Strabismus

Strabismus

1. Danylo Halytsky Lviv National Medical University Department of Ophthalmology Topic : STRABISMUS Name : Mohamed Mahmoud Abbass Group : 7 th Course : 4 th

2. Definition Strabismus or squint or simply deviation of the eye refers to a misalignment of the visual axis. Strabismus originates from the Greek. Hippocrates used the word streblos , ‘‘turned,’’ ‘‘twisted,’’ when he talked about strabismic subjects and the word is derived from the verb strephein , ‘‘to twist,’’ ‘‘to turn .’’ A worldwide estimate would be 130 to 260 million

3. • Visual axis ; line of vision ; extending from the point of fixation to the fovea • Strabismus ; misalignment of the visual axes • orthophoria ; perfect alignment of the visual axes. Most individuals have heterophoria • Heterophoria ; (latent squint) tendency of the eyes to deviate. Ocular alignment maintained with effort. • Heterotropia ; (manifest squint) which is present at all times

4. • Esophoria ; latent squint inwards turning of the eyes • Esotropia ; manifest squint inwards turning of the eyes • Exophoria ; latent squint outwards turning of the eyes • Exotropia ; manifest squint outwards turning of the eyes • Hyperphoria / hypertropia ; latent/manifest squint upwards turning of eyes • Hypophoria / hypertropia ; latent/manifest squint downwards turning of eyes • Anatomical axis ; is a line passing from the posterior pole through the centre of the cornia . • Angle kappa is the angle subtended by the visual and anatomical axes .

5. Type of Deviation Horizontal Esodeviation or exodeviation Vertical Hyperdeviation or hypodeviation Torsional Incyclodeviation or excyclodeviation Combined Horizontal, vertical, torsional , pattern or any combination thereof

6. Laws of ocular motility Agonist ; antagonist – muscles of the same eye moving the eye in opposite direction; medial and lateral rectus Synergists = muscles of the same eye moving it in the same direction; superior rectus and inferior oblique causing elevation Yoke muscles = muscles of both eyes moving the eyes in same direction; medial rectus of both eyes Sherrington law ; increase in innervations to one muscle causes decreased innervations to its antagonist; medial and lateral rectus Hering law ; equal innervations flows to yoke muscles in eye movement ; medial rectus of both eyes

7. Extraocular muscles Horizontal muscles; – Medial rectus-; Its sole action in the primary position is adduction. occulomotor nerve supply – Lateral rectus- Its sole action in the primary position is abduction.; abducens nerve supply Vertical muscles; – Superior rectus- Primary action elevation (secondary actions are adduction and intorsion . Oculomotor nerve supply – Inferior rectus ; The primary action is depression ; secondary actions are adduction and extortion . oculomotor nerve supply

8. Extraocular muscles • Oblique muscles; – Superior oblque ; Originates superomedial to the optic foramen. It passes forwards through the trochlea at the angle between the srperior and medial walls and is then reflected backwards and laterally to insert in the posterior upper temporal quadrant of the globe. The primary action is intorsion ;secondary actions are depression and abduction. – oculomotor nerve supply – Inferior oblique; Orginates from a small depression just behind the orbital rim lateral to the lacrimal sac. It passes backwards and laterally. To insert in the posterior lower temporal quadrant of the globe, close to the macula. The prmary action is extorsion ;;secondary action are elevation and abduction .

9. Heterophoria when the influence of fusion is interrupted, the visual axis of the non-fixing eye deviates from the orthoposition . Depending upon the direction of deviation, heterophoria may be classified into: 1. Esophoria 2. Exophoria 3. Right hyperphoria 4. Left hyperphoria 5. Incyclophoria 6. Excyclophoria

10. Consequences of squint Suppression , amblyopia , confusion and diplopia , postural changes according to strabismus Amblyopia – Definition – unilateral or bilateral decrease of best corrected visual acuity caused by stimulus deprivation or abnormal interaction for which there is no pathology of the eye or the visual pathway – Types • Strabismic amblyopia ; abnormal interaction • Stimulus deprivation amblyopia ; form vision deprivation • Anisometropic amblyopia ; difference of refractive errors in both eye ; one eye is amblyopic • Ametropic amblyopia ; form vision deprivation of both eyes • Meridional amblyopia ; because of astigmatism

11. Medical Treatment Treatment of Amblyopia – Occlusion therapy • Initial stage • Maintenance stage – Atropine therapy • Optical Devices – Spectacles – Prisms • Botulinum Toxin • Orthoptics

12. Surgical Treatment Surgical procedures – Resection and recession – Shifting of point of muscle attachment – Faden procedure • Choice of muscles for surgery • Adjustable sutures

13. THANKS