Bowman lecture. Current concepts of infantile esotropia

Clinical features and change in incidence of acute acquired comitant esotropia: a 15-year single-centre study in South Korea

BACKGROUND/OBJECTIVES

We investigated the clinical features and change in incidence of AACE in South Korea.

SUBJECTS/METHODS

We reviewed the medical records of AACE patients who visited the Strabismus Clinic of at a tertiary referral hospital from 2007 to 2021. Clinical features were retrieved, including age at onset, angle of deviation, refractive errors, neuroimaging findings, and treatment outcomes. For each year, the proportion of new AACE patients among all new patients who visited the clinic, and the ratio of new AACE patients to new intermittent exotropia (IXT) patients, were analysed to estimate the incidence of AACE.

RESULTS

Overall, 59 patients were included in the study. The mean age of the patients was 24.7 ± 9.3 years; the incidence of AACE was highest in teenagers and young adults. No patients had a history of visual occlusion, recent physical or psychological stress, or uncorrected myopia, unlike to classic AACE; moreover, no patients exhibited abnormalities in neuroimaging. There was a significantly increasing trend in the proportion of new AACE patients among all new patients (linear regression analysis, R2 = 0.778, p < 0.001). There was also a significantly increasing trend in the ratio of new AACE patients to new IXT patients (R2 = 0.803, p < 0.001).

CONCLUSIONS

A new type of AACE, distinct from the classic types, is increasingly common in South Korea; this increasing incidence also appears to be a global phenomenon. Large-scale investigations are needed to define the exact clinical features, incidence, and pathophysiology of this new type of AACE.

Revisiting Posterior Fixation Sutures Surgery: Unveiling Novel Approaches for Primary Management of Diverse Esotropia Cases

INTRODUCTION

Strabismus, specifically esotropia, presents a significant challenge in ophthalmic surgery, while several treatment options exist. This study aims to evaluate the results of posterior fixation sutures (PFS) on the medial rectus as a primary approach for some types of esotropia.

METHODS

The medical records of consecutive patients who underwent surgery for esotropia over 11 years and had at least 1 year of follow-up were reviewed retrospectively. Patients were classified into one of three types of deviation: infantile (IE), partially accommodative (PAE) and basic (BE) esotropias. An alignment within 16 prism diopters (PD) of orthotropia was a successful outcome.

RESULTS

A total of 404 patients were included: 67 IE, 180 PAE and 157 BE. Before surgery, a deviation greater than 30 PD was present in 88.1% and 80.1%, and a deviation greater than 50 PD was present in 66.5% and 52.9% of patients (near and distance, respectively). In the BE group, PFS was the baseline surgery in a smaller number of cases (75%) compared to the other two groups (versus 86.6% [IE] and 88.3% [PAE], p = 0.002). The need for an additional procedure was significantly higher in the infantile esotropia group (44.8% vs. 18.9% and 24.8%, p < 0.001). Final surgical success was achieved in 95.3% of all patients. Orthotropia was achieved in 19.4% (IE), 29.6% (PAE) and 25.5% (BE) of cases.

CONCLUSION

PFS of the medial rectus without recession proved successful as a first-line procedure for esotropia in the subtypes of patients evaluated in this study.

Occurrence and subsequent development of vertical deviations in patients treated surgically for infantile esotropia

Purpose

The purpose of this study was to evaluate the onset of dissociated vertical deviation (DVD) and inferior oblique overaction (IOOA), their subsequent development, and their correlation with pre and postoperative parameters.

Methods

Medical records of patients with infantile esotropia who underwent surgery between 2005 and 2017 were retrospectively reviewed. DVD and IOOA were measured before and after surgery. Patients were divided into two groups based on horizontal and vertical deviation at the time of presentation: those with infantile esotropia only (group A) and patients with infantile esotropia who developed vertical deviation (group B).

Results

Out of a total of 102 patients, DVD occurrence was seen in 53 patients (51.9%) and IOOA was seen in 50 patients (48.04%). DVD was seen in 22 patients at the time of initial examination and in 31 patients postoperatively. IOOA at presentation was seen in 45 patients (44.1%) and 5 patients (8.8%) postoperatively. No statistical difference was found in the age of surgery, angle of deviation, mean follow-up, and mean refractive error within both groups. The postoperative motor outcome was statistically comparable between the two groups (P = 0.29). Sensory outcomes of fusion (P = 0.048) and stereopsis (P-value = 0.00063) were better in group A.

Conclusion

No correlation was found between the age of occurrence and development of vertical deviation with refractive error, angle of deviation, age, or type of surgery. We found that motor outcomes are not affected but sensory outcomes are affected in patients with vertical deviations. This indicates that DVD and IOOA are developed due to inherent disruption of fusion and stereopsis.

Timing of surgery in essential infantile esotropia - What more do we know since the turn of the century?

This review summarizes the results and interpretations of studies pertaining to the long-standing debate regarding the timing of surgery in infantile esotropia, more recently referred to as essential infantile esotropia. A systematic search of studies from the year 2000 onward pertaining to the timing of surgery in infantile esotropia as listed in PubMed, Google Scholar, and the Cochrane database was performed. Appropriate cross-references from the articles were also included. Data collected included demographics, presentation, time of surgery, complications, and outcomes. Very early surgery, that is, within 6 months of the onset of infantile esotropia, offers significant advantages in terms of the quality of stereopsis and binocular vision as well as promoting the development of cortical visual processing, thereby benefiting cortical development in human infants. However, the postoperative alignment was not found to be significantly different in the very early, early, or late surgery groups. The reduction in the incidence of manifest dissociated vertical deviation postoperatively in the very early surgery group also showed measurable benefits. The results of this recent literature review demonstrated that very early surgery, within 6 months of misalignment, showed demonstrable benefits in essential infantile esotropia.

Accommodative esotropia: the state of the art

PURPOSE

To review the state of the art of Accommodative Esotropia (AE) through careful study of what has been reported up to the point in literature.

METHODS

A literature search was done on PubMed using key words including "Accommodative esotropia", "Infantile esotropia", "Strabismus" and "Accommodation". We systematically reviewed and critically appraised what has been written about AE and we tried to analyze that according to the current management of AE.

RESULTS

Accommodative Esotropia (AE) is a form of strabismus characterized by convergent misalignment of the visual axes that can be associated with hyperopia and abnormal fusional divergence. Also abnormal accommodative convergence/accommodation ratio could be found. In lots of cases, AE initially presents as an intermittent esodeviation at age 1.5 to 4 years. The prevalence of AE has been estimated near 1-2% in the United States. The only treatment with an optical correction usually is successful in re-establishing alignment, but surgical correction is necessary in approximately 30% of cases.

Esotropia with an accommodative component after surgery for infantile esotropia compared to primary accommodative esotropia

PURPOSE

To compare the clinical outcomes of patients with an esotropia with an accommodative component after infantile esotropia surgery and patients with primary refractive accommodative esotropia.

METHODS

The medical records of patients with postoperative (secondary group) and primary refractive accommodative esotropia (primary group) were reviewed retrospectively. Changes in ocular alignment, refractive error, weaning rate, decompensation rate over time, and sensory outcomes were compared.

RESULTS

The overall change in ocular deviation with glasses correction was -0.5^Δ/year in the secondary group and -0.2^Δ/year in the primary group (P = 0.010). The overall change in spherical equivalent refractive error was -0.2 D/year in the secondary group and -0.3 D/year in the primary group (P < 0.001). The latest stereoacuity result was poorer in the secondary group than in the primary group (P = 0.027). No significant differences in the decompensation or weaning rates were detected between groups.

CONCLUSIONS

The changes in refractive error and the amount of esotropia over time were different between the secondary group and the primary group. Although refractive error was significantly lower and stereoacuity was poorer in the secondary group compared to the primary group, the majority of patients in the secondary group maintained good control of ocular alignment after hyperopic correction.

Essential infantile esotropia with inferior oblique hyperfunction: long term follow-up of 6 muscles approach

AIM

To evaluate long term follow-up (10y) of 6 muscle surgical approach in essential infantile esotropia (EIE).

METHODS

A 6 muscle approach to EIE was retrospectively evaluated in patients with inferior oblique (IO) hyperfunction and lateral rectus (LR) pseudoparalysis, who underwent surgery at different ages. Different clinical characters were analyzed pre- and postoperatively, in patients who underwent a 6 muscles approach ≤4 years of age. All patients underwent a multiple muscles approach: bilateral medial recti (MR) recession (4-5 mm), bilateral LR resection (lower than 7 mm) and bilateral IO recession and anteroposition. Of 108 children with preoperative angle ≥+30 prism diopters (PD) and IO hyperfunction were selected from larger cohort of patients (n=213, 103 females and 110 males) after excluding patients with: angle variability, who underwent reoperation and with incomplete follow up. Preoperative assessment and complete orthoptic examination were performed. Follow-up was performed 3mo, 2, 5 and 10y after surgery. Statistical analysis was performes using SAS statistical software package (version 9.1, SAS Institute Inc., Cary, NC, USA).

RESULTS

Ten years follow up data analysis showed the following percentage of orthotropic patients: (0 PD): 3mo, 22.2%; 2y, 16.7%; 5y, 25.0% and 10y, 27.8%. A slight, significant (P<0.01), increase of 2y follow up residual deviation was found when compared to 3mo one. Stationary surgical results is reported during time, with a trend of mean residual deviation reduction (P=0.04).

CONCLUSION

Our results confirm the reliability of multiple muscles surgical approach in the treatment of patients affected by EIE with OI hyperfunction.

Essential Infantile Esotropia: Postoperative Sensory Outcomes of Strabismus Surgery

BACKGROUND

The optimum age for Essential Infantile Esotropia surgery is a controversial subject. Sensory status was evaluated in patients who underwent surgery at different ages in a retrospective study. The setting of the study is the ophthalmology department of a teaching hospital.

METHODS

Different clinical characters were analyzed pre- and postoperatively; nine different surgeries were performed. A total of 188 patients presented valid postoperative sensorial data, divided in two groups: surgery at ≤2 years (n=69) or >2 years (n=119). Sensory status was dichotomized in binocular single vision (BSV) and exclusion. Univariate differences were assessed with the chi-square test (or Fisher exact test). To identify the independent role of factors associated with the sensory status, all variables showing in univariate analyses a significant association (p<0.05) with the outcome variable were entered into a multivariate logistic regression model. All statistical tests were two-sided.

RESULTS

Multivariate analysis confirmed that children operated >2 years were 0.4 times less likely to obtain BSV compared with children operated at ≤2 years (AOR. 0.38, 95% C.I. 0.17-0.89, p=0.025). Patients operated on by OO MR rec.+ OO LR res. + OO IO rec.-ap. (intervention type 6) were about 11 times more likely to have BSV than those by OO rec.MR + unilateral res. LR (operation type 2); AOR.: 10.67, 95% C.I.: 1.34 - 85.29, p=0.026). Twenty-nine patients (12.1%) operated at ≤2 years of age underwent a reoperation, compared to 33 (8.6%) who underwent surgery after two years (p>0.05).

CONCLUSIONS

Our findings suggest to perform EIE surgery between age 1 and 2 and, when indicated, to prefer a six-muscle approach in order to achieve a better sensory function.

Relative roles of luminance and fixation in inducing dissociated vertical divergence

PURPOSE

We evaluated the roles of luminance and fixation in the pathophysiology of dissociated vertical divergence (DVD).

METHODS

Vertical eye position was measured in 6 subjects with DVD (ages 11-47 years, 5 females) and 6 controls (ages 16-40 years, 5 females) using video-oculography (VOG) under conditions of change in fixation and luminance.

RESULTS

Subjects with DVD showed the following VOG responses. When fixation was precluded with a translucent filter and bright light was shone into one eye to produce a marked binocular luminance disparity, we found some subjects had a small induced vertical divergence causing the illuminated eye to be lower than the nonilluminated eye (mean -1.6° ± 1.5°, P = 0.06 compared to no vertical divergence using the signed rank test). When fixation was precluded with a translucent filter, while alternate occlusion produced a mild binocular luminance disparity, we found a smaller vertical divergence of the eyes that was not statistically significant (1.2° ± 2.1°, P = 0.3). When alternate occlusion produced reversal of monocular fixation in the dark (with essentially no change in peripheral luminance disparity), there was a significant vertical divergence movement causing the covered eye to be relatively higher than the uncovered eye (7.2° ± 3.1°, P = 0.03). The amplitude of this vertical divergence was similar to that measured under conditions of alternate occlusion in a lighted room (where there also was a significant average relative upward movement of the covered eye of 8.1° ± 2.9°, P = 0.03). Control subjects showed no vertical divergence under any testing conditions.

CONCLUSIONS

Dissociated vertical divergence is mediated primarily by changes in fixation and only to a minor degree by binocular luminance disparity.

DVD--a conceptual, clinical, and surgical overview

Dissociated vertical deviation (DVD) is a slow, disconjugate hypertropic deviation of a nonfixating eye. It is usually bilateral, asymmetrical, and often associated with congenital esotropia. The deviating eye elevates, abducts, and excyclotorts. This type of strabismus is often variable, making measurement and clinical quantification difficult. Specific knowledge of the mechanisms and characteristics of the dissociated deviation are required for proper assessment and effective treatment. There is currently no consensus on the mechanisms and pathophysiology of DVD. In this workshop, participants discuss the characteristics and most current methods for assessing and quantifying the deviation and explore the potential etiologies, clinical characteristics, and indications for surgical intervention and nonsurgical management of DVD.

Essential infantile esotropia: postoperative motor outcomes and inferential analysis of strabismus surgery

BACKGROUND

The aim of this retrospective study is a long-term evaluation of postoperative motor outcomes and the inferential analysis of strabismus surgery in infant eyes with essential infantile esotropia.

METHODS

576 patients were compatible with the criteria: confirmed EIE diagnosis, angle ≥ 30 pD, absence of associated ocular anomalies, onset by 6 months of age, absence of hyperopia > 3 Diopters, operation before age 4. Preoperative deviation classes (30-40 pD, 41-59 pD, ≥ 60 pD) were established, different types of surgery were performed. Follow-up was conducted for 5 years after surgery. Longitudinal data were analyzed using general linear mixed models stratified according to the class of pre-operative deviation. A random intercept and a random slope with time (in months) was assumed with an unstructured within subject correlation structure for repeated measurements.

RESULTS

In patients with preoperative angle ≤ 40 pD, a significant interaction effect for intervention by time (F5,155.9 = 3.56, p = 0.004) and a significant intervention effect (F5,226.1 = 6.41, p < 0.001) on residual deviation were observed; only the intervention 5 showed a residual deviation inside the limits of a partial success. In Class 41-59, a significant interaction effect for intervention by time (F4,166.7 = 5.16, p = 0.001), intervention (F4,178.1 = 2.48, p = 0.046) and time (F1,174.6 = 9.99, p = 0.002) on residual deviation were observed; intervention 7 had the highest degree of stability showing an outcome within the range of a partial success. In Class ≥ 60 pD no significant effect for intervention (F4,213.9 = 0.74, p = 0.567), time (F1,169.5 = 0.33, p = 0.569) or intervention by time (F4,160.9 = 1.08, p = 0.368) on residual deviation was observed; intervention 3,6 and 7 resulted in a residual deviation within the range of a partial success.

CONCLUSIONS

We suggest, where possible, a two-horizontal muscles approach in small angle EIE, while a multiple muscles surgery in large angle EIE.

Evaluating a new surgical dosage calculation method for esotropia

Purpose:

To evaluate a simplified method for correction of ocular deviation in patients of infantile and acquired basic esotropia.

Materials and Methods:

Thirty-six consecutive patients of infantile and acquired basic esotropia were selected for this study. Patients underwent unilateral recession–resection surgery as per the new norm gram. Patients underwent 3.5-7 mm recession of medial rectus (MR) in one eye depending on the pre-operative deviation and patient's age. Together they also underwent 6 or 7 mm resection of the lateral rectus (LR) in the same eye depending on patient's age (6 mm for 3 years and below and 7 mm for older age). In patients 3 years and below, a correction of 6, 7, or 8 PD/mm of recession of MR was expected when the pre-operative deviation was lesser than 30 PD, between 30 and 60 PD, or above 60 PD, respectively. Similarly, these values were 5, 6, and 7 PD/mm of MR recession in patients above 3 years. A ratio between achieved and expected correction was calculated and the calculation was deemed successful for a patient if this ratio fell between 0.9 and 1.1.

Methods:

Thirty-six consecutive patients of infantile and acquired basic esotropia were selected for this study. Patients underwent unilateral recession-resection surgery as per the new norm gram. Patients underwent 3.5-7 mm recession of medial rectus (MR) in one eye depending on the pre-operative deviation and patient's age. Together they also underwent 6 or 7 mm resection of the lateral rectus (LR) in the same eye depending on patient's age (6 mm for 3 years and below and 7 mm for older age). In patients 3 years and below, a correction of 6, 7, or 8 PD/mm of recession of MR was expected when the pre-operative deviation was lesser than 30 PD, between 30 and 60 PD, or above 60 PD, respectively. Similarly, these values were 5, 6, and 7 PD/mm of MR recession in patients above 3 years. A ratio between achieved and expected correction was calculated and the calculation was deemed successful for a patient if this ratio fell between 0.9 and 1.1.

Results:

The calculation procedure was successful in 33 out of 36 patients (91%). The two-tailed probability on paired Wilcoxon test was 0.187.

Conclusions:

This simplified method of surgical dosage calculation using MR recession as basis is predictable in patients of infantile and basic Esotropia. It may serve as a useful tool for minimizing variability of surgical results.

Asymmetrical interhemispheric connections develop in cat visual cortex after early unilateral convergent strabismus: anatomy, physiology, and mechanisms

In the mammalian primary visual cortex, the corpus callosum contributes to the unification of the visual hemifields that project to the two hemispheres. Its development depends on visual experience. When this is abnormal, callosal connections must undergo dramatic anatomical and physiological changes. However, data concerning these changes are sparse and incomplete. Thus, little is known about the impact of abnormal postnatal visual experience on the development of callosal connections and their role in unifying representation of the two hemifields. Here, the effects of early unilateral convergent strabismus (a model of abnormal visual experience) were fully characterized with respect to the development of the callosal connections in cat visual cortex, an experimental model for humans. Electrophysiological responses and 3D reconstruction of single callosal axons show that abnormally asymmetrical callosal connections develop after unilateral convergent strabismus, resulting from an extension of axonal branches of specific orders in the hemisphere ipsilateral to the deviated eye and a decreased number of nodes and terminals in the other (ipsilateral to the non-deviated eye). Furthermore this asymmetrical organization prevents the establishment of a unifying representation of the two visual hemifields. As a general rule, we suggest that crossed and uncrossed retino-geniculo-cortical pathways contribute successively to the development of the callosal maps in visual cortex.

Why do the eyes cross? A review and discussion of the nature and origin of essential infantile esotropia, microstrabismus, accommodative esotropia, and acute comitant esotropia

PURPOSE

To try to explain the long-term stability of bilateral medial rectus botulinum toxin (botox) chemo-denervation in essential infantile esotropia; to evaluate divergent fusion amplitude in accommodative esotropia and acute comitant esotropia of emmetropes; to look for accommodation anomalies in high AC/A ratio accommodative esotropia and acute comitant esotropia of myopes; and to discuss characteristics of microstrabismus.

METHODS

Retrospective analysis of 61 essential infantile esotropia patients with early treatment with one botox injection in both medial rectus; measurement of divergent fusion amplitude in accommodative esotropia and acute comitant esotropia; measurement of Near point of accommodation in high AC/A ratio accommodative esotropia and acute comitant esotropia of myopes.

RESULTS

Stable results were found in 85.24% of essential infantile esotropia treated patients; reduced divergent fusion amplitude was detected in accommodative esotropia and acute comitant esotropia; hypo-accommodation was found in some patients with high AC/A ratio accommodative esotropia and a convergence spasm in acute comitant esotropia of myopes.

CONCLUSIONS

Very early botox treatment probably eradicates the effect of an excessive convergence tonus in essential infantile esotropia. A prevention of accommodative esotropia with full retinoscopic correction is only mandatory with a significantly reduced amplitude of fusional divergence. A deficit in accommodation should be looked for in high AC/A ratio accommodative esotropia, before bifocal lenses prescription. Early diagnosed acute comitant esotropia of myopic patients can be treated as a convergence spasm. Only surgery treats acute comitant esotropia, in patients with emmetropia or moderate hypermetropia.

Changes in the functional binocular status of older children and adults with previously untreated infantile esotropia following late surgical realignment

BACKGROUND

Most studies of infantile esotropia concern patients diagnosed in infancy and treated throughout childhood. This prospective study addresses changes in the functional binocular status of older children and adults with previously untreated infantile esotropia, following late surgical realignment.

SUBJECTS AND METHODS

Seventeen patients aged 8 years or more with a history of untreated esotropia occurring within the first 6 months of life were included in this study. All had monocular optokinetic asymmetry, a visual acuity of 20/30 or better in the worse eye, and binocular function assesment preoperatively and postoperatively. All were surgically aligned within 8(Delta) of orthotropia. None had neurologic disease.

RESULTS

Preoperatively, all 17 patients demonstrated a monocular response to Bagolini lenses, while postoperatively 15 (88%) of the 17 demonstrated binocular function with Bagolini lenses (in that they could constantly perceive the major part of both arms of the X generated by the Bagolini lenses) and 13/17 (76%) demonstrated an increase in the binocular field. All 17 had no sensory fusion, either preoperatively or postoperatively, when tested with the Worth 4-Dot test or synoptophore, and no stereopsis with the Titmus stereo test.

CONCLUSIONS

Older children and adults with previously untreated infantile esotropia derive some functional benefits following late surgical realignment. The degree of binocular function may be lower than that achieved in patients aligned before 24 months of age.

Decision analysis with Markov processes supports early surgery for large-angle infantile esotropia

PURPOSE

To assess tradeoffs in time spent with aligned visual axes or stereopsis and risked reoperations between three strategies for the treatment of large-angle infantile esotropia: first surgery at 6, 24, or 48 months of age.

DESIGN

Decision analysis.

METHODS

We simulated three hypothetic cohorts of children with this condition until their eighth year. Potential achievement of stereopsis, the diagnosis of dissociated vertical divergence or inferior oblique overaction, and various complications were modeled. Probability estimates were obtained from a comprehensive literature review. Analyses aimed to determine the strategy that was associated with longer time spent with aligned eyes and/or stereopsis and fewer reoperations.

RESULTS

Eight-year-old children are expected to spend 72.6 vs 58.0 vs 37.8 months with aligned eyes and 26.8 vs 9.0 vs 1.5 months with stereopsis and to receive on average 1.76 vs 1.67 vs 1.46 surgeries, if they first underwent operation at 6 vs 24 vs 48 months, respectively. Children at 8 years are expected to have stereopsis at the rate of 36.1% vs 17.2% vs 5.1%, respectively. Operation at 6 months instead of 48 months is expected to yield an additional 9% of total follow-up time in health states with eye alignment and 11% in health states with stereopsis, per 5% increase in risk for extra operations (5% and 7%, respectively, per 5% increase in risk for operation at 6 vs 24 months). Wide-range sensitivity analyses and long-term projections point to the same direction.

CONCLUSION

Given the benefit/risk tradeoffs, it is probably warranted to attempt to correct large-angle infantile esotropia as early as possible.

Amblyopia characterization, treatment, and prophylaxis

Amblyopia has a 1.6-3.6% prevalence, higher in the medically underserved. It is more complex than simply visual acuity loss and the better eye has sub-clinical deficits. Functional limitations appear more extensive and loss of vision in the better eye of amblyopes more prevalent than previously thought. Amblyopia screening and treatment are efficacious, but cost-effectiveness concerns remain. Refractive correction alone may successfully treat anisometropic amblyopia and it, minimal occlusion, and/or catecholamine treatment can provide initial vision improvement that may improve compliance with subsequent long-duration treatment. Atropine penalization appears as effective as occlusion for moderate amblyopia, with limited-day penalization as effective as full-time. Cytidin-5'-diphosphocholine may hold promise as a medical treatment. Interpretation of much of the amblyopia literature is made difficult by: inaccurate visual acuity measurement at initial visit, lack of adequate refractive correction prior to and during treatment, and lack of long-term follow-up results. Successful treatment can be achieved in at most 63-83% of patients. Treatment outcome is a function of initial visual acuity and type of amblyopia, and a reciprocal product of treatment efficacy, duration, and compliance. Age at treatment onset is not predictive of outcome in many studies but detection under versus over 2-3 years of age may be. Multiple screenings prior to that age, and prompt treatment, reduce prevalence. Would a single early cycloplegic photoscreening be as, or more, successful at detection or prediction than the multiple screenings, and more cost-effective? Penalization and occlusion have minimal incidence of reverse amblyopia and/or side-effects, no significant influence on emmetropization, and no consistent effect on sign or size of post-treatment changes in strabismic deviation. There may be a physiologic basis for better age-indifferent outcome than tapped by current treatment methodologies. Infant refractive correction substantially reduces accommodative esotropia and amblyopia incidence without interference with emmetropization. Compensatory prism, alone or post-operatively, and/or minus lens treatment, and/or wide-field fusional amplitude training, may reduce risk of early onset esotropia. Multivariate screening using continuous-scale measurements may be more effective than traditional single-test dichotomous pass/fail measures. Pigmentation may be one parameter because Caucasians are at higher risk for esotropia than non-whites.

Is it mandatory to treat amblyopia prior to surgery in esotropia?

PURPOSE

To determine whether presence of amblyopia has any influence on the outcome of motor and sensory success in cases of esotropia.

METHODS

100 patients were taken for this study. Patients were divided into two groups of 50 each. Amblyopia was fully treated in group I and patients in group II underwent surgery before full treatment of amblyopia. Motor success (+/- 10 PD of orthophoria) was assessed three months after surgery and at the child's most recent visit by comparing the motor alignment at 6 meter and 0.33 meter distance using accommodative target in primary position. Sensory success was assessed by comparing the frequency of detectable stereoacuity.

RESULTS

There was no significant difference in motor success (84% vs 75%) and sensory success (55% vs 50%) whether amblyopia was fully treated or partially treated.

CONCLUSION

It is not mandatory to treat ambloypia prior to surgery, unless it is a case of infantile esotropia with moderate amblyopia and amblyopia therapy is continued post operatively.

The relationship between nystagmus and surgical outcome in congenital esotropia

PURPOSE

Congenital esotropia is often associated with congenital nystagmus. This study examines the relationship between the presence of nystagmus and surgical outcome in the treatment of patients with congenital esotropia.

METHODS

In this institutional retrospective study, we reviewed the charts of 200 consecutive patients who underwent surgical correction for congenital esotropia between 1991 and 1995. Preoperative clinical characteristics and subsequent need for additional strabismus surgery for a residual or consecutive deviation were noted. Minimum follow-up was 6 months after the original operation.

RESULTS

Of the 84 patients who met the inclusion criteria, 15 patients (18%) had latent or manifest latent nystagmus, and 69 patients (82%) had no nystagmus. Eight of the 15 patients with nystagmus had or required reoperation according to our criteria (53%). Nineteen of the 69 patients (28%) without nystagmus had or required reoperation (P =.155).

CONCLUSIONS

Nystagmus, when associated with congenital esotropia, may increase the risk of requiring additional strabismus surgery for residual or consecutive deviations. Appropriate and complete preoperative counseling of patients with congenital esotropia who also have nystagmus should include this increased risk.

Infantile esotropia in very low birth weight (VLBW) children

VLBW children are known to have a high frequency of early onset strabismus, which is related to the high prevalence of pre- and perinatal cerebral disturbances reported in these children. It is unknown if the early onset strabismus in VLBW children has the characteristics of infantile esotropia. If so, then (acquired) cerebral damage may play an important role in the origin of this type of strabismus. For this reason, the charts of 265 VLBW children were retrospectively reviewed. Strabismus was present in 55 (20.7%) children. Mean follow-up was 75 weeks, with 29.8% of the children having a follow-up of less then 6 months. Only 5 children (1.9%) with characteristics of infantile esotropia could be identified. Another 8 children (3.0%) possibly had infantile esotropia, but follow-up had been too infrequent during the first year of life to determine the time of onset of strabismus precisely. The other 42 children with strabismus all had ophthalmological disorders (i.e. ROP, optic nerve atrophy, cortical blindness) explaining early disruption of binocular visual development. Therefore, VLBW children are at risk for early onset strabismus. However, infantile esotropia is not typical for VLBW children and may be an indication that early acquired cerebral damage does not play an important role in the pathogenesis of infantile esotropia.

Binocular vertical perceptual adaptation in essential infantile esotropia

This study assessed whether dissociated vertical deviation, corresponding to an occasional elevation of the deviated eye, is accompanied by a binocular vertical perceptual adaptation. Dissociated vertical deviation was elicited by means of neutral filters in 16 patients, 8 who had undergone operations for the disorder of essential infantile esotropia and 8 who had not. Neutral filters elicited dissociation vertical deviation, which was accompanied by binocular vertical perceptual adaptation. This effect was significantly greater for patients who had operations and was enhanced by the filter density. Surgical elimination of inhibitory mechanisms for dissociated vertical deviation in patients with essential infantile esotropia appears to facilitate a loose sensory adaptation, which permits a binocular vertical perceptual adaptation.

Untreated essential infantile esotropia: factors affecting the development of amblyopia

PURPOSE

A concomitant esotropia, presenting within the first 6 months of life, associated with a high incidence of dissociated vertical deviation, manifest latent nystagmus and asymmetric optokinetic nystagmus is termed essential infantile esotropia. Most studies concern patients diagnosed in infancy and treated throughout childhood. This paper addresses the factors that may influence the development of amblyopia in patients who remain untreated until visual adulthood.

METHODS

During a 3 year period 113 patients aged 8 years or more with a history of esotropia occurring within the first 6 months of life were examined for the study. All patients underwent full ocular motility assessment and cycloplegic refraction, and only those with one or more signs of essential infantile esotropia were included.

RESULTS

Of the 113 patients, 16 (14.3%) had a difference of 2 or more lines in the visual acuity of the two eyes and were diagnosed as having amblyopia. Anisometropia was present in 10 of the 16 (62.5%). The correlation between anisometropia and amblyopia was statistically significant (p = 0.0001).

CONCLUSIONS

Amblyopia following early surgical intervention in essential infantile exotropia is well documented, but the risk is outweighed by the chance of obtaining some form of binocular vision. However, where access to ongoing therapy is not available, patients with essential infantile esotropia, free alternation and no anisometropia have a significant chance of retaining good visual acuity in both eyes if surgery is delayed until visual adulthood.

Clinical characteristics and long-term postoperative results of infantile esotropia and myopia

PURPOSE

To determine the short-term (6 month) and long-term (4 year) surgical results of infantile esotropia in a control group of 100 patients, as compared to a myopia (-2.0 to -5.0 diopters [D]) group of 13 patients and to a high-myopia (greater than -8.0 D) group of 14 patients.

METHOD

A retrospective chart review with selection according to inclusion criteria.

RESULTS

All 14 high-myopic patients (100%) achieved short-term unacceptable result of large-angle (greater than 20 prism diopters) deviation as compared to 29 (29%) and four (31%) of the patients in the control and myopia groups, respectively (P < 0.0001). Eighty (80%) of the patients in the control group and 10 (77%) in the myopia group achieved long-term favorable postoperative results of subnormal binocular vision, microtropia, or small-angle (less than 20 prism diopters) deviation, with no statistical differences between the two groups. In contrast, 10 (71%) of the patients in the high-myopia group achieved a final unacceptable result of large-angle deviation, as compared to 20 (20%) and three (23%) in the control and myopia groups, respectively (P < 0.0001). Persistent preoperative amblyopia was associated with a higher percentage of unfavorable surgical results and was more frequent in the high-myopia group (50%) as compared to the control group (14%) (P = 0.0004).

CONCLUSIONS

Careful attention must be directed preoperatively toward reversing amblyopia and correcting refractive errors because persistent amblyopia at the time of surgery was associated with a higher percentage of unacceptable postoperative large-angle deviation. The conventional amount of recession or resection of muscles should be increased in high-myopic cases with infantile esotropia, because less effect is produced per millimeter of recession/resection initially and, in the long-term, the constant stimulus to accommodative convergence apparently causes recurrent esotropia.

Preschool vision screening: rationale, methodology and outcome

Although population outcome studies support the utility of preschool screening for reducing the prevalence of amblyopia, fundamental questions remain about how best to do such screening. Infant photoscreening to detect refractive risk factors prior to onset of esotropia and amblyopia seems promising, but our current understanding of the natural history of these conditions is limited, thus limiting the prophylactic potential of early screening. Screening for strabismic, refractive and ocular disease conditions directly associated with amblyopia is more clearly proven, but the diversity of equipment, methods and subject populations studied make it difficult to draw precise summary conclusions at this point about the efficacy of photoscreening. Sensory-based testing of preschool-age children exhibits a similar combination of promise and limitations. The visual acuity tests most widely used for this purpose are prone to problems of testability and false negatives. Moreover, the utility of random-dot stereograms has been confused by misapplication, and new small-target binocularity tests, while attractive, are as yet inadequately field-proven. The evaluation standard for any screening modality is treatment outcome. However, variables in amblyopia classification and quantitative definition differences, timing of presentation, nonequivalent treatment comparisons, and compliance variability have been uncontrolled in virtually all extant studies of amblyopia treatment outcome, making it difficult or impossible to evaluate either the relative efficacy of different treatment regimens for amblyopia or the effects of age on treatment outcome within the preschool age range. The latter issue is a central one, since existence of such an age effect is the primary rationale for screening at younger rather than older preschool ages. The relatively low prevalence of amblyopia makes it difficult to achieve a high screening yield in terms of predictive value, but functionally increasing prevalence by selective screening of high risk populations causes further problems. Unless a "supertest" can be devised, with very high sensitivity and specificity, health policy decisions will be required to determine which of these two characteristics should be emphasized in screening programs. Performance of screening tests can be optimized, however, with adequate training, perhaps via instructional videotapes.

Clinical characteristics and long-term postoperative results of infantile esotropia

We classified 103 patients (206 eyes) with infantile esotropia and an average of 8.7 years of postoperative follow-up into four outcome groups. Of 103 patients, 28 (27%) had subnormal binocular vision; 24 (23%) had microtropia; 43 (42%) had small-angle deviation (< 20 prism diopters); and eight (8%) had large-angle deviation. A chi 2 analysis showed a significant difference (chi 2 = 16.22, P = .005) in the distribution of amblyopia among these four outcome groups. Visual acuity of 20/30 or better was attained in 174 of the 206 eyes (84%). The eyes of all 28 patients in the subnormal binocular vision group remained aligned after an average of eight years. In contrast, the eyes of six of 30 patients (20%) in the microtropia group and 11 of 43 (26%) in the small-angle deviation group lost the stability of horizontal alignment. We found that the two variables of latent-manifest nystagmus and persistent amblyopia at the time of surgery lead to less satisfactory outcomes. In contrast, patients with smaller preoperative angle of deviation or surgery completed before 1 year of age demonstrated an increased incidence of optimal (subnormal binocular vision) or desirable (microtropia) results. We recommend performing surgery after amblyopia has been thoroughly treated, and, whenever possible, completing the surgical treatment by 1 year of age.

Timing of amblyopia therapy relative to strabismus surgery

BACKGROUND

It is taught that amblyopia must be fully reversed before surgery for esotropia is undertaken to achieve the best surgical outcome. In some cases, this means delaying surgery for many months. The alternative of operating early, before the completion of amblyopia therapy, and continuing to treat the amblyopia postoperatively has not been evaluated previously.

METHODS

Forty-seven children younger than 8 years of age were identified with a history of both amblyopia and esotropia. They had no other ocular, medical, or neurologic abnormalities. They had no prior strabismus surgery. Of these 47 patients, 26 had their amblyopia fully treated before surgery, and 21 underwent surgery before completing amblyopia therapy. Five of the latter group did not require amblyopia therapy after surgery even though they were still amblyopic before operation. The motor outcome was assessed by comparing the motor alignment at 6 and 0.33 m using accommodative targets in primary position before surgery, at 6 months after surgery, and at the child's most recent visit. Motor success was defined in this study as a postoperative deviation at distance fixation of 8 prism diopters or less. The sensory result was assessed by comparing the frequency of detectable stereoacuity.

RESULTS

The treatment groups did not differ significantly in age, depth of amblyopia, refractive error, or preoperative angle. There was no significant difference detected in motor or sensory outcome whether amblyopia was fully or only partially treated before surgery.

CONCLUSION

Performing corrective surgery in children with esotropia before full resolution of amblyopia is safe and efficient if the amblyopia therapy is continued after surgery. This strategy permits earlier surgery without postponing the operation until full resolution of amblyopia. The finding that five patients did not require amblyopia therapy after surgery suggests that eye re-alignment itself can help reverse amblyopia in some cases.

19th annual Frank Costenbader Lecture--the origins of congenital esotropia

Congenital esotropia develops in the first 4 months of life in an infant who lacks the inborn mechanism for motor fusion. It manifests as an esotropia which is not eliminated by correction of hyperopia and occurs in an otherwise neurologically normal infant. The earliest practical time for surgery is 4 months of age. The eye is anatomically suited for surgery at this age and also, this is the earliest age that congenital esotropia can be diagnosed with confidence. The best attainable result of treatment of congenital esotropia is subnormal binocular vision. This result is more likely to be attained if infants are aligned by 18 months of age. Satisfactory alignment is produced in 80% to 85% of infants in one procedure with an appropriate bimedial rectus recession. An array of motor defects including DVD, latent nystagmus, oblique dysfunction, and A- and V-pattern appear at varying times after successful alignment. These associated findings are commonly found with, but are not unique to, congenital esotropia. The onset and clinical picture of congenital esotropia is satisfactorily explained by a theory first suggested by Worth that the strabismus is caused by an inborn defect in the motor fusion mechanism and aggravated by esotropital factors as suggested by Chavasse. In contrast to congenital esotropia, all other strabismus can be thought of as occurring on a secondary basis in a person with the inborn capacity for motor fusion, but who failed to maintain it because of conatal insurmountable strabismus (congenital third nerve palsy), who lost it because of acquired (postnatal) strabismus, who uses a strategy such as head posture alteration to retain fusion under favorable circumstances (Duane syndrome), who has intermittent strabismus with part-time suppression (X(T)), or who is maintaining alignment with nonsurgical means (refractive esotropia). For the future, I believe that advances in the management of congenital esotropia will depend on a better understanding of etiology leading to design and use of innovative nonsurgical techniques to discourage convergence and stimulate bifoveal fusion.

The outcome of strabismus surgery in childhood esotropia

The results of squint surgery in 118 children with non-paralytic childhood esotropia are analysed. A 'favourable outcome', defined as a final alignment within +/- 10 dioptres of straight, or within +/- 20 dioptres of straight if there was evidence of binocular single vision, was achieved in 86 (72.9%) children. The factors affecting the final outcome are discussed, including age of onset, age at the time of surgery, pre-operative and post-operative amblyopia, refractive error, anisometropia, the surgical procedures used, and post-operative ocular alignment.

Characteristics of early onset esotropia

Some 115 patients with a reported onset of esotropia within the first six months of life were studied retrospectively to assess ocular findings and the evolution of any changes with time. All patients had been treated by one ophthalmologist and one orthoptist since 1972. Of the 115 patients, 27% had an accommodative element associated with the esotropia. Patients with an accommodative esotropia had higher levels of hypermetropia when compared to the non-accommodative group, but there were no other distinguishing characteristics. The groups exhibited a large variation in angle size, ranging from four to 45 degrees at the initial visit. The presence of fusion, amblyopia and the degree of hypermetropia had no significant effect on the course of the squint. Amblyopia was noted in 67% of cases and appeared to stabilise at a later-than-expected age, with 66% of patients with amblyopia stabilising between eight and 11 years. Surgical intervention had no effect on the incidence of amblyopia at the initial or final visits.

The long-term results of surgical correction of childhood esotropia

The results of surgical management by one ophthalmologist of 102 patients with congenital esotropia and 74 patients with acquired esotropia in childhood were analysed. The majority of patients had undergone a monocular recession-resection procedure, with 91% and 93% of patients showing a reduction in the angle, of more than five degrees, following surgery for congenital and acquired esotropia respectively. Unexpectedly, varying the amount of lateral rectus resection from 3 to 6 mm, when combined with a constant 5 mm medial rectus recession, did not produce significantly different amounts of change in the ocular alignment after surgery. Patients with congenital esotropia generally developed a stable postoperative angle later than patients with acquired esotropia. The degree of improvement of ocular alignment with surgery was independent of hypermetropia, presence of preoperative amblyopia or fusion.

Results of early surgery for infantile esotropia in normal and neurologically impaired infants

A prospective study was performed over a 4-year period of 56 infants presenting with infantile esotropia to assess development of binocularity after surgical alignment before 2 years of age. In 50% of cases infantile esotropia was associated with neurological problems or prematurity. Forty-three cases have undergone surgery (mean age 15.7 months +/- 3.46); 86% were aligned (+/- 10 dioptres) at 2 years. Eighty-seven per cent of normal children and 74% of children with neurological problems or prematurity were aligned at last follow-up (mean 27.2 months since surgery). Tests of fusion and stereopsis have to date been possible upon 21 'successfully' aligned infants and although most have evidence of peripheral sensory fusion none showed stereopsis to more than one test. Although early surgery achieves a good cosmetic result in normal children and those with neurological problems, our findings question its ability to promote the development of even gross stereopsis in most children.

Outcome of strabismus surgery in congenital esotropia

The results of squint surgery in 40 children with congenital esotropia are analysed. A 'favourable outcome' was achieved in 23 (57.5%) children. The factors affecting the final outcome including ocular alignment in the immediate postoperative period, age at the time of surgery, amblyopia, associated inferior oblique overaction, dissociated vertical deviation, latent or manifest latent nystagmus, and the surgical procedures used are discussed.

Accommodative convergence in hypermetropia

We compared the clinical characteristics of esotropic, hypermetropic children whose strabismus was fully corrected with spectacles (refractive accommodative esotropia) with those who remained orthotropic (that is, had no manifest strabismus on the cover test) in the presence of uncorrected hypermetropia. In addition to a standard ophthalmologic and orthoptic examination, we determined the stimulus accommodative convergence/accommodation (AC/A) ratio by using the gradient method over a range of 6 diopters, the near point of accommodation, and random dot stereopsis. Hypermetropic patients without esotropia or significant esophoria were found to have a low AC/A ratio in contrast to those patients with refractive accommodative esotropia. This finding explains why esodeviations may be absent in some hypermetropic patients with uncorrected vision. We found a high prevalence of abnormally low near points of accommodation and defective or absent stereopsis in both groups of patients.

Human amblyopia: structure of the visual field

Kittens raised with different kinds of abnormal early visual experience (monocular and binocular deprivation, convergent strabismus, eye rotation, asymmetric alternating occlusion, early callosal split) show systematic deficits in the nasal visual field of the affected eye. To test whether abnormal visual experience produces similar deficits in the human visual system, we measured the monocular visual field of humans with subnormal binocular vision (strabismic and anisometropic amblyopes, strabismics with alternating fixation). Eight amblyopes were tested with a computer-assisted static perimetry (Octopus 2000). Twenty other subjects were tested with kinetic perimetry (Goldmann 940), 11 subjects with static perimetry (Goldmann 940). In some of these subjects, we measured the latency of saccades and the accuracy of visually guided pointing toward stimuli presented in the peripheral visual field. Both strabismic and anisometropic amblyopes frequently showed deficits of visual sensitivity in the central part of the visual field, but no systematic deficits in the peripheral field of the amblyopic eyes. Strabismic alternators had practically equal fields in the two eyes. Neither saccadic latency nor pointing accuracy showed a systematic impairment in the nasal visual field. The discrepancy between the field losses in strabismic humans and in cats raised with a surgically induced squint cannot be due to methodological differences, but rather to anatomical differences, or to the different origin of strabismus in the two species.