Journal of Pediatric Ophthalmology and Strabismus

Original Article Supplemental Data

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

Pinar Topcu Yilmaz, MD; Özlem Ural Fatihoglu, MD; E. Cumhur Sener, MD

Abstract

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.]

Abstract

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.]

Introduction

Acquired comitant esotropia that develops in older children and early adulthood is a relatively rare type of esotropia, characterized by the subacute onset of esotropia and diplopia without evidence of a sixth nerve palsy.1,2 Diplopia or confusion is initially noticed at distance in most of the patients and may later progress to involve near vision. Historically, acquired comitant esotropia has been classified into three main categories.3 The Swan type (type 1) is acute onset comitant esotropia that develops secondary to interruption of fusion.4 Burian-Franceshetti type (type 2) is characterized by the presence of a minimal amount of hyperopia and is usually precipitated by physical or psychological stress.2,3 Type 3 acquired comitant esotropia (also referred to as Bielschowsky type esotropia) is associated with moderate myopia. Patients with this type of acquired comitant esotropia present initially with a small angle of intermittent esotropia at distance and gradually develop a larger constant deviation at both near and distance fixation. The close-up working distance due to uncorrected myopia and the resulting increase in medial rectus muscle tone are believed to play an important role in this type of acute esotropia.2,3 Apart from these three types, acquired comitant esotropia has also been reported to be associated with accommodative spasm and intracranial disease.2,5–7 A thorough neurological evaluation and neuroradiological imaging may be necessary in select cases with acquired comitant esotropia to rule out an associated intracranial or neurological pathology.

The use of mobile touch screen devices by older children and young adults has dramatically increased within the past decade, and we have noticed that the number of patients presenting to our clinic with acquired comitant esotropia has significantly increased since this rapid rise in smartphone use. Smartphones and tablets, with their smaller font sizes, have significantly replaced paper-based information and outdoor recreational activities. Recently, two case series have drawn attention to a possible association between increased smartphone use and acquired comitant esotropia.8,9 The purpose of this study was to analyze the clinical characteristics and surgical outcome in patients with acquired comitant esotropia and to determine the prevalence of excessive mobile touch screen device use in these patients.

Patients and Methods

The medical records of consecutive patients who presented to our clinic with diplopia due to acquired comitant esotropia between January 2006 and December 2019 were reviewed retrospectively. Patients who met the following criteria were included in this study: age of onset 6 years or older; acute or subacute onset of concomitant esotropia; corrected visual acuity of 20/20 in both eyes; minimum follow-up period of 6 months after surgery; no history of eye problems, systemic disease, or head trauma; absence of a known cause for interruption of fusion; and normal neurological evaluation and neuroimaging. Patients with a history of amblyopia, prematurity, and cerebral palsy, head trauma or febrile illness before the onset of acquired comitant esotropia, accommodative or partially accommodative esotropia, infantile esotropia, incomitant strabismus, myopic strabismus fixus, sagging eye syndrome, accommodative spasm, and divergence paralysis were excluded from the study. The study was performed with approval from the Institutional Review Board of Ankara Numune Education and Research Hospital and adhered to the European Good Clinical Practice Guidelines and the tenets of Declaration of Helsinki.

Preoperative and postoperative measurements and strabismus surgery were performed by a single surgeon (ECS). The following data were collected from the patient records: the type of onset (patients with a history of sudden development of esotropia were classified as acute onset, patients with a history of intermittent diplopia and esotropia that later progressed to constant esotropia were classified as sub-acute onset), age at onset, age at the time of surgery, gender, history of excessive (≥ 4 hours/day) mobile touch screen device use, visual acuity, manifest and cycloplegic refraction, angle of deviation at near and distance before and after the prism adaptation test, ocular motility in all directions of gaze, surgical treatment, recurrence of esotropia after surgery, results of the Worth-4 dot test, and stereoacuity with the Titmus test.

The angle of deviation was measured by alternate prism cover test (APCT) at 6 m and 33 cm with appropriate refractive correction in place. The power of the prism found with APCT was adapted using Fresnel prism trial glasses on both eyes. The prism-adapted angle was defined as the maximum amount of prism needed to neutralize the deviation at near and distance with resolution of the diplopia after approximately 30 minutes of prism adaptation. The simple mathematical summation of the prisms on both eyes was used to calculate the total amount of prism power. Patients were classified as prism responders if they achieved stable motor alignment and the angle of deviation increased 10 PD or more, at either near or distance, compared to the initial prism measurement.10 Ocular alignment measurements at the final follow-up visit were used to report the postoperative outcomes. Surgical dose was planned for the maximum amount of prism-adapted deviation.

All patients in the study underwent a complete physical and neurological examination, cranial magnetic resonance imaging with contrast, and a myasthenia work-up. Some ambiguous cases received a trial of pyridostigmine treatment despite negative laboratory work-up results, at the discretion of the neurologist.

SPSS version 17.0 software (SPSS Institute, Inc) was used for analysis. The paired t test was used to evaluate the change in the angle of deviation before and after prism adaptation test. A P value of less than .05 was considered statistically significant.

Results

The review of medical records identified 35 patients who had presented to our clinic with diplopia due to acquired comitant esotropia during the 13-year study period. Two of these patients were excluded from the study due to a history of accommodative esotropia in childhood and one patient was excluded due to history of previous strabismus surgery for acute esotropia elsewhere. The yearly distribution of the remaining 32 patients is shown in Figure 1. Twenty-seven of these 32 patients, who had surgery for acquired comitant esotropia in our clinic and completed 6 months of follow-up after surgery, were included in the statistical analysis. The baseline clinical characteristics of these 27 patients is summarized in Table 1. None of the patients had a history of occlusion therapy, recent inflammatory disease, trauma, or significant psychological stress prior to the development of acquired comitant esotropia. Twenty-one of 27 (78%) patients had a history of intensive mobile touch screen device use.

Yearly distribution of patients (including those who elected not to have surgery) who presented to the clinic with acute comitant esotropia between January 2006 and December 2019.

Figure 1.

Yearly distribution of patients (including those who elected not to have surgery) who presented to the clinic with acute comitant esotropia between January 2006 and December 2019.

Clinical Characteristics of Patients With Acute Acquired Comitant Esotropia

Table 1:

Clinical Characteristics of Patients With Acute Acquired Comitant Esotropia

The mean age at onset of diplopia was 17.8 ± 10.3 years (range: 6 to 44 years), the mean age at presentation to our clinic was 20.5 ± 11.0 years (range: 6 to 46 years), and the mean age at surgery was 21.5 ± 11.1 years (range: 7 to 47 years). The mean spherical equivalent was −1.90 ± 2.50 D (range: −7.00 to +1.50 D) for the right eyes and −1.90 ± 2.40 D (range: −7.75 to +1.25 D) for the left eyes. Eighteen (67%) patients were myopic and in 2 of them myopia was greater than 6.00 D. Five (18%) patients had hypermetropia and 4 (15%) patients had emmetropia.

All patients had best corrected visual acuity of 20/20, normal anterior segment examination, and funduscopy examination of both eyes. The refraction in all patients was checked with cycloplegic retinoscopy to ensure that they were not overcorrected or undercorrected. The neurological evaluation and cranial magnetic resonance imaging were normal in all patients.

The detailed history revealed that diplopia was initially noticed on distance fixation and gradually progressed to near fixation in all patients. The mean duration of diplopia at presentation to our clinic was 31.3 ± 22.2 months (range: 6 to 84 months). Patients with myopia had gone through a trial of undercorrection of their refractive error with the intention of reducing the accommodative stimulus. However, none of them showed an improvement in esodeviation after undercorrection.

The mean angle of esotropia with appropriate correction was 35.6 ± 10.3 PD at distance and 38.0 ± 10.5 PD at near. The prism adaptation test was positive in 23 (85%) patients. After prism adaptation, there was a significant increase in the mean angle of esotropia at distance (49.1 ± 11.6 PD) and at near (52.2 ± 10.6 PD) (P < .001). Ocular ductions and vergences were normal.

Eleven patients underwent unilateral medial rectus recession and lateral rectus plication, 14 patients underwent bilateral medial rectus recession (modified loose loop recession in 7 patients), and 2 patients underwent a simultaneous three-muscle procedure of bilateral medial rectus recession and unilateral lateral rectus plication. At the first postoperative day, 21 patients were found to be orthophoric at distance and near, 5 patients had less than 8 PD of esophoria at near, and 1 patient (case 2) had 8 PD of intermittent exotropia. The intermittent exotropia in case 2 resolved spontaneously in 2 months and the patient was orthophoric at 4 years postoperatively. Diplopia resolved and bifoveal fusion and some level of stereovision (40 to 100 seconds of arc) was achieved in all patients after surgery.

During follow-up, 3 patients (cases 1, 7, and 8) developed recurrent esotropia (Table A, available in the online version of this article).

Detailed Clinical Characteristics of Patients With Acquired Comitant Esotropia Detailed Clinical Characteristics of Patients With Acquired Comitant Esotropia

Table A:

Detailed Clinical Characteristics of Patients With Acquired Comitant Esotropia

Case 1 had undergone unilateral medial rectus recession and lateral rectus plication surgery and was orthophoric in the early postoperative period. At the 12-month follow-up visit, he presented with recurrent diplopia and intermittent esotropia of 8 PD. He was treated with prism glasses, which were gradually weaned during follow-up. At his 5-year visit, he had 3 PD of esophoria without prisms and his stereoacuity was 40 seconds of arc. Case 7 had undergone unilateral medial rectus recession and lateral rectus plication surgery and had an esophoria of 8 PD in the early postoperative period. Despite our suggestions, she did not reduce the hours per day spent on her smart-phone, esophoria gradually progressed to an esotropia of 8 PD at distance at 2 years postoperatively, and she was treated with prism glasses. Case 8 had undergone bilateral medial rectus recession and was orthophoric after surgery. At the 4-year follow-up visit, she presented with recurrent diplopia and esotropia of 30 PD at distance and 45 PD at near. The neurological evaluation and cranial magnetic resonance imaging were normal. Presence of myopia and persistence of excessive smartphone use after surgery were the common points in the last two cases.

Discussion

Acquired comitant esotropia is a relatively rare form of strabismus and is historically categorized into three types depending on the presumed etiology, refractive error, and clinical features.3 The disruption of binocular fusion due to temporary or permanent monocular occlusion, psychological stress, and uncorrected myopia leading to excessive convergence during near viewing are the most commonly accepted precipitating factors in patients with acquired comitant esotropia.3,6,11 None of the patients in the current study had experienced an event that could lead to disruption of fusion; thus they did not meet the criteria for the Swan type.4 Acquired comitant esotropia of Burian-Fransechetti type is associated with a low amount of hypermetropia, and is usually reported after psychosocial problems.3 Five patients in the current study had hyperopia ranging from 0.50 to 1.25 D. However, none of them had encountered a preceding physical or psychological stress.

Eighteen of 27 patients in this series had myopia ranging between 0.50 and −7.75 D (16 of them had < −6.00 D of myopia), and the esotropia in these patients showed a close resemblance to the Bielschowsky type of acquired comitant esotropia. However, the myopic refractive error was already corrected prior to the development of acquired comitant esotropia and none of our patients had abstained from wearing their glasses prior to the development of diplopia. Thus, Bielchowsky's hypothesis implicating uncorrected myopia leading to excessive convergence during near viewing can be set aside as a precipitating factor in this series.2,3

Acquired esotropia can also be the presenting sign of an intracranial tumor, Arnold Chiari malformation, or idiopathic intracranial hypertension. The presence of nystagmus, abduction deficiency, greater deviation at distance, and lateral incomitancy can be the warning signs that point the physician toward a neurological insult.2 However, studies have shown that absence of these signs or the concomitancy of esotropia does not always exclude this possibility.7,12 All of the patients in our study had normal neurological examination and neuroimaging and none of them developed a neurological sign during follow-up. Some of the patients had even gone through a trial period of pyridostigmine treatment, but none of them responded positively.

The restoration of bifoveal fusion and stereopsis in our patients after surgery excludes the possibility of a decompensated monofixation syndrome. This normal fusional capacity and motor alignment within 8 PD of esophoria were preserved in 25 (93%) patients at long-term follow-up. This high success rate is in agreement with the previous studies, and is associated with the normal development of binocular vision prior to the onset of acquired comitant esotropia.8,10,13

A notable finding in the current study was the high frequency (78%) of patients with a history of intensive (> 4 hours/day) near work with digital displays. During the past decade, there has been a sharp increase in the number of patients presenting with acute esotropia and diplopia to our clinic (Figure 1) and we believe that this is related to the exponential increase in the use of smartphones and tablets for educational and recreational purposes. Despite the growing number of studies that have linked ocular symptoms related to eye fatigue, asthenopia, dry eye, and myopia to intensive use of smartphones14–16 and other mobile touch screen devices, few studies have addressed the possible association between acute esotropia and excessive smartphone use.8,9,17 Excessive accommodation and convergence spasm has been previously suggested as an etiological factor in Bielschowsky's acute comitant esotropia.11

The preferred reading distance for mobile devices is significantly shorter than the distance for reading books.18 The use of smartphones and other mobile touch screen devices for long hours at this shorter reading distance requires greater accommodation that can trigger excessive convergence. The resulting increase in medial rectus muscle tone in susceptible individuals with low fusional capacity can be the cause of acquired comitant esotropia in this patient population.19 Intensive use of a mobile touch screen device can also induce decompensation of an existing esophoria, and this can gradually progress to an acquired esotropia, as stated by Ali et al.20

While writing this article, we have seen two patients who presented to our clinic within 2 weeks after the onset of intermittent diplopia at distance. Prism cover test revealed a small amount of intermittent esotropia at distance and near in these patients. The parents reported excessive use of smartphone and prohibition of its use resulted in resolution of diplopia and intermittent esotropia at the 3-month follow-up visit. We believe that the recovery observed in our patients presenting in the acute phase and the decreased angle of esotropia after restriction of smartphone use in the study by Lee et al8 supports the possible association between excessive near work with digital displays and development of acquired comitant esotropia.

The last possible cause of diplopia in patients with excessive smartphone use is acute esotropia due to accommodation spasm.9 This was excluded in our patient group on the basis of normal visual acuity at distance, absence of miosis, and consistency of refractive error after cycloplegia.

In the current study, the prism adaptation test was positive in 23 patients (85%) and the mean amount of esodeviation increased significantly after prism adaptation. The patients in the prism responder group would have been undercorrected if we planned the surgery for the amount of esodeviation found with the APCT. Ali et al20 drew attention to the inadequate response to conventionally dosed strabismus surgery in patients with acquired comitant esotropia and suggested augmenting the surgical target angle by 10 PD in this patient population. Targeting the prism-adapted angle resulted in an overall success rate of 93%1 at the last follow-up visit in our study group, and avoided an undercorrection in the early postoperative period. We believe that in patients with acquired comitant esotropia, targeting the prism-adapted angle is a safer approach than an arbitrary augmentation in surgical dosage.

We have presented the clinical characteristics and surgical outcome in a series of children and young adults with acquired comitant esotropia. The concomitant non-accommodative esotropia with horizontal diplopia, normal neurological evaluation, and potential for normal binocular fusion after surgical correction were the salient features that merit attention in this case series. The high frequency of patients with acquired comitant esotropia with a history of excessive mobile touch screen device use is a cause of concern and requires further investigation.

References

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Clinical Characteristics of Patients With Acute Acquired Comitant Esotropia

Characteristic Valuea
Age at onset of diplopia (y) 17.8 ± 10.3 (6 to 44)
Age at surgery (y) 21.5 ± 11.1 (7 to 47)
Sex (M/F) (no.) 14/13
Spherical equivalent (D)
  Right eye −1.90 ± 2.50 (−7.00 to +1.50)
  Left eye −1.90 ± 2.40 (−7.75 to +1.25)
Follow-up (months)
  Preoperative 14.6 ± 16.8 (3 to 72)
  Postoperative 27.3 ± 17.4 (6 to 66)
Preoperative esotropia (PD)
  Far 35.6 ± 10.3 (20 to 65)
  Near 38.0 ± 10.5 (25 to 65)
Esodeviation after prism adaptation test (PD)
  Far 49.1 ± 11.6 (35 to 75)
  Near 52.2 ± 10.6 (40 to 75)
Final deviation (PD)
  Far 1.4 ± 5.9 (0 to 30)
  Near 2.0 ± 8.7 (0 to 45)
Authors

From Ankara Numune Education and Research Hospital, Ankara, Turkey (PTY); Iskenderun State Hospital, Hatay, Turkey (ÖUF); and Private Practice, Ankara, Turkey (ECS).

The authors have no financial or proprietary interest in the materials presented herein.

Correspondence: E. Cumhur Sener, MD, Cinnah Street, 96/4, Cankaya, Ankara, Turkey. Email: ecsener@gmail.com

Received: February 04, 2020
Accepted: April 14, 2020

10.3928/01913913-20200422-02

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