) was observed in binocular treatment group, with similar improvements in patching group in stereoacuity (0.40 log-arcseconds, p0.0001) and binocular VA (0.09 logMAR, p0.0001), with no significant difference between improvements in the two groups for both stereoacuity (difference 0 95% CI[-0.27, -0.27]; p=0.76) and binocular VA (difference 0.041 95% CI[-0.002, 0.085]; p=0.07). A significantly higher adherence was observed in treatment compared with patching group (91% vs. 83%, difference 8% 95% CI[-4.0%-21%]; p=0.011). No serious adverse events were found.Binocular treatment was well tolerated, noninferior to patching in amblyopic children aged 4 to ≤9 years. High adherence may provide an alternative treatment option for amblyopia.

The Covid-19 pandemic has led to a marked increase in the use of videoconferencing for social interaction. Many people report discomfort and disaffection with this modality, which has been labeled "Zoom Fatigue." Common videoconferencing hardware setups necessitate that if a user looks at the image of the person with whom they are in videoconference, they will not be looking directly at the camera and will appear to not be making direct eye contact. This study determined the minimum threshold of eccentric gaze in a videoconferencing setup above which subjects are perceived as not making direct eye contact by the majority of untrained observers.Image captures were made of four subjects successively fixating at small increments eccentric to a video camera, both vertically and horizontally ranging from 0.9 degrees to 19 degrees of eccentricity. The images were embedded in separate Powerpoint files for each subject. Each file was assessed by seven graders who indicated whether or not they felt the subject was looking directly at them in each slide.The threshold for which 75% of the graders could detect that the subject was not looking at them ranged from only 2.7 degrees for horizontal eccentricity to 5.4 degrees for vertical eccentricity.The hardware setups commonly used for videoconferencing result in persistent eccentric gaze of the participating individuals if they look at the image of the other participants. In theory, this could be a contributing cause of Zoom Fatigue.

When performed prior to visual maturity, strabismus surgery can result in the development or recovery of binocularity. When strabismus surgery is performed after visual maturity, the functional benefits of the surgery should be dichotomized according to whether the onset of the strabismus was before or after visual maturity. If the onset was after visual maturity, patients typically are diplopic. Specific success rates for eliminating diplopia vary according to the nature of the strabismus; however, overall the success rate is quite high. There is a common misperception that surgery in adults for strabismus that began prior to visual maturity is merely cosmetic. Numerous studies contradict this misconception. Even if the strabismus has been longstanding, most adults will experience some improvement in binocular function after strabismus surgery. In esotropic patients, this improvement typically takes the form of an expansion of binocular visual fields; however, some patients may also regain stereopsis. There are many psychosocial benefits to adult strabismus surgery. This is reflected in the finding that the majority of adults surveyed with strabismus would trade a portion of their life expectancy to be rid of their strabismus.

Summary The purpose of this review was to identify areas of consensus and disagreement among experts for the definition of success following strabismus surgery using the Delphi process. Three rounds of electronic questionnaires were sent to a panel of 28 strabismus experts. Throughout the process, members of the panel were masked to one another’s identities to minimize the possibility of influence among members. Prior to data collection, we defined consensus as an 85% agreement on the answer to each question. Questions for which there was no consensus were reworded, and the resultant new questions were used in each subsequent round of questioning. We arrived at consensus for 23 of the 36 questions (64%). Consensus was obtained for recommending unique criteria for the definition of success for certain specific strabismus conditions. In addition, it was considered important that stereopsis and the range of single binocular vision be included in the definition of success for certain types of strabismus.

Background The Delphi process has been widely used to delineate guidelines for the treatment of disorders for which there is little or no evidence in the published literature. The purpose of this study was to use the Delphi process to identify areas of consensus and disagreement on the definition of success after surgery for each type of strabismus. Methods Two rounds of electronic questionnaires were sent to 28 members of the Strabismus Success Definition Delphi Study Group. For the first round, responses to 70 questions were captured as agree (= 1) and disagree (= 2). For round 2, a total of 89 questions were captured on a Likert scale ranging from 1 (strongly disagree) to 7 (strongly agree). Consensus was determined a priori at 85%. Results In both the first and second rounds, inter-rater agreement of 85% consensus was reached for only 20% of questions. Intra-rater agreement per question was low, with κ values ranging from −0.11 to 0.62. Intra-rater agreement was also low among themes, ranging from poor to fair agreement: κ = 0.25 for motor, κ = 0.28 for sensory, and κ = 0.35 for follow-up. Conclusions This study highlights consensus areas that could be considered by researchers in designing studies and identifies areas where lack of consensus indicates that further research is needed.

To outline a systematic approach to strabismus reoperations. Many strabismologists have a formulaic approach to strabismus reoperations, e.g., treat it as a fresh case, advance previously recessed muscles to the original insertion, etc. Patients and methods: This paper is a collection of pearls gained from the author's 40+ years in practice.Effective strategies for strabismus reoperations are not formulaic and should be tailored to the specific history and findings of the patient. The first, and most important decision, is whether to operate on previously operated muscles or fresh muscles. This should be influenced, in part, by whether one is treating an overcorrection or undercorrection. Limitations of rotations and incomitance patterns should be addressed. Many important decisions should be made intraoperatively based on where muscles are found, their integrity (slipped in the capsule, stretched scar, etc.), repeated intraoperative forced ductions, and spring back balance testing.A proper plan for a strabismus reoperation takes into account a number of preoperative factors, and the surgeon should be prepared to modify the plan based on intraoperative findings.

PURPOSE: To compare long-term outcomes after bilateral lateral rectus recession (BLRc) or unilateral recess-resect (R&R) for primary treatment of childhood intermittent exotropia (IXT). DESIGN: Multicenter randomized clinical trial PARTICIPANTS: 197 children, age 3 to

Purpose Amblyopia is associated with a broad array of perceptual and neural abnormalities in the visual system, particularly in untreated or unsuccessfully treated populations. Traditionally, it has been believed that the neural abnormalities are confined to the visual cortex and subcortex (e.g., lateral geniculate nucleus). Here, we investigate the presence of neuroanatomical abnormalities earlier in the visual stream, in the optic nerves and tracts, of participants with two predominant forms of amblyopia. Methods We used diffusion magnetic resonance imaging and probabilistic tractography to compare the microstructural properties of five white matter visual pathways between 15 participants with amblyopia (eight anisometropic, five strabismic, and two exhibiting both etiologies), and 13 age-matched controls. Results Participants with amblyopia exhibited significantly smaller mean fractional anisotropy in the optic nerve and optic tract (0.26 and 0.31 vs. 0.31 and 0.36 in controls, respectively). We also found greater mean diffusivity in the optic radiation compared to controls (0.72 μm2/s vs. 0.68 μm2/s, respectively). Comparing etiologies, the abnormalities in the precortical pathways tended to be more severe in participants with anisometropic compared to strabismic amblyopia, and anisometropic participants' optic nerves, optic tracts, and optic radiations significantly differed from control participants' (all, P < 0.05). Conclusions The results indicate that amblyopia may be associated with microstructural abnormalities in neural networks as early as the retina, and these abnormalities may differ between amblyopic etiologies.

Purpose To describe the usefulness of anterior nasal transposition of the inferior oblique muscle in the fixing eye to treat nystagmus-mediated head tilt recurring after prior torsional surgery. Methods The medical records of patients who underwent anterior nasal transposition of the inferior oblique muscle in the fixing eye to treat recurrence of head tilt after prior successful torsional surgery were retrospectively reviewed. Results Three patients met inclusion criteria. In all 3 patients head tilt was eliminated after inferior oblique anterior nasal transposition with 2, 5, and 9.5 years’ follow-up. In no case did surgery result in any further intorsion of the eye. We postulate that the surgery was successful by stabilizing the normal compensatory and anticompensatory torsional movements that occur with head tilt. Conclusions Anterior nasal transposition of the inferior oblique muscle effectively treats a recurrent nystagmus-mediated head tilt after prior successful torsional surgery. It does not, however, intort the eye further in this clinical setting and must work via a different mechanism.

BACKGROUND AND PURPOSE When patients with intermittent exotropia show an increase in their near deviation after prolonged monocular occlusion, they have been said to have tenacious proximal fusion (TPF). That term is not adequately descriptive, since this finding can occur without the patient having been allowed to fuse. The purpose of this study is to investigate the possibility that this phenomenon is mediated by the preponderance of binasal retinal disparity and uncrossed localization that occurs with near fixation. PATIENTS AND METHODS Ten patients with intermittent exotropia who manifested TPF were measured at 6 m, 1/3 m, again at 1/3 m after 1 hour of monocular occlusion, and at 1/3 m with a peripheral crossed localization stimulating device (PCLSD) that simulated the retinal bitemporal disparity and peripheral crossed localization usually found with distance fixation. RESULTS For the ten patients, the mean measurement at distance was 28.3Δ±3.1, initially at near was 4Δ±3.9, at near after prolonged monocular occlusion was 25.3Δ±5.3, and at near with the PCLSD was 18.5Δ±4.1. The differences between the initial near measurement and the measurement with the PCLSD, and between the PCLSD and post-prolonged monocular occlusion were significant with P

Although it is normal to have some degree of pain and irritation after strabismus surgery, one must always be attentive to the remote possibility of a cellulitis, which requires systemic antibiotics, or the even more remote possibility of endophthalmitis. Usually, swelling and discomfort are most prominent the morning after surgery and improve as the day progresses. However, if the symptoms are worsening, and particularly if the pain is of a deep nature, as opposed to surface irritation, the patient should be seen to rule out a serious problem. Common causes of surface pain include suture irritation (if conjunctival sutures were used), deleon formation, or filamentary keratitis. For reasons that are not clear, preseptal cellulitis can occur and is more common than orbital cellulitis after strabismus surgery. One also must consider an allergic conjunctivitis to be the cause if postoperative topical antibiotics were used. If bilateral surgery was performed, and the irritation is unilateral, you are not dealing with an allergic problem. Treatment of allergic conjunctivitis includes discontinuing the offending medication, and if severe a short course of mild topical steroids.

The terms A-pattern and V-pattern describe horizontal strabismus that is vertically incomitant and has a substantial difference in the horizontal deviation between the midline upgaze and midline downgaze positions. A patient with a V-pattern is more esotropic or less exotropic in downgaze than upgaze and an A-pattern is characterized by the converse. By convention, the difference between upgaze and downgaze must be 15 prism diopters (∆) or greater to diagnose a clinically significant V-pattern and 10 ∆ to diagnose an A-pattern. Less commonly, there are variations of pattern strabismus in which there is minimal change from downgaze to the primary position, but the eyes diverge in upgaze, resulting in a Y-pattern. Converse to a Y-pattern, the main exo shift may be between the primary position and downgaze to form a “λ” (lambda) pattern. Divergence in both upgaze and downgaze constitutes an X-pattern.

This chapter addresses the surgical treatment of third and sixth cranial nerve palsy. The treatment of fourth cranial nerve palsy is discussed in Chap. 8, “Vertical Deviations.”

As stated in Chap. 8, “Vertical Deviations,” not all causes of overelevation in adduction are a result of inferior oblique muscle (IO) “overaction” (OA) . There are many causes of overelevation in adduction that are not caused by “OA” of the IO and will have an unsatisfactory response to surgical weakening of that muscle. These include pseudo-IO OA [1], anti-elevation syndrome (AES) [2], dissociated vertical divergence (DVD), Duane syndrome , pulley heterotopia [3, 4], inferior restrictions in the contralateral eye, and many cases with craniofacial syndromes.

When the extraocular muscles (EOMs) and orbital contents are affected in patients with clinical or subclinical thyroid disorders , a variety of terms have been used to describe the ocular condition. These include Graves’ disease, Graves’ orbitopathy, endocrine ophthalmopathy , thyroid ophthalmopathy, and thyroid eye disease (TED). It is also called thyroid-associated eye disease, because it can occur in patients who are euthyroid or have hypothyroid chronic autoimmune thyroiditis. I will use the term TED.

Most PCPs tend to think of orthomuscular causes for AHPs like muscular torticollis. All strabismologists know of children who were sent for physical therapy when in fact they had a fourth cranial nerve palsy. Conversely, strabismologists may tend to think that all patients with an AHP have an ocular cause. The truth lies somewhere in between. In one prospective multidisciplinary study of 63 children presenting to PCPs with an AHP [1], the cause of the AHP was orthopedic in 35 (56%), ocular in 25 (40%), and neurologic in 5 (8%). No specific cause could be found in the remaining eight (13%) patients (total is more than 100% as some patients had multiple etiologies). Congenital muscular torticollis was the most common orthopedic cause accounting for 31 patients (49%). The most common ocular cause was superior oblique muscle palsy, which accounted for 12 patients (19%). In two patients (3%) with fourth cranial nerve palsy there was secondary neck muscle contracture suggesting an orthopedic cause.

The original term for this condition was double-elevator palsy , because it was felt to be due to a paralysis of both the ipsilateral superior rectus muscle (SR) and inferior oblique muscle (IO). We now recognize that it can be caused by inferior rectus muscle (IR) restriction in isolation [1, 2], supranuclear causes [3, 4], or paralysis of the SR without ipsilateral IO weakness [2, 3, 4]. There also can be IR restriction secondary to ipsilateral SR paresis. It is characterized by an inability to elevate above the midline in all horizontal gaze fields.

I welcome you to the new Journal of Binocular Vision and Ocular Motility (BVOM). I am really excited about being the co-editor of this publication with Kyle Arnoldi, CO as my co-editor. Before I ac...

Objective To investigate the relationship between objective and subjective torsion in patients with cyclovertical strabismus and determine whether objective torsion differs according to which eye is fixing. Design A prospective evaluation of tests of objective and subjective torsion. Participants Thirty-six patients with various types of cyclovertical strabismus. Methods Subjective torsion was assessed with the double Maddox rod, and objective torsion was graded in a masked manner from fundus photographs. Main Outcome Measures Quantification of objective or subjective torsion. Results Objective torsion was the same regardless of which eye was used for fixation. However, after prolonged occlusion of the nonaffected eye, there was often an increase in objective torsion in the nonaffected eye. Subjective torsion typically was absent in patients with objective torsion if they did not have bifoveal fusion but was similar to objective torsion in patients with bifoveal fusional potential. Conclusions Assessment of objective and subjective torsion are each important but play separate roles in the evaluation of cyclovertical strabismus. There is no immediate torsional motor shift when fixation switches from the nonaffected to the affected eye. However, prolonged fixation of the affected eye may possibly result in a motor torsional change in the nonaffected eye in some patients. Financial Disclosure(s) The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Purpose To report results of extraocular muscle surgery for superior oblique myokymia when medical treatment fails. Methods A retrospective review of 14 consecutive patients undergoing superior oblique tenectomy and inferior oblique myectomy between 1976 and 2008. Results The mean age of onset of symptoms was 35.4 ± 12.6 years (range, 16-59.5), with a mean duration of oscillopsia of 5 ± 4 years (range, 1.5-17) prior to surgery. Medical treatment was unsuccessful in all 14. Preoperatively, 2 had a small hypertropia that was consistent with an ipsilateral fourth (trochlear) nerve palsy; 12 had no manifest tropia. Postoperatively, all had complete elimination of oscillopsia, and 12 of 14 were free of diplopia in the primary position at 6 meters and 1/3 meter. The only 2 with diplopia in the primary position after surgery were the 2 with a manifest hypertropia preoperatively. Of the remaining 12 patients, 5 had a hypertropia of the affected eye limited to downgaze after surgery (mean of 6.2Δ ± 1.6Δ). Of the 5, 3 needed contralateral inferior rectus surgery, and 1 required prism for downgaze. The mean follow-up was 4.1 ± 2.4 years (range, 0.5-10). At the final visit, none had oscillopsia or uncontrolled diplopia, but 3 (21%) needed prisms. Conclusions Superior oblique tenectomy and inferior oblique myectomy effectively eliminate oscillopsia associated with superior oblique myokymia but result in diplopia in downgaze in approximately 36% of patients, which may cause symptoms in patients who require a bifocal for near work.

Background Antipodean strabismus is a rare clinical entity in which a patient manifests an esotropia when fixating with one eye and an exotropia when fixating with the other eye. It has been described in the settings of marked uncorrected anisometropia, dissociated strabismus or combinations of paresis, and mechanical restriction of eye movement. Methods A retrospective review of four patients with antipodean strabismus. Results All patients demonstrated a unique and uncommon pattern in which there was esotropia with one eye fixating and exotropia with the other eye fixating. None of the patients demonstrated anisometropia or signs of dissociated horizontal deviation. One patient developed antipodean strabismus after prior surgery to correct a traumatic sixth nerve palsy. Another patient had an associated pseudotumor cerebri. The other two patients had no pertinent medical history and, on clinical examination, demonstrated markedly asymmetric accommodative convergence/accommodation (AC/A) ratios. Conclusions Antipodean strabismus is an atypical heterotropia, which can be associated with a variety of clinical findings. This article demonstrates the uniqueness of this clinical entity and illustrates the first association of this pattern with a markedly asymmetric AC/A ratio.

The surgical approach to esotropia with a high AC/A ratio in teenagers should be dichotomized based on whether or not there is satisfactory alignment at distance with the cycloplegic correction in place. If there is not, surgery should target the near angle with glasses on. If there is good alignment at distance, bifocals should be used, and surgery deferred until the patient is approximately 18 years of age. At that time, surgery could be entertained to eliminate the need of a bifocal, by targeting the near angle measured through the distance correction. Surgery for the purpose of eliminating a bifocal in younger teenagers may be unnecessary as 99% of those who maintained satisfactory distance alignment outgrew the need of a bifocal by 18 years of age. However, many still needed a bifocal in their early teenage years.

Background: Muscle slippage is an adverse outcome of strabismus surgery. Its incidence is increased if adjustable sutures are used or if surgery is performed on the inferior or medial rectus muscles. Although there are no firm numbers for this complication, studies have suggested incidence rates between 7% and 41% when adjustable suture surgery is performed on the inferior rectus muscle. In theory, the semiadjustable suture procedure should decrease this adverse outcome. This procedure involves suturing the corners of the muscle firmly to the sclera and placing the center of the muscle on an adjustable suture. This study evaluates semiadjustable suture surgery with respect to muscle slippage. Methods: The primary treatment group consisted of 57 patients who underwent semiadjustable suture surgery on a total of 61 muscles that either had never previously undergone surgery or had undergone surgery and had not previously slipped postoperatively. Fifty-five were inferior rectus muscles and 6 were medial rectus muscles. An additional 7 patients had semiadjustable suture surgery on muscles that had slipped after prior surgery and were analyzed separately. The outcome evaluation was at least 6 months after surgery. Results: None of the 57 patients in the primary treatment group demonstrated muscle slippage after semiadjustable suture surgery. One of the 7 patients who had history of prior muscle slippage also had slippage after semiadjustable suture surgery. Conclusion: The semiadjustable suture procedure appears to decrease the incidence of muscle slippage.

Background Traditional teaching holds that there is a partial compensatory countertorsion after head tilt because the intorters in the eye on the side of the head tilt and the extorters in the contralateral eye are stimulated. This teaching is inconsistent with a number of clinical observations. Methods Review of existing literature, reanalysis of data from the investigator's previous experiments, and inductive and deductive reasoning were used to reconcile inconsistencies and present a theory on why torsional movements occur. Results The inconsistencies can be reconciled if one considers that during the dynamic phase of head tilt, there is an alternating series of intorsional and extorsional movements of both eyes. Each eye has slow dynamic compensatory counterrolling phases that serve as torsional “doll's-head” movements to stabilize the image during head tilt. This counterrolling is partially eliminated by a series of anticompensatory torsional saccades in the direction of head tilt, which is in contrast to traditional teaching. Conclusion Dynamic compensatory counterrolling occurs during head tilt. It is largely eliminated by anticompensatory torsional saccades in the opposite direction so that by the end of head tilt only minimal static countertorsion remains. The dynamic compensatory counterrolling motion is necessary to minimize peripheral visual movement during head tilt. The elimination of most of the counterrolling by the end of head tilt is necessary to preserve convergence and stereopsis.

Traditional teaching is that convergence resulted from accommodation, and this relationship could be used to help manage patients with exotropia by prescribing overcorrecting minus lenses to stimulate accommodative convergence. The relationship between accommodation, convergence, and its role in managing exotropic deviations always seemed straightforward. In this issue of the Journal of AAPOS, Brodsky and colleagues present a creative and thoughtful hypothesis that turns our prior understanding of the relationship between accommodation and convergence on its head. It is based on prior work by Horwood and her coinvestigators. All strabismologists and orthoptists are intimately familiar with how to calculate the accommodation to accommodative convergence ratio (AC/A). Most are less familiar with the concept of the convergence accommodation to convergence ratio (CA/C)—specifically the accommodation that is driven by convergence. Although the common methods for calculating AC/A ratios have proven clinically useful, they are also somewhat flawed, because they are “stimulus” AC/A ratios. This means that the calculation assumes the amount of accommodation occurring is equal to the stimulus to accommodate. So for a gradient AC/A calculation, it is assumed that if one introduces a lens of 1D or 2D power, the patient in fact accommodates 1 D or 2 Ds more, respectively; for a heterophoria calculation based on comparing the change of alignment when fixation changes from 6 M to 1/3 M, it is assumed that the patient is accommodating 3 D more for the latter measurement. This contrasts with “response” AC/ A calculations, which involve measuring how much accommodation actually occurs. Such calculations require equipment not routinely found in the clinic. Similarly, determination of the CA/C requires special equipment which is probably why most clinicians are not accustomed to calculating it. Using excellent methodology, Horwood and Riddell and Horwood and colleagues published some fascinating observations