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

Medial rectus insertion site in cases of acute acquired comitant esotropia associated with excessive digital device usage

PURPOSE

To compare the distance of the medial rectus muscle insertion to the limbus (DMIL) between patients with acute acquired comitant esotropia (AACE) associated with excessive digital device usage (EDDU) and exotropic patients.

STUDY DESIGN

Retrospective study.

METHODS

The medical records of 72 eyes of 44 patients with EDDU were retrospectively analyzed. The DMIL was measured from the anterior part at the midpoint of the medial rectus muscle insertion into the anterior limbus using a caliper after dissecting the medial rectus muscle with two control sutures at 12 o'clock and 6 o'clock. The DMIL in the non-fixation eye was compared between 44 patients with AACE and 23 patients with exotropia.

RESULTS

The mean daily EDDU was 6.5 ± 3.1 h. The mean cycloplegic refractive errors (spherical equivalent: SE) were - 3.18 ± 2.52 diopters (D) OD and - 3.03 ± 2.42 D OS. The mean DMIL in the 72 eyes of 44 patients with AACE associated with EDDU was 4.30 ± 0.66 mm. The difference in DMIL of non-fixation eyes between 44 AACE patients and 23 exotropic patients was significant (4.28 ± 0.65 mm vs. 5.28 ± 0.50 mm, p < 0.0001). However, the SE in 44 non-dominant eyes of AACE was - 3.08 ± 2.56 D, significantly stronger than - 1.22 ± 1.93 D in the 23 exotropic eyes (p = 0.008).

CONCLUSION

DMIL in patients with AACE associated with EDDU was significantly shorter. This anatomical anomaly may be an etiology of AACE associated with EDDU.

Clinical characteristics of acute acquired concomitant esotropia before and after the COVID-19 pandemic: a retrospective analysis

PURPOSE

This study aimed to observe the clinical characteristics of acute acquired concomitant esotropia (AACE) patients in recent five years and to examine the changes in the proportion of AACE cases before and after the COVID-19 pandemic.

METHODS

A retrospective study included 148 patients who underwent strabismus correction surgery for AACE between January 1, 2017, and December 31, 2021. The study analyzed the changing proportion of AACE cases before and after the COVID-19 pandemic and analyzed its clinical characteristics.

RESULTS

Abnormalities in the worth 4 dot examination (both distance and near) were present in 134 cases (90.54%) before surgery, while 140 cases (94.59%) showed normal results after surgery. Near stereoacuity was present in 135 cases (91.22%). The near and distance deviations were (55.01 ± 18.77) PD and (57.30 ± 17.64) PD, respectively, and there was no significant difference between the two (p = 0.279). There were significant differences in the ratio of refractive status among different age groups (p < 0.001), while no statistically significant difference was observed in the ratio of refractive status for near deviation (p = 0.085) or distance deviation (p = 0.116). The proportion of AACE cases after the COVID-19 pandemic was significantly higher than that before the COVID-19 pandemic (p = 0.042). There was no statistically significant difference in the clinical characteristics between the two groups (p > 0.05).

CONCLUSIONS

Myopia is the most common refractive status in AACE. More than half of patients had occupations that involved long hours of close work. The proportion of AACE cases increased significantly after the COVID-19 pandemic.

Effects of cycloplegia on crystalline lens morphology and location in acute acquired concomitant esotropia

PURPOSE

The study aims to compare morphology and location of crystalline lens between acute acquired concomitant esotropia (AACE) patients and control subjects, both before and after cycloplegia.

METHODS

This is a prospective and observational clinical study. Morphological and locational parameters of the crystalline lens in 53 AACE patients and 32 control subjects were assessed before and after cycloplegia using CASIA2 system, which represents the latest swept-source anterior segment optical coherence tomography. Cycloplegic refraction was recorded by administering 1% atropine in patients younger than 12 years and 1% cyclopentolate in those > 12 years old. Morphological parameters included anterior radius of curvature (ARC), posterior radius of curvature (PRC), lens thickness (LTH), and equivalent diameter of lens (LED). Locational parameters comprised lens decentration (LD) and lens tilt (LT). Comparison of these parameters before and after cycloplegia were conducted between AACE and controls. Additionally, the study analyzed and compared the changes in these parameter post-cycloplegia.

RESULTS

Our findings suggest no significant difference in morphological parameters including ARC, PRC, LTH and LED between AACE patients and controls before or after cycloplegia. However, 2D-modeling data in the 0° meridian revealed that variation post-cycloplegia of LD (lens shift) in right eyes was different in AACE patients, measuring - 0.03(0.08) [median(interquartile range)] which was significantly distinct from the control group, exhibiting a measurement of 0.01(0.06) (z =  - 2.373, p = 0.018). In left eyes, a similar trend was observed with lens shift in the 0° meridian being 0.02(0.06) in AACE, significantly differing from control group's measurement of - 0.02(0.08) (z =  - 2.809, p = 0.005). Further, correlation analysis revealed that larger temporal shift of lens was associated with greater changes in ARC (r = 0.294, p = 0.006) and LTH (r =  - 0.230, p = 0.031).

CONCLUSIONS

The morphological features of the crystalline lens were similar in AACE patients and controls; however, the change of lens location by cycloplegia was observed only in AACE patients, suggesting an association with excessive accommodation.

The etiology, diagnostics, and treatment of the spasm of the near reflex - a narrative review

Physiological adaptation of the eye to the visual perception of near objects consists of the "near triad": convergence, accommodation, and pupil miosis. Normally, these tend to revert when one stops fixating on a near object. Spasm of the near reflex (SNR) is a pathological phenomenon, which manifests itself by the persistence of the above-mentioned adjustments, which prevents the eye from returning to its relaxed state. In this narrative review, we aim to summarize the etiology, diagnostics, treatment, and prevention of SNR. The literature review was performed by searching online databases. The clinical presentation of SNR is diverse; it presents as isolated accommodative spasm more frequently than impairment of all three components of the near triad. Patients usually present with fluctuations in visual acuity, blurred vision, diplopia, and asthenopia. The etiology is not fully understood. Potential causes include neuroanatomic, organic, and psychogenic disorders. The diagnosis is clinical, based on the constellation of symptoms and assessment of the near triad. The diagnostic golden standard is a cycloplegic examination of refraction, preferably using cyclopentolate hydrochloride (1%, 0.5%, or 0.1% solution). The first-line treatment requires the administration of a cycloplegic drug in combination with plus lenses, flipper lenses, optical fogging, or miotics. For secondary cases, causal treatment should be implemented. Prevention of SNR should be based on eliminating modifiable risk factors. We propose including screening for SNR symptoms in every ophthalmic examination, especially among patients with psychogenic or neural disorders, after brain trauma, or young adults spending much time in front of computer screens.

Vestibular Rehabilitation Considerations in an Uncommon Optic Neuritis: A Case Report

Optic neuritis is an inflammatory condition that leads to inflammation and damage to the optic nerve, causing visual disturbances and pain. It is commonly associated with disorders such as multiple sclerosis and often manifests as sudden, unilateral loss of vision or blurred vision. This disorder can affect individuals of any age and may lead to decreased binocular vision, potentially resulting in difficulties with depth perception and visual coordination. Physiotherapy plays a crucial role in treating optic neuritis by addressing various aspects of the illness. We report the case of a 14-year-old male with diminution in both eyes, which was sudden in onset and painless in nature, with no history of falls, trauma, or diabetes. Magnetic resonance imaging reveals hyperintensity on short-tau inversion recovery (STIR) with mild contrast enhancement in the posterior aspects of the bilateral optic nerves (intracranial part), extending to the optic chiasm in optic neuritis. Physiotherapists employ a range of techniques to enhance the patient's overall well-being, including gaze stability exercises, eye-hand coordination exercises, and habituation exercises aimed at improving visual tracking and coordination. Additionally, physiotherapy can help reduce related symptoms such as muscle weakness, balance issues, and posture problems caused by impaired visual perception. Physical therapists endeavor to improve the quality of life for patients with optic neuritis by enhancing functional independence and contributing to a more effective approach to treatment. Notably, there was an improvement in visual scanning, spatial awareness, and eye movement control in this case.

Conformation of Horizontal Extraocular Muscle Insertions in Acute Acquired Concomitant Esotropia Induced by Excessive Digital Device Usage

Purpose

Acute acquired concomitant esotropia induced by excessive digital device usage, especially smartphones (SAACE), has been increasing over the past few years. Convergence spasm induced by excessive near work has been suggested as a mechanism. Anatomical differences could also potentially contribute to SAACE onset. The present study investigated the conformation of horizontal recti between SAACE patients and normal subjects.

Patients and Methods

In 15 SAACE patients (SAACE group), the distances between the limbus and insertion of the horizontal recti (LI distance) and the widths of horizontal recti on the insertion (insertion width) were measured. The control group consisted of 30 patients who underwent retinal detachment surgery. Differences in LI distances and insertion widths were compared between SAACE and control groups.

Results

While there were no differences between the two groups for LI distances and insertion widths of lateral recti, there were significantly shorter LI distances for the medial recti in the SAACE group (P<0.05). Moreover, the SAACE group tended to exhibit larger insertion widths of the medial recti. Medial/lateral ratio of LI distances were significantly lower and insertion widths were significantly higher in the SAACE compared to the control group (P<0.05).

Conclusion

Based on the observations of more anterior insertion and larger muscle widths, this suggests there are stronger forces of medial recti in SAACE. In addition to excessive accommodation followed by increases in medial recti tonus, the results also suggest that an anatomical imbalance between lateral and medial recti contributes to esotropia onset following excessive near work.

Simultaneous Development of Acute Acquired Concomitant Esotropia in Two Siblings during the COVID-19 Pandemic: A Case Report

Aim

To report a case of two siblings who near-simultaneously developed a large angle concomitant esotropia during the COVID-19 pandemic, and to describe their treatment and outcomes.

Method

A 5-year-old boy and his 11-year-old sister were presented to the hospital eye service in early 2021, having both developed acute-onset large angle esotropia within three months of each other. Neither had any significant past medical, ophthalmic, or family history. The siblings lived in the same household, and both experienced lifestyle changes as a result of the UK lockdown in response to COVID-19.

Results

Each sibling was treated with right medial rectus recession (5.5 mm) and right lateral rectus resection (7 mm), and at a three-month follow-up, both were minimally esophoric with restored binocularity.

Conclusion

The unusual and abrupt changes in lifestyle imposed by the COVID-19 pandemic highlight the likelihood of an environmental aetiology for some forms of esotropia and raise the possibility that extended screen time may be a contributory factor.

Surgical Outcomes with and without Prism Adaptation of Cases with Acute Acquired Comitant Esotropia Related to Prolonged Digital Device Use

Purpose

To analyze surgical results of 32 cases with acute acquired comitant esotropia (AACE) related to prolonged use of digital devices (DDs).

Patients and Methods

Medical records of cases with AACE related to prolonged use of DDs that had undergone surgery were retrospectively revised. Complete medical history and full ophthalmological examinations before and surgery were obtained for all cases. All cases also underwent neurological examinations using brain and orbital imaging. Motor success was considered as alignment within 10 prism diopters (Δ) at both near and distance. Sensory success was defined as stereopsis ≤60 arcsec. Nineteen cases (Group S) underwent surgery alone and 13 cases were treated with surgery and prism adaptation (Group S+P). Motor and sensory outcomes were compared between groups.

Results

Mean age at first visit was 22.0 ± 9.0 years and mean daily use of DDs use was 6.3 ± 3.4 hours. Mean angle of preoperative alignment for distance and near were 26.5 ± 13.0Δ and 24.6 ± 16.4Δ, respectively. Surgery was performed at a mean of 23.3 ±3.5 years old and mean angle of alignment at final examination for distance and near were 5.8 ± 7.7Δ and 3.5 ± 5.7Δ, respectively. Final motor and sensory success rate were 84% and 53%, respectively. No significant differences in motor or sensory outcomes were evident between groups at initial or last visit.

Conclusion

Favorable motor and sensory outcomes were achieved with surgical intervention with and without prism adaptation for AACT related to prolonged use of DDs.

The effects of topical cycloplegics in acute acquired comitant esotropia induced by excessive digital device usage

Background

Acute acquired comitant esotropia induced by excessive digital device usage, especially smartphones (SAACE), has been increasing over the past few years. One suggested mechanism is convergence spasm induced by excessive near work, with refraining from digital device use considered to be an effective method for decreasing the degree of esodeviation. However, if symptoms persist and are untreated over time, recovery becomes more difficult. The present study evaluated the effects of topical cycloplegics on persistent SAACE untreated for over 1 year.

Methods

Patients with sustained SAACE that was untreated for over 1 year were evaluated. Digital device usage was discouraged and a topical cycloplegic, 0.4% tropicamide, was prescribed at bedtime. After obtaining informed consent, the 14 out of 23 enrolled patients who agreed to eye drop administration were defined as the study group, with the others serving as the controls. After a 3-month follow-up, patients who elected to undergo surgery were analyzed as the surgery group. Changes in esotropia angles, stereoacuity and diplopia complaints were evaluated after a 3-month follow-up.

Results

Esotropia angles decreased and stereoacuity improved after a 3-month treatment in the study group (P < 0.01). Diplopia disappeared in 13 patients (92.9%, totally disappeared or disappeared when using glasses with built-in prisms). Among 11 patients with untreated esotropia ranging from 1–3 years, decreases in esotropia angles were correlated to untreated esotropia duration (near: R = -0.6; distance: R = 0.7; both P < 0.05). Esotropia angles in the control group exhibited a tendency to increase while stereoacuity tended to deteriorate after the 3-month follow-up. As diplopia did not disappear in any patients, 7 elected to undergo surgery and were enrolled as the surgery group. While esotropia angles decreased in the study group, they were lower than the surgery group (P < 0.01), but higher than the control group (P < 0.01). Stereoacuity was worse in the control versus the study and surgery groups (both P < 0.05).

Conclusion

Results suggest short-acting topical cycloplegics are effective in SAACE patients with long untreated periods. Decreases in esotropia angles were negatively correlated to untreated esotropia duration, which suggests the necessity of early treatment.

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.

Effect of the base-out recovery point as the surgical target for acute acquired comitant esotropia

PURPOSE

To evaluate the treatment efficacy of the preoperative base-out recovery point as the surgical target angle for acute acquired comitant esotropia.

METHODS

Prospective study. Twenty-two patients with acute acquired comitant esotropia (AACE) underwent strabismus surgery based on the target angle of the preoperative base-out recovery point. The postoperative deviation, positive fusional vergence, and negative fusional vergence were evaluated and compared with those of 23 normal individuals.

RESULTS

The mean follow-up period was 18.68 ± 19.48 months. At the last follow-up, 19 (86.4%) of 22 subjects had orthophoria, whereas 3 (13.6%) had minimal esophoria. The postoperative angle of deviation was significantly smaller than the preoperative angle of deviation at near (P < 0.001) and distance (P < 0.001). Postoperative sensory fusion was significantly better than preoperative fusion at near (P < 0.001) and distance (P < 0.001). The postoperative stereoacuity improved significantly after the surgery at near (P < 0.001) and distance (P < 0.001). Compared with the controls, the convergence and divergence amplitudes in the AACE patients were similar at distance (P > 0.05) but were still narrower at near (P < 0.001).

CONCLUSION

Good alignment and binocular balance were obtained with the surgical target angle of the base-out recovery point in AACE.

Series of cases of acute acquired comitant esotropia in children associated with excessive online classes on smartphone during COVID-19 pandemic; digital eye strain among kids (DESK) study-3

Extra time of sitting in front of a digital device is required for e-learning by children during Corona virus (COVID-19) pandemic which can lead to many ocular problems including digital eye strain (DES). In view of increased incidence of DES in children, multiple studies had been conducted in central India to assess the eye strain in children due to excessive online classes as a research project named "Digital eye strain among kids (DESK) study." This study DESK-3 aimed to report series of cases of acute acquired comitant esotropia (AACE) in children attending online classes during COVID-19 pandemic. Children aged 6-18 years with recent onset of esotropia of < 1-month duration without any similar history in past presented in month of July-August 2020 at a tertiary children eye care hospital were evaluated. Data collection included age and gender of child, presence or absence of diplopia, visual acuity, duration of smartphone use, duration of online classes, angle of deviation for near and distance and cycloplegic refraction. Total eight children of AACE were included in the study. The mean age of children was 12.5 ± 4.2 years. All eight were males. The mean duration of smartphone use was 4.6 + 0.7 hours per day. All children were attending online classes > 4 hours per day on smartphone of average size 5.5 inches. Five children were emmetropic, one myopic, one pseudomyopic and one hyperopic. The angle of deviation for near and distance were 48.1 ± 16.4 PD and 49.3 ± 15.9 PD respectively with normal ocular motility. Seven children complained of horizontal diplopia in all gazes. Neurological examination and CT scan of brain and orbit was normal in all patients.  Two months before the lockdown only one case was identified as compared to eight during the lockdown. Prolonged near work during smart phone use for e-learning might lead to the development of AACE in children.

Acquired Comitant Esotropia in Children and Young Adults: Clinical Characteristics, Surgical Outcomes, and Association With Presumed Intensive Near Work With Digital Displays

PURPOSE

To describe the clinical characteristics and surgical outcomes of acquired comitant esotropia with symptomatic diplopia.

METHODS

The clinical features and surgical outcomes of 27 patients with diplopia due to acquired comitant esotropia were retrospectively reviewed. Exclusion criteria were a history of prematurity, cerebral palsy, head trauma, or febrile illness before the onset of acquired comitant esotropia, incomitant strabismus, accommodative spasm, and divergence paralysis. Neurological evaluation and neuroimaging was normal in all patients.

RESULTS

Mean age at onset of esotropia and diplopia was 17.8 ± 10.3 years (range: 6 to 44 years). Eighteen patients had simple myopia (range: -0.25 to -7.75 diopters [D]), 5 patients had hypermetropia (range: 0.50 to 1.50 D), and 4 patients had emmetropia. The angle of deviation prior to surgery was 35.6 ± 10.3 prism diopters (PD) for far and 38.0 ± 10.5 PD for near fixation. Twenty-three patients (85%) were prism responders. A history of excessive near work (≥ 4 hours a day) with digital displays was present in 21 (78%) patients. Diplopia resolved and some level of stereovision was achieved in all patients postoperatively. Three patients had recurrence of esotropia in long-term follow-up.

CONCLUSIONS

The differentiation of a serious pathology from a straightforward optically or medically treatable condition in patients with a subacute or chronic history of diplopia is challenging for the clinician. The recognition of acquired comitant esotropia due to presumed intensive near activities with digital display may avoid time-consuming and costly laboratory investigations. Most of the patients in this series were prism responders and surgery for the prism-adapted angle was successful in restoring binocular vision. [J Pediatr Ophthalmol Strabismus. 2020;57(4):251-256.].

Is infantile esotropia subcortical in origin?

Essential infantile esotropia (EIE) is often attributed to a primary disturbance within the visual cortex based upon the findings of monocular horizontal optokinetic asymmetry and correlative horizontal motion detection asymmetry. However, these physiologic aberrations conform to what would be observed if the visual cortex secondarily reconfigured itself to the preexisting subcortical optokinetic motion template. This analysis examines the perspective that the measured cortical aberrations can be explained by prolonged subcortical neuroplasticity, leading to a secondary rewiring of cortical motion pathways. Evolutionary evidence indicates that EIE is generated by subcortical ocular motor centers that subserve nasalward optokinesis. These phylogenetically older subcortical visuo-vestibular pathways include the nucleus of the optic tract, accessory optic system, inferior olive, cerebellar flocculus, and vestibular nucleus. In normal humans, the subcortical visual system becomes inactivated after the first few months of infancy. Mutations or other perturbations that prolong subcortical neuroplasticity may create a persistent simultaneous nasalward optokinetic bias in both eyes to generate 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.

Increase in esodeviation under cycloplegia with 0.5% tropicamide and 0.5% phenylephrine mixed eye drops in patients with hyperopia and esotropia

Backgroud

To evaluate the manifestations of increased esodeviation under cycloplegia with 0.5% tropicamide and 0.5% phenylephrine in children with hyperopia and esotropia.

Methods

We reviewed the medical record of 34 children with hyperopia and esotropia who underwent a prism alternate cover test before and after instillation of mixed eye drops containing 0.5% tropicamide and 0.5% phenylephrine between November 2014 and October 2015. Increased angle of deviation was defined as 10 prism diopters (PD) or greater deviation after cycloplegia. The factors related to increased angle of deviation were evaluated using univariable and multivariable logistic regression analysis.

Results

The median age was 5.0 years (interquartile range, 3.75 to 5.0) and 12 patients (35.3%) were male. The median manifested refractive (MR) was +2.13 diopters (D) (+0.92 to +4.47) and cycloplegic refractive (CR) was +3.50 D (+1.72 to +5.66). The median difference between MR and CR was +0.88 D (+0.50 to +1.28). Thirteen patients (38.2%) showed increased esodeviation under cycloplegia and all had accommodative esotropia. A larger difference between MR and CR was the only significant factor affecting increased esodeviation in both univariable (OR = 4.72, P = 0.029) and multivariable (OR = 5.22, P = 0.047) analyses.

Conclusion

Children with hyperopia and esotropia often showed an increased angle of deviation after instillation of 0.5% tropicamide and 0.5% phenylephrine. This phenomenon reminded the clinicians that cycloplegics can have a different effect on esodeviation and suggested that increased angle of esodeviation may help to reveal the latent deviation in some patients with hyperopia and esotropia.

Acute acquired comitant esotropia related to excessive Smartphone use

Background

To describe the clinical characteristics and outcomes of acute acquired comitant esotropia (AACE) related to excessive smartphone use in adolescents.

Methods

The medical records of 12 patients with AACE and a history of excessive smartphone use were retrospectively reviewed, and the duration of smartphone use, angle of deviation, refractive error, stereopsis, and treatment options were analyzed.

Results

All patients showed convergent and comitant esotropia ranging from 15 to 45 prism diopters (PD; average: 27.75 ± 11.47 PD) at far fixation. The angle of deviation was nearly equivalent for far and near fixation. Every patient used a smartphone for more than 4 h a day over a period of several months (minimum 4 months). Myopic refractive errors were detected in eight patients (average:−3.84 ± 1.68 diopters (D]), and the remaining four patients showed mild hyperopic refractive error (average: +0.84 ± 0.53 D). Reductions in esodeviation were noted in all patients after refraining from smartphone use, and bilateral medial rectus recession was performed in three patients with considerable remnant esodeviation. Postoperative exams showed orthophoria with good stereoacuity in these patients.

Conclusion

Excessive smartphone use might influence AACE development in adolescents. Refraining from smartphone use can decrease the degree of esodeviation in these patients, and remnant deviation can be successfully managed with surgical correction.

Extraocular Muscles Tension, Tonus, and Proprioception in Infantile Strabismus: Role of the Oculomotor System in the Pathogenesis of Infantile Strabismus-Review of the Literature

The role played by the extraocular muscles (EOMs) in the etiology of concomitant infantile strabismus is still debated and it has not yet definitively established if the sensory anomalies in concomitant strabismus are a consequence or a primary cause of the deviation. The commonest theory supposes that most strabismus results from abnormal innervation of the EOMs, but the cause of this dysfunction and its origin, whether central or peripheral, are still unknown. The interaction between sensory factors and innervational factors, that is, esotonus, accommodation, convergence, divergence, and vestibular reflexes in visually immature infants with family predisposition, is suspected to create conditions that prevent binocular alignment from stabilizing and strengthening. Some role in the onset of fixation instability and infantile strabismus could be played by the feedback control of eye movements and by dysfunction of eye muscle proprioception during the critical period of development of the visual sensory system. A possible role in the onset, maintenance, or worsening of the deviation of abnormalities of muscle force which have their clinical equivalent in eye muscle overaction and underaction has been investigated under either isometric or isotonic conditions, and in essence no significant anomalies of muscle force have been found in concomitant strabismus.

Surgery for infantile esotropia: is timing everything?

Infantile esotropia affects binocular alignment and development of binocular vision. Delayed correction may lead to loss of stereopsis. Waiting for the angle of deviation to stabilise prior to surgery does not impact overall postoperative outcomes greatly. Early surgical intervention produces better outcomes in terms of sensory and motor development, binocular vision and stereoacuity. The period of misalignment has the greatest effect on postoperative outcome therefore early surgery is recommended.

Accommodative and vergence responses to conflicting blur and disparity stimuli during development

Accommodative and vergence responses of the typically developing visual system are generated using a combination of cues, including retinal blur and disparity. The developmental importance of blur and disparity cues in generating these motor responses was assessed by placing the two cues in conflict with each other. Cue-conflicts were induced by placing either -2 D lenses or 2 MA base-out prisms before both eyes of 140 subjects (2.0 months to 40.8 years) while they watched a cartoon movie binocularly at 80 cm. The frequency and amplitude of accommodation to lenses and vergence to prisms increased with age (both p < 0.001), with the vergence response (mean +/- 1 SEM = 1.38 +/- 0.05 MA) being slightly larger than the accommodative response (1.18 +/- 0.04 D) at all ages (p = 0.007). The amplitude of these responses decreased with an increase in conflict stimuli (1 to 3 D or MA) (both p < 0.01). The coupled vergence response to -2 D lenses (0.31 +/- 0.06 MA) and coupled accommodative response to 2 MA base-out prisms (0.21 +/- 0.02 D) were significantly smaller than (both p < 0.001) and poorly correlated with the open-loop vergence (r = 0.12; p = 0.44) and open-loop accommodation (r = -0.08; p = 0.69), respectively. The typically developing visual system compensates for transiently induced conflicts between blur and disparity stimuli, without exhibiting a strong preference for either cue. The accuracy of this compensation decreases with an increase in amplitude of cue-conflict.