Strabismus-Clinical Examinations

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<p>STRABISMUS Classification and Examination</p> <p>STRABISMUSClassification and ExaminationDr.Puskar GhoshPGTBurdwan Medical CollegeStrabismus: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</p> <p>PHORIA:latent visual axis deviation,held in check by fusion.</p> <p>TROPIA:a manifest visual axis deviation.</p> <p>Intermittent Tropia:deviation may exist in only certain gaze positions or target distance.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.</p> <p>Extraocular muscles:</p> <p> of the eye:Uniocularly-DuctionBinocularly-Version.-Same directionOpposite direction-VergenceAdduction-nasally horizontalAbduction-temporally horizontalSursumduction or elevation-upwardDeorsumduction or depression-downwardIncycloductionExcycloduction</p> <p>Eye movements:</p> <p>Yoke musclesFor co ordinated eye movements one muscle of the each eye act togather.These are called yoke muscle.Herings law,for a binocular movement the corresponding muscle (yoked) receive equal and simultaneous innervation.Sheringtons law of reciprocal innervation,for any binocular movement the direct antagonist receives an equal and simultaneous inhibition of its innervation.</p> <p>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.</p> <p>Correspondence:</p> <p>Grades of BSV:Simultaneous perception</p> <p>Fusion</p> <p>Stereopsis</p> <p>Ability to fuse points outside corresponding retinal areaAbility to fuse image projected in corresponding retinal pintsAbility of perception of depthBinocular vision and Squint:Confusion-due to different image viewed by two foveaImmediately checked by cortical or retinal rivalry mechanism.</p> <p>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 eyeMonocular diplopia-in astigmatism,neurological conditionsUncrossed diplopia-esodeviationCrossed diplopia-exodeviation</p> <p>Adaptation Mechanisms:Motor Adaptation:FusionBeyond fusional reserve-asthenopia</p> <p>Head posturesChin elevation or depressionFace turn Head tilt </p> <p>3. Blind spot mechanism: esotropia of 15,other image fallsOn blind spot-no diplopia.</p> <p>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.FacultativeObligatoryAnomalous 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.</p> <p>orthophoria ; perfect alignment of the visual axes. Most individuals have heterophoria.</p> <p>Hypophoria/hypertropia; latent/manifest squint downwards turning of eyes</p> <p>Hyperphoria/hypertropia; latent/manifest squint upwards turning of eyes</p> <p>Exophoria; latent squint outwards turning of the eyesExotropia; manifest squint outwards turning of the eyes</p> <p>Esophoria; latent squint inwards turning of the eyesEsotropia; manifest squint inwards turning of the eyes</p> <p>Classification: StrabismusConcomitant:deviation same in all gazeIncomitant:inequal deviationHorizontalEsotropiaExotropiaVerticalHypertropiaHypotropiaTorsionalIncyclotropiaExcyclotropiaUnderactionOveractionRestrictiveParalyticNeurogenicSupraneuclearInfraneuclearNeuclearMyogenicDIFFERENCE INCOMITANTCONCOMITANTAgeLateearlyMagnitude of squintVaries with eye positionSame in all gazesDiplopiaPresentUsually absentOnsetSuddenGradualPrecipitating eventHead injuryRareHead posturePresentAbsentSecondary deviation&gt;primary=primaryOcular movementRestrictedFullFalse projectionPresentAbsentMechanismDefect in efferent pathwayDefect in afferent pathOr central mechanismSensory adaptationRarefrequentCyclotropiaUsually presentAbsent (expt A,V patterns)Clinical Evaluation:History:H/O present illness- Age of onsetDuration of the squintChief Complaints:Symptoms-Asthenopia:UniocularBinocularOnset:Recent onset squint manifested with DiplopiaPast pointingVertigoProstration</p> <p>Diplopia:Diplopia may not be complained of in case of adoption of head postureOr,when sensory adaptation occurs.Decompensation of pre existing heterophoria-diplopia of intermittent onset.Recent onset acquired squint-sudden onset diplopia.Type of diplopia-horizontal,cycloverticalDirection of gaze in which it predominantWhatever BSV is retainedCosmetic defects:Whether the defect is Intermittent or constantWhether unilateral or alternatingHead Posture.Precipitating factor:like injury,illness,shock.Past medical historyDevelopmental 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/occlusionSurgery for squint One or both eye Which muscle How much What Sx.</p> <p>Birth HistoryAntenatal history-drugs taken/illness during pregnancyGestational age &amp; birth weight at deliveryType and length/problem during labour.Family history</p> <p>EXAMINATION:Visual Acuity:In Preverbal Children- Fixation and followingComparison between behavior of the two eyes.Fixation Behavior10 testRotation test Preferential lookingTeller Acuity cardsCardiff Acuity cardsVEP</p> <p>Verbal children:2 years:picture naming (crowded Kay picture)</p> <p>3 years:matching the letter optotypes (Keelaer logMar)</p> <p>B.RefractionC.Examination of Anterior and Posterior chamberLid problems,ptosis,media opacities</p> <p>Pupillary reflexes</p> <p>Fundus</p> <p>D.Tests for stereopsis:SynoptophoreTNO test:480-15 sec of arcFrisby:600-15 sec of arcLang:200-1200 sec of arc</p> <p>Test for fusion:Synoptophore</p> <p>Jl.j24E.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 DeviationBy ordinary mm scaleSynoptophore</p> <p>What to see?DirectionFrequencyMagnitudeComitancyLateralityAC/A ratio</p> <p>Ocular Alignment tests:Cover Tests:Prerequisites:Ability to fixate the targetHave central fixationNo gross/severe mobility defects</p> <p>Alternate Cover Cover uncover testPrism Bar Cover tests</p> <p>abCover Uncover test for tropia:</p> <p>Prism Bar Cover test</p> <p>Corneal light reflex tests:Hirschberg test:</p> <p>Krimsky test</p> <p>A pen-torch is shone into the eyes from arms 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).</p> <p>placement of prisms in front of the fixating eye until the corneal light reflections are symmetrical Hirschberg testNo obvious squintManifest squintCover test(either eye)Cover test(fixing eye)Other eye moves for fixationNo movementRemove coverSquint remains momentarily then alignedIntermittent Cover other eyeNo movementMovement fellow eyeUncover testCover eye straightenNo movementImmediate: latentSometime:intermittentAlternate coverLatent/intermitentNo movementMicrotropiaNext slide Cover Test(fixing eye)Other eye remain deviatedBlind eyeEccentric fixationImmobilePseudosquintOther eye moves for fixationRemove coverEye deviate againEye remain straight,other eye deviatesManifest constant squintManifest alternating squintPseudosquint:Epicanthic folds-esotropia Abnormal interpupillary distance- short:esotropia wide:exotropia Angle kappa Positive:exotropia Negative:fovea is situated nasal to the posterior pole (high myopia and ectopic fovea):esotropia</p> <p>Subjective test of deviation:Maddox wing test</p> <p>Maddox rod test:</p> <p>Maddox Double PrismUsed in case of cyclodeviation</p> <p>Two prism of 4pdPt 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.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.</p> <p>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.Grading:Adduction:Normal-if nasal 1.3rd of the cornea crosses the lower punctumAbduction: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.</p> <p>Near point convergence:nearest point on which the Pt. can maintain binocular fixationNear Point of accomodation:nearest point on which the eyes can maintain clear focus</p> <p>RAF RuleFusional 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. F.Examination of Sensory status:Test for supression- Worth 4 dot test:Four dots-NRC/HARCFive Dots-Esodeviation-uncrossed (red on right)Exodeviation-crossed(red on left)Vertical-vertically displacedThree green Dots-Supression of Rt.eye.Two red dots-Supression of left eye.</p> <p>Bagalinis striated glass test:</p> <p>Symetrical cross-NRC or ARC of Harmonious typeAsymetrical Cross-incomitant squint with NRCSingle line-supression of the other eyeCross with gap-central supression scotoma</p> <p>C.4 Prism test:</p> <p>In bifoveal fixationIn MicrotropiaD.After Image Testing:Flash-horizontal-REVertical-LEResponse:Cross-NRC(irrespective of deviation)Asymmetrical crossing-ARCAmount of separation depends on angle of anomaly.</p> <p>Tests for Paralytic squint:Past Pointing:</p> <p>Measurement of Deviation:Diplopia charting:</p> <p>Image is separated by red green glass.To quantify the separation between the double imageMaximum separation-field of action of paralytic muscleHess/Lees charting:</p> <p>Forced duction Test:</p> <p>AnaesthesiaSupine positionLids retractedPt is asked to look in the direction of the muscle being tested (to relax antagonist)Eye is held in the limbusRotated in the direction of action of the muscleMoves freely-negativeRestricted-positivePush posteriorly-false +ve for recti,desired for obliques.Parks Three steps test: (for 4th nv palsy)1.Assess which eye is hypertropic in primary position.</p> <p>2.Any increase in hypertropia in horizontal gaze3.Bielschowsky Head tilt test:to see if any increase of hypertropia on tilting of head to any side</p>