Squint Share DIVERGENT STRABISMUS - Copy.pptx

Strabismus
Squint

1. DIVERGENT STRABISMUS

2. DIVERGENT STRABISMUS/EXOTROPIA Exotropia is characterised by outward deviation of one eye while other eye fixate. TYPES C ongenital exotropia /Infantile exotropia Primary exotropia Sensory/secondary strabismus Consecutive exotropia XT of divergent excess type.

3. CONGENITAL EXOTROPIA It is an extremely rare condition Infantile exotroia has been defined as large(>30 d) constant exotropia that develops during first 6 to 12 months of life. Size of the angle may increase over time. Chance for amblyopia is much greater in this exotropia.

4. SYMPTOMS OF INFANTILE EXOTROPIA Cosmetic disfigurement. SIGNS OF INFANTILE XT Large angle constant exo deviation mostly more than 35 PD. Poor fusion Patient may have co existing craniofacial-ocular or systemic abnormality Eg; A lbinism, cerebral palsy,

5. TREATMENT OF INFANTILE XT Amblyopia therapy to be treated as early as possible Surgical procedure; recession of bilateral lateral rectus .

6. PRIMARY EXOTROPIA It may be unilateral or alternating and may present as intermittent or constant XT. INTERMITTENT XT It is the most common type of exodeviation . Age of onset is usually early between 2-5 years. Deviation become manifest at times and latent at others. Precipitating factors include bright lights, fatigue, ill health and day dreaming. Sensory testing usually reveals good fusion, stereopsis and no amblyopia.

7. CONSTANT XT If not treated in time the intermittent XT may decompensate to become constant XT. TYPES Convergence insufficiency type : XT greater for near than distance. Divergent excess type: XT greater for distance than near. Basic or non-specific type: XT equal for near and distance

8. It usually starts at the age of 2 yrs & associated with normal fusion and no amblyopia. Stereopsis is usually absent.

9. SENSORY/ SECONDARY STRABISMUS It is a constant unilateral condition that develops as a result of poor visual function in one eye. Common causes are traumatic cataract, unilateral aphakia , corneal opacity, optic atrophy, anisometropic amblyopia, retinal detachment, organic macular lesions and any other organic cause of unilateral loss of vision.

10. CLINICAL FEATURES Monocular vision loss Cosmetic complaints SIGNS Large angle(30-60PD) unilateral strabismus. VA is decreased in the affected eye There may be relevant history of congenital cataract, ROP, trauma etc.

11. TREATMENT Surgery

12. CONSECUTIVE XT It refers to occurrence of XT in an eye which was previously esotropic . CLINICAL TYPES Surgical overcorrection of esotropia. Spontaneous consecutive exotropia is change of esotropia into exotropia without exogenous mechanical factors or an acquired paralysis of medial rectus muscle. Hypermetropia >+4.50D is the srongest risk factor for the non-surgical development of XT,

13. SYMPTOMS Cosmetic problems. Diplopia is rare, but it may occurs in the strabismus deviation changes in adulthood. SIGNS Moderate to large angle usually constant exotropia is present. The deviation may not be concomitant if the patient had prior surgery. There may be H/O infantile esotropia that may have been treated surgicaly .

14. TREATMENT Reduction of the hyperopic correction or the use pf overcoorecting minus lenses (it stimulate accommodation). Surgery.

15. XT OF DIVERGENT EXCESS TYPE It is an intermittent XT whose angle of deviation at distance is atleast 10-15PD grater than at near. SYMPTOMS Photophobia Cosmetic problems Asthenopic symptoms and diplopia are rare.

16. SIGNS A concomitant XT is greater at distance than at near. An XT of V-pattern may be present. When eyes are in orthoposition , patients generally exhibits normal retinal correspondence, good steriopsis and good NPC. When the deviation is present either NRC with suppression or ARC.

17. TREATMENT Vision therapy or surgery.

18. A-V PATTERN Horizontal deviations (esotropia & exotropia) which may be comitant in horizontal gazes, may not be comitant in vertical gazes, on looking up and looking down. They are said to be ‘vertically incomitant-comitant horizontal deviations’. In simpler terms they are described as A-V pattern. Thus an exodeviation , which becomes more divergent in up gaze and less divergent in down gaze is said to have a ‘V’ pattern. An eso deviation with ‘V’ pattern would be more converge in down gaze and less converge in up gaze.

19. The reverse is ‘A’ pattern. In addition to these four common patterns, other patterns are also seen there.

20. 1 A - EXOTROPIA Exo deviation more in down gaze & less in up gaze 2 A - ESOTROPIA Eso deviation more in up gaze and less in down gaze 3 V - EXOTROPIA Exodeviation more in up gaze & less in down gaze 4 V – ESOTROPIA Eso deviation more in down gaze & less in up gaze 5 X - EXOTROPIA No deviation/ only a small one in primary position, but a significant XT is present in up gaze as well as in down gaze. 6 Y – EXOTROPIA Exotropia only in up gaze 7 λ – EXOTROPIA Exotropia only in down gaze 8 E - EXOTROPIA (DIAMOND) Exodeviation is more in primary position only and not in the up and down gaze.

21. M

22. ETIOLOGY 1. HORIZONTAL SCHOOL It says the role of horizontal recti by assuming that the lateral recti are more effective in up gaze and medial recti are more effective in down gaze. So overaction of the lateral recti causes V- exptropia and underaction of medial recti causes A- exotropia.

23. PATTERN CAUSE V- EXOTROPIA OVERACTION OF LR V- ESOTROPIA OVERACTION OF MR A- EXOTROPIA UNDERACTION OF MR A-ESOTROPIA UNDERACTION OF LR

24. V PATTERN EXO TROPIA

25. V PATTERN ESOTROPIA

26. A -PATTERN EXOTROPIA

27. A -PATTERN

28. V PATTERN

29. 2. STRUCTURAL FACTORS Variation of skull and orbital bones are known to have underaction or overaction of oblique muscle. This may be due to variations in the site of origin or insertion of inferior oblique or superior oblique.

30. 3. ANOMALIES OF MUSCLE INSERTION Anomalies of insertion of vertical and horizontal rectii or oblique muscle are also known to cause A-V pattern 4. VERTICAL SCHOOL It says the role of vertical rectii , in the etiology of A-V pattern The principle behind being the adducting property of vertical recti. Thus weak SR would result in less adducting power in upgazes causing a V- pattern.

31. Since the action of vertical recti and oblique muscles are linked inseperably . Thus underaction of SR would have underacting SO ( ipsilateral antagonist of contralateral synergist). It is also called as cycloverical school.

32. OVERACTING MUSCLE & PATTERN CAUSED OVERACTING MUSCLE UNDERACTING MUSCLE PATTERN CAUSED IR, IO SR, SO V- PATTERN SR, SO IR, IO A- PATTERN

33. INVESTIGATION Horizontal deviations are measured in 25* upgaze and 35* downgaze in addition to primary position. A 15 PD difference is taken as significant for V- pattern and 10PD difference is taken as significant for A-pattern.

34. Treatment Pre Treatment Evaluation Detailed History Assessment of BCVA Cycloplegic Refraction and correction Measurement of angle of deviation in all the 9 positions of gaze for near and far, with and without optical correction Uniocular and binocular motility.

35. If the pattern is significant and syptomatic it needs to be operated. all cases of exodeviations & esodeviations should be checked for A & V patterns. In case of muscles over action , it should be weakened In case of muscles under action , it should be strengthen.