Development of normal ocular alignment

Spontaneous consecutive esotropia

PURPOSE

Although less frequent than consecutive exotropia, consecutive esotropia is a well-known type of strabismus when it follows the surgical correction of an exotropia. Spontaneous conversion from initial constant, large-angle exotropia beyond the age of 3 months to esotropia or orthophoria, however, is not common. We describe a series of infants who presented a spontaneous evolution from a large-angle infantile exotropia to either an orthophoria or a spontaneously consecutive esotropia.

METHODS

Cases of infants examined in the pediatric neuro-ophthalmology clinic of a tertiary ophthalmology department between 2009 and 2015, and having presented an early large-angle exotropia that spontaneously converted into an esotropia or orthophoria-i.e., without any previous surgery or botulinum toxin injection-were studied.

RESULTS

Ten cases (6 M:4 F) were followed up. Median age at first exotropia assessment was 3.88 months (SD = 6.35). Median age at spontaneous conversion to esotropia or orthophoria was 7.23 months (SD = 14.73). Six patients suffered from severe neurologic or metabolic diseases, three had neonatal respiratory distress syndrome, and one was healthy.

CONCLUSION

Spontaneous conversion from initial large-angle exotropia to esotropia or orthophoria can be encountered. The cerebral maturation of visual structures probably accounts for this uncommon strabismus sequence.

2016 International Orthoptic Congress Burian Lecture: Folklore or Evidence?

The theme of the 2016 Burian Lecture is how our understanding of strabismus has been changed by the research carried out in our laboratory in Reading over the years. Accommodation and convergence are fundamental to orthoptics, but actual responses have often been very different compared to what we had expected. This paper outlines how our laboratory's understanding of common issues such as normal development of accommodation and convergence, their linkage, intermittent strabismus, anisometropia, orthoptic exercises, and risk factors for strabismus have changed. A new model of thinking about convergence and accommodation may help us to better understand and predict responses in our patients.

Eye disorders in newborn infants (excluding retinopathy of prematurity)

A screening eye examination is an essential part of the newborn assessment. The detection of many ocular disorders in newborn infants can be achieved through careful observation of the infant's visual behaviour and the use of a direct ophthalmoscope to assess the ocular structures and check the red reflex. Early diagnosis and subspecialty referral can have a critical impact on the prognosis for many ocular conditions, including potentially blinding but treatable conditions such as congenital cataracts, life-threatening malignancies such as retinoblastoma and harbingers of disease elsewhere such as sporadic aniridia and its association with the development of Wilms tumour.

Ophthalmologic findings in patients with nonsyndromic plagiocephaly

The purpose of this article was to study the prevalence of strabismus and astigmatism in children with nonsyndromic plagiocephaly. Children with deformational plagiocephaly do not have an increased prevalence of strabismus compared with the general population but do have an increased prevalence of astigmatism, whereas children with nonsyndromic craniosynostotic plagiocephaly have an increased prevalence of strabismus and astigmatism. This observational cohort study retrospectively reviewed patients in a multidisciplinary craniofacial clinic between 1993 and 2001. Patients were referred for evaluation and management of plagiocephaly or craniosynostosis. One hundred eleven patients had deformational plagiocephaly, and 45 had synostotic plagiocephaly. Patients with lambdoid craniosynostosis, hemifacial microsomia, any syndromic form of craniosynostosis, or without a formal diagnosis were excluded. All patients underwent detailed ophthalmologic, ocular motility, and craniofacial examinations. Diagnosis was based on clinical and radiographic findings. Patients were evaluated between birth and age 14 years (mean = 13 months; SD = 22 months). Only 1 of 111 (<1%) patients with deformational plagiocephaly had an esodeviation, and none had an exodeviation. Three of 45 patients (7%) with synostotic plagiocephaly had an exodeviation, and none had an esodeviation. Eight of 93 patients (9%) with deformational plagiocephaly had unilateral astigmatism, and 14 (15%) had bilateral astigmatism (mean = 1.82 diopters). Three of 43 patients (7%) with synostotic plagiocephaly had unilateral astigmatism, and 9 (21%) had bilateral astigmatism (mean = 1.83 diopters). Patients with deformational plagiocephaly do not appear to have a higher prevalence of horizontal strabismus than the normal population. Exotropia is more common in patients with nonsyndromic craniosynostotic plagiocephaly than in the general population. The prevalence of astigmatism in patients with nonsyndromic craniosynostotic plagiocephaly appears to be greater than in the general population, but this higher prevalence requires further study.

Prevalence of systemic and ocular disease in infantile exotropia: comparison with infantile esotropia

OBJECTIVE

Exotropia in infancy is believed to be associated with an increased prevalence of neurologic, ocular, and craniofacial abnormalities; however, the prevalence of coexisting ocular and systemic disease in these patients is unknown. In this study, the prevalence of ocular disease and systemic illness was determined in patients diagnosed with exotropia in infancy.

DESIGN

Observational comparative case series.

PARTICIPANTS

Medical records of 70 patients diagnosed with exotropia in the first year of life were reviewed and compared with records of 136 patients diagnosed with esotropia before 1 year of age.

INTERVENTION

Patients with no disorders (other than latent nystagmus, dissociated vertical deviation, or oblique muscle overaction) were grouped as "simple" strabismus. Patients with systemic disorders (including prematurity, neurologic disease, and genetic disease) and patients with ocular disorders (including congenital nystagmus, other strabismus, ptosis, and any condition associated with loss of vision [except amblyopia]) were grouped as "complex" strabismus.

MAIN OUTCOME MEASURES

Prevalence of coexisting systemic and ocular disorders. The demographics, strabismus measurements, and types of coexisting disease in the simple and complex groups were compared.

RESULTS

A high percentage of both exotropia (67%) and esotropia (49%) patients had a coexisting ocular or systemic abnormality. Exotropia patients with a constant strabismus were more likely to have coexisting ocular or systemic disease than those with an intermittent strabismus. Smaller angles of exotropia or esotropia were associated with a higher likelihood of coexisting ocular or systemic diseases. Systemic disorders were found more frequently than ocular disorders in both the exotropia and esotropia groups. In 25% of all patients referred for evaluation of strabismus, an additional ocular or systemic abnormality was discovered by the ophthalmologist.

CONCLUSION

Patients presenting to a university hospital-based practice in the first year of life with exotropia were more likely than those presenting with esotropia to have coexisting ocular and systemic disease. Both groups had a notably high prevalence of associated disorders. The percentages measured in this population may not be applicable to other practices because of referral bias. However, clinicians should consider that children presenting with infantile exotropia and esotropia appear to be at risk for coexisting ocular or systemic disease.

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.

Botulinum toxin management of childhood intermittent exotropia

OBJECTIVE

Intermittent exotropia is a common form of childhood strabismus that has a late onset and presents a difficult and frustrating management dilemma. Surgical treatments have a high recurrence rate, and multiple surgeries often are required to achieve a desirable motor outcome. This study presents long-term observations on the use of botulinum toxin for the treatment of intermittent exotropia in children.

DESIGN

This study is a nonrandomized, case-controlled study of consecutive pediatric patients who had intermittent exotropia.

PARTICIPANTS

Thirty-two neurologically normal children ranging from 3 to 144 months in age were diagnosed with intermittent exotropia with a minimum distance deviation of 15 prism diopters (PD).

INTERVENTION

Simultaneous bilateral injections of 2.5 units botulinum toxin type A were made into the lateral rectus muscles with the patient receiving nitrous oxide-ethrane inhalation anesthesia. Patients were observed for 12 to 44 months after the initial injection.

MAIN OUTCOME MEASURES

A satisfactory outcome was considered to be stable binocular alignment of the eyes to an orthophoric range of +/-10 PD.

RESULTS

Bilateral lateral rectus muscle injections of botulinum toxin were effective in reducing the mean preinjection deviation of -29 PD to an average exotropic angle of -6 PD. Stable orthophoria (+/-10 PD) was achieved in 22 patients (69%). Overall, male patients required significantly fewer injections than did female patients. All patients between 24 and 56 months of age, irrespective of gender, required only a single bilateral injection to achieve a favorable motor outcome.

CONCLUSIONS

Botulinum toxin is at least as effective as surgical outcomes reported previously for the treatment of intermittent exotropia in children. This treatment method is particularly effective in children between 2 and 4.5 years of age irrespective of the initial strabismic angle and is not associated with any secondary abnormalities.

Infantile exotropia

BACKGROUND

Exotropia is uncommon in healthy children between 6 months and 1 year old.

METHODS

The charts of patients treated in our practice between January 1980 and August 1994 were reviewed for a diagnosis of infantile exotropia. All of them had an exodeviation during the first year of life. Children with neurologic defects, prematurity, trauma, craniofacial syndromes, or orbital abnormalities or ocular defects that would reduce vision were eliminated.

RESULTS

Sixty-six healthy patients with normal eyes had an exodeviation of 15 prism diopters (delta) or more that persisted through the first year of life. Fifty-four were eliminated because the diagnosis had not been confirmed by a pediatric ophthalmologist before they were 1 year old or they had not been followed for more than 4 years. The 12 remaining patients were followed for at least 4 years (mean, 7.9 years). The mean age at the first examination was 7.8 months (range, 4 to 12 months). On early evaluation, exotropia was intermittent in four and constant in eight. Three had amblyopia. Ten required surgical correction. Exotropia was corrected with one operation in six patients; four required additional procedures, mostly to correct oblique muscle overaction and dissociated vertical deviation (DVD). At the most recent visit, all 12 patients had equal visual acuity in both eyes and satisfactory ocular alignment. Five had fusion at distance and near, but only two had stereo acuity of 100 seconds of arc or better.

CONCLUSION

Infantile exotropia is rare. But, like patients with infantile esotropia, those with exotropia can be expected to have good visual acuity but unstable ocular alignment. Also, as with early-onset esotropia, although surgical intervention is usually required, high levels of binocular function develop in some patients with exotropia. Oblique muscle overaction and DVD are common, often becoming manifest by the first year of age. Unlike infantile esotropia, nystagmus is rare.

Binocular alignment and vergence in early infancy

Vergence to static targets presented at five distances between 25 and 200 cm from the subject was measured in 631 infants aged between 17 and 120 days. Photographic images of the eyes were magnified and measured to yield information on the monocular and binocular eye positions for each target. Vergence data were fit by a linear function and compared to the vergence calculated from target distance and each infant's measured interpupillary distance. Differences in vergence across targets were also evaluated for each subject by calculating the change in angle of rotation for each eye. Many of even the youngest infants showed good ocular alignment both monocularly and binocularly, although the youngest infants showed the greatest variability in vergence. However, the median difference in vergence angle between the eyes for even the youngest group was < 4 deg (6.8 prism D), and some of this difference is attributed to versional eye movements and to slightly off-axis head position across trials. The average infant of 1-2 months showed substantially better vergence than has been reported in some recent studies. Apparently, oculomotor constraints are not a significant barrier to the development of the higher forms of binocularity that begin to emerge in the months immediately following the interval studied here, and may form the substrate for later developments in binocular vision.

Flash visual evoked response binocular summation in normal subjects and in patients with early-onset esotropia before and after surgery

Flash visual evoked responses were recorded and visual evoked response binocular summation was assessed in normal children between the ages of 1 and 58 months, in normal adults and in children with early-onset esotropia before and longitudinally for 1 year after surgical binocular alignment. Normal flash visual evoked response binocular summation started in the range of facilitation (> 2.0) at 1 month of age and decreased to adult levels by 3.7 months of age. The shape of the flash visual evoked response binocular summation function obtained from the patients with early-onset esotropia, appeared similar to that of normal subjects; however, the rapid decrease in flash visual evoked response binocular summation from facilitation to normal adult levels occurred after surgical binocular alignment. In normal adults, flash visual evoked response binocular summation was significantly reduced by a 40-diopter base-in prism, suggesting that binocular misalignment was not the reason for the facilitation in flash visual evoked response binocular summation in either childhood population. It is proposed that this facilitation may reflect a process that leads to binocularity and that develops rapidly with binocular 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.

Maternal observations of ocular alignment in infants

Seventy-five infants of state-registered orthoptists were observed by their mothers from birth to at least 6 months of age, with particular attention paid to the nature of any deviations noticed in the first few weeks. Most of the infants showed brief periods of inaccurate vergence during the first 2 months, with a wide variation in the amount of deviation seen, despite going on to develop normal binocular single vision. Most deviations were transient, unilateral, alternating esodeviations. There was a statistically significant relationship between the time that deviations were noticed and the development of demonstrable binocular convergence. Few exodeviations were found, contrasting with previous studies, and it is suggested that neonates are more likely to achieve binocular single vision when interacting with their mothers.

Clinical evidence for the onset of the sensitive period in infancy

Seven neonates had a IIIrd or VIth nerve palsy or afferent visual pathway pathology at birth. These abnormalities resolved within 6 weeks and the children have developed normal visual acuity, motor fusion, and stereopsis. We conclude that there is a latent period of 6 weeks before the onset of the sensitive period.

Strabismus in infancy

In order to prospectively study the development of strabismus in infancy, the ocular alignment of a large population of normal neonates was studied and follow-up examinations were obtained in a subset of these infants. The characteristic findings of congenital esotropia subsequently developed in three infants who were either orthotropic or exotropic at birth. Pathologic exotropia developed in two infants; both were exotropic at birth, but no more so than most normal neonates. In infants with congenital esotropia or pathologic exotropia, the characteristic deviation appears to develop between 2 and 4 months of age, a period during which normal infants are becoming increasingly orthotropic.