Anatomy and Physiology of Extraocular Muscles PDF

q Anatomy of EOM q Basic Physiology of EOM q In the eye 6 (7) EOM: q4 rectus muscles: § Medial rectus § Superior rectus § Inferior rectus...

q Anatomy of EOM q Basic Physiology of EOM q In the eye 6 (7) EOM: q4 rectus muscles: § Medial rectus § Superior rectus § Inferior rectus § Lateral rectus Anatomy of EOM q2 oblique muscles § Superior oblique § Inferior oblique q1 levator superioris  q Primary position: qEye is straight ahead & qPrimary action of the muscle: the head is also straight qIts major effect on the position of the eye when the muscle is contracted while the eye is in primary position q Some muscles also having secondary actions Medial Rectus Muscle q Arises from annulus of Zinn q Courses along medial orbital wall q Inserts 5.5 mm from the limbus q Risk of injury during ethmoid sinus Ii surgery q Innervated by inferior division of III q Recti muscles arise from a common tendinous ring that (Oculomotor) CN surrounds the optic canal and lies over the superior orbital q In primary position it is adductor fissure (Annulus of Zinn) t i  Lateral Rectus Muscle Superior Rectus Muscle q Arises from annulus of Zinn q Arises from annulus of Zinn q Courses anterior, upward over the eyeball & q Courses along lateral orbital lateral forming angle 23° with visual axis in primary wall position q Inserts 6.9 mm from the q Inserts 7.7 mm from the limbus limbus q Innervated by superior division of III CN q Innervated by VI CN (Oculomotor nerve) (Abducent) q In primary position: q In primary position it is abductor § Its primary action is: elevation § Its secondary actions are: intorsion and adduction Inferior Rectus Muscle Superior Oblique Muscle q Arises from annulus of Zinn q Arises from orbital apex above annulus q Courses anterior, downward & lateral of Zinn along the floor of the orbit q Passes ant & upward along supero- q Inserts 6.5 mm from the limbus medial wall of the orbit q Innervated by inferior division of III CN q Becomes tendinous before passing (Oculomotor nerve) through trochlea (Cartilaginous saddle attached to the frontal bone in the supero- q In primary position: nasal orbit, it redirects the tendon forming § Its primary action is: depression angle of 51° with visual axis in primary § Its secondary actions are: extorsion and adduction position)  Superior Oblique Muscle Inferior Oblique Muscle q Arise from periosteum of the maxillary q It passes under SR muscle bone, post to orbital rim & lateral to the q Inserts to post. Sup quadrant and orifice of the lacrimal fossa laterally q Passes: lat., sup. & post., inferior to the q Innervated by IV CN (Trochlear nerve) IR muscle q In primary position: q Inserts under LR muscle in post. Lat. § Its primary action is: intorsion take Portion of the globe, near to the maculacare § Its secondary actions are: depression (in the adducted q Form an angle of 51° with visual axis of position) and abduction eye in primary position visetrain Insertion of rectus muscle relationships Inferior Oblique Muscle q A continuous curve drawn through the insertion q Innervated by inferior division of III of the 4 rectus muscles known as Spiral of Tillaux CN (Oculomotor) q In primary position: Anticlock § Its primary action is: extorsion § Its secondary actions are: limbus elevation and abduction § It is the only muscle that is capable of elevating the eye Kwest when it is in a fully adducted position.  Nine diagnostic positions of gaze q Six cardinal positions q The primary position qElevation and depression R gaze of Blood Supply Venous System q Ophthalmic A è Muscular branch: q Parallels the arterial system qMedial Bra: IR – MR – IO q Emptying into sup & inf orbital veins qLateral Bra: LR – SR - SO q 4 vortex veins 8 isoes  Basic terminology of the Muscles q Agonist è The primary muscle that moves an eye in a given direction (e.g: Rt SR = supraduction) helping q Synergistic è A muscle in the same eye that moves the eye in the same direction as the agonist (e.g.: Rt SR + Rt IO= Supraduction) q Antagonist è A muscle in the same eye that moves the eye in Physiology of EOM the opposite direction of the agonist (e.g.: Rt LR and Rt MR) q Yoke muscle è oidf.ee The primary muscles in each eye (two eyes) that accomplish a given version (contralateral synergist) (e.g.: Rt LR + Lt MR = looking to Rt) Espot Basic terminology of the Muscles Yoke Muscles q Are pairs of muscles, (one in each eye) → that produce conjugate ocular movements one I rs Ei it  7 Y Ie f Wyo Sherrington’s law Tease Hering’s law (Equal innervation) (Same eye - reciprocal innervation) q Yoke muscles receive equal & simultaneous innervation qIncreased innervation to 5 any muscle (agonist) is nffered accompanied by →a corresponding decrease in innervation to its (antagonists) with 1419 611 Hering’s law (Equal innervation) Hering’s law (Equal innervation) q The magnitude of innervation is determined by the fixating eye, which means that the angle of deviation between eyes may vary depending on Rt 6th N paresis which eye is fixating (paralytic strabismus): 1) If Normal eye is fixating → The primary deviation ix a 2) If Paretic eye is fixating → Secondary deviation → typically larger than the primary deviation. S2nddewq§ S2nddewq§ if I remove 0 the cover ff 35 PD 45 PD 41 s sina.si 2 a a  iii Hering’s law (Equal innervation) S2nddewq§ Lt 6th N paresis 1) If Normal eye is fixating → The primary deviation (30 PD) 2) If Paretic eye is fixating → Secondary deviation → typically larger than the primary deviation (45 PD)  Basic Principles & Terms Terminology s Terminology Binocular single vision (BSV): Strabismus: the ability to fuse the images from the two eyes & to perceive binocular depth From the Greek word (strabismós) = to squint Orthophoria: Ideal condition of ocular balance Prefixes Eso: nasal rotation/ convergence Exo: temporal rotation/ Suffixes S E divergence Phoria: latent deviation Hyper: superior rotation Hypo: inferior rotation Incyclo: sup pole rotated nasally Excyclo: sup pole rotated temporally Tropia: manifest deviation q The eye deviates inside toward the nose q Esotropia q Exotropia q Hypertropia q Types: Eses I. Accommodative fully II. Non-accommodative  to I. Accommodative: II. Non-accommodative: suffers Infra Iiiii High hyperopia Presented by the age of 2-3 years § Examples: High risk of amblyopia Fully Accommodative Esotropia 1. Infantile esotropia A. Partially accommodative: 2. Sensory esotropia q Treatment: 3. Paralytic esotropia § Glasses + surgery/BOTOX injection (6th nerve palsy) I B. Fully accommodative: 6th Nerve Palsy a in q Treatment: Glasses 2 1. Infantile esotropia: 1. Paralytic esotropia (6th nerve palsy) surgery q Manifest by the age of 6 months q Characterized by: 2. Sensory esotropia § Large angle of esotropia (>30 PD) § Latent Nystagmus § Treatment: § Low hyperopia (+1/+2 D) Ø Surgery § Alternate fixation good § § Inferior oblique over action (IOOA)Ugood Dissociated vertical deviation (DVD) if q Treatment: it 6th Nerve Palsy q BOTOX (FIRST YEAR OF LIFE) I q SURGERY i  a pi Pseudoesotropia p if q 9 MONTHS OLD CHILD I NO i p q Illusion of crossed eyes qCause: § Flat- broad nasal bridge (abnormal interpupillary distance) 0 § Prominent epicanthal folds (cover portion of sclera) 96 q 5 YEARS OLD CHILD q The eye deviates outside away from the nose Exotropia qTypes: qIntermittent Ø (rarely develops amblyopia) qConstant: 2 Ø paralytic: 3rd nerve palsy 3rd Nerve Palsy Ø sensory exotropia trauma 1 qTreatment: surgery squat a  I go Variation of deviation with gaze position or fixating eye q The eye deviates up a) Comitant (concomitant) 1 b) Incomitant (noncomitant) 1 qe.g.: mild stook 4th nerve palsy (vertical diplopia) New fii i.nin Variation of deviation with Variation of deviation with gaze position or fixating eye gaze position or fixating eye a) Comitant (concomitant) I b) Incomitant (noncomitant) 2 ET 40 PD -deviation vary in size -deviation not vary in size with changesof direction of with direction of gaze of gaze or fixating eye ET 40 PD ET 40 PD ET 40 PD fixating eye -usually congenital -usually acquired & sudden -primary deviation = ET 40 PD secondary deviation - Secondary deviation > primary deviation j or ps acquierd  Hering’s law (Equal innervation) fgy congenital S2nddewq§ Lt 6th N paresis Examination of a 1) If Normal eye is fixating → The primary deviation (30 PD) patient with strabismus 2) If Paretic eye is fixating → Secondary deviation → typically larger than the primary deviation (45 PD) Examination of a patient 1. Inspection and History with strabismus q Age of onset 23infantile 1) Inspection and history q Symptoms 2) Visual acuity q Variability 3) Sensory tests q General Health 4) EOM movements q Birth history 5) Measurement of deviation 6) Cycloplegic refraction q Family history 7) Fundus exam q Previous ocular history FIE.sn  2. Visual Acuity 2. Visual Acuity a) Preverbal a) Preverbal b) Verbal (Infants) (Infants) q Blink to light (at birth) q Eye contact 6-8/52 2) School aged & 1) Toddlers older q Fixation and following 3-4/12 ayatore 3yd q Preferential looking 4/12 2. Visual Acuity 3. Sensory Tests Te b) Verbal qFusion/ suppression: 1) Toddlers: Optotypes 2) School aged & older: Snellen chart § Worth 4-dots test § Bagolini striated glasses I gñ q Sterioacuity: § Titmus test  4. EOM Movement 5. Measurement of Deviation movingoneeye q Duction: § Movement of one eye § Other is covered § Extreme field of gaze shining thelightonly q Version: 5 q Corneal light Reflex: (Hirshberg test) § Binocular eye § Each1 mm of deviation is approximately movement c together = 7° (1°≈ 2 prism diopters). § Should be in 9- § Pupil margin 15° (30 PD ET) positions § Graded(+4)/0/(-4) § Mid iris Temp (60 PD ET) § Limbus Temp 45° (80 PD ET) notification ESOTROPIA our EXOTROPIA  5. Measurement of 5. Measurement of Deviation Deviation q Krimsky test: qCover test: § placement of prisms inin (cover/uncover) drifting 2 front of the fixating eye § Cover test to detect a until the corneal light heterotropia reflections are symmetrical § Uncover test to detect heterophoria u Useful for: EE § Cover for 1-2 sec, remove Kiwi patient on§ Uncooperative & observe the eye under cover ge a § Sensory strabismus who a.itsee IIIa 5. Measurement of Deviation 6. Cycloplegic Refraction is qUsing: (Retinoscope) § Cyclopentolate 1% § Phenylephrine 2.5% qAlternate cover test: 7. Fundus Exam § Measures full deviation for both tropia & phoria qAlternate prism cover test: 40 discede § Measures angle of deviation qRule out ocular pathology EYE § If no movement is the angle of surgical correction  Management of Strabismus 1. Glasses 2. Treatment of amblyopia baking 3. Surgical management Hefford Management of Strabismus 4. Botox injection is Surgical Management Surgical Management a) Weakening b) Strengthening - Recession: Moving it away from its insertion -Resection: Shortening the muscle to - Myectomy: enhance its effect The muscle is severed from its insertion without reattachment 661 42  Botox q Neurotoxin derived from Gm –ve anaerobic bacteria (Clostridium botulinum) q Prevents acetylcholine release from peripheral nerve q Temporarily paralyze the muscle 3-6/12  q Amblyopia § Definition § Causes § Diagnosis § Treatment qLeukocoria q Unilateral or less commonly bilateral q Caused by abnormal visual experience 0 reduction of best corrected visual acuity in early in life (before the age of 7 the absence of detectable organic disease years=before visual maturity) q It is a developmental disorder of the CNS q Primarily a defect of central vision that results from the abnormal processing e (peripheral visual field is usually normal) of visual images → reduced VA me_ a  Causes of Amblyopia 1. Strabismic Amblyopia q Most common cause of ① Strabismus In amblyopia ② Visual deprivation q Develops in consistently deviating eye: non-alternating, ③ Anisometropia (unequal tropias, typically ESOTROPIA refractive error) q Uncommon with intermittent exotropia and if present is mild 2. Anisometropia 2. Anisometropia Refractive Amblyopia Refractive Amblyopia q Second most common cause q Amblyopia may develop because q Unequal refractive error in the of untreated unilateral or bilateral two eyes (image on the retina of refractive errors one eye is chronically defocused) ü Mild hyperopic or astigmatic q Bilateral refractive amblyopia anisometropia (1 – 2 D) can cause (isoametropic) (high hyperopia or amblyopia dungeons very ü Mild myopic anisometropia (< 3 D) high myopia) is a less common cause not iii of amblyopia e usually will not cause amblyopia a de  0 3. Deprivation Amblyopia Diagnosis of Amblyopia faking q Caused by obstruction of visual axis q reduced visual acuity can not be explained entirely on the basis of physical abnormality q Least common but the most damaging & difficult to treat (+): EE § Difference in visual acuity ( ≥2 lines) q Can occur unilateral or bilateral it between the two eyes q Most common cause: § Crowding phenomena (Visual acuity in § Congenital or early cataract amblyopia is usually better while 2 I § Corneal opacity reading single letters than letters in a § Vitreous hemorrhage 0 row) se 4 2 § Blepharoptosis § Fixation preference can give a clue but insatism not a must 2 Treatment Fei Itanathology aol.at g ① Elimination of any obstacle to the vision e.g: cataract è Do cataract surgery ② Correct any significant refractive error ③ Force use of poorer eye by limiting the use of good eye by: a Leukocoria § Part time occlusion (occlusion of the good eye) § Penalization (using cycloplegic/ Atropin drops to the good eye)  Red reflex q White pupil q Can be seen as white spot No flash light through infants pupil or the pupil may appear normal in room light but have no red reflex by direct ophthalmoscopy q The lesion can present at the With flash light level of the lens or behind the lens (vitreous - retina) His g Causes Work-up your q Retinoblastoma must be ruled out first q Other Causes: q History § Cataract q Complete ocular § Persistent fetal vasculature examination/ EUA ex § Retinopathy of prematurity q B-Scan ultrasonography Ixesia advanced stages q CT or MRI 5 § Active Uveitis § Vitreous Hemorrhage in § Retinal detachment  Treatment qAny child with leukocoria needs to be seen urgently and treated accordingly Laborroom check