1. Strabismus Dr HAN Wei The 1 st Affiliated Hospital, Medical College, Zhejiang University

2. Basic knowledge of ocular motility Extraocular muscles Not playing role in vision procedure directly, but critically important for eyeball motility and binocular vision function.

3. Anatomy of extraocular muscles Six extra-ocular muscles for the human eye. Namely: Medial rectus m. Lateral rectus m. Superior rectus m. Inferior rectus m. Superior oblique m. Inferior oblique m.

4. Insertion positions of four rectus m. MR: Medial rectus m. LR: Lateral rectus m. SR: Superior rectus m. IR: Inferior rectus m.

5. Nerve innervation for extraocular m. III cranial n. III cranial n. Medial rectus m. Superior rectus m. Inferior rectus m. Inferior oblique m. IV (Trochlea) cranial n. IV (Trochlea) cranial n. Superior oblique m. VI (Abduction) cranial n. VI (Abduction) cranial n. Lateral rectus m.

6. Basic motility function of the eye ball Elevation and depression (A, B) Adduction and abduction (C, D) Intorsion and extorsion (E, F)

7. Motility functions of right eye’s extraocular muscle Inferior oblique m. Extorsion Elevation Adduction Superior rectus m. Elevation Intorsion Adduction Inferior rectus m. Depression Adduction Extorsion Superior oblique m. Intorsion Depression Abduction Lateral rectus m. Abduction Medial rectus m. Adduction

8. Terminology of extra-ocular muscle regarding their physiological functions Antagonist m.: Antagonist m.: the muscle that counteracts the agonist (or the prime mover); lengthening when the agonist muscle contracts. e.g., medial rectus and lateral rectus m.. Yoke m. : Yoke m. : The contra-laterally paired extra-ocular muscles of two fellow eyes that work synergistically to direct the gaze in a given direction. Example: in directing the gaze to the right, the right lateral rectus and left medial rectus operate together as yoke muscles. Synergist m.: Synergist m.: The muscles moving one single eye ball in the same direction as the prime moving muscle. e.g., inferior oblique m. is the synergist of superior rectus m. when the eye turns upward.

9. Nervous innervation laws Sherrington law: A muscle will relax when its antagonist muscle (e.g., lateral and medial m.) is activated. Hering law: The yoke m. are innervated equally by nervous system in eye movement.

10. Eye position for examination Primary position: With condition in which head being put vertically and straightforward and two eyes looking straightforward. Secondary position: The two eyes being in adduction or abduction or elevation or depression position. Tertiary position: Two eyes gazing in oblique directions (up or downward).

11. Left superior rectus m. Right inferior oblique m. Right superior rectus m. Right medial rectus m. Left lateral rectus m. Left inferior rectus m. Right inferior rectus m. Right superior oblique m. Right Superior rectus m. Left inferior oblique m. Left superior rectus m. Left medial rectus m. Right lateral rectus m. Right inferior rectus m. Left superior oblique m. Left inferior rectus m. Right Superior rectus m. Left Superior rectus m. Right Inferior rectus m. Left Inferior rectus m.

12. Definitions Strabismus: A condition in which the eyes are not properly aligned with each other, i.e., manifest deviation of the eyes exist. Heterophoria: A condition in which the visual axes of two eyes fail to remain parallel after elimination of visual fusional stimuli. e.g, covering one eye e.g, covering one eye

13. Classification Based on concomitancy Concomitant: Angle of squint is the same in all directions of gaze. Exotropia Esotropia Inconcomitant: Angle differs in different directions of gaze. Special types: e.g., Duane syndrome Based on etiology Functional Paralytic (secondary to traumatic or pathological lesions) Based on constancy Constant Single eye deviation Alternative deviation Intermittent

14. Examination and diagnosis Disease and familial history Disease and familial history Onset age Onset age Visual acuity Visual acuity Refraction Refraction Strabismus type Strabismus type Compensative head position Compensative head position Test for strabismus* Test for strabismus*

15. Epicanthal fold – should be ruled out in child patients

16. Simulated esotropia

17. Cover test and uncover test Cover test and uncover test Alternative cover test Alternative cover test Unilateral gaze (A) or alternative gaze (B) Strabismus test (1) ABAB

18. Strabismus test (2) Corneal reflex test Corneal reflex test Simple, easy method Simple, easy method Broadly applied in clinic Broadly applied in clinic

19. Strabismus test (2) Other methods Other methods Prism and cover test Prism and cover test Perimeter arc test Perimeter arc test Maddox rod test Maddox rod test Synoptophore test Synoptophore test

20. Concomitant strabismus Accommodative Complete accommodative Partially accommodative Non-accommodative First deviation angle = Secondary deviation angle First deviation angle: When the normal eye gazing target, the strabismus angle of the deviated eye. Second deviation angle: When deviated eye gazing target, the strabismus angle of the normal eye.

21. Concomitant esotropia Most commonly seen type, closely associated with accommodation function. Most commonly seen type, closely associated with accommodation function. First angle = Second angle First angle = Second angle Usually no diplopia Usually no diplopia Normal ocular motility Normal ocular motility Intermittent in incipient stage and turn to be constant gradually. Intermittent in incipient stage and turn to be constant gradually.

22. Treatment Spectacle correction for ametropia Spectacle correction for ametropia Treat amblyopia Treat amblyopia Eye position training Eye position training Surgery Surgery

23. An example of concomitant esotropia After operation, the two eyes ’ position is corrected to be normal. (Lower figure)

24. An example of partially accommodative concomitant esotropia With spectacle, squint was partially corrected, but still existed. (lower figure)

25. Concomitant exotropia Associated with: Associated with: Central nervous biocular balancing function, Central nervous biocular balancing function, Imbalance of accommodation and convergence, Imbalance of accommodation and convergence, Anisometropia Anisometropia Visual impairment in one eye Visual impairment in one eye Intermittent early stage to constant stage. Intermittent early stage to constant stage. Treatment: Treatment: Ametropia correction Ametropia correction Prism spectacle Prism spectacle Surgery Surgery

26. An example of concomitant exotropia treated by surgery Deviation was correctly after surgery. (Figure left)

27. An example of concomitant exotropia due to visual impairment in left eye

28. Nonconcomitant strabismus Usually paralytic secondary to: Embryo development anomalies Trauma Inflammation Hypertension and hemorraghe & ischemia Tumor Metabolism disorder like diabetes, thyroidism, etc

29. Symptoms Diplopia Diplopia Compensation head position Compensation head position Deviation of affected eye Deviation of affected eye First angle ＜ second angle First angle ＜ second angle Compromise of ocular motility Compromise of ocular motility

30. Hess screen test Shift of the square denotes the muscle being paralytic. Shift of the square denotes the muscle being paralytic.

31. Compensation head position in paralysis of the right eye’s lateral rectus muscle

32. An example of paralytic esotropia Lateral rectus m. of right eye paralysis. Note the 1 st angle (figure right) is less than second angle (figure left)

33. An example of paralytic vertical strabismus of right inferior rectus m.

34. Treatment Primary diseases treatment Primary diseases treatment Drug Drug Vit B1, B12, ATP Vit B1, B12, ATP Steroid Steroid Antibiotics Antibiotics Botulinum A injection to relief the muscle spasm Botulinum A injection to relief the muscle spasm Prism Prism Surgery Surgery Usually 6 months after onset, with deviation being stable. Usually 6 months after onset, with deviation being stable.

35. Differentiation of paralytic and concomittent strabismus ParalyticConcomittent OnsetSuddenlyGradually Eye motility Compromised in affected m. movement direction Normal Deviation angle 2 nd angle > 1 st angle Equal DiplopiaYesNo Compensative head positionYesNo

36. Amblyopia Definition of amblyopia: otherwise known as lazy eye, is a disorder of the visual system that is characterized by poor or indistinct vision in an eye that is otherwise physically normal.disordervisual systemvision It has been estimated to affect 1–5% of the population. Etiology: The nerve pathway from one eye to the brain does not develop during childhood or the abnormal eye sends a blurred image to the brain.

37. Category of etiology Strabismus Strabismus (Most common type, due to crossing eye) (Most common type, due to crossing eye) Anisometropia Anisometropia (Imbalance of visual input) (Imbalance of visual input) Ametropia Ametropia (Double eye onset) (Double eye onset) Form deprivation Form deprivation (Refractive media opacity) (Refractive media opacity) Others Others (Pathological lesions) (Pathological lesions)

38. Symptoms Vision acuity loss Vision acuity loss Mild:0.6-0.8 Mild:0.6-0.8 Moderate:0.2-0.5 Moderate:0.2-0.5 Severe: less than 0.1 Severe: less than 0.1 Abnormal fixation Abnormal fixation Crowding phenomenon Crowding phenomenon

39. Treatment (1) Early treatment. Early treatment. As early as possible. Critically important! As early as possible. Critically important! Treatment effect is poor after 9 years old. Treatment effect is poor after 9 years old.

40. Ametropia correction: spectacle even LASIK, surgery for congenital cataract. Ametropia correction: spectacle even LASIK, surgery for congenital cataract. Occlusion therapy Occlusion therapy Occluding normal eye, allowing amblyopic eye to develop Occluding normal eye, allowing amblyopic eye to develop Red light therapy Red light therapy Stimulating the macular function development Stimulating the macular function development After image therapy After image therapy Depression therapy Depression therapy Using atropine or over- or under-correction lens Using atropine or over- or under-correction lens Synoptophore therapy Synoptophore therapy Drug (L-Dopa) Drug (L-Dopa) Treatment (2)

41. Nystagmus A condition of involuntary rhythmically oscillation of the globe. According to the rhythm, it is divided into two sorts: jerky and pendular. Physiological and pathological Category: Perpetual Opticokinetic Labyrinthine Environmental

42. Binocular vision Normal human’s vision is the matter of the co- ordination of the two eyes. Normal human’s vision is the matter of the co- ordination of the two eyes. The eyes must be capable of aligning themselves in such a manner: the retinal images of a fixated target can easily be placed and maintained on the foveae of the two eyes. The eyes must be capable of aligning themselves in such a manner: the retinal images of a fixated target can easily be placed and maintained on the foveae of the two eyes. Normal binocular vision is established in about 5-6 years. Normal binocular vision is established in about 5-6 years.

43. Binocular vision Condition of the normal binocular vision : Condition of the normal binocular vision : (1) in good focus; (1) in good focus; (2) similar image size (within 5% disparity); (2) similar image size (within 5% disparity); (3) similar image shape; (3) similar image shape; (4) normal eyes ’ motility; (4) normal eyes ’ motility; (5) fusion ability and area; (5) fusion ability and area; (6) normal neural pathways. (6) normal neural pathways.

44. Grade of binocular vision Simultaneous perception Ability to simultaneously percept the retinal image of the two eyes Fusion Images formed on the retina of the two eyes are combined into a single percept. Stereopsis Highest grade of binocular vision. Perception of depth and distance.

45. Normal binocular vision Sensory aspects Sensory aspects Corresponding retinal points Corresponding retinal points Panum fusional areas Panum fusional areas Horopter Horopter Physiological diplopia Physiological diplopia Motor aspects Motor aspects Conjugate movement Conjugate movement Saccadic movement Saccadic movement Following movement Following movement Disconjugate movement Disconjugate movement Convergence Convergence Divergence Divergence Motor fusion Motor fusion

46. Abnormal binocular vision Diplopia Diplopia pathological pathological Confusion Confusion misalignment of the two eyes in paralytic strabismus misalignment of the two eyes in paralytic strabismus Suppression Suppression amblyopia amblyopia Abnormal retinal correspondence Abnormal retinal correspondence strabismus strabismus Eccentric fixation Eccentric fixation amblyopia amblyopia

47. Low vision Definition of low vision (WHO 1992) Best corrected visual acuity <0.3, Semi-visual field narrower than 10 degree Treatment Etiological diseases if viable Visual aid instruments Telescope Magnifier Electronic apparatus like CCTV, computer display

48. Low vision aid products

49. Questions State refractive components of the eye’s optical system. The category of myopia and the clinical management? The classification of the concomittent strabismus and the clinical management?