Lateral rectus
- originates at the annulus of Zinn
- inserts 6.9 mm behind the temporal limbus
- abduction
Superior rectus
- originates at the annulus of Zinn
- inserts 7.7 mm behind the superior limbus
- forms an angle of 23 degrees with the visual axis
- primary: elevation
- secondary: adduction, intorsion
Medial rectus
- originates at the annulus of Zinn
- inserts 5.5 mm behind the nasal limbus
- adduction
Inferior rectus
- originates at the annulus of Zinn
- inserts 6.5 mm behind the inferior limbus
- forms an angle of 23 degrees with the visual axis
- primary: depression
- secondary: adduction, extorsion
Superior oblique
- originates superiomedial to the optic foramen
- passes forward through the trochlea
- inserts in the posterior upper quadrant of th globe
- forms an angle of 51 degrees with the visual axis
- primary: intorsion
- secondary: depression, abduction
Inferior oblique
- originates from a small depression just behind the orbital rim lateral to the lacrimal sac
- inserts in the posterior lower temporal quadrant of the globe close to the macula
- forms an angle of 51 degrees with the visual axis
- primary: extorsion
- secondary: elevation, abduction
Ductions ; Versions ; Vergences
Ductions: monoocular movements
Versions: binocular, simultaneous, conjugate movements
Vergences: binocular, simultaneous, disconjugate movements
AC/A ratio
3-5 🔺
Synergists
Yoke muscles
Synergists: muscles of the same eye that moves the eye in the same direction
-R superior rectus & R inferior oblique (elevation)
Yoke muscles: contraleteral synergists
-L superior oblique & R inferior rectus
Sherrington law
increased innervation to an extraocular muscle is accomponied by a reciprocal decrease in innervation to its antagonist
-R medial rectus & R lateral rectus
Hering law
during any conjugate eye movement, equal and simultaneous innervation flows to the yoke muscles
🔷in a paretic squint: secondary deviation > primary deviation
Horopter and Panum fusional space
Objects on the horopter: seen single and in one plane
Objects in Panum fusional areas: seen singly and stereoscopically
Objects outside Panum fusional areas: appear double
Normal values for fusional vergence
Convergence: 15-20🔺(distance), 25🔺(near)
Divergence: 6-10🔺(distance), 12-14🔺(near)
Vertical: 2-3🔺
Cyclovergence: 8*
Sensory adaptations to strabismus
- Supression: ➖ adaptation
- central / peripheral
- monoocular / alternating
- facultative / obligatory - Abnormal retinal correspondance (ARC): ➕ adaptation
Motor adaptations to strabismus
1- Face turn
2- Head tilt
3- Chin elevation/depression
Classification of amblyopia
- Strabismic ⚠️7-8 years
- Anisometropic ⚠️longer into the teens
- Stimulus deprivation
- Bilateral ametropic
- Meridional
Hirschberg test
Border of the pupil: 15 degrees
Limbus: 45 degrees
Cover test
Uncover test
Cover - TROPIA
Uncover - PHORİA
When to prescribe👓
Hypermetropia: >4⃣ D
-0-1 yaş: >5⃣ D, 1-3 yaş: >4⃣ D
-no squint: 2/3 correction
-esotropia: full correction
Astigmatism: >1.5 D
Myopia:
-5⃣ D
-2-4 years: >3⃣ D
->4 years: even low
-0-1 yaş: >4⃣ D, 1-2 yaş: >3⃣ D, 2-3 yaş: >2⃣ DEarly-onset esotropia
- within the first 6 months
- > 30🔺
- surgery by the age of 12 months
- inferior oblique overaction ➡️ V pattern
- DVD (%80)
- amblyopia in %50
Accomodative esotropia
- Refractive: AC/A ↔️
- presents at the age of 18 months to 3 years
- fully / partially - Non-refractive: AC/A ⬆️
- convergence excess / hypoaccomodative convergence excess
Treatment: 8 years: manifest hypermetropia is prescribed
Early-onset exotropia
- presentation is often at birth
- neurological anomalies are frequent ⚠️
- treatment: surgery
Duane retraction syndrome
- failure of innervation of the hypoplastic 6⃣th nerve and anomalous innervation from the 3⃣rd nerve instead, to the lateral rectus
- associated systemic defects⚠️: deafness, external ear abnormalities, speech disorder, skeletal abnormalities
- face turn
- restriction of abduction
- retraction of the globe on adduction
- majority do not need surgery
Möbius syndrome
- congenital non-progressive bilateral 6⃣th and 7⃣th cranial nerve palsies
- bilateral facial palsy
- limb anomalies, mild mental handicap may be present
