Congenital esotropia with a bifixation result. Report of a case

Multiple Short Daily Periods of Normal Binocular Vision Preserve Stereopsis in Strabismus

Purpose

Infantile strabismus impedes the development of stereopsis. In optically strabismic monkeys, 2 continuous hours of normal binocular vision per day has been shown to preserve near-normal stereopsis. In this study, we investigated whether, as in learning, multiple shorter periods of intervention would further boost performance.

Methods

To simulate infantile esotropia, infant monkeys were reared with 30 prism diopters base-in starting at 4 weeks of age. Daily periods of normal binocular vision were provided by replacing prisms with plano lenses. Altogether, 14 monkeys were prism reared: 2 with continuous prism, 2 with 2 continuous hours of normal binocular vision per day, 6 with 2 noncontinuous hours, and 4 with 1 noncontinuous hour of binocular vision each day. Seven normally reared monkeys provided control data. Behavioral methods were employed to measure spatial contrast sensitivity, eye alignment, and stereopsis.

Results

One monkey reared with continuous prism had poor stereopsis, and the other had no stereopsis. Ten of the 12 monkeys reared with periods of normal binocular vision had stereopsis, and those with longer and more continuous periods of binocular vision had stereopsis approaching that of normally reared monkeys.

Conclusions

During early development, multiple short periods of binocular vision were effective in preserving clinically significant stereopsis in monkeys. These results suggest that by providing relatively short multiple daily intervention periods, stereopsis may be preserved in strabismic human children.

Short-Term Motor and Sensory Outcomes in Acquired Nonaccommodative Esotropia of Childhood

Information on the management of acquired nonaccommodative esotropia (ANAET) of childhood is incomplete. Most prior reports combine the results of patients with both accommodative and nonaccommodative esodeviations. The primary objective of this study was to describe the early postoperative motor and sensory results of children with acquired nonaccommodative esotropia. The medical records of 72 consecutive children with ANAET who underwent surgical correction at East Tennessee State University College of Medicine from August 1, 1995 through October 1, 2001 were retrospectively reviewed. The median age at surgery for the 72 study patients was 43.8 months with a median angle of deviation of 30 prism diopters (PD) at both distance and near. Ten patients (13.9%) required a second surgical procedure while one patient (1.4%) required a third. The cumulative probability of a second surgery within two years of the first procedure was 24% (95% CI 4-43%). During a median postoperative follow-up period of 7.1 months, 64 (88.9%) patients were within 8 PD of orthotropia on the last postoperative examination. Normal postoperative stereoacuity was achieved in several children whose deviation began after 30 months of age, as well as in one child who was misaligned for at least two years prior to surgery. Although the postoperative follow-up on these patients with acquired nonaccommodative esotropia managed without prism adaptation is short, the motor results are similar to other studies on patients with acquired esotropia, with sensory outcomes superior to those obtained in children with congenital esotropia.

Long-term follow-up of congenital esotropia in a population-based cohort

PURPOSE

To report the long-term outcomes of a population-based cohort of children diagnosed with congenital esotropia during a 30-year period.

METHODS

The medical records of all patients diagnosed with congenital esotropia as residents of Olmsted County, MN, from January 1, 1965, through December 31, 1994, were retrospectively reviewed.

RESULTS

A total of 130 children were diagnosed during the 30-year period at a median age of 7.4 months with a mean deviation of 30(Delta). During a median follow-up of 11.9 years, 126 patients underwent a mean of 1.8 strabismus surgeries. The risk for undergoing a second surgery was significantly greater in patients with a larger presenting angle (p = 0.017) and a younger age at first surgery (p = 0.006). The Kaplan-Meier rate of having a second surgery was 51% at 10 years and 66% at 20 years. For those with 6 weeks or more of follow-up from the final surgery, last examined at a mean age of 15.1 years, 42 of 94 (45%) were within 8(Delta) of orthotropia and 30 of 98 had some level of stereopsis (</=3000 arcsec).

CONCLUSIONS

In this population-based study of children with congenital esotropia, a second surgery was necessary in half the patients after 10 years and was more likely in those patients with a larger presenting angle and a younger age at first surgery. Approximately half of the patients were within 8(Delta) of orthotropia and one-third had measurable stereopsis after a mean of 10.9 years of follow-up.

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.

Binocular visual function in congenital esotropia after bilateral medial rectus recession with loop suture

PURPOSE

Our aim was to evaluate the binocular visual function in congenital esotropia after bimedial rectus recession with loop suture and to address the factors that could take part in the attainment of binocular function.

SUBJECTS AND METHODS

Forty children with congenital esotropia who were operated on between 12 and 48 months of age were included in the study group. Postoperative follow-up ranged from 2 to 10 years. In order to determine the factors affecting the sensory results in congenital esotropia, we classified our patients into two groups according to their fusion status. We compared the preoperative and postoperative characteristics of patients in these two groups.

RESULTS

Twenty-one of 40 patients (52.5%) fused the Worth four-dot at near (Group 1), 19 patients (47.5%) did not (Group 2) at the final examination. No patient showed evidence of stereopsis. We found significant differences between these two groups in respect to the final angle of vertical deviation, the age at surgery, the presence of postoperative inferior oblique overaction, dissociated vertical deviation and abnormal head position. Correlation analysis revealed that early alignment of the eyes and the absence of postoperative vertical deviation were associated with increased incidence of achieving some degree of binocular vision.

CONCLUSION

In congenital esotropia, not all infants may have the potential for normal binocular function owing to yet unknown constitutional factors. We determined that achieving some degree of binocular function may be related to early alignment of the eyes. Additionally, close follow-up and precise treatment of the accompanying vertical deviation, especially inferior oblique overaction and dissociated vertical deviation, in a timely manner may enhance the attainment of binocular sensory function.

Factors associated with horizontal reoperation in infantile esotropia

PURPOSE

Risk factors for requiring multiple surgeries in infantile esotropia remain unclear. We identified clinical and demographic factors associated with horizontal reoperation in this disease.

METHODS

A retrospective chart review of patients who underwent surgery from 1994-1997 was performed. Subjects were divided into 2 groups: those requiring only one operation and those requiring 2 or more operations to achieve orthotropia +/-10 PD.

RESULTS

In 149 patients, the overall horizontal reoperation rate was 34%. There were no statistically significant differences between the 2 groups with respect to mean age at first surgery, mean preoperative deviation, gender, prematurity, Medicaid coverage, parental age, family history of strabismus, or refractive error. The presence of nystagmus, oblique muscle dysfunction, dissociated vertical deviation (DVD), or a variable angle of esotropia was not associated with increased horizontal reoperation rate. There was a greater frequency of horizontal reoperation in patients with amblyopia, although not significant. Premature infants and infants with neurologic dysfunction had a lower incidence of horizontal reoperation, but also not significant. Deviations of less than 30 PD were associated with fewer horizontal reoperations (16% vs 31%, P =.047). Significantly more patients underwent horizontal reoperation when initial surgery was performed at less than or equal to 15 months of age (67% vs. 47%, P =.022).

CONCLUSIONS

Several factors thought to predispose to poor sensorimotor outcome (dissociated vertical deviation, oblique muscle dysfunction, and nystagmus) were not associated with an increased incidence of horizontal reoperation. Horizontal reoperation was less frequent in patients with angles less than 30 PD. Although some studies suggest that early surgical intervention in patients with infantile esotropia affords better sensory outcome, it may be associated with a higher horizontal reoperation rate.

The clinical spectrum of early-onset esotropia: experience of the Congenital Esotropia Observational Study

PURPOSE

To describe historical and presenting features of infants with the onset of esotropia in early infancy to provide a better understanding of the clinical spectrum of the disorder.

DESIGN

Prospective multicenter cohort study.

METHODS

Eligibility criteria included age at enrollment 4 to < 20 weeks and an esotropia at near measuring at least 20 prism diopters (pd). Historical information was elicited from the parent or guardian. The esotropia was measured at near and characterized as constant, variable, or intermittent.

RESULTS

175 infants were enrolled. Their average age at enrollment was 97 +/- 26 days. The esotropia was characterized as constant in 56% of the patients, variable in 25%, and intermittent in 19%. Forty-nine percent of the deviations were > or = 40 pd. Most of the larger angle deviations were constant whereas the majority of the smaller angle deviations were intermittent or variable. The majority of patients first seen after 12 weeks of age had constant deviations (65%), whereas the majority seen before 12 weeks of age had intermittent or variable deviations (57%). At enrollment, amblyopia was diagnosed in 19% of patients.

CONCLUSION

The clinical presentation of esotropia in early infancy shows more variation in the esotropia's size and character than has been previously appreciated. Only a minority of the infants who are diagnosed to have esotropia before 20 weeks of age have the commonly accepted profile for congenital esotropia of a large-angle constant deviation. Amblyopia frequently develops, so an evaluation for amblyopia should be an integral part of the examination of an infant with esotropia.

Spontaneous resolution of early-onset esotropia: experience of the Congenital Esotropia Observational Study

PURPOSE

To determine the probability of spontaneous resolution of esotropia with onset in early infancy.

DESIGN

Prospective multicenter cohort study.

METHODS

Eligibility criteria included age at enrollment 4 to < 20 weeks and an esotropia measuring at least 20 prism diopters (pd). The primary outcome measure was ocular alignment at 28 to 32 weeks of age. The esotropia was classified as resolved when there was a misalignment of 0 to 8 pd at the outcome examination either with or without spectacle correction.

RESULTS

Outcome data were available for 170 of the 175 enrolled patients. The esotropia was classified as resolved in 46 of the 170 patients (27%, 95% confidence interval = 21% to 34%). Most of the resolved cases had an intermittent or variable deviation at enrollment. Resolution occurred in only one of 42 cases that had a constant esotropia > or = 40 pd on both the baseline and first follow-up examination and had a refractive error < or = + 3.00 diopters. In another patient, who had an esotropia of 35 pd at baseline and 40 pd at the outcome examination, the esotropia resolved subsequent to the outcome examination.

CONCLUSIONS

Esotropia with onset in early infancy frequently resolves in patients first examined at less than 20 weeks of age when the deviation is < 40 pd in size and is intermittent or variable. Cases with a constant deviation > or = 40 pd presenting after 10 weeks of age have a low likelihood of spontaneous resolution. Our results can be used to define a clinical profile for which persistence of the esotropia is sufficiently likely that surgical correction at 3 to 4 months of age could reasonably be considered.

Acquired nonaccommodative esotropia in childhood

PURPOSE

Acquired nonaccommodative esotropia (ANAET) in childhood is reported to occur infrequently and is often associated with an underlying neurologic or neoplastic disorder. The primary objective of this study was to ascertain the prevalence and clinical characteristics of this form of childhood esotropia.

METHODS

A cohort of all children younger than 11 years with esotropia from a predominantly rural Appalachian region was prospectively identified from August 1, 1995, through July 31, 1998. The age at onset, family history of strabismus, perinatal and medical history, ophthalmologic findings, and surgical results were reviewed for all patients with ANAET.

RESULTS

Twenty-three (10.4%) of 221 consecutive children with esotropia were diagnosed with ANAET compared with 12 (5.4%) diagnosed with congenital esotropia. The median age at esotropia onset for the 23 children with ANAET was 31.4 months (range, 8-63 months) with a mean initial angle of esotropia of 24 PD. Although at least 2 children presented with diplopia, none of the 23 patients were known to have harbored intracranial tumors or other lesions of the central nervous system during the follow-up period. Fourteen of the 19 patients who underwent surgery attended follow-up visits for at least 6 months after their last surgical procedure: 13 were within 8 PD or less of orthotropia, whereas the final patient had persistent esotropia. Twelve of the 13 patients within 8 PD of orthotropia demonstrated some level of stereopsis, including 2 children with bifoveal fixation. Two (10.5 %) of the 19 operated patients later required a low hyperopic spectacle correction to control their deviation.

CONCLUSIONS

ANAET was more prevalent than congenital esotropia in this cohort of children with esotropia. This clinically distinct form of strabismus typically begins between 1 and 5 years of age and appears to be infrequently associated with underlying disease. The angle of deviation is relatively small and early surgical correction is more likely to achieve bifoveal fixation for these patients than for those with congenital esotropia.

Results of early alignment of congenital esotropia

OBJECTIVE

To determine the long-term motor and sensory results after early surgical correction of patients with congenital esotropia.

DESIGN

Noncomparative interventional case series.

PARTICIPANTS

Ten infants with congenital esotropia.

INTERVENTION

Patients had bimedial rectus recession between 83 and 159 days of age; were re-examined in a regular follow-up program; and were retreated when required for strabismus, amblyopia, and refractive errors.

MAIN OUTCOME MEASURES

Final alignment, stereo acuity, variations in vision, alignment, refraction, and number and types of retreatments required during the period of observation.

RESULTS

All patients were aligned initially with bimedial rectus recession of 8.0 to 10.0 mm measured from the limbus. A total of 11 additional surgical procedures were performed on 7 patients to maintain alignment. Four patients required hyperopic spectacle correction to maintain alignment, and two patients required short periods of patching. Visual acuity was 20/40 or better in 19 eyes at the most recent examination, which was between 8.3 and 11.8 years after initial surgery. All patients had final alignment to within 10 prism diopters (PD) of orthotropia at either distance or near. Nine of ten patients had dissociated vertical deviation (DVD), and four of ten patients had latent nystagmus. Four patients had measurable stereo acuity at their last visit, with two achieving a stereo acuity of 3000 seconds (the Titmus fly), one 400 seconds, and one 140 seconds.

CONCLUSION

Surgical alignment of congenital esotropia can be achieved in the 4-month-old with bimedial rectus recession, but this does not ensure continued alignment. At least one additional surgical procedure is required on average to maintain alignment in the first 10 years after initial successful surgery. These patients can also be expected to have one or more of the following: DVD, latent nystagmus, refractive component, or latent strabismus. Regardless of outcome, patients with congenital esotropia have optokinetic asymmetry. Attainment of stereo acuity, including high-grade stereo acuity, may be enhanced by attainment of orthotropia or small-angle esotropia but is likely to be ultimately dependent on constitutional factors rather than age of alignment.

The timing of surgical alignment for congenital (infantile) esotropia

At this time, the beneficial effect of accurate alignment by age 2 in congenital esotropia has been well established by clinical and laboratory studies. There is, however, only scanty clinical evidence that alignment before age 1, much less before 6 months of age, may yield a better quality of binocularity (i.e., refined stereoacuity) than alignment by age 2. Pitfalls of very early alignment are present. In addition, the ophthalmologist must be vigilant in following the initially aligned patient and be ready to treat vertical motor defects, amblyopia, and acquired refractive errors. The need for additional horizontal surgery after initial alignment is also common. The optimum result in the surgical treatment of congenital esotropia generally shows binocularity that is within the confines of a monofixation syndrome, and refined stereoacuity remains an elusive target and a rare outcome, no matter at what age the alignment is achieved.

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.

Stereopsis and disparity vergence in monkeys with subnormal binocular vision

The surgical treatment for strabismus in infants generally results in microtropia or subnormal binocular vision. Although the clinical characteristics of these conditions are well established, there are important questions about the mechanisms of binocular vision in these patients that can best be investigated in an appropriate animal model. In the present psychophysical investigations, spatial frequency response functions for disparity-induced fusional vergence and for local stereopsis were studied in macaque monkeys, who demonstrated many of the major visual characteristics of patients whose eyes were surgically aligned during infancy. In six rhesus monkeys, unilateral esotropia was surgically induced at various ages (30-184 days of age). However, over the next 12 months, all of the monkeys recovered normal eye alignment. Behavioral measurements at 4-6 years of age showed that the monkeys' prism-induced fusional vergence responses were indistinguishable from those of control monkeys or humans with normal binocular vision. Investigations of stereo-depth discrimination demonstrated that each of the experimental monkeys also had stereoscopic vision, but their stereoacuities varied from being essentially normal to severely stereo-deficient. The degree of stereo-deficiency was not related to the age at which surgical esotropia was induced, or to the presence or absence of amblyopia, and was not dependent on the spatial frequency of the test stimulus. Altogether, these experiments demonstrate that a temporary, early esotropia can affect the binocular disparity responses of motor and sensory components of binocular vision differently, probably because of different sensitive periods of development for the two components.

Abnormal motion processing and binocularity: infantile esotropia as a model system for effects of early interruptions of binocularity

Infantile esotropia, a common form of strabismus with onset prior to 6 months of age, occurs at a time of rapid visual development. While monocular visual acuity is relatively unaffected in these patients, the majority of them fail to achieve fully normal stereopsis. In addition, these patients show a spectrum of abnormalities in their ocular following responses, visual perception and visual evoked potentials (VEPs) that suggest a failure to develop a normal complement of motion processing mechanisms. While abnormalities of of stereopsis have been studied for many years, motion processing in strabismus is a rapidly evolving area of current research. Motion mechanisms are normally binocular and may form a distinct binocular sub-system. This review summarises which is known about sensory and motor abnormalities in infantile esotropia, with special emphasis on recent motion VEP recordings. The monocular motion VEP shows directional biases early in infancy that are consistent with a nasalward/temporalward response bias. Patients with infantile esotropia maintain their neonatal biases beyond the age at which they normally disappear. The motion VEP biases persist into visual maturity in patients whose strabismus is treated after about 2 years of age. Treatment prior to age 2 can lessen the magnitude of the motion VEP asymmetry and these improvements can be maintained into visual maturity. A recording from the striate cortex of a visually deprived macaque monkey indicates that the motion VEP asymmetry arises early in the visual pathway.

Motor and sensory fusion in monkeys: psychophysical measurements

Motor and sensory fusion, the basic processes of binocularity, must be present for bifoveal fixation with true fusion and stereopsis during ordinary viewing. The characteristics of motor and sensory fusion have been established for patients with normal and subnormal binocular vision; the present report describes our psychophysical studies of these processes in the macaque monkey. Three recent investigations of motor and sensory fusion in monkeys are described. The studies involved: (1) the comparability of motor and sensory fusion in monkeys and humans with normal binocular vision, (2) the effects of an early period of abnormal binocular vision on motor and sensory fusion in monkeys, and (3) the contrast sensitivity for binocular disparity in monkeys with stereo-deficiencies. The results of these studies demonstrated an excellent homology between the normal binocular vision of monkeys and humans. We also found that a period of esotropia during infancy caused deficiencies in sensory fusion, but not motor fusion. In some monkeys, the sensory deficiency persisted over the entire range of binocular disparities that were compatible with stereopsis, while other subjects demonstrated normal stereo-sensitivity for the largest fusible binocular disparities. The stereo-deficiencies of these monkeys, along with other visual attributes, suggest that their binocular vision is a viable model for the binocularity of patients with subnormal binocular vision or the monofixation syndrome.

Outcome study of surgical alignment before six months of age for congenital esotropia

BACKGROUND

Recently, several ophthalmic surgeons have reported surgical alignment with congenital esotropia in patients younger than 6 months of age to improve the quality of the binocular result.

METHODS

The author performed a multicenter independent study of the motor and sensory results obtained in a group of patients younger than 6 months of age. These patients underwent surgical alignment by other investigators to within 10 prism diopters for a minimum of 6 months. The patients had been followed for a minimum of 4 years and were required to have sufficient maturity and normal neurologic status to reliably respond to tests for fusion and stereopsis. The patients were examined and analyzed by the author before any knowledge of the clinical record.

RESULTS

Sixteen patients underwent surgical alignment at an average age of 4.2 months. Follow-up examination took place at an average age of 7.1 years. Motor and sensory tests showed 11 patients to have a small or negligible motor misalignment at near point with both binocular fusion and gross stereopsis ability. One patient, aligned by 3 months of age, demonstrated reproducible refined stereoacuity on sensory testing. The author observed, however, that alignment by 4 or 5 months of age did not result in better quality of binocularity than a previously studied group of patients who underwent alignment at 6 months of age.

CONCLUSION

Binocularity that includes refined stereoacuity remains an elusive target and rare outcome for the ophthalmologist treating congenital esotropia, despite the use of very early surgical alignment.

Plasticity of human motion processing mechanisms following surgery for infantile esotropia

Monocular oscillatory-motion visual evoked potentials (VEPs) were measured in prospective and retrospective groups of infantile esotropia patients who had been aligned surgically at different ages. A nasalward-temporal response bias that is present prior to surgery was reduced below pre-surgery levels in the prospective group. Patients in the retrospective group who had been aligned before 2 yr of age showed lower levels of response asymmetry than those who were aligned after age 2. The data imply that binocular motion processing mechanisms in infantile esotropia patients are capable of some degree of recovery, and that this plasticity is restricted to a critical period of visual development.

Surgical alignment prior to six months of age for congenital esotropia

PURPOSE

To complete the first independent and largest multicenter outcome investigation to analyze the motor and functional results of a series of patients surgically aligned prior to age 6 months and followed for a minimum of 4 years.

METHODS

Sixteen patients, surgically aligned at an average age of 4.2 months, were examined at an average of 7.1 years to assess their motor and functional outcomes.

RESULTS

Motor and sensory tests showed 11 patients to have a small or negligible motor misalignment at near point with both binocular fusion and gross stereopsis ability. A single patient aligned by 3 months of age demonstrated reproducible refined stereoacuity on sensory testing. However, the patients who achieved alignment by 4 or 5 months did not demonstrate any better quality of binocularity than that found in a previously studied group of patients aligned at 6 months.

CONCLUSION

Binocularity that includes refined stereoacuity remains an elusive target and a rare outcome for an ophthalmologist treating congenital esotropia, despite very early surgical alignment.

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.

Fusion after surgical alignment of longstanding strabismus in adults

BACKGROUND

Fusion and the development of the monofixation syndrome are well recognized after surgical alignment of congenital esotropia to within 8 delta of orthotropia. However, in adults with longstanding strabismus and a history of congenital esotropia who are not surgically aligned within the first few years of life, the prognosis for the development of fusion is believed to be poor.

METHODS AND RESULTS

Twenty-four adults, 12 with a history of congenital esotropia (onset before 6 months age), 1 of congenital exotropia, and 11 with the onset of esotropia between 6 months and 2 years, were included in this study. All patients had longstanding strabismus, and none had been surgically aligned within the first 2 years of life. No patient had visual acuity worse than 20/30 in the worse eye. Preoperatively, no patient demonstrated fusion with the red glass test, Worth four-dot, or Titmus test. Postoperatively, all were aligned to within 8 delta of orthotropia, and all demonstrated peripheral fusion with the Worth four-dot at near. Twelve patients (50%), 8 of whom were in the congenital group, achieved stereopsis of 200 seconds of arc or better using the Titmus stereo test.

CONCLUSION

These findings suggest that surgery in this group of patients not only eliminates the ocular alignment deformity but can confer the functional benefits of fusion and increased field of binocular vision.

18th annual Frank Costenbader Lecture. Fusion and suppression: development and loss

A retrospective study (coauthored with Geraldine Tillson) of 118 patients with the congenital esotropia syndrome is described. All patients were aligned with surgery and, in some cases, glasses as well, within 10 prism diopters of orthotropia before the age of 2 years and had remained so aligned for at least a year. A standardized final examination was performed on patients over the age of 6 years, after at least 5 years' follow up, to study the effect of significant refractive error, amblyopia, nystagmus, dissociated vertical divergence, and inferior oblique overaction on the sensory outcome. None of the patients obtained central fusion. Fifty-three of 118 obtained peripheral fusion with at least 5 delta of fusional amplitude. Twenty-eight of the 53 fusers had stereopsis. The findings did not show any factors to explain why 65 did not obtain fusion. A congenital lack of the potential to develop fusion is postulated. The development of fusion and suppression is discussed with relevant references. Evidence is presented that the anatomical location of the lesion in central fusion disruption is in the midbrain. Fusion may be lost, in visual adults, without developing suppression from prolonged sensory deprivation. Examples include unilateral cataract, uncorrected unilateral aphakia, and unilateral severe herpetic keratitis.

Primary infantile-onset esotropia--20 years later

Of 286 cases of primary infantile onset esotropia operated upon early, 42 were reviewed after 20 years. Four of them achieved normal bifoveal stereoscopic vision (40" arc) despite the fact that at review after 3-4 years of age none had better stereopsis than 80" arc. Emphasis is laid on three main factors which may influence the result of early surgery and on the eventual attainment of normal binocularity, i.e. pre-operative alternating occlusion, accurate and repetitive muscular surgery, post-operative occlusion until parallelism is achieved in all directions of gaze and meticulous follow-up into the mid-teens.

A reassessment of infantile esotropia. XLIV Edward Jackson memorial lecture

Essential infantile esotropia is an early acquired, not a congenital, condition, although congenital factors may favor its development between the ages of 3 and 6 months. It must be distinguished from other forms of esotropia with an onset between birth and the first six months of life. The cause of essential infantile esotropia remains unknown, but advances in our knowledge can be expected from the rapidly emerging discipline of infant psychophysics. In analyzing treatment results, a clear distinction must be made between normal, subnormal, and anomalous forms of binocular cooperation. While complete restoration of normal binocular function is rarely, if ever, achieved, anomalous binocular cooperation has many functional advantages over suppression or diplopia and should not be disturbed by overzealous treatment. Subnormal binocular vision is considered to be an optimal, microtropia a desirable, and a residual small angle heterotropia an acceptable end stage of surgical therapy. In a study of 358 surgically treated patients with a documented onset of essential infantile esotropia before age 6 months, subnormal binocular vision was present in 71 (20%), a microtropia in 25 (7%), and a small angle esotropia or exotropia in 140 (39%) of the patients. Surgical alignment before completion of the second year of life improved the chances for an optimal treatment result.(ABSTRACT TRUNCATED AT 250 WORDS)

After the eyes are straightened what is the ophthalmologist's responsibility?

Occlusion, glasses, prism therapy, miotics, fusional vergence stimulation, plus more surgery are required frequently in various combinations for a high percentage of patients whose strabismic eyes are straightened by surgery. Amblyopia is a serious sequelae befalling children who are dismissed following satisfactory surgery. Their best possible postoperative status is monofixation (absence of bifixation), despite having straight eyes. Unless they alternate fixation, amblyopia is prone to either occur or recur. Also, either a gradual change in motor innervation to the extraocular muscles or a cicatricial scarring process may subtly cause subsequent strabismus. Hence, despite straight eyes postoperatively the surgeon's responsibility continues.

Stereopsis in normal infants and infants with congenital esotropia

We used electro-oculographic recordings of eye movement responses to a dynamic random-dot stereogram to assess stereopsis in normal infants and in infants with congenital esotropia. Normal infants showed an onset of stereopsis at about 4 months of age, consistent with previous reports. Four of nine infants with congenital esotropia demonstrated stereopsis when tested within two weeks of surgical alignment. No patient with congenital esotropia showed evidence of stereopsis when tested at a postoperative interval of more than two weeks.

Incidence of strabismus in neonates

In an attempt to learn whether esotropia is present at birth or develops later in infancy, we observed 1,219 alert infants in a normal newborn nursery at a city hospital. Of these, 593 (48.6%) had orthotropic findings; 398 (32.7%) had exotropia, 40 (3.2%) had esotropia (intermittent in 17 with 14 varying between esotropia and exotropia and nine with a variable esotropia), and 188 (15.4%) were not sufficiently alert to permit classification. No infant displayed typical signs of congenital esotropia. We concluded that congenital-infantile esotropia is not connatal but rather develops in the first few weeks or months after birth.