Clinical characteristics and aetiology of acute acquired comitant esotropia

ABSTRACT

Clinical relevance

Acute acquired comitant esotropia (AACE) is characterised by the acute onset of diplopia which affects work and life.

Background

To describe the clinical characteristics and discuss the aetiology of acute acquired comitant esotropia.

Methods

The medical records of 51 patients with AACE were retrospectively analysed, and their age, occupation, daily average time spent on near work, angle of deviation, refractive error and aetiology were analysed.

Results

The age at onset of AACE was eight to 55 years. Thirty-nine patients were aged 12 to 36 years (76.5%), and 42 patients (82.4%) were myopic. The angle of deviation was 20^Δ (12^Δ to 35^Δ) during near fixation and 25^Δ (18^Δ to 40^Δ) during distance fixation. The deviation during distance fixation was larger than that during near fixation, the difference being statistically significant (p < 0.001). The daily average time of near work before onset was 9.0 h (8.0 h to 10.0 h); 35 patients (68.6%) spent more than 8 h performing near work. Their occupations included students, accountants, information technology staff, and those who required electronic use for a long time. There is no correlation between the angle of deviation and the time of near work (p > 0.05). Among the 51 patients, three had intracranial diseases. Diplopia resolved in 47 cases following treatment. The angle of deviation post-treatment was 0^Δ (0^Δ to 5^Δ) during near and 0^Δ (0^Δ to 3^Δ) during distance fixation.

Conclusion

AACE occurs mostly in myopic older children and adults. The onset of esotropia is related to long-term near work. AACE patients mostly present an angle of deviation that is larger during distance than near fixation. Intracranial disease is an infrequent but important cause of AACE that needs to be excluded in all cases.

KEYWORDS:

• Acute acquired
• aetiology
• comitant esotropia
• Intracranial disease

Introduction

Acute acquired comitant esotropia (AACE) is an infrequent subtype of esotropia characterised by the acute onset of comitant esotropia with diplopia. It mostly occurs in older children and adults.^1,2 Historically, AACE was divided into three categories according to the clinical characteristics and distinct aetiologies: type I (Swan type): esotropia due to the disruption of fusion; type II (Franceschetti type): esotropia likely related to physical or psychological stress, characterised by hypermetropia without an accommodative element; and type III (Bielschowsky type): esotropia due to myopia.^3,4

Other causes of AACE, such as intracranial diseases, anatomic abnormalities of the medial rectus, excessive smartphone use, multiple sclerosis, and sinus vein thrombosis, have also been reported.^5–9 In this report, the characteristics of 51 cases are presented to describe the clinical characteristics, high-risk occupations, and aetiologies of AACE.

Methods

The medical records of all patients with acute acquired comitant esotropia from June 2018 to October 2019 at the Eye Center, Renmin Hospital of Wuhan University, were reviewed. Patients who met the following criteria were included in this study: (1) patients experiencing diplopia; (2) patients with acute onset of comitant strabismus and same deviation in all gaze directions (deviation difference ≤ 5^Δ); (3) patients with corrected visual acuity of 6/6 in both eyes; (4) patients with normal eye movement; and (5) patients who agreed to be followed for ≥ 4 months.

Patients with acute incomitant esotropia were excluded. Incomitance was defined as a large deviation (deviation difference > 5^Δ) on side gaze measured by prism therapy and alternate cover tests. In total, 51 patients fulfilled the inclusion criteria.

The study was conducted by the tenets of the Declaration of Helsinki and was approved by the Ethics Committee of Renmin Hospital of Wuhan University (No.:WDRY2020-K211), Wuhan, China. Informed consent was obtained from all participants and their families.

The following information was obtained for each patient: sex, age, occupation, presenting complaint, past history, symptoms, signs, best corrected visual acuity, cycloplegic refraction, deviation during near and distance fixation, fusion and stereopsis, daily average time spent performing near work at least six months before onset, treatment, and follow-up time.

All patients underwent ophthalmic examinations and cranial and orbital computed tomography (CT) or magnetic resonance imaging (MRI). Cycloplegic refraction measurement was performed after the administration of 1% atropine ointment twice daily for five days in patients under 12 years old and 1% cyclopentolate eye drops every five minutes three times for those > 12 years old. Manifest refraction and cycloplegic spherical equivalents of the refractive error were calculated by using the algebraic sum of the dioptric powers of the sphere and half of the cylinder.

Ocular motility and nystagmus were evaluated clinically. The angle of strabismus was measure using prisms and alternate cover test at a near (33 cm) and distance (6 m). Synoptophores were used to assess the three grades of binocular function. Stereoacuity was evaluated with a Titmus test card at 40 cm.

SPSS version 18.0 (SPSS Institute Inc., Chicago, IL, USA) was used for the statistical analyses. The Wilcoxon signed rank test was used to compare the deviation at near and distance fixation. P values < 0.05 were considered statistically significant.

Results

A total of 51 AACE patients were included in this study; 33 were males, and 18 were females. The follow-up period was 7.5 months (range: four to 16 months). The mean age of the 51 patients was 24 (21 to 34) years (range, eight to 55 years). Three patients were younger than 12 years (5.9%), 39 patients were aged 12 to 36 years old (76.5%), and nine patients were older than 36 years (17.6%). None of the patients had a family history of strabismus.

Anterior segment and fundus examinations were normal in all patients. AACE mainly occurs in people aged 12 to 36 years. Out of the 51 patients, three patients had neurological diseases according to cranial MRI: one patient had a pituitary tumour, one patient had a brainstem tumour, and one patient had Arnold-Chiari malformation type I. The other 48 patients were neuroradiologically negative. Among the 51 patients, two patients had psychosis treated with antipsychotic drugs, and one patient had systemic lupus erythematosus treated with glucocorticoids.

All the patients had a corrected visual acuity of 6/6 with their glasses. AACE patients mostly presented with myopic refractive error. Forty-two patients (82.4%) were myopic, and nine patients had hypermetropia (17.6%). The mean cycloplegic refractive error was R: −3.75 D (−4.75 to −1.63 D) and L: −3.68 D (−4.75 D to −1.25 D) (Table 1).

Table 1. Clinical characteristics of the patients with AACE

Patient number	Age (years)/sex	Occupation	Associated diseases	Cycloplegic refraction (SE), R/L (D)	Esodeviation, distance/near (PD)	Time of near work per day (hours)
1	14/M	Student	-	+0.38/+0.63	60/50	8.5
2	23/M	Student	-	+1.25/+0.50	50/40	8.0
3	12/M	Student	-	+0.25/+0.63	50/45	9.0
4	32/M	Designer	-	+1.00/+0.75	50/45	9.0
5	36/M	Civil servant	-	+0.75/+1.00	60/45	9.0
6	37/M	City Management	-	−2.88/-2.75	35/12	5.5
7	29/M	Accountant	-	−9.25/-8.63	12/12	9.5
8	21/F	Student	-	−4.38/-2.50	30/30	8.0
9	55/M	Taobao shop owner	-	−4.38/-4.50	25/20	11.0
10	50/F	Accountant	-	−3.38/-3.38	12/12	9.0
11	23/M	Student	-	−4.13/-4.25	14/12	10.0
12	14/M	Student	-	−2.50/-1.25	16/12	9.0
13	16/M	Student	-	−4.63/-4.75	25/20	11.0
14	25/F	Cashier	-	−4.75/-5.00	14/12	10.5
15	36/M	Waiter	-	−1.63/-1.50	35/30	10.5
16	45/F	Accountant	-	−4.38/-4.38	25/20	9.5
17	43/F	Accountant	-	−3.50/-3.63	25/18	9.5
18	23/F	Student	-	−3.75/-4.00	35/30	9.5
19	30/F	IT staff	-	−4.75/-4.50	60/50	10.0
20	22/F	Student	-	−7.00/-6.88	18/12	9.5
21	49/M	Courier	-	−4.75/-4.63	35/30	6.0
22	32/M	IT staff	-	−4.13/-5.25	40/30	9.0
23	34/M	Labourer	-	−4.38/-4.88	20/20	4.5
24	19/M	Student	Psychosis	−4.50/-4.00	20/25	11.0
25	35/F	Garment factory staff	-	−1.50/-1.25	16/14	12.0
26	52/M	Driver	-	−3.00/-3.68	8/6	8.0
27	22/M	Student	-	−8.25/-7.00	14/16	11.0
28	16/M	Student	-	−0.38/-0.63	10/8	10.5
29	29/M	Unemployed	Psychosis	−5.00/-5.25	25/20	5.0
30	19/F	Student	-	−4.50/-4.50	20/18	11.0
31	28/F	Bank staff	-	−4.50/-4.25	18/16	9.0
32	23/F	Student	SLE	−6.50/-6.50	40/30	8.0
33	23/F	Student	-	−3.75/-3.50	18/14	7.0
34	22/M	Student	-	−4.75/-4.50	20/20	7.5
35	24/F	Accountant	-	−3.25/-3.25	18/12	9.5
36	30/F	Constable	-	−2.50/-2.75	35/30	8.0
37	12/M	Student	Pituitary tumour	+1.00/+1.25	40/40	8.0
38	10/M	Student	Brainstem tumour	+1.50/+1.38	40/35	7.5
39	22/M	Student	-	−1.00/-1.00	8/8	9.0
40	21/M	Baker	-	−2.00/-1.75	30/30	11.0
41	21/M	Student	-	−5.50/-5.50	40/30	8.5
42	26/F	Estate agent	-	−6.25/-6.25	50/50	7.5
43	29/M	IT staff	-	−3.75/-3.50	35/30	9.0
44	22/M	Student	-	−7.75/-7.25	60/60	8.5
45	32/M	IT staff	-	−4.38/-4.00	18/12	10.5
46	23/M	Model	-	−3.25/-3.25	40/35	10.0
47	37/F	Accountant	-	−4.63/-4.50	16/16	9.0
48	32/F	Nurse	-	−1.75/-2.25	40/30	10.0
49	55/M	Ticket inspector	-	−6.25/-6.50	18/12	9.5
50	9/M	Student	Arnold-Chiari malformation	+3.25/+2.75	60/60	7.5
51	8/M	Student	-	+1.00/+1.25	50/45	7.0

Abbreviations: SLE, systemic lupus erythematosus; R, right; L, left; PD, prism dioptres; SE, spherical equivalent; D, dioptres.

All the patients stated that they mostly used their eyes for near work (< 33 cm), including reading, writing, and viewing smartphones or computers. The daily average time of near work before onset was 9 h (8.0 h to 10.0 h) (range 4.5 h to 12.0 h); 35 patients (68.6%) reported a daily time of near work of more than 8 h hours. Occupations included students, accountants, information technology staff and occupations that used electronic devices for a long period (Table 1).

The angle of deviation was 20^Δ (12^Δ to 35^Δ) during near and 25^Δ (18^Δ to 40^Δ) during distance fixation. In 37 patients, the deviation during distance fixation was larger than that during near fixation. Two cases presented a deviation at distance fixation that was less than that at near fixation. The other 12 patients had the same deviation during both near and distance fixation. The deviation of AACE patients during distance fixation was larger than that during near fixation, and the difference was statistically significant (p < 0.001) (Table 2).

Table 2. Comparison of the angle of deviation between near and distance fixation

	Angle of deviation
Near (33 cm)	20^Δ (12^Δ to 35^Δ)
Distance (6 m)	25^Δ (18^Δ to 40^Δ)
p	< 0.001

There is no correlation between the angle of deviation at distance fixation and the time of near work (p = 0.08), and no correlation between the angle of deviation at near fixation and the time of near work (p = 0.16).

Among the 51 cases, diplopia disappeared in 47 cases, 4 cases remained diplopia. Two cases—a driver and a labourer—resigned and used Aesculus digitalis glycoside eye drops, and the diplopia disappeared. Ten cases of diplopia resolved after being corrected with the bilateral base out prisms of 4^Δ to 8^Δ. Fifteen cases were treated with botulinum toxin A and two of them remained diplopic for residual deviation. Twenty-four cases treated with surgery included 21 strabismus surgeries and three brain surgeries. All the 21 cases of diplopia disappeared with strabismus surgeries. Among the three brain surgeries, two cases diplopia remained and one case with Arnold-Chiari malformation type I diplopia disappeared.

The angle of deviation post treatment was 0^Δ (0^Δ to 5^Δ) (range, 0^Δ to 25^Δ) during near and 0^Δ (0^Δ to 3^Δ) (range 0^Δ to 25^Δ) during distance fixation. Two of 15 cases treated with botulinum toxin A remained diplopia, one case of residual deviation was 20^Δ (near = distance), and another case of residual deviation was 25^Δ (near = distance). Two of three cases treated with brain surgeries remained diplopic, the residual deviation of one pituitary tumour patient was 18^Δ during near and 20^Δ during distance fixation, and another brainstem tumour patient had a residual deviation of 25^Δ (near = distance).

Discussion

AACE is a special subtype of esotropia characterised by the acute onset of comitant esotropia with diplopia and equal deviation in all gaze directions. Ocular motility is generally normal without evidence of paralysis of the extraocular muscles. AACE is more common in older children and adults than in younger children.

AACE is classified into three types according to the clinical characteristics and aetiologies: (1) the Swan type, which was first described by Swan, is due to the disruption of fusion resulting from monocular occlusion or visual loss⁴; (2) the Franceschetti type, which manifests as an acutely large angle of deviation with mild hyperopia without an accommodative element and is thought to be associated with physical or psychological stress¹⁰; and (3) the Bielschowsky type – first reported by Bielschowsky, is due to myopia – which occurs mostly in adolescents and adults.

The pathogenesis is related to uncorrected myopia. Near work induces excessive convergence, and an increase in the tension of the medial rectus muscle, resulting in an imbalance in the strength between the convergence and divergence of the eyes, finally resulting in esotropia.

The development of AACE has been associated with the disruption of fusion, myopia, decompensation of a pre-existing phoria or monofixation syndrome, and physical or psychological stress.^4,11,12 Among the 51 patients with AACE, the daily average time of near work before the onset of esotropia was 9 h (8.0 h to 10.0 h), and the daily time of near work in 35 patients was more than 8 h. Most were students, accountants, information technology staff, and the people who need to use electronic devices for a long time.

In daily life and work, patients used computers and smartphones, read books, wrote, or worked on factory assembly lines for a long time, requiring close vision. The situation persisted for at least half a year before the presence of diplopia and strabismus manifested. The cause of esotropia may be related to prolonged near work, whereby increasing the tension of the medial rectus muscle results in esotropia when the balance between the convergence and divergence of the eyes is interrupted.

The development of electronic products such as computers, smartphones, iPads, and mobile network technologies has changed lifestyles, as these have become the most common video display terminals (VDTs) and entertainment appliances for the public. It is estimated that almost 84% of the population of the world used these devices by the end of 2018.¹³

VDT syndrome is a constellation of ocular and extraocular symptoms associated with the use of VDTs. It is associated with visual blurring, dry eye, and some musculoskeletal symptoms.^13,14 A study of 11,365 VDT workers found that the global prevalence of dry eye is 49.5% (95% CI, 47.5 to 50.6).¹⁵ Book reading, usage of electronic devices, and extracurricular homework can significantly increase near work time and the likelihood of developing strabismus.

Interestingly, a driver in the present study exhibited diplopia and strabismus after driving while fatigued. He resigned and used eye drops that relieved visual fatigue, and the symptoms disappeared after approximately half a year. A male model in this study developed diplopia after playing with a smartphone for eight hours. The symptoms disappeared after resting for one night. Diplopia reappeared after working while tired and using his smartphone for a long time. After several recurrences, diplopia did not disappear even after rest.

Mehta et al.¹⁶ reported the case of a teenager who developed esotropia due to excessive smartphone use. Lee et al.⁷ believes that the occurrence of AACE is related to the excessive use of smartphones in adolescents. Smartphone restriction for a month led to a deviation decrease in all patients. In the present study, three of the 51 patients had neurological diseases according to cranial MRI: one had a pituitary tumour, one had a brainstem tumour and one had Arnold-Chiari malformation type I. All three patients were children who presented with diplopia and esotropia as the initial symptoms, and fundus examinations were normal.

Previous studies have found that brain tumours, such as astrocytoma of the corpus callosum, brain stem or cerebellum tumours, etc., can cause AACE.^17,18 Arnold-Chiari malformation has been associated with AACE in several studies, and esotropia might be an early manifestation or even the only symptom.^19,20 Liu et al.²¹ reported that AACE is associated with meningitis and basilar artery aneurysm. Among the comitant esotropia patients (51 patients), two had psychosis treated with antipsychotic drugs, and one had systemic lupus erythematosus treated with glucocorticoids. AACE onset may be related to long-term near work but also may be associated with mental illness, systemic lupus erythematosus, or their associated drugs. Parentin et al.²² reported that a nine-year-old girl developed acute common esotropia after receiving recombinant human growth hormone. The development of esotropia may be related to idiopathic intracranial hypertension.

Among the 51 patients in the present study, 42 were myopic, and nine had hypermetropia. AACE patients mostly presented with a myopic refractive error. The angle of deviation was 20^Δ (12^Δ to 35^Δ) at near and 25^Δ (18^Δ to 40^Δ) at distance fixation. The angle of deviation at distance fixation was larger than that at near fixation. The reason may be that patients stare at objects at close distances for a long time, resulting in increasing tension of the medial rectus muscle and decreasing the use of the lateral rectus muscle.

The treatment of AACE was prism, botulinum toxin A and surgery.^23,24 Active treatment can restore binocular vision in some AACE patients. Patients with a small angle of deviation can be treated with prism therapy, and strabismus surgery is suitable for those with a large angle of deviation. In the present study, two patients treated with botulinum toxin A developed a reoccurrence of strabismus after four months. The efficacy and stability of Botulinum toxin A treatment require further clinical observation. Patients with AACE caused by the intracranial disease should be actively treated for their primary neurological diseases.

Conclusion

AACE occurs mostly in myopic older children and adults. There is increased epidemiological evidence of digital eyestrain and high prevalence of myopia. The onset of esotropia is related to long-term near work, including reading, writing, and using computers, smartphones, and other electronic products. Intracranial disease is an infrequent but important cause of AACE that needs to be excluded in all cases. Psychosis, systemic lupus erythematosus, and taking associated drugs may induce esotropia. AACE patients mostly present an angle of deviation that is larger during distance than during near fixation.

Disclosure statement

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Additional information

Funding

This study is supported by the Central Guided Local Science and Technology Development (Number 2019ZYYD058). Funders: Department of Finance of Hubei Province; Department of Science and Technology of Hubei Province.