4. Basics of Orthoptics

[Audio] Orbit Eye Center for Pediatrics & Oculoplasty.

[Audio] Basics of Orthoptics. [image] Orbit Eye Center for Pediatrics & Oculoplasty.

[Audio] STRUCTURE Introduction Objectives Classification Detailed Overview a) Horizontal Deviations b) Vertical Deviations c) Torsional Deviations Summary Multiple Choice Questions Reference.

[Audio] "Imagine seeing the world with one eye looking straight ahead and the other wandering off to the side. This is the reality for millions of individuals living with strabismus, a condition that affects 2-4% of the population worldwide. Strabismus, commonly known as crossed eyes, is a condition where the eyes do not properly align with each other when looking at an object. This misalignment can be constant or intermittent and can affect one or both eyes. Beyond the obvious cosmetic concerns, strabismus can lead to severe visual impairments such as double vision, impaired depth perception, and amblyopia (lazy eye). These visual deficits can significantly impact an individual’s quality of life, affecting their ability to read, drive, and perform everyday tasks..

[Audio] The causes of strabismus are multifaceted, ranging from genetic predispositions and muscle imbalances to neurological disorders and trauma. Strabismus can manifest in various forms, including esotropia (inward turning of the eye), exotropia (outward turning), hypertropia (upward turning), and hypotropia (downward turning). Each type presents unique challenges and requires tailored approaches to diagnosis and treatment This lecture aims to provide a comprehensive understanding of strabismus...

[Audio] OBJECTIVES By the end of this lecture, you will be able to: • Describe the different types of strabismus (squint). • Classify each type of strabismus. • Identify the clinical features of different types of strabismus..

[Audio] CLASSIFICATION Phoria • Latent deviation: Controlled by fusion, eyes remain straight under binocular vision. Tropia • Manifest deviation: Uncontrolled fusion, eyes not aligned.

[Audio] ORTHOPHORIA Orthophoria is the state of ocular balance where the external muscles of the eyeball are evenly matched, allowing for fusion without any effort. In this condition, even if the fusion mechanism is disrupted, the position of the eyeballs remains unchanged, maintaining single binocular vision..

[Audio] Squint may be further divided in to two categories. Heterophoria Heterotropia HETEROPHORIA: Latent (hidden) ocular deviation, which can still be overcome by the fusion mechanism & becomes apparent when fusion is disturbed (for example: esophoria, exophoria, hyperphoria, hypophoria). HETEROTROPIA: Manifest (real) deviation, which cannot be overcome by the fusion mechanism (for example: esotropia, exotropia, hypertropia, hypotropia..

[Audio] TYPES OF DEVIATION THAT OCCUR IN STRABISMUS: Horizontal (Esodeviation/Exodeviation) Vertical (Hyper deviation/Hypo deviation) Torsional (Incyclodeviation/Excyclodeviation).

[Audio] Horizontal deviation Esodeviation Eso- visual axis is deviated medially and the fovea is rotated temporally. Eso deviations = convergent strabismus Esotropia Manifest: -Intermittent or Constant -Unilateral or Alternating Esophoria Latent: Controlled by fusion..

[Audio] PSEUDO-ESOTROPIA Negative angle alpha / kappa Wide Epicanthus / Epicanthal Folds Narrow IPD A large <) angle alpha (nasally displaced fovea) produces a temporal corneal reflection Epicanthal skin folds can cover the medial cantus - hides part of medial sclera giving the appearance of ET. Represents a lack of development of the bridge of the nose. Improves by-age 4 Produces closeness of the eyes and apparent ET.

[Audio] PSEUDO-ESOTROPIA Narrow Palpebral Fissure Enophthalmos If the palpebral fissure of one eye is more narrow than the other eye, can give the appearance of an ET. Recession of the globe into the orbit can give the appearance of an ET..

[Audio] ESOPHORIA In this condition, when fusion is interrupted, the non-fixating eye becomes convergent, i.e., deviate nasally. OR Eye moves nasally under cover. Classification of Esophoria: According to Ocular Movements Concomitant Incomitant According to Type of Deviation Esophoria Divergence weakness (distance phoria > near phoria) Convergence excess (near phoria > distance phoria) Non- specific (near phoria = distance phoria).

[Audio] ESOTROPIA CONCOMITANT INCOMITANT RESTRICTIVE PARALYTIC SPASTIC •Musculofacial •Other •Neurogenic •Myogenic NON ACCOMODATIVE ACCOMODATIVE PARTIALLY ACCOMODATIVE •Essential Infantile •Essential Acquired •Acute Comitant •Microtopia •Cyclic Esotropia •Sensory Esotropia •Nystagmus Blockage syndrome •Refractive •Non- Refractive.

[Audio] CONCOMITANT ESOTROPIAS Concomitant Esotropias is a manifest squint in which one eye is turned inwards and in which the angle of squint is the same with either eye fixing and the deviation is the same in all gazes. There is no restriction of ocular movement . There are three stages the development a manifest squint: Stage of Latent Esodeviation (Esophoria): Here there is an esophoria which is kept latent by a good fusional divergence reserve. Stage of Intermittent Deviation(Intermittent Esotropia): Here the fusional divergence reserve is sometimes inadequate and results in an intermittent convergent squint. Stage Of Constant Esodeviation: When the fusional divergence reserve ones inadequate to maintain latency, the deviation becomes constant(Esotropia) , they be unilateral or alternating.

[Audio] CLASSIFICATION Esotropia can be Accommodative or Non-Accommodative. The different types of Esotropias are given below. Primary Esotropia Secondary Esotropia • Sensory esotropia • Consecutive esotropia Accommodative Esotropia • Refractive esotropia. • Non-refractive esotropia • Mixed or partially accommodative esotropia • Hypo accommodative esotropia Non-Accommodative Esotropia • Essential infantile esotropia • Essential acquired esotropia • Basic esotropia • Convergence excess esotropia • Divergence deficiency esotropia • Acute concomitant esotropia. • Microtropia. • Nystagmus blockage syndrome. • Cyclic esotropia.

[Audio] Primary Esotropia 1.Accommodative Esotropia Accommodative Esotropia is a condition where in excessive effort of accommodation results in an inward deviation of the eyes. Depending upon the method of occurrence accommodative esotropia is of the following types: TYPE CRITERION • RECTRACTIVE ACCOMMODATIVE (Normal AC/A ratio) Esotropia at distance >/= near fixation. (fully corrected by hyperopic correction for distance) • NON-RECTRACTIVE ACCOMMODATIVE (High AC/A ratio) Esotropia at near fixation>distance or manifesting only at near.(fully corrected by an additional hyperopic correction for near work) • MIXED (Partially Accommodative) Esotropia partly corrected by the use of refractive correction. Require surgery for the non-accommodative part. • HYPO-ACCOMMODATIVE ESOTROPIA (Normal AC/A ratio) Weak accommodative mechanism, Over accommodation..

[Audio] Primary Esotropia 2.Non-Accommodative Esotropia 1) Essential Infantile Esotropia Age of Onset: Presents before 6 months of age. Angle of Deviation: Large angle of deviation for near and distance (30° or more). Fixation Patterns: • Alternate fixation in primary gaze. • Crossed fixation in lateral gaze (left eye for right field of vision and right eye for left field of vision). • Abduction- No need for abduction due to cross fixation, which can mimic bilateral 6th nerve palsy. Differentiation from 6th Nerve Palsy: • Doll’s Head Movement Test: Quick turn of the head to right and left; if no 6th nerve palsy, the left eye moves quickly to the left when head is turned to the right and vice versa. • Alternate Patching Test: Patching one eye forces the child to abduct the non- amblyopic eye for objects in the temporal field of vision. Visual Acuity: Usually normal and equal in both eyes due to alternate fixation. If one eye is preferred, amblyopia in the other eye may be present. Refractive Errors: No significant refractive errors..

[Audio] ASSOCIATIONS There is a marked inferior oblique muscle over action of one or both eyes in patients above one year of age. Dissociated vertical deviation is a classical finding seen in 70 to 90% of cases. Latent nystagmus- Jerk nystagmus of the non-amblyopic eye may occur on occluding the other eye. BSV is usually absent..

[Audio] 2) Essential Acquired Esotropia This is the esotropia that occurs in later childhood and cannot be grouped with other forms of esotropia. It includes: • Basic esotropia. • Convergence excess esotropia • Divergence deficiency esotropia. 3) Basic Esotropia Concomitant esodeviation with gradual onset after 6 months of age. Near and distant deviations are almost equal. No significant refractive error and normal AC/A ratio. Clinical Features: Onset: After 6 months of age. Deviation: Initially small, increases to 30-70 prism diopters. Refractive Error: None significant. AC/A Ratio: Normal. Possible Cause: Increased convergence tonus. Exclusion: Always rule out 6th nerve paralysis or eye tumor in acquired esotropia cases..

[Audio] 4) Convergence Excess Esotropia Esotropia larger for near than for distance (by difference of least 15 prism diopters) in an optically corrected patient with a normal AC/A ratio. Clinical Features: Onset: Between ages 2-3 years. Deviation: Orthotropic for distance or small angle strabismus (20-40 prism diopters). AC/A Ratio: Normal. Possible Cause: Excessive convergence due to tonic innervation. Bifocals: Do not decrease near deviation. 5) Divergence Deficiency Esotropia Greater deviation for distance than for near. Clinical Features: Greater deviation for distance than for near..

[Audio] 6) Acute Acquired Concomitant Esotropia Clinical Features: Young Children: Onset of acute esotropia. May close one eye to avoid diplopia (do not usually complain of double vision). Older Children and Adults: Presenting complaint is sudden onset of diplopia. Examination: Rule out paralysis of the lateral rectus muscle. Perform neurological examination to exclude other pathologies..

[Audio] 7) MICROTROPIA Microtropia (monofixation syndrome), may be primary or follow surgery for a large deviation. It may occur in apparent isolation, but it is often associated with other conditions such as anisometropic amblyopia. Microtropia is more a description of binocular status than a specific diagnosis. For example, a patient with fully accommodative esotropia may control to a microtropia rather than true Bifoveal BSV with glasses. It is characterized by the following : • Very small angle manifest deviation measuring 8∆ or less, which may or may not be detectable on cover testing. • Central suppression scotoma of the deviating eye. • ARC with reduced stereopsis and variable peripheral fusional amplitudes. • Anisometropia is often present, commonly with hypermetropia or hypermetropic astigmatism. • Symptoms are rare unless there is an associated decompensating heterophoria. • Treatment involves corrections of refractive errors and occlusion for amblyopia as indicated. Most patients remain stable and symptom free..

[Audio] 8) Cyclic Esotropia Rare form of strabismus with alternating strabismic and non-strabismic phases lasting 24-48 hours each. Clinical Features: Onset: Typically starts in infancy. Angle of Deviation: Usually large during the strabismic phase. Suppression: The deviated eye is suppressed during the strabismic phase. Non-Strabismic Phase: No deviation. Fusion and stereopsis (depth perception) are usually present. Cause: Unknown.

[Audio] 2.Secondary Esotropia 1. Sensory Esotropia It refers to the esotropia which develops due to poor visual function in one eye in the childhood. Clinical type – • Monocular visual loss • Deviation • Amblyopia 2. Consecutive Esotropia Consecutive esotropia refers to occurrence of esotropia in an eye which was previously exotropia. It has been reported to occurs under following two clinical situations: • Surgical overcorrection of exotropia • Spontaneous consecutive esotropia.

[Audio] EXODEVIATIONS Exo -visual axis is deviated laterally and fovea rotated nasally. Exodeviations = divergent strabismus. Exophoria Exotropia Manifest • Intermittent or constant • Unilateral or alternating Latent controlled by fusion.

[Audio] PSEUDOEXOTROPIA • Appearance of exodeviations • Wide interpupillary distance • Large positive angle kappa- hyperopia, ROP.

[Audio] EXOPHORIA In this condition, when fusion is interrupted, the non-fixating eye become divergent, i.e. deviates temporally. OR Eye moves temporally under cover..

[Audio] Classification of Exophoria According to Ocular Movements • Concomitant • Incomitant According to Type of Deviation Esophoria • Divergence excess (distance phoria >near phoria) • Convergence weakness (near phoria < distance phoria) • Non- specific (near phoria = distance phoria).

[Audio] TYPES : COMITANT Primary Infantile exotropia Intermittent exotropia Secondary Sensory exotropia Consecutive exotropia B. Incomitant Paralytic Restrictive Musculofascial innervational anomalies.

[Audio] EXOTROPIA Exotropia is manifested by outward turning of the eye. It is the term used to describe any manifest deviation of the visual axes outwards, in which the extent of the deviation of the squinting eye remains constant in all positions of gaze and there is no limitation of ocular movements. There are three types: 1.Primary exotropia 2. Sensory exotropia 3. Consecutive exotropia.

[Audio] 1) Primary Exotropia The main feature is the deviation itself, unlike other exodeviations where the deviation is caused by obstacles to developing or maintaining binocular single vision (BSV). Various theories are there to explain the cause of primary exotropia. • Mechanical Theory: These factor include shape, axes of the orbit which is facing outwards, interpupillary distance, size of the eyeball, mechanical properties of the conjunctiva; Tenon's capsule and extra ocular muscle. • Innervational Theory: Duane proposed that exodeviations caused either by hypertonicity of divergence or convergence insufficiency or both. Duane classified Exodeviation in four types : 1.Basic exotropia 2.Pseudo divergence excess 3.True divergence excess 4.Convergence insufficiency.

[Audio] TYPE DEFINITION Basic Distance and near measurements are equal Pseudo divergence excess Distance measurement initially exceeds near, but the near measurement approaches distance after 30-60 min of monocular occlusion True divergence excess Distance measurement exceeds near measurement by >10 prism dioptres even after 30-60 min of monocular occlusion Convergence insufficiency Near measurement exceeds distance measurement by >10 prism dioptres.

[Audio] In terms of the state of fusion, Exodeviation are classified as: Exophoria Intermittent exotropia Constant Exotropia.

[Audio] 2.Intermittent Exotropia Intermittent exotropia X(T) is the latent tendency (phoria) for the eyes to tum out, which is intermittently controlled by fusional convergence. Most common exotropia Manifest with inattention, fatigue, end of the day ( loose ability to convert) . Exposure to bright light cause reflex closure of one eye. Good binocular vision, no diplopia . Amblyopia is rare..

[Audio] 3.Primary Constant Exotropia Prevalence: Less common than intermittent exotropia. Infantile Form: Very rare, occurring shortly after birth with a large angle exodeviation equal for near and distance. Progression: Usually follows the decompensation of intermittent exotropia. Types: 1. Alternating Exotropia: Fixation: Patients use each eye alternately. Visual Acuity: Nearly equal in both eyes. Deviation: Usually large and equal for near and distance. Suppression: Deviating eye is suppressed; normal retinal correspondence (NRC) is present. 2.Unilateral Exotropia: Fixation: One eye constantly fixates. Deviation: Usually large, often with vertical deviations. Suppression: Deviating eye is suppressed. Amblyopia: May be present but less severe than in esotropia..

[Audio] Sensory Exotropia Exotropia, which develops because of poor vision of one eye. This can develop due to • Anisometropia, • Unilateral cataract, • Unilateral aphakia, • Corneal opacity, • Optic atrophy, • Macular lesion etc..

[Audio] Consecutive Exotropia This refers to exotropia in an eye that was previously esotropic. Types: 1) Due to surgical over-correction of esotropia. 2) Spontaneous consecutive exotropia-Change from esotropia to exotropia without any external factors or muscle paralysis. • Poor Vision: Can occur in cases of esotropia with poor vision in the deviating eye. • Infantile Esotropia: May occur in infantile esotropia with high hypermetropia..

[Audio] VERTICAL DEVIATION. VERTICAL DEVIATION. [image] Orbit Eye Center for Pediatrics & Oculoplasty.

[Audio] Vertical squint, or vertical strabismus, is a condition where there is a misalignment of the visual axes in the vertical direction, causing one eye to be higher than the other Vertical squints are less common than horizontal squints. Most associated with horizontal deviations It can be hyper or hypotropia (Non fixating eye upper/lower than the fixating.

[Audio] Vertical Eye Muscles: Each eye has four vertical muscles: Superior Rectus: Elevates the eye in abduction. Inferior Rectus: Depresses the eye in abduction. Superior Oblique: Depresses the eye in adduction. Inferior Oblique: Elevates the eye in adduction. These muscles work in pairs, known as yokes, where a rectus muscle of one eye pairs with the oblique muscle of the other eye. Ocular motility disturbances of vertical recti and oblique muscles are inseparable, and they will be conjointly termed as Cyclovertical muscles. Vertical strabismus can be paralytic/non-paralytic. Special Entity: Dissociated Vertical Deviation (DVD) Does not obey Hering's Law. Can be constant or intermittent, latent or manifest. Often associated with other ocular conditions.

[Audio] Classification Concomitant Incomitant Refractive Restrictive Paralytic Oblique muscle dysfunction Restrictive Mechanical restriction 4th nerve palsy 3rd nerve palsy IO palsy DEP/DDP Ophthalmoplegia SO overaction IO overaction.

[Audio] Other motility defects: 1)Brown's syndrome: Limitation of deviation of eye in abduction due to fibrous tightening of superior oblique muscle. 2) Double elevator palsy: It is associated with ptosis characterized by paresis of superior rectus and inferior oblique of same eye. 3) Congenital fibrous syndrome: Congenital disorder associated with defective movements in elevation. 4) Mobious syndrome: It is the congenital aplasia of 6th, 7th and sometimes 9th and 12th cranial nuclei. 5) Oculomotor Palsy: This implies a palsy of the Ill cranial nerve with associated defect in movements of elevation, depression and adduction. 6) Trochlear palsy: This implies a palsy of the IV cranial nerve with associated defect in the movements of the superior oblique muscle..

[Audio] Dissociated vertical deviation Etiology- 50% of patients with infantile esotropia Clinical features- Head tilt Excycloduction of the elevated eye and incycloduction of the fixating eye Latent nystagmus.

[Audio] . LE moves up RE moves up. [image] Orbit Eye Center for Pediatrics & Oculoplasty.

[Audio] Pattern Strabismus Pattern strabismus is present when a horizontal deviation change in magnitude between up gaze and down gaze..

[Audio] Most common types of pattern strabismus is A and V pattern so commonly called AV pattern strabismus Types of pattern strabismus V pattern. A pattern X pattern Y pattern.

[Audio] Aetiology of A and V pattern Abnormalities of vertical or horizontal muscles action. Anatomical anomalies. Disorder of muscle innervation. Anomalous insertion of muscle tendon. Sensory torsion.

[Audio] A and V Pattern A pattern A pattern esotropia A pattern exotropia V pattern V pattern esotropia V pattern exotropia.

[Audio] A-Pattern Horizontal Heterotropia Second most common type A-pattern horizontal heterotropia is a vertically incomitant horizontal deviation characterized by changes in convergence and divergence based on gaze direction. A deviation is clinically significant if the difference between up gaze and downgaze is at least 10 prism diopters. A-esotropia - Esotropia will increase in up gaze and decrease in downgaze A-exotropia - Exotropia will decrease in up gaze and increase in downgaze..

[Audio] A-pattern exotropia. Note A-pattern esotropia. Note left esotropia in primary gaze which increases in up gaze decreases in downgaze. left exotropia in primary gaze which decreases in up gaze increases in downgaze.

[Audio] V-Pattern Horizontal Heterotropia Most common type V-pattern horizontal heterotropia is a vertically incomitant horizontal deviation characterized by changes in convergence and divergence based on gaze direction. A deviation is clinically significant if the difference between up gaze and downgaze is at least 15 prism diopters. V-esotropia - The esotropia will increase in downgaze and decrease in up gaze V-exotropia - The exotropia will increase in up gaze and decrease in downgaze.

[Audio] V-pattern esotropia. Note V-pattern exotropia left esotropia which decreases in up gaze increases in downgaze left exotropia which increases in up gaze and decreases in downgaze.

[Audio] X Pattern When the deviation in primary position increase in both up gaze and down gaze( relative divergence) Commonly seen in pt with large angle exotropia X-pattern exotropia. Note (A) no deviation in primary gaze and (B) exotropia in up gaze (c) and downgaze ..

[Audio] Y Pattern When there is relative divergence on up gaze but no significant change in angle from primary position to down gaze Pseudo overaction of I.0 But there is no fundus torsion, negative head tilt test, no S.O under action Its due to abberant innervation of LR in up gaze. Y-pattern exotropia. Note (A) left exotropia in up gaze and (B) no deviation in primary gaze and (C)downgaze..

[Audio] Torsional Deviations Excyclodeviation: Rotation of the top of the eye away from the nose. Incyclodeviation: Rotation of the top of the eye towards the nose..

[Audio] Summary Strabismus, or squint, is a condition where the eyes do not align properly. It can be classified into different types based on the direction of deviation and whether the deviation is latent (phoria) or manifest (tropia). Understanding these classifications is crucial for diagnosing and treating the condition effectively..

[Audio] References Ahuja, L. (2001). Manual of Squint (2nd ed.). New Delhi, India: Jaypee Brothers Medical Publishers. Sharma, P. (2017). Strabismus Simplified (3rd ed.). New Delhi, India: CBS Publishers & Distributors. Irfan, S. (2012). Understanding Strabismus: A Comprehensive Text and Atlas. Lahore, Pakistan: Paramount Books. Khurana, A. K. (2018). Theory and Practice of Squint and Orthoptics. New Delhi, India: CBS Publishers & Distributors..