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squint evaluation new.pptx
- 1. Dr. Ritu Chaturvedi HOD,Departmentof Ophthalmology SRVS Medical College
- 2. ⚫Strabismus is misalignmentof eyes. ⚫GOALS OF STRABISMUS EVALUATION • To find the etiology of strabismus • To assess the binocular status • To measure the amount of deviation • To diagnose amblyopia, • To define a plan of management. ⚫
- 3. ⚫A strabismus patientmay be examined in the following order: • Eliciting a detailed history • Visual acuity assessment • Cycloplegic refraction • Fundus examination • Sensory tests • Measurement of deviation • Ocular motility examination • Special tests for specific diagnosis
- 4. ⚫requires special typesofequipments ⚫
- 5. HISTORY ⚫Presenting complaintsshould berecorded in the patient’swords. ⚫The age of onset and duration of squint is very important for the prognosis regarding attainmentand maintenanceof binocularsinglevision. ⚫Whether thedeviation is intermittentorconstant, unilateral or alternating has to beasked ⚫History of treatment taken in the past like spectacles, patching, previous surgery (for strabismus ,glaucoma implant, retinal detachment, etc) should be noted.
- 6. ⚫Family historyshould betaken forpresence of hereditary formsof strabismus. ⚫historyof significant head posture, confirmed byold photographs, may indicate good binocularpotential. ⚫Antenatal and perinatal history is important forany squintappearing since birth. ⚫ A patientwith recentonsetof squint may presentwith diplopia, past-pointing, abnormal eye movementsand headache.
- 7. EXAMINATION ⚫General Inspection ofthe Patient Observationof thedegree and direction of squint. –Presence of wide nasal bridge with increased interpupillarydistanceand epicanthal foldswhich may be thecauseof pseudoesotropia, needs to be noted. – Observationof facial asymmetry. – Presence of an abnormal head posture is noted
- 8. ⚫ Upward ordownwardslanting of palpebral fissures. – Ptosis. – Any lid/conjunctival scarring. –Pupillary reactions are abnormal in patients with sensory deviation due to diseases of retina and the optic nerve ⚫ Assessment of Visual Acuity : In children above 5 years various Snellen’s charts can be used Media and fundus examination: ⚫ It is important to evaluate the eye for any organic abnormality that could be causing visual loss and secondaryor sensory strabismus.
- 9. ⚫It is thestarting point forevaluation forstrabismus. ⚫A refractiveerrorcould be the primary ora contributing causeof the strabismus. ⚫ Correction of the refractive error is paramount to the managementof strabismus. ⚫ It is performed at the end of strabismusexamination and preferably under full cycloplegia forchildren.
- 13. ⚫Assessment of Visionin Nystagmus near acuity targets visible with binocular viewing must be ascertained Before assessing monocular vision in nystagmus patients ⚫When assessing monocular vision, an occluder placed in front of one eye worsens the nystagmus and leads to a decline in visual acuity. ⚫ This decline can be avoided by high plus lenses by fogging or neutral density filters
- 14. ⚫Examination of squintcanbeconsidered in two aspects: a. Examination of sensory status b. Examination of motorstatus
- 15. ⚫ Sensory testingis an essential part of strabismus evaluation. Itcomprises theassessmentof the binocular status of theeyes ⚫ different sensory adaptations that can take place in response toclinical situations thatdisrupt binocularvision are ⚫ 1. Visually mature (occurring after thevisual system is mature) 2. Visually immature (occurring during visual development ) ⚫
- 16. ⚫Visually Mature:sensoryadaptationsoccurafter the developmentof bifoveal fusion, when the visual system is mature. ⚫Theseareassociated with normal retinal correspondence. ⚫ Visual neural development is said to mature by around 9 to 10 years of age. ⚫at this point there is not enough cortical plasticity foradaptations such as cortical suppressionand ARC
- 17. ⚫Diplopia: The patientswithdiplopia fixatewith one fovea, and suppress the foveaof thedeviated eye. ⚫Thediplopic imagescome from the perifoveal retinaof thedeviated eye. ⚫The foveal image from the fixing eye is perceived as being located directly in frontof the patient. ⚫while the perifoveal retinal image from thedeviated eye projects to itscorresponding visual field. ⚫
- 18. ⚫Exotropia causes theimage to fall temporal to the fovea, which projects to the nasal field producing “crossed diplopia” ⚫Esotropiacauses the image to fall on the nasal retina, which projects temporallyand causes “uncrossed diplopia “ ⚫
- 19. ⚫Confusion: Instead ofdiplopia, strabismicpatients with confusion perceive two different images superimposed on topof each other. ⚫Confusion iscaused by the simultaneous perceptionof twodifferent images from the two foveae thatare pointing todifferentobjects ⚫It is rarely seen clinically.
- 20. ⚫Rivalry: is acondition where a patient with normal binocularvision is presented with different images to corresponding retinal pointsof each eye. ⚫Instead of seeing twodifferent images superimposed on each other (confusion) ⚫the subject perceives patchydropoutof each image where the images binocularlyoverlap
- 22. ⚫The following sensoryadaptationsoccurwhenthe binocularity is disrupted during the first fewyears of life, usually before 8 to 10 yearsof age. ⚫Monofixation and suppression: Small angle strabismus (<10 PD), or mild to moderateunilateral retinal image blur, in young children and infants causes -a central suppressionscotomaof thedeviated or blurred eye, - central fixation of the preferred eye, - but peripheral fusion is maintained
- 23. ⚫It refers tothe ability of the sensory system to appreciate the perceived direction of the foveaand otherretinal elements in each eye relative to theother. ⚫The twoeyes havecorresponding retinal elements that haveacommonvisual direction ⚫The two foveae represent the highestdegree of correspondence ⚫Abnormal retinal correspondence (ARC) is a sensory adaptationof the immaturesensoryvisual system toan abnormal motorposition of theeye.
- 24. ⚫Worth’s Four DotTest: The patientwearsa red glass in front of right eye and a green glass in front of left eye. ⚫ He then viewsa boxwith four lights; one red, two green and onewhite
- 25. ⚫If all fourlightsare seen, normal fusion is present. •If all four lightsare seen in the presenceof a manifest deviation, ARC is present. • If twored lightsare seen, leftsuppression is present. •If threegreen lightsare seen, right suppression is present. • If twored and threegreen lightsare seen, diplopia is present. •If the red and green lightsalternate, alternating suppression is present.
- 27. ⚫Bagolini’s Striated Glasses:Each lens is covered with fine striations which convert a point source of light intoa line, similar to the Maddox rod. ⚫ The two lenses are placed at 45 degrees and 135 degrees in frontof each eyeand the patient fixatesa punctate light sourceplaced at 6 meteraway. ⚫
- 29. ⚫This is theleastdissociativeof all diplopia tests. Itpermitsdeterminationof whetherthe patient is: • Fusing • Suppressing oneeye • Suppressing centrallyonly • The typeof retinal correspondence present.
- 30. ⚫After Image Test:This testdemonstrates thevisual direction of the fovea. ⚫One fovea is stimulated byavertical bright flash of light and the felloweye is stimulated bya horizontal flash of light. ⚫Thevertical flash of light is harder tosuppressand should beapplied to thedeviating eye. ⚫ The patient then draws the relativepositionsof the after images.
- 31. ⚫Synoptophore: This isan instrument for - assessing strabismus, -Quantifying binocularsinglevision (BSV) -DetectsARC and suppression
- 32. ⚫Grades of binocularvision: Binocularvision isgraded on the basisof Synoptophore. ⚫Firstgrade–(simultaneous macularperception) is tested by introducing twodissimilar but not mutually antagonistic pictures. ⚫one picture is smaller than the other so that the smallerpicture is seen by the foveaof oneeyeand the larger picture is seen by the parafoveal area of the othereye.
- 33. ⚫Second grade–(fusion) isthe ability of the two eyes to produceacompositepicture from twosimilarpictures each of which is incomplete in one small different detail. ⚫Third grade–(stereopsis) is the ability to obtain an impression of depth by the superimposition of two picturesof the sameobjectwhich has been taken from slightlydifferentangles …
- 35. ⚫These tests useonefixation target that is seen by both eyes. Here wedisrupt fusion byobscuring or eliminating peripheral fusion clues, or providing different images toeach eye . .Diplopiacharting test • Maddox rod (Mostdissociating) • Worth fourdot test • Red filtertest • Bagolini’s lenses (leastdissociating)
- 36. ⚫ Diplopia test:Plotting of diplopia fields is indicated in patients complaining of confusion ordoublevision. ⚫ The patient is asked to wear red-green charting goggles; red in frontof the righteyeand green in frontof the lefteye. ⚫ The patient is made to sit with his head straight in a semi dark room and is shown a fine linear light fromadistanceof 4 feet. ⚫ The light is moved from primaryposition intoall of othereight directions of gaze. ⚫ For each direction, the patient is asked to comment on the position, brightness, separation between the red and green imagesand the relativeangleof one imageto theother.
- 39. ⚫ The Maddoxrod consists of a series of parallel glass cylinders of higher power (usually red color) set together in a metallicdisk. ⚫ The Maddox rod produces a linear imageof a point light, when viewed through the rod the line image is formed perpendicularto theaxis of thecylinders. ⚫ The rod is placed in front of the righteye. Thisdissociates the two eyes because the red streak seen by the right eye cannot be fused with the unaltered white light seen with the left eye. ⚫ does not differentiate between tropiaand phoria. ⚫
- 41. ⚫Maddox Wing Test:Maddox wing is an instrument by which the amount of heterophoria for near (1/3rd m) can be measured subjectively. ⚫ The instrument is constructed in such away that the right eye sees only a white vertical arrow and a red horizontal arrow, ⚫ whereas the lefteye sees the horizontal and vertical rowsof numbersonly
- 43. ⚫The horizontal deviationis measured by asking the patient towardswhich numberthewhitearrow points. ⚫Thevertical deviation is measured byasking the patients regarding the number the red arrow intersects. ⚫The amount of cyclophoria is measured by asking the patient to movethe red arrow so that it is parallel with the horizontal rowof numbers.
- 44. ⚫Itutilizes the principleofHering’s lawof equal innervation. ⚫The test is performed with each eye fixating in turn. The patient wears the red and green dissociating glasseswith the red glass overright eye. ⚫ sits at 50 cm from an illuminated screen on which each red targetcan be lit up in turn and its position indicated by the patientusing a lineargreen light. ⚫In orthophoria, the two lights are more or less superimposed in all nine positions of gaze. The relativepositionsareconnected with straight lines. ⚫
- 46. ⚫Lee’s Screen: Theapparatus consists of two opalescent glass screens at right angles to each other, bisected by a twosided plane mirrorwhich dissociates the twoeyes. ⚫
- 47. ⚫Interpretation of Hess/Lee'sScreen Test • The twochartsare compared. •The smallerchart indicates theeyewith the paretic muscle. •The largerchart indicates theeyewith theoveracting muscle. •The smallerchartshows itsgreatest restriction in the main direction of action of the paretic muscle. •The largerchartwill shows its expansion in the main directionof action of theyoke muscle.
- 49. Theexaminationof motorstatus includes: 1)Headposture 1) Measurementof oculardeviation 2)Limitationof ocular movements 4)Fusional vergences
- 50. ⚫Head posture hasthreecomponents: a. Chin elevationordepression (vertical) b. Face turn to the right or leftside (horizontal) c. Head tilt to the right or leftshoulder (torsional). ⚫These three components at three different joints between the head and the neck correct for the motility disturbances in the threedimensions ⚫The patientchooses the head posture where theoculardeviation is least, theocular alignment is maximumand where the imagescan be fused.
- 52. ⚫ Light ReflexTests Hirschberg test:A pen torch is shone into the eyes from arm’s length and the patient is asked to fixate upon the light. ⚫If theeyes are deviated, the light reflex fallson different locations instead of thecenter. ⚫1 mm deviation = 7 degrees deviation =14 pd deviation ⚫
- 54. ⚫Krimsky test: Itis a modification of the Hirschberg test. ⚫A prism is placed in front of one eye with the apex towards thedeviation, a pen light is then thrown into both eyes and the patient is asked to fixate on the accommodativetarget. ⚫The prism is then increased or decreased until the reflex becomes symmetricallycentered in the pupil. ⚫
- 55. ⚫Bruckner test: Thistest is performed by using the directophthalmoscope toobtaina red ref lex from botheyes simultaneously. ⚫In patientswith strabismus, the testshowsasymmetric reflexes with the brighter reflex coming from the deviated eye. ⚫
- 56. ⚫based on thepatient’sability to fixate, ⚫both eyes should havecentral fixation. ⚫They allow the examiner to differentiate tropia from phoria, ⚫Assess the degree of control of deviation, and note fixation preference and strength of fixation of each eye.
- 57. ⚫Gold standard objectivemethod ⚫Use: todifferentiate -between phoriaand trophia -detectpseudostrabismus -differentiate concomitant from incomitant squint done for both near (33cm) and distance (6 meter) ⚫Consistof 3 parts 1)covertest -confirms tropia 2)uncovertest – todiagnose phoria 3)alternatecovertest –measure total deviation
- 58. Ask pt tofixateon targetand look forany deviation Deviationvisible ,eg:LE exo Do COVER TEST,By covering fixing eye,i.e RE withoccluder Deviated LE moves inward to take fixation,so RE under occluder also moves due to herrings law. CONFIRMS EXOTROPHIA No movement, Indicate pseudosquint Deviation notvisible Do COVER TEST If no movement of uncovered eye no tropia But fusion is broken ,socovered eye moves to position of least resistance.now do UNCOVER TEST
- 59. ⚫On uncovering ,thecoveredeye is seen to move inward ⚫ Indicate PHORIA
- 61. ⚫This test isdone todissociate binocular fusion in order todetermine the full deviation, including any latentphoria. ⚫Alternately each eye is occluded and refixation movementof uncovered eye to midline isobserved. ⚫Noshift in thealternatecovertest indicates orthophoria. ⚫A refixation shift to indicates thatstrabismus is present, eithera tropia, phoria.
- 62. ⚫This testdetermines theamountofprism necessary to neutralize the full deviation including any latent phoria, by quantitating the shift associated with alternatecovertesting. ⚫A prism is placed in frontof thedeviating eye with theapex towards thedeviation. ⚫Alternate cover testing is then performed with the prism in place, the prism is changed (either increased ordecreased) depending on the refixation shift.
- 63. ⚫Simultaneous prism covertest: It is used to measure the tropiacomponentof the monofixation syndrome withoutdissociating the phoria. ⚫therefore it is used in patientswith small angle strabismus. ⚫A prism and occluder is presented simultaneously in frontof eithereye and this process is repeated until there is no shift of the deviated eye when the fixing eye is covered
- 64. ⚫ When measuringpatients with restrictiveor paralytic deviations the primary and secondarydeviation should be considered. ⚫ In accordance with Hering’s law, thedeviation is larger when theeyewith limited duction is fixing (secondary deviation) than when the “good eye” fixes (primary deviation). ⚫ While measuring adeviation with prisms, theeyewithout the prism is considered the fixing eyeand theeyewith the prism is the non-fixing eye, irrespective of presence of amblyopia. ⚫ This is because theeyewithout the prism mustcome to the primary position to take up fixation.
- 65. ⚫ Ductions :Monoocular movementsand are examined with oneeyeoccluded, -abduction -elevation -intortion -adduction -depression -extortion ⚫Versions : are binocular ,simultatneous eye movements In the samedirection ,i.econjugate movements -Dextroversion -Dextroelevation -Dextrodepression -Sursumduction -Levoversion -Levoelevation -Levodepression -Deorsumduction
- 66. ⚫ Both horizontaland vertical ductions arequantified with agraded 0 to minus 4 scale, ⚫ with minusone limitation meaning slight limitationand minus four limitation meaning severe limitation ⚫ Evaluation of versions include eye movements through all 9 cardinal gaze positions. Abnormal versions can be noted on a scale of + 4 through 0 to – 4, with 0 indicating normal movement, ⚫ + 4 indicating maximumoveraction, while – 4 indicates severe underaction. ⚫ The rest of thegrades fall in between.
- 68. - Binocular ,simultaneous movements in opp direction - i.e disgugate movements -Vergenceamplitudesare tested in three planes: 1. Horizontal: Convergenceand divergence 2. Vertical: Sursumvergenceand deosumvergence 3. Torsional:Incyclovergenceand excyclovergence. - Measurementcan either be donewith prismsor the synoptophore
- 69. ⚫Near point ofconvergence: The simplest way to measure convergence is to bring a point drawn on papercloserto theeyes, till the point becomesdouble. ⚫This in the nearpointof convergence. The pointat which it becomes blurred is the near point of accommodation ⚫Normally, the nearpointof convergence is 8 to 10 cm.
- 70. ⚫Convergenceand divergence fornear (33 cm) and distance (6 m) can be measured with the helpof a prism barorrotary prisms. ⚫Using base-outprisms, theconvergence amplitudescan be measured ⚫using base-in prisms, thedivergenceamplitudesare measured.
- 71.