1. SQUINT Strabismus Introduction:
Six extraocular muscles insert in the sclera of each eye.. Normally they move the two eyes simultaneously, in a harmonious way so that the image of the object formed by each eye will lie at its fovea (Bifoveal Imaging)..

2. Extraocular Muscles

3. Sup. Rectus Oculomotor 1. Elevation (in abd.)
Muscle Nerve Action
Sup. Rectus Oculomotor 1. Elevation (in abd.)
2. Intorsion
3 Adduction
Inf. Rectus Oculomotor 1. Depression (in abd.)
2. Extorsion
3. Adduction
Med. Rectus Oculomotor 1. Adduction
Lat. Rectus Abducens 1. Abduction

4. L6SO4 3 Muscle Nerve Action .
Sup. Oblique Trochlear 1. Depression (in add.)
2. Intorsion
3 Abduction
Inf. Oblique Oculomotor 1. Elevation (in abd.)
2. Extorsion
3. Abduction
L6SO4 3

5. Strabismus:
Ocular misalignment, so that the image of an object does not fall on the fovea of both eyes simultaneously..
2-5% of population
Significance:
1. Common problem
2. It causes visual impairment.
3. May be caused by visual problem, e.g. hypermetropia, optic n. hypoplasia
4. Underlying serious pathology, e.g. Retinoblastoma
5. Cosmetic and social impact..

6. Squint (Strabismus)

7. Squint (Strabismus)

8. Pseuedosquint
1- Epicanthal folds: a prominent vertical fold of skin hanging over the inner canthus, and covering part of the nasal sclera  false impression of converging squint (Pseudo esotropia).. But normal results of squint diagnostic tests [ corneal light reflection, cover test]..
More common in Orientals.
usually lessen and may disappear with age
Treat. 1. Reassurance
2. Some cases need plastic surgery, e.g. Z- plasty.

9. Epicanthal folds

10. 2- Hypertelorism:
Wide IPD  pseudoextropia
3-Macular Dragging (Heterotopia maculae):
e.g.: ROP (Retinopathy of prematurity)
Or Cong. Toxocara chorioretinitis

11. Hypertelorism

12. Classification of Strabismus
1- According to Direction:
Eso deviation  Convergent squint
the eye in turned inward
Exo deviation  Divergent squint
the eye in turned outward
Hyper
Hypo

13. Exo & Eso Squint

14. 2- According to Severity:
Tropia  Apparent squint
Phoria  Latent squint (discovered only by cover test)
e.g.: Rt. Esotropia =
apparent convergent squint of the right eye..

15. A- Concomitant Squint:
3- Pathological classification
A- Concomitant Squint:
the angle of deviation of the squinting eye is constant on any direction of the gaze..
Early childhood + No correction 
amblyopia and loss of binocular vision
e.g.: - Congenital Esotropia
- Accommodative Esotropia
- Exotropia

16. B- Paralytic Squint (Incomitant):
* Due to complete or partial palsy of one of the nerves that supply EOM.
* Here, the angle of direction of gaze, being maximal in the direction of action of the weak muscle.
Eg.: - Oculomotor Palsy 
- Abducens Palsy 
- Trochlear Palsy

17. Paralytic Squint

18. Congenital Esotropia
1st 6 months of life (Infantile/Essential)
Large angle of deviation
Concomitant [D.Dx: Abducens palsy]
Refraction: normal or mild hypermetropia
Needs surgical correction preferably to start before 12 months age

19. Accommodative Esotropia
Concomitant
2-3 years
Usually high degree of hypermetropia
 excessive accommodation. (accompanied by convergence)  convergent squint which is more severe, or may be only present on looking at near objects.
Usually treated with prescribing glasses with full cycloplegic correction of the refractive error (hypermetropia) for the child..
.. if fail  surgery..

20. Intermittent Exotropia: Concomitant diverging squint
Periods of exotropia
Fatigue
Inattention, distraction
Emotional upset
May be myopic
Treat.: full myopic correction with glasses + observation
If attacks ↑ in frequency, or duration  surgery..

21. Intermittent Exotropia

22. Management of child with squint
History:
1. Birth: prematurity, method
2.Medicalproblem,developmental abnormality
3. Age of onset
4. Direction
5. Constant or intermittent
6. Association with fatigue.
7. Family history

23. Examination:
1- General appearance:
* craniofacial abnormality.
* abnormal head posture  to avoid diplopia
* epicanthal fold
2- Visual assessment:
* different techniques
* amblyopia
3- Corneal reflection test:
Pen torch, distance, symmetry, position
E.g.: if one reflex is nasally positioned then the eye is turned outward..

24. Corneal Reflex

25. 4- Cover test: distance & near
.. cover one eye & look for movement of the other eye to take up fixation.
5- Ocular movements: should be tested in different directions of gaze..
6- Cycloplegic Refraction
7- Dilated Fundus Examination

26. Cover Test

27. Treatment:
1- Full cycloplegic correction of refractive errors.
2- Treatment of Amblyopia (vision ↓ but no apparent ocular pathology)
.. By occlusion of the “Good” eye
3- Surgery frequently needed to restore alignment & achieve binocular vision.
* Strengthening & Weakening procedures of the extraocular muscles
E.g.: Esotropia: 
MR. Recession, LR. Resection

28. Amblyopia Definition:
•Loss of the visual acuity, •in one or both eyes, •without identifiable organic lesion of the visual pathways, •occurring during the critical period of early visual development..

29. Aetiology:
1- Stimulus Deprivation: lesion obstructing the visual axis, e.g.: congenital cataract, ptosis, corneal opacity, vitreous hemorrhage, padding..
2- Strabismus..
3- Anisometropic (asymmetry of refractive error) – the more hypermetropic eye (or the least myopic)
4- Refractive: high degree of refractive error may result in bilateral amblyopia
The younger the age 
1- Amblyopia easier to occur
2- Amblyopia is more dense
3- Amblyopia is easier to reverse (treat)

30. Pathology:
Few human data
Atrophy of cells in LGN and visual cortex serving the amblyopic eye..
These changes may be partially or wholly reversed if the amblyopia is successfully treated..

31. Early discovery is important
Diagnosis:
Early discovery is important
Chance of successful management is much reduced after age 6-9 years
Child objects occlusion of one eye but not the other
Crowding Phenomenon: VA is better when the test letter is presented singly rather than in row with other letters.
Neutral density filter: when put in front the normal eye, the VA is reduced, but if put in front of amblyopic eye, VA is either unchanged or even slightly improves..

32. Rule out any organic lesion e.g.: Macular scar.
Management:
Rule out any organic lesion e.g.: Macular scar.
Define the underlining cause and correct it, e.g.: removal of cataract, full correction of refractive error
Patching of the sound eye
Usually part time (few hours a day)
Duration depends on age, 1week/1year age
6 years old child  6 weeks
Beware of inducing amblyopia to the sound eye..
Alternative to patching:
a. Density filters
b. Atropine eye drops
c. Incomplete or no correction of refractive error of the better eyes..

33. Patching method