Strabismus-Clinical Examinations

A vast topic of examination methods of squint cases,with few highlights on the basic fundas.

1. STRABISMUS Classification and Examination Dr.Puskar Ghosh PGT Burdwan M edical C ollege

2. Strabismus: It is a condition in which the visual axis of the two eyes does not meet at the point of regard. Greek word-” strabos ”:crooked PHORIA : latent visual axis deviation,held in check by fusion. TROPIA : a manifest visual axis deviation. Intermittent Tropia : deviation may exist in only certain gaze positions or target distance.

3. Visual axis (line of vision) : extending from the point of fixation to the fovea. Anatomical (Pupillary) axis :is a line passing from the posterior pole through the centre of the cornea . Angle kappa : is the angle subtended by the visual and anatomical axes . +5 ˚ exotropic .

4. Extraocular muscles: 5.5 6.6 7.0 7.7

5. Movements of the eye: U niocularly-Duction Binocularly-Version.-Same direction Opposite direction- Vergence Adduction-nasally horizontal Abduction-temporally horizontal Sursumduction or elevation-upward Deorsumduction or depression-downward Incycloduction Excycloduction

6. Eye movements: Yoke muscles For co ordinated eye movements one muscle of the each eye act togather.These are called yoke muscle . Hering’s law,for a binocular movement the corresponding muscle (yoked) receive equal and simultaneous innervation . Sherington’s law of reciprocal innervation ,for any binocular movement the direct antagonist receives an equal and simultaneous inhibition of its innervation.

7. Binocular vision: Definition: It is the state of simultaneous vision with two seeing eyes that occurs when a person fixes his visual attention on an object of regard.

8. Correspondence:

9. Grades of BSV: Simultaneous perception Fusion Stereopsis Ability to fuse points outside corresponding retinal area Ability to fuse image projected in corresponding retinal pints Ability of perception of depth

10. Binocular vision and Squint: Confusion- due to different image viewed by two fovea Immediately checked by cortical or retinal rivalry mechanism. Diplopia- one object is perceived by one of the fovea of one eye and other object is perceived by extrafoveal point of the other eye which has a different localization value in space . Binocular diplopia- single image on closing one eye Monocular diplopia- in astigmatism,neurological conditions Uncrossed diplopia- esodeviation Crossed diplopia- exodeviation

11. Adaptation Mechanisms: Motor Adaptation: Fusion Beyond fusional reserve- asthenopia Head postures Chin elevation or depression Face turn Head tilt 3. Blind spot mechanism: esotropia of 15 ˚, other image falls On blind spot-no diplopia.

12. Adaptation Mechanism: Sensory Adaptation: Supression : Confusion is takled by foveal rivalry which is actually a suppression . extrafoveal image suppression is readily occurs if the visual potential of the extrafoveal point is poor. Facultative Obligatory Anomalous Retinal Correspondence: It is the binocular functional adaptation to strabismus at the cortical level.The fovea of the fixing eye develops a correspondence (binocular relationship) with an extrafoveal point of the other eye.

13. orthophoria ; perfect alignment of the visual axes. Most individuals have heterophoria . Hypophoria / hypertropia ; latent/manifest squint downwards turning of eyes Hyperphoria / hypertropia ; latent/manifest squint upwards turning of eyes Exophoria ; latent squint outwards turning of the eyes Exotropia ; manifest squint outwards turning of the eyes Esophoria ; latent squint inwards turning of the eyes Esotropia ; manifest squint inwards turning of the eyes

14. Classification: Strabismus Concomitant:deviation same in all gaze Incomitant:inequal deviation Horizontal Esotropia Exotropia Vertical Hypertropia Hypotropia Torsional Incyclotropia Excyclotropia Underaction Overaction Restrictive Paralytic Neurogenic Supraneuclear Infraneuclear Neuclear Myogenic

15. DIFFERENCE INCOMITANT CONCOMITANT Age Late early Magnitude of squint Varies with eye position Same in all gazes Diplopia Present Usually absent Onset Sudden Gradual Precipitating event Head injury Rare Head posture Present Absent Secondary deviation >primary =primary Ocular movement Restricted Full False projection Present Absent Mechanism Defect in efferent pathway Defect in afferent path Or central mechanism Sensory adaptation Rare frequent Cyclotropia Usually present Absent ( expt A,V patterns)

16. Clinical Evaluation: History: H/O present illness- Age of onset Duration of the squint Chief Complaints: Symptoms- Asthenopia : Uniocular Binocular Onset: Recent onset squint manifested with Diplopia Past pointing Vertigo Prostration

17. Diplopia: Diplopia may not be complained of in case of adoption of head posture Or,when sensory adaptation occurs. Decompensation of pre existing heterophoria -diplopia of intermittent onset. Recent onset acquired squint-sudden onset diplopia. Type of diplopia- horizontal,cyclovertical Direction of gaze in which it predominant Whatever BSV is retained

18. Cosmetic defects: Whether the defect is Intermittent or constant Whether unilateral or alternating Head Posture. Precipitating factor :like injury,illness,shock . Past medical history Developmental history (children with cerebral palsy) H/O glass- Regularity of use Power of the glass Proper cycloplegia for correction for his age. Use of prisms/convergence exercise/occlusion Surgery for squint One or both eye Which muscle How much What Sx .

19. Birth History Antenatal history-drugs taken/illness during pregnancy Gestational age & birth weight at delivery Type and length/problem during labour . Family history

20. EXAMINATION: Visual Acuity: In Preverbal Children- Fixation and following Comparison between behavior of the two eyes. Fixation Behavior 10 ∆ test Rotation test Preferential looking Teller Acuity cards Cardiff Acuity cards VEP

21. Verbal children: 2 years:picture naming (crowded Kay picture) 3 years:matching the letter optotypes ( Keelaer logMar )

22. B.Refraction C.Examination of Anterior and Posterior chamber Lid problems,ptosis,media opacities Pupillary reflexes Fundus

23. D.Tests for stereopsis: Synoptophore TNO test:480-15 sec of arc Frisby:600-15 sec of arc Lang:200-1200 sec of arc

24. Test for fusion: Synoptophore

25. E.Examinations of the Motor status: Head posture: To be noted when pt is unconcious about it. Eye is out of the field of action. Ocular Deviation By ordinary mm scale Synoptophore What to see? Direction Frequency Magnitude Comitancy Laterality AC/A ratio

26. Ocular Alignment tests: Cover Tests: Prerequisites: Ability to fixate the target Have central fixation No gross/severe mobility defects Alternate Cover C over uncover test Prism Bar Cover tests a b

27. Cover Uncover test for tropia : Prism Bar Cover test

28. Corneal light reflex tests: Hirschberg test: Krimsky test A pen-torch is shone into the eyes from arm’s length and the patient asked to fixate the light. The distance of the corneal light reflection from the centre of the pupil is noted; each mm of deviation is approximately equal to 7° (one degree ≈ 2 prism dioptres ). placement of prisms in front of the fixating eye until the corneal light reflections are symmetrical

29. Hirschberg test No obvious squint Manifest squint Cover test(either eye) Cover test(fixing eye) Other eye moves for fixation No movement Remove cover Squint remains momentarily then aligned Intermittent Cover other eye No movement Movement fellow eye Uncover test Cover eye straighten No movement Immediate: latent Sometime:intermittent Alternate cover Latent/ intermitent No movement Microtropia Next slide

30. Cover Test(fixing eye) Other eye remain deviated Blind eye Eccentric fixation Immobile Pseudosquint Other eye moves for fixation Remove cover Eye deviate again Eye remain straight,other eye deviates Manifest constant squint Manifest alternating squint

31. Pseudosquint : Epicanthic folds - esotropia Abnormal interpupillary distance - short:esotropia wide:exotropia Angle kappa Positive:exotropia N egative:fovea is situated nasal to the posterior pole (high myopia and ectopic fovea ): esotropia

32. Subjective test of deviation: Maddox wing test

33. Maddox rod test:

34. Maddox Double Prism Used in case of cyclodeviation Two prism of 4pd Pt looks at a horizontal line (other eye ocluded ) two lines,parellal but shifted vertically from each other. Pt opens other eye (not have double prism) Line in between above two lines.

35. Motility Tests: Versions towards the eight eccentric positions of gaze are tested by asking the patient to follow a target. A quick cover test is performed in each position of gaze to confirm whether a phoria has become a tropia or the angle has increased and the patient is questioned regarding diplopia . Ductions are assessed if reduced ocular motility is noted in either or both eyes. The fellow eye is occluded and the patient asked to follow the torch into various positions of gaze .

36. Grading: Adduction: Normal-if nasal 1.3 rd of the cornea crosses the lower punctum Abduction: Normal-if temporal limbus touches the lateral canthus. Oblique overaction - Angle of adducting eye makes with horizontal line as it elevates,abducts on lateral version to opposite side.

37. Near point convergence: nearest point on which the Pt. can maintain binocular fixation Near Point of accomodation : nearest point on which the eyes can maintain clear focus RAF Rule

38. Fusional Vergence : It determines the capability of the motor system to cope with an induced misalignment of visual axes.If it is large,even a large angle squint remains latent. They may be tested with prisms bars or the synoptophore . An increasingly strong prism is placed in front of one eye, which will then abduct or adduct (depending on whether the prism is base-in or base-out), in order to maintain bifoveal fixation. When a prism greater than the fusional amplitude is reached, diplopia is reported or one eye drifts the other way, indicating the limit of vergence ability.

39. F.Examination of Sensory status: Test for supression - Worth 4 dot test: Four dots -NRC/HARC Five Dots- Esodeviation - uncrossed (red on right) Exodeviation -crossed (red on left) Vertical-vertically displaced Three green Dots- Supression of Rt.eye . Two red dots- Supression of left eye.

40. Bagalini’s striated glass test: Symetrical cross-NRC or ARC of Harmonious type Asymetrical Cross- incomitant squint with NRC Single line- supression of the other eye Cross with gap-central supression scotoma

41. C.4∆ Prism test: In bifoveal fixation In Microtropia

42. D.After Image Testing: Flash- horizontal-RE Vertical-LE Response: Cross-NRC(irrespective of deviation) Asymmetrical crossing-ARC Amount of separation depends on angle of anomaly.

43. Tests for Paralytic squint: Past Pointing:

44. Measurement of Deviation: Diplopia charting: Image is separated by red green glass. To quantify the separation between the double image Maximum separation-field of action of paralytic muscle

45. Hess/Lees charting:

46. Forced duction Test: Anaesthesia Supine position Lids retracted Pt is asked to look in the direction of the muscle being tested (to relax antagonist) Eye is held in the limbus Rotated in the direction of action of the muscle Moves freely-negative Restricted-positive Push posteriorly-false + ve for recti,desired for obliques .

47. Park’s Three steps test : (for 4 th nv palsy) 1.Assess which eye is hypertropic in primary position. 2.Any increase in hypertropia in horizontal gaze 3.Bielschowsky Head tilt test:to see if any increase of hypertropia on tilting of head to any side