Squint ,types,heterophoria.pptx..........

1st part of squint

1. STRABISMUS Caption

2. Definition A misalignment of the visual axes of the two eyes is called squint or strabismus. Normally, visual axis of the two eyes are parallel to each other in the ‘primary position of gaze’ and this alignment is maintained in all positions of gaze.

3. Directions of deviation .esotropia .exotropia .hypertropia .hypotropia .Incyclotropia .Excyclotropia

4. 1. Pseudoesotropia or apparent convergent squint may be associated with: • Prominent epicanthal fold (which covers the normally visible nasal aspect of the globe and gives a false impression of esotropia). • Negative angle kappa. 2. Pseudoexotropia or apparent divergent squint may be associated with: • Hypertelorism, a condition of wide separation of the two eyes (i.e., wide IPD), and • Positive angle kappa. PSEUDOSTRABISMUS In pseudostrabismus (apparent squint), the visual axes are in fact parallel, but the eyes seem to have a squint:

5. Orthotropia : This is the condition where the eyes are perfectly aligned and remain so without needing muscular effort or compensation . It is the natural state of alignment of the eyes, with no tendency for deviation either at rest or during binocular vision. Orthophoria : This is a condition where the eyes are naturally aligned when at rest, but this alignment is maintained due to muscle balance and control . The eyes would deviate if binocular vision is disrupted (like covering one eye), but under normal circumstances, they stay straight. It’s a latent condition where the tendency to misalign is held in check by the brain’s fusion mechanism. Some Terminologies

6. DIPLOPIA CONFUSION Seen in Small angle squint Large angle squint Image formation Two images of same object formed at non-corresponding point in both retina Two images of two different objects due to both eyes looking at different direction Motor adaptation Fusion extra work performed by extraocular muscles to overcome small angle deviation Change in head posture Sensory adaptations Anamolous retinal correspondence formation of new correspondence points with deviation up to 5° Supression of visual sensory impulse from the deviated eye, causing Amblyopia(lazy eye) Consequences of squint

7. tendency of the eyes to deviate is kept latent by fusion. when the influence of fusion is removed the visual axis of one eye deviates away. Heterophoria/latent squint

8. Types of heterophoria Esophoria or latent convergent squint Exophoria or latent divergent squint Hyperphoria Cyclophoria

9. Etiology 1. Orbital asymmetry. 2. Abnormal interpupillary distance (IPD). A wide IPD is associated with exophoria and small with esophoria. 3. Faulty insertion of extraocular muscle. 4. A mild degree of extraocular muscle weakness. 5. Anomalous central distribution of the tonic innervation of the two eyes. 6. Anatomical variation in the position of the macula in relation to the optical axis of the eye. ANATOMICAL factor

10. Etiology PHYSIOLOGICAL factor 1. Age . Esophoria is more common in younger age group as compared to exophoria which is more often seen in elderly. 2. Role of accommodation . Increased accommodation is associated with esophoria (as seen in hypermetropes and individuals doing excessive near work) and decreased accommodation with exophoria (as seen in simple myopes). 3. Role of convergence . Excessive use of convergence may cause esophoria (as occurs in bilateral congenital myopes) while decreased use of convergence is often associated with exophoria (as seen in presbyopes). 4. Dissociation factor such as prolonged constant use of one eye may result in exophoria (as occurs in individuals using uniocular microscope and watch makers using uniocular magnifying glass).

11. Symptoms Compensated no subjective symptoms. Compensation of depends upon the reserve neuromuscular power to overcome the muscular imbalance and individual’s desire for maintenance of binocular vision. Divided into Decompensated Headache,eye ache, difficulty in changing the focus, photophobia, blurring of vision, intermittent diplopia, intermittent squint, defective postural sensation

12. EXAMINATIOM Testing for vision and refractive error It is most important, because a refractive error may be responsible for the symptoms of the patient or for the deviation itself. Preferably, refraction should be performed under full cycloplegia, especially in children.

13. EXAMINATIOM Cover uncover test one eye is covered with an occluder and the other is made to fix an object. In the presence of heterophoria, the eye under cover will deviate. After a few seconds, the cover is quickly removed and the movement of the eye (which was under cover) is observed. Direction of movement of the eyeball tells the type of heterophoria (e.g., the eye will move outward in the presence of esophoria) and the speed of movement tells whether recovery is slow or rapid.

14. EXAMINATION The prism and cover test (prism bar cover test i.e., PBCT) Prisms of increasing strength with apex towards the deviation are placed in front of one eye and the patient is asked to fixate an object with the other. The cover-uncover test is performed till there is no recovery movement of the eye under cove r. This will tell the amount of deviation in prism dioptres. Both heterophoria as well as heterotropia can be measured by this test.

15. EXAMINATIOM Maddox rod test Maddox rod (which consists of many glass rods of red colour set together in a metallic disc) is placed in front of one eye with axis of the rod parallel to the axis of deviation The Maddox rod converts the point light image into a line . Thus, the patient will see a point light with one eye and a red line with the other. Due to dissimilar images of the two eyes, fusion is broken and heterophoria becomes manifest

16. From right eye, he will see vertical beam of light and from left eye, he will see A light source Here, both fused Here, crossed Here uncrossed

17. From right eye, he will see Horizontal beam of light and from left eye, he will see A light source

18. Examination It can be done with the help of a synoptophore or prism bar. The normal values of fusional reserve are as follows: • Vertical fusional reserve: 1.5°–2.5° • Horizontal negative fusional reserve (abduction range): 3°–5 ° • Horizontal positive fusional reserve (adduction range) : 20°–40°. Measurement of fusional reserve

19. Examination Important in planning the management of heterophoria Near point of convergence and Near point, accommodation is measured Measurement of convergence and accommodation

20. Treatment indicated mainly in patients with decompensated heterophoria 1. Correction of refractive error when detected, is most important. It may correct the phoria and/or relieve the symptoms. 2. Orthoptic treatment. It is indicated in patients with heterophoria without refractive error and in those where heterophoria and/or symptoms are not corrected by glasses. Aim of orthoptic treatment is to improve convergence insufficiency and the fusional reserve. Orthoptic exercises can be done with synoptophore. Simple exercises to be carried out at home should also be taught to the patient.

21. Treatment 3. Prescription of prism in glasses. It may be tried in selected cases of hyperphoria and in troublesome cases of esophoria and exophoria. Prism is prescribed with apex towards the direction of phoria to correct only half or at the most two-thirds of heterophoria. 4. Surgical treatment. It is undertaken in patients with marked symptoms which are not relieved by other measures. Aim of the surgical management is to strengthen the weak muscle or weaken the strong muscle.

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