Esodeviations and Associated Syndromes

Abstract

Esodeviations refer to misalignments where one or both eyes are turned toward the nose. Various factors contribute to this misalignment, such as disorders in horizontal rectus muscles, refractive errors, and accommodative convergence. The classification of esotropia is based on manifestations, accommodation issues, and consistency with gazes. Latent deviations, termed esophoria, arise due to weak fusional amplitudes and become apparent when fusion is disrupted. Intermittent esotropias manifest under stress or fatigue. Constant esotropias are categorized by comitance, with comitant esotropias involving constant deviation in all gaze directions, likely caused by refractive or accommodative problems. Incomitant esotropias, prevalent in lateral rectus paralysis or medial rectus entrapment, also occur in conditions such as Duane's retraction syndrome, Mobius syndrome, and heavy eye syndrome. Abducent Nerve Palsy arises from damage or dysfunction of the sixth cranial nerve, leading to weakness or paralysis of the lateral rectus muscle. Duane syndrome, a congenital eye movement disorder, restricts eye movement, especially outward, and Moebius syndrome, a rare congenital disorder affecting cranial nerves, results in difficulties with eye coordination. Treatment for esodeviations varies based on the underlying cause and severity, including options such as vision therapy, glasses, prisms, botulinum toxin injections, or surgery to correct muscle imbalances and enhance eye alignment.

1. Introduction

Esodeviations are the misalignments, in which one or both eyes are positioned towards the nose. Esodeviations are the most common childhood strabismus and equally prevalent to the exodeviations in adults. A lot of factors are responsible for the misalignment of eyes, which include horizontal rectus muscles disorders [1], refractive errors, accommodative convergence etc. The risk factors include hyperopia, anisometropia, low birth weight, prematurity, neural developmental impairment [2].

Esotropia can be classified on the basis of manifestation, accommodation problems and consistency with gazes. The deviation may be manifest or latent. The latent deviations are known as the esophoria, while manifest deviations are known as esotropia, which are further classified as constant or intermittent, comitant or incomitant esotropias.

Esophorias are latent esodeviations, which are caused by weak fusional amplitudes and become prominent as fusion is break under cover. Intermittent esotropias, on the other hand, include the esodeviations which become manifest during stress or fatigue.

Constant esotropias are further grouped on the basis of comitance. In comitant esotropias both eyes remain constantly deviated to each other’s in all gaze directions, these are most likely due to refractive or accommodative problems. While incomitant esotropias are present mostly in lateral rectus paralysis or medial rectus entrapment in medial orbital wall fractures [3]. The other causes of incomitant esotropia include syndromes like, Duane’s retraction syndrome, Mobius syndrome, heavy eye syndrome etc.

Treatment of esotropia include refractive correction, convergence exercises and muscle surgery.

2. Esophoria

As fusion controls the alignment and keeps the eyes straight with binocular single vision. Sometimes the fusional amplitudes are not much strong to keep eye aligned as fusion breaks. Esophoria is the latent esodeviation that affects eye coordination. Due to insufficient fusional amplitudes, the covered eye tends to deviate nasally as fusion is broken by cover or both eyes focus on different objects.

2.1 Treatment

• Refractive correction

• Prisms; Temporary stick-on Fresnel prisms or spectacles incorporated, maximally 10∆–12∆ split between both eyes.

• Surgery; occasionally for large esophorias.

3. Comitant esotropias

These are manifest esodeviations in which the angle of deviation remains constant in all directions of gaze. A variety of comitant esotropic deviations are known.

3.1 Essential infantile esotropia

• Manifest by 6 months of age (Figure 1)

• Large esodeviation >40Δ–50 Δ (Figure 2)

• Equal at distance & near

• Normal to age refractive error (hypermetropic)

• Cross fixation is common.

• Amblyopia is uncommon.

• Prohibits fusion and binocular vision.

• Inferior oblique overaction

• Latent nystagmus

• Dissociated vertical deviation may present.

Figure 1.

Infantile esotropia in a 4-month-old child.

Figure 2.

Infantile esotropia in a 2-year-old child, presented late in a screening clinic.

3.1.1 Management

• Cycloplegic refraction to rule out refractive causes.

• Early bilateral medial rectus recession

3.2 Acquired nonaccommodative esotropia

• Develops after 6 months of age (Figure 3).

• Esodeviation not corrected by convex lenses (Figure 4).

• Starts as intermittent, became as constant.

• Small esodeviation, 20Δ–35Δ

• Diplopia may present.

Figure 3.

Acquired non-accommodative esotropia, patient dilated for cycloplegic refraction.

Figure 4.

Refractive correction not effective.

3.2.1 Management

• Bilateral medial rectus recession

• In children <6 years, MRI brain must be done to exclude posterior fossa pathology [4].

3.3 Accommodative esotropia

It is the esodeviation which is associated with the activation of near or accommodative reflex. In accommodation eyes focus on near objects by increasing the curvature of crystalline lens, known as accommodation power (A) and simultaneously converge to focus on object of interest, known as accommodation convergence (AC). Abnormalities in AC/A ratio causes accommodative type of esodeviation. It may present between 6 months and 6 years of age (mean 2½ years). It is further classified into;

3.3.1 Refractive accommodative esotropia

• Mostly present between 1½ year and 3 years (Figures 5 and 6)

• AC/A ratio is normal

• Excessive hyperopia +2.0D - +10.0D, which cause

• High accommodation convergence (beyond fusional amplitude)

• Small esodeviation 20Δ–30Δ (Figures 5 and 6)

• Amblyopia may present

Figure 5.

Refractive accommodative esotropia.

Figure 6.

Refractive accommodative esotropia.

3.3.1.1 Fully accommodative esotropia

• Can be fully aligned by hyperopic correction (Figure 7)

• BSV is present

Figure 7.

Fully accommodative esotropia, orthophoric with refractive correction.

3.3.1.2 Partially accommodative esotropia

• Deviation is reduced but not fully corrected by refraction (Figure 8)

• Amblyopia is common as suppression of squinting eye

• ARC may occur

• Surgical correction is usually performed on squinting or amblyopic eye

Figure 8.

Partially accommodative esotropia, lessen with refractive correction.

3.3.2 Non-refractive accommodative esotropia

• High AC/A ratio

• Independent of refractive error (hyperopia and myopia) but hyperopia is frequent

• Straight eyes for distance (with BSV)

• Esotropia for near, suppression is usually present in squinted eye

3.3.2.1 Convergence excess

• Increased accommodation convergence (AC) with normal accommodation (A)

• Near point of accommodation is normal

• Orthophoric with bifocals, executive type is preferred

• Bilateral medial rectus is performed

3.3.2.2 Hypo-accommodative convergence excess

• Normal accommodation convergence (AC) with decreased accommodation (A)

• Near point of accommodation is remote

• Executive type bifocals may be advised for near work

• Surgical correction may be considered only when refractive correction is not sufficient.

3.4 Non-accommodative convergence excess/near esotropia

• Presents in young adults and older children (Figure 9)

• Esotropia for near

• Orthophoric/small esophoria with BSV for distance

• Non-significant refractive error (Figure 10)

• Normal or low AC/A ratio

• Near point of accommodation is normal

Figure 9.

Non-accommodative convergence excess esotropia.

Figure 10.

Non-significant refractive error, which is also not correcting esotropia.

3.4.1 Treatment

Bilateral medial rectus recessions.

3.5 Distance esotropia

• Presents in myopic healthy young adults

• Esotropia for distance, may be intermittent

• Orthophoric for near

• Normal bilateral abduction

• Reduced fusional divergence amplitudes

• No neurological deficit

3.5.1 Treatment

• Prisms until spontaneous resolution

• Surgery if persists

3.6 Acute esotropia/late-onset esotropia

• Presents usually around 5 years–6 years of age but in young adults too

• Sudden onset of esotropia and diplopia (Figure 11).

• Non-significant refractive error

• Normal ocular motility

• Underlying neurological disorder may present

Figure 11.

Acute onset esotropia in 17-year-old male with history of sudden onset of diplopia 2 weeks ago. Fundus examination reveals bilateral disc swelling.

3.6.1 Management

• Cranial nerve examination

• Pupil reflexes

• Fundus examination for optic disc pathology

• Re-establishing BSV

• Prevent suppression

3.6.2 Treatment

• Prisms with glasses

• Botulinum toxin in medial rectus

• Strabismus correction surgery

3.7 Sensory-deprivation esotropia

In children younger than 4 years of age, many organic conditions cause impaired focusing to light to retina and perception by the visual cortex, thus hindring the fusion development. This causes the eye to deviate inwards nasally. In older children and adults these cause the sensory exotropia. These conditions may be uniocular or binocular as;

• Uncorrected refractive errors

• Anisometropic hypermetropia

• Severe ptosis (Figure 12)

• Buphthalmos

• Corneal opacities

• Congenital corneal dystrophies

• Congenital cataracts

• PHPV and persistent fetal vasculature

• Retinopathy of prematurity

• Retinal and optic disc colobomas

• Retinal detachments

• Macular dystrophies

• Retinoblastoma

• Coats disease

• Optic nerve anomalies etc.

Figure 12.

Sensory-deprivation esotropia due to severe ptosis secondary to lid hemangioma in 8 months old child.

3.7.1 Treatment

• Dilating fundus examination to establish the cause.

• Treating the underlying cause first.

• Amblyopia therapy

• Cosmetic strabismus correction

3.8 Consecutive esotropia

Consecutive esotropia is said when an exotropic person becomes esotropic. It is usually caused by the surgical correction of exotropia, with incidence rate reported between 6 and 20%. The factors involve in the overcorrection of divergent squints;

• Poor vision

• Congenital retinal or optic nerve anomalies

• Intermittent distance exotropia (IDEX)

3.8.1 Treatment

• Comitant small deviation (10Δ–15Δ) should be observe for 2 weeks for spontaneous resolution.

• Re-do strabismus correction by medial rectus recession or lateral rectus advancement in patients with good vision.

• Repeated botulinum toxin injections in medial rectus muscle is preferred in patients with poor vision.

3.9 Divergence insufficiency

• Common in elderly patients

• Esotropia; distance fixation > near fixation

• Diagnosis of exclusion

• Caused by the weakening or rupturing of connective tissue between lateral rectus muscle and superior rectus muscle, causing sagging of lateral rectus muscle [5].

• Associated with neurologic trauma, pontine tumors, raised intracranial pressure.

3.9.1 Management

• Spontaneous resolution

• Base out prisms in glasses.

3.10 Cyclic esotropia

It is a rare condition which is mostly characterized by esotropia lasting for 24 hours alternating with 24 hours of orthophoria. The incidence is 1 in every 3000–5000 patients. Cyclic esotropia may persist for months or years until it develops into a constant esotropia.

3.10.1 Treatment

Both eyes medial rectus recession has good results. Measurement is done on the basis of photographic evidence or the orthoptic assessment during the esotropic cycle, or until the esotropia becomes constant.

4. Incomitant esodeviations

In contrast to the comitant esodeviations, in which the degree of deviation remains constant in all directions of gazes, angle of deviation increases in lateral gaze while fixating distantly in incomitant esodeviation. Incomitant esodeviations are caused by;

4.1 Central nervous system pathologies

• Increased intracranial pressure

• Acquired sixth nerve palsy

4.2 Medial rectus restriction

• Thyroid eye disease

• Muscle entrapment in medial orbital wall fracture

4.3 Lateral rectus weakness

• Isolated sixth nerve palsy

• Slipped/detached lateral rectus muscle from trauma/surgery.

5. Abducens nerve palsy

Abducens Nerve is the Sixth Cranial nerve and responsible for the movement of the Lateral rectus nerve. The sixth nerve palsy is the most common extraocular muscle palsy in adults and second most common in children.

5.1 Presentation

• Convergent squint due to unopposed action of antagonist Medial rectus

• The esotropia is incomitant, greater in looking towards affected gaze and more at fixing distance than near.

• Diplopia; binocular and horizontal, worsen for distant vision and in direction of paretic muscle.

5.2 Etiology

As the abducens nerve has the longest intracranial course among all cranial nerves, hence it is more prone to the damage.

In children the causes of palsy include,

• Congenital [6]

  • Associated with birth trauma,

  • Hydrocephalus

  • Cerebral palsy,

• Acquired [7]

  • Tumor,

  • Trauma,

  • Inflammation,

  • Infection

  • Idiopathic.

In adults the causes of the sixth nerve palsy are divided into [8].

• Common causes

  • Vasculopathies due to microvascular ischemia,

  • Trauma (Figure 13)

  • Idiopathic

• Other causes include:

  • Stroke

  • Multiple sclerosis,

  • Raised intracranial pressure,

  • Cavernous sinus mass; aneurysm, meningioma, tumor metastasis

  • Sarcoidosis

  • Vasculitis

  • Lymes disease

  • Neurosyphilis

Figure 13.

Traumatic left sixth nerve palsy in 45-year-old female.

5.3 Differential diagnosis

The differentials of limited abduction involve:

5.3.1 Thyroid eye disease

• Proptosis (Figure 14) [8]

• Lid Retraction

• Lid Lag

• Injection over involved rectus

• Positive FDT (Forced Duction Test)

Figure 14.

Esodeviation in thyroid eye disease. Right eye supro-nasal misalignment. Proptosis and lid retraction are also notable in both eyes.

5.3.2 Myasthenia gravis

• Diplopia is fluctuating, variable and fatigable [8].

• Ptosis is common.

• Generalize fatigability may present.

• Shortness of breath and hoarseness

• Positive ice and rest tests

5.3.3 Duane retraction syndrome, type 1

• Congenital

• Narrowing of the palpebral fissure in adduction (Figure 15)

• Retraction of globe

Figure 15.

Duane retraction syndrome, right eye induced ptosis and left eye abduction deficit.

5.3.4 Mobius syndrome

• Congenital

• Bilateral facial paralysis

5.3.5 Convergence spasm

• Intermittent, variable convergence

• Miosis

• Deficient Abduction in versions but with full ductions

5.3.6 Primary divergence insufficiency

• Acquired

• Esotropia

• Diplopia at distance with binocular single vision (BSV) at near

5.3.7 Giant cell arteritis GCA

• Extraocular muscle ischemia

• Age > 55 years

5.4 Management & work up

5.4.1 Children

• History:

  • Birth trauma,

  • Recent illness,

  • Neurological symptoms,

  • Ear infections

• Complete Ophthalmic & Neurological Examination

• MRI brain

5.4.2 Adults

• History:

  • Onset & progression,

  • Systemic diseases; hypertension, diabetes, thyroid dysfunction,

• Complete Ophthalmic & Neurological Examination:

  • Extraocular movements,

  • Corneal sensation,

  • Fundus examination for optic disc (swelling /papilledema)

• Hess Chart (Figure 16)

  • Underation of ipsilateral lateral rectus muscle

  • Normal/overaction of contralateral medial rectus muscle

• Systemic Examination; blood pressure,

• Laboratory Examination:

  • Fasting blood sugar

  • HbA1c,

  • Serum lipid profile

  • ESR

  • CRP

  • CSF analysis

  • Lyme antibody titer

  • FTA-ABS or treponemal-specific assay, VDRL or RPR

• MRI Brain

  • In all patients younger than 45 years,

  • Non-isolated sixth nerve lesion,

  • History of neoplasms,

  • Patients without microvascular diseases.

  • Papilledema

Figure 16.

Hess chart of 45-year-old patient, with history of road traffic accident 8 month ago, showing left lateral rectus under-action. Medial rectus muscles of both eyes showing no overaction. Due to compensatory head posture towards left the patient has no complaint of diplopia.

5.5 General treatment

• Treat the underlying etiology.

• Abducens nerve palsy due to microvascular causes are observed as they recover within 3 to 6 months.

• Diplopia is managed by [9].

  • Occlusion; Bangerter filter, eye patch, central glass patch. It eliminates confusion and diplopia, prevents suppression and amblyopia, and minimizes contracture of ipsilateral medial rectus. In patients <10 years, patching is avoided due to high risks of amblyopia.

  • Base-out Fresnel or ground in prisms. Limited role in maintaining BSV as the deviation is incomitant.

• Botulinum Toxin: it is injected into medial rectus to prevent secondary contracture and to weak medial rectus in transposition procedures.

• Surgical intervention is advised only in patients having stable deviations for at least 6 months.

• Follow up every 6 weeks until the resolution of palsy or stabilization of deviation.

5.6 Surgical management

5.6.1 Aim

Surgical correction is always planned for realignment of the globe in primary position [10].

5.6.2 Surgical protocols

Surgical management of the Lateral Rectus disorder in patients having stable orthoptic measurements for more than 6 months, depends upon [11];

• Medial rectus fibrosis

• Lateral rectus residual function

For medial rectus fibrosis, forced duction test is performed. If FDT is positive that shows tight medial rectus, recession of the medial rectus is done (Figure 17).

Figure 17.

Surgical management for lateral rectus palsy, based on the standard treatment protocol described by American Academy of ophthalmology.

For lateral rectus, active force generation test (FGT) is performed.

• Active FGT present; Resection of LR

• Active FGT absent; transposition procedures

If lateral rectus shows any residual function, then recession of ipsilateral MR along with supra-maximum (12–14 mm) resection of lateral rectus is performed.

5.7 Transposition surgeries for lateral rectus muscle palsy

When there is no LR function on active FGT, a variety of transposition surgeries can be planned for realigning the eyes in primary position, these include; (Figure 18).

Figure 18.

Diagrammatic presentation of surgeries to treat lateral rectus palsy/disorders. A. Full tendon transposition; B. Full tendon transposition with cross-adjustable technique; C. Hummelsheim procedure; D. Jensen’s procedure; E. Nishida’s procedure; F. LR recession with possible Y-splitting for treating leash phenomenon in Duane’s retraction syndrome.

5.7.1 Full tendon transposition

Disinsertion of full width tendons of superior and inferior recti and transposing them towards lateral rectus insertion [12]. This procedure has risk of anterior segment ischemia which can be minimized by conserving muscular branches of anterior ciliary artery, and avoiding extensive dissection (Figure 18A).

5.7.2 Cross-adjustable technique

To increase the effectiveness of the full tendon transposition by increasing path length to avoid the resection of vertical rectus muscles, the tendons are passed beneath the LR tendon and attached at the opposite corners of LR Insertion [13]. This technique also decreases the need of ipsilateral MR recession in many cases (Figure 18B).

5.7.3 Hummelsheim

Vertical recti are split half tendon width up to 14 mm approximately from the insertion. The temporal halves of superior and inferior recti are disinserted and transposed to the lateral rectus insertion [14]. Care must be taken to preserve the anterior ciliary vessels during procedure (Figure 18C).

5.7.4 Augmented/modified Hummelsheim

Transposed half tendons are further resected to increase the effectiveness of Hummelsheim procedure along with medial rectus recession. It is reported to correct deviation up to 40Δ ± 5Δ [15].

5.7.5 Jensen’s procedure

First described by Jensen et al. in 1964 [16], the bellies of superior and inferior recti are split half tendon width and tied to lateral rectus muscle without disinsertion, 12–14 mm behind from the insertion with non-absorbable suture (Figure 18D). To avoid anterior segment ischemia, at least one ciliary artery must be protected. In vessel sparing modification of Jensen’s procedure, the split muscles are stitched together by looping stitch underneath the vessels.

5.7.6 Nishida’s procedure

This procedure was described by Nishida et al. in 2003 [17]. In this technique the vertical rectus muscles are exposed by limbal based peritomy. After dissecting intermuscular septum along lateral margin of each muscle, vertical recti are split half tendon width up to 15 mm from the insertion. With 6–0 nylon sutures, lateral half of each muscle is secured at 8–10 mm from the insertion and anchored at 8 mm posterior to LR insertion to sclera (Figure 18E).

5.7.7 Superior rectus transposition

Jhonston et al. described transposition of the superior rectus muscle only to the lateral rectus insertion [18]. It was postulated to prevent anterior segment ischemia and to simplify the procedure. The procedure improves esotropia, abduction and head turn with minimal vertical misalignment.

5.7.8 Inferior rectus transposition

Alternative to superior rectus transposition, this procedure is helpful to improve esotropia, abduction limitation and head turn, along with the correction of hypertropia [19].

5.8 Follow up

Postoperatively, patients should be managed under close observation. Prisms should be prescribed for any residual diplopia. Since there are increased chances of anterior segment ischemia in the first 6 months of the primary surgery, hence the repeat surgery should always be planned after 6 months of primary surgery, providing the ample time for collaterals to develop.

5.9 Surgical complication

• Anterior segment ischemia [20]

• Under correction; of primary esotropia and head posture

• Over correction; consecutive exotropia

• Diplopia

• Induced vertical deviations [21].

• Conjunctival cyst

• Conjunctival prolapse.

• Corneal dellen

• Tenon’s prolapse.

• Scleral perforation

• Lost/Slipped Muscle

• Bradycardia

• Secondary infections.

5.10 Prognosis

Rush JA reported an overall recovery rate of 49.6%, with 71% recovery in patients with systemic diseases (diabetes mellitus, hypertension, atherosclerosis etc.) [22].

6. Duane syndrome

It is also known as Stilling-Turk-Duane syndrome. Duane syndrome was first described in 1905 by Alexander Duane [23]. It is congenital, non-progressive syndrome [24] characterized by some or all of the following:

• Abduction limitation, usually complete (Figure 19)

• Globe retraction on attempted adduction

• Induced Ptosis; narrowing of palpebral fissure on adduction (Figure 19).

• Adduction limitation, usually partial [25]

• Oblique movement on attempted adduction

• Leash Phenomenon, Upshoot or downshoot of globe with adduction

• Widening of palpebral aperture on abduction

• Convergence insufficiency

Figure 19.

Duane type 1, right small angle esotropia in primary gaze.

6.1 Types

Duane retraction syndrome is divided into three types with multiple subgroups; the difference in clinical features are;

6.1.1 Type 1

• 75–80% of patients [26]

• Esotropia in primary gaze (Figure 19)

• Compensatory head turn to the involved side.

6.1.2 Type 2

• 5–10% of patients [26]

• Exotropia in primary gaze

• Compensatory head turn to the uninvolved side.

6.1.3 Type 3

• 10–20% of patients [26]

• Present with either an esotropia or exotropia in primary gaze

• Compensatory head turn to the involved side

• The ability to adduct in this type is absent to restricted as compared to normal to mildly restricted in types 1 and 2.

6.2 Etiology

• About 90% of the cases are sporadic and commonly unilateral [27].

• Remaining 10% cases are bilateral and inherited [27]:

  • Type 1: Autosomal Dominant (locus 8q13) [24]

  • Type 2: Autosomal Dominant (CHN1 gene mutation at DURS 2 locus 2q31-q32.1) [24] & Autosomal recessive [28]

6.3 Pathophysiology

Duane syndrome results from aberrant lateral rectus innervation by third nerve as abducens motor neurons are absent or dysplastic.

6.3.1 Myogenic theory

It suggests that lateral rectus is fibrosed or inelastic and medial rectus has abnormal far posterior insertion [26].

6.3.2 Neurogenic theory

It was suggested by postmortem studies at John Hopkins University in 1980 [29]. At 4–8 weeks of gestation, a disturbance in embryologic development results in abducens nerve absent which causes aberrant lateral rectus innervation by third nerve [29]. Hence both MR & LR are innervated by oculomotor nerve, their simultaneous activation results in globe retraction [30].

6.4 Diagnosis

Duane syndrome is diagnosed primarily based on clinical features:

• Paralytic squint: 76% have tropias in primary gaze [24].

• Abduction limitation

• Narrowing of fissure on adduction

• Globe retraction

• Upshoot or downshoot with adduction

• Compensatory head posture

• Good visual Acuity [24]

6.5 Management

6.5.1 Evaluation

• History: onset, trauma, family history, other ocular or systemic diseases [27].

• Complete ophthalmic examination; visual acuity, extraocular movements, aberrant movements and retractions, compensatory head position,

• Systemic examination, cranial nerves evaluation

• Forced duction and active force generation tests to evaluate tight muscles.

• Genetic evaluation and counseling when familial pattern is noted [26].

• MRI brain and orbit, for visualization of anatomy.

6.5.2 Non-surgical management

• Refractive correction by glasses or contact lens [26]

• Corrective prisms for abnormal head posture [26]

• Amblyopia prevention & treatment; new cases must be evaluated 3–6 monthly [26].

• Botulinum Toxin: to minimize leash phenomenon [31].

• Children >7 years with good vision and binocularity can be evaluated annually [26].

6.6 Surgical management

6.6.1 Limitations

• Cannot fully cure the disease.

• Only correct tropias in primary gaze

• Improve head posture.

• Improve leash phenomenon [26]

• Either recessions only or transpositions are done; muscle resections can never be planned.

6.6.2 Indications

• Compensatory head posture (CHP) ≥ 15ͦ° [32]

• Neck discomfort due to CHP

• Significant tropia, Cosmesis issues [32]

• Severe induced ptosis; PFH ≤ 50% of normal on adduction [33]

• Severe co-contraction [34]

6.6.3 Contraindications

• Orthophoria [33]

• Normal head posture [33]

• Young age [33]

6.6.4 Surgical procedures

A variety of surgeries have been advised depending upon the type and clinical features of the disease.

• DRS type 1 & 3 + face turn

Based on FDT; MR recession only or Transposition of vertical rectus muscles to lateral rectus [35].

• Full tendon transposition of vertical recti (Figure 18A).

• Full tendon transposition with cross-adjustable technique

• Jensen’s procedure (Figure 18D).

• Nishida’s procedure (Figure 18E).

• Superior rectus transposition

• Inferior Rectus transposition

• DRS type 1 & 3 + Leash phenomenon/severe globe retraction

  • Recession of both MR & LR with possible Y-splitting of LR [26] (Figure 18F).

• DRS type 2 + face turn (fixation with uninvolved eye)

  • Ipsilateral LR recession [26]

• DRS type 2 + face turn (fixation with involved eye)

  • Contralateral LR recession [26]

• DRS type 2 + Leash phenomenon

  • Ipsilateral LR recession with possible Y-splitting (Figure 18F) [26].

6.6.5 Surgical complications

Under correction; of primary esotropia and head posture [33].

Over correction; consecutive exotropia [33].

Induced vertical deviations; post transposition procedures [33].

7. High myopia esotropia

In patients with high myopia and large axial lengths, tenon muscle pulleys of superior rectus and lateral rectus muscles may become instable. This causes the bulging of globe through the defect of muscle pulleys resulting in inferior displacement of the lateral rectus muscle and nasal displacement of the superior rectus muscle.

7.1 Management

Magnetic resonance imaging (MRI) should be done in every high myope with acquired esotropia to diagnose the condition. The esotropia is treated by repairing muscle pulleys by plication of the superior rectus muscle and lateral rectus muscle with a non-absorbable suture.

8. Moebius syndrome

It is a rare congenital, non-progressive syndrome involving both abducens and facial nerve palsies.

8.1 Clinical features

• It is characterized by;

• Lagophthalmos

• Esotropia

• Limitation in abduction and/or adduction

• Intact vertical movements & bell’s phenomenon, saving cornea intact.

• Unilateral/bilateral, partial/complete facial nerve palsy

• Mask like face appearance

• Cranial nerves V, VIII, X & XII may be affected too.

• Tongue atrophy, limbs and chest deformities may occur.

8.2 Management

• No definitive treatment

• Behavioral management; suction aids

• Rehabilitation; Orthopedics surgeons

• Temporary tarsorrhaphy to prevent dry eye.

• Medial rectus recession for esotropia

• Transposition surgeries; inconsistent results

9. Idiopathic orbital inflammatory syndrome

Idiopathic orbital myositis is relatively less common, non-infective, non-granulomatous, non-neoplastic inflammation of isolated or multiple extraocular muscles. Lateral rectus is usually less involved than medial rectus.

9.1 Features

• Tendon involving muscle enlargement.

• Pain, more on eye movements

• Proptosis

• Periorbital edema

• Diplopia

9.2 Management

• Systemic evaluation

• Autoimmune profile (CBC, ESR, ACE, ANA, cANCA, pANCA, LDH)

• Imaging: Orbital MRI with DWI protocol

• Corticosteroids (1 mg/kg/day)

• Low dose radiation

• Steroid sparing agents (methotrexate, cyclophosphamide)

10. Conclusion

Esodeviations involve a variety of disorders which cause eyes to move nasally inwards, the management depends upon addressing these disorders. In general, the management protocol involves;

10.1 Observation and systemic evaluation

Acute onset esodeviations are usually lateral rectus palsies secondary to systemic hypertension, diabetes mellitus, atherosclerosis and benign intracranial hypertension, which are usually self-resolving, subject to the treatment of underlying etiology and any life-threatening condition, if present. Systemic evaluation for the above-mentioned diseases along with the laboratory profiles and radiological imaging are key steps in observing these acute lesions.

In case of trauma involving the sixth nerve, only the emergency traumatic repairs must be performed first. The esotropia associated with traumatic sixth nerve palsy is left observed for at least 6 months before offering any surgical intervention. Non-surgical treatment options must be offered to all patients during the observation to relive diplopia and asthenopia.

10.2 Non-surgical treatment

Non-surgical treatments are aimed to restore vision, relive diplopia and asthenopia. Patching can help to treat amblyopia and minimize diplopia. In children and young adults with esotropias associated with underlying amblyopia, the healthy eye is completely patched to enhance the sensory perception of the lazy eye. While, in elder adults with lateral rectus palsy, patching the center part of glasses helps in minimizing the diplopia in primary gaze with keeping side vision intact. Full refractive correction by hyperopic convex lenses and bifocals helps in treating the accommodative esotropias and convergence excess esotropias respectively. In divergence insufficiency, divergence orthoptic exercises are advised with or without prisms. Prescribing prisms may relieve diplopia well. Prism glasses and Fresnel prisms are tolerated well in patients who are kept under observation before planning any surgical procedure. Medical management is necessary for the esotropia associated with systemic diseases. In addition to the systemic medicines, some of the drugs used are vitamin B12, corticosteroids and disease modifying agents. Corticosteroids by their anti-inflammatory effects are prescribed in thyroid eye disease, myositis and traumatic brain and orbital injuries. Botulinum toxin has gained much popularity for non-surgical chemo-denervation of the medial rectus muscle in treating infantile and acute esotropias. It also helps to prevent medial rectus fibrosis in lateral rectus palsy and also help to prevent anterior chamber ischemia by sparing medial rectus recession in transposition procedures.

10.3 Surgical treatment

The main aim of surgical treatment is to attempt in developing a good binocular single vision by restoring the regular alignment of both eyes and addressing any pathology causing sensory deprivation. Treating ptosis, cataract and other causes are sometimes more important than to treat the esotropia alone. In medial rectus muscle entrapments, medial orbital wall is repaired as early as possible to avoid the development of muscle fibrosis and ischemia. in treating abnormal head posture and diplopia, surgical options must be considered to offer, only when there are more than 6 months passed with static orthoptic measurements. It is advised to treat amblyopia prior to surgery but sometimes surgery, itself, is the only option to treat the amblyopia as early as possible, before development of any degeneration at the level of lateral geniculate nucleus. Intermittent esotropias have good surgical prognosis over constant and alternating ones. The typical surgical approach for comitant esotropia is bilateral medial rectus recession or unilateral medial rectus recession and lateral rectus resection (recess-resect procedure). In incomitant esotropias surgical approaches vary with the type of esotropia, as transposition of vertical recti. Different transposition procedures of vertical rectus muscles are done to compensate for the limited abduction. These procedures include full tendon transposition, partial tendon vertical transposition, split muscle transpositions etc. The main complication of these surgeries is the anterior segment ischemia, which can be avoided by preserving muscular arteries during surgery. Other complications include under corrections and induced vertical deviations. Loop myopexy is considered for myopic esotropia /heavy eye syndrome.

Acknowledgments

I would like to acknowledge the motivation given by Dr. Muna Malik, and her help in typing, proofreading and reviewing this manuscript.

The project is not funded by any sponsor and all the expenses were borne by the author himself.

Conflict of interest

The author declares no conflict of interest.

Notes/thanks/other declarations

Thanks to my colleagues and patients who gave me strength to write this chapter.

All pictures are taken with the consent of patients, subjected not to disclose their particulars and full-face identity. The diagrams are made by the author.