Diagnosis Assessing Comitancy Handout 8 PDF

Anomalies of Binocular Vision II – Strabismus/Amblyopia Diagnosis and Management– YC Tea DIAGNOSIS – ASSESSING CONCOMITANCY Handout #8 Study Questions From this lecture, you should be able to answer the following questions: What is the definition of...

Anomalies of Binocular Vision II – Strabismus/Amblyopia Diagnosis and Management– YC Tea DIAGNOSIS – ASSESSING CONCOMITANCY Handout #8 Study Questions From this lecture, you should be able to answer the following questions: What is the definition of a nonconcomitant deviation? What are the three general etiological factors that cause strabismus? What are the common etiologies of nonconcomitant strabismus? Based on Rush and Younge’s paper, what is the etiology that accounts for most acquired 3,4,6 cranial nerve palsies? What is the primary diagnostic question when evaluating a suspected nonconcomitant deviation? What is generally the cause of any overacting muscle action seen? Diagram the physiological H pattern used to isolate individual muscle action. What would you see during version testing if a patient had a LLR paresis? What would you observe in right and left gaze during Hirschberg testing? When would you do duction testing? Forced duction testing? What would be the results on spatial localization testing for a patient with a RLR paresis? What is the difference between a primary and secondary deviation? What would be the ACT plot for a patient with a LLR paresis? LSO, RSO? In each case, the deviation would be larger with which eye fixating? What are the steps for the three-step method circling technique for isolating the affected muscle? What are the steps for the red lens method for assessing concomitancy? Why is the underacting eye’s image projected further into the affected field than the normal eye’s image? Why isn’t the Red lens method reliable in cases of heterophoria or intermittent strabismus? What is the Hess-Lancaster Method? Is the plot with the affected eye fixating generally larger or smaller than the plot with the normal eye fixating? What is a criteria for classifying the severity of nonconcomitancy? 1. Introduction a. Concomitant – angle of deviation remains the same throughout all positions of gaze and with either eye fixating b. Nonconcomitant – angle of deviation changes in different fields of gaze or with either eye fixating. c. Strabismus in general can be caused by three broad factors: Anatomical – effects of tendons, abnormalities of EOM’s, check ligaments, orbital contents. (low prevalence) Optical – refractive anisometropia, high refractive error, media opacities. (high prevalence) Innervational – muscle tonus or innervational changes from, intoxication, medications, trauma or disease, innervational anomalies, congenital, high or low AC/A ratios. (high prevalence) 1 Anomalies of Binocular Vision II – Strabismus/Amblyopia Diagnosis and Management– YC Tea d. If the magnitude of the deviation cannot be overcome by fusional vergence, the deviation may manifest. Also, any disruption of the sensory fusion system may result in the deviation being manifest. e. Most concomitant deviations are supranuclear in origin, where most nonconcomitant deviations are nuclear or infranuclear. f. Rush & Younge (1981) 1000 cases of acquired 3,4,6 nerve paresis 90% patients older than 19 Summary of etiologies: i. 26.2% cause undetermined ii. 19.7% head trauma iii. 17.2% vascular iv. 14.3% neoplasm v. 7.1% aneurysm vi. 15.4% other 3 Most common causes i. Adults: trauma, vascular, neoplasm ii. Children: acute viral illness, trauma, congenital nerve paresis Nonconcomitant deviations may represent a life-threatening situation which might necessitate an immediate referral! Ask about diplopia! 2. Review of Anatomy and Muscle Actions a. 3 main reasons for muscle underactions Muscles themselves may be paretic as in cases of direct traumatic injury Mechanical reasons such as faulty muscle insertions and ligament or tendon abnormalities that may restrict ocular motility Innervational deficiencies due to impairment of the cranial nerves (3, 4, 6). b. Possible reasons for muscle overactions Mechanical reasons, faulty muscle insertion giving mechanical advantage to particular muscle MORE OFTEN – overaction can be explained by Hering’s law of equal innervation (i.e. Underacting contralateral synergist). 2 Anomalies of Binocular Vision II – Strabismus/Amblyopia Diagnosis and Management– YC Tea c. Rectus Muscles 23° angle between the lines of insertion and the visual axis Inserted forward of the equator of the eye. d. Oblique Muscles 51° angle between the lines of insertion and the visual axis Inserted behind the equator of the eye. Caloroso and Rouse, Clinical Management of Strabismus. Ch 2 3 Anomalies of Binocular Vision II – Strabismus/Amblyopia Diagnosis and Management– YC Tea e. How do you isolate the action of single muscles or yoked muscle pairs? Position eyes so the visual axis and the lines of insertion are coincident. i. Adduct the eye ~50 and which muscle is responsible for depressing the globe? ___________ ii. Use physiological “H” pattern to investigate the integrity of oculomotor innervation balance between the two eyes in each diagnostic action field. a. Up and down gazes are added to detect possible A-V syndromes. f. Hering’s Law of Equal Innervation Contralateral synergists are equally innervated g. Sherrington’s Law Contraction of a muscle is accompanied by a simultaneous and proportional relaxation of its antagonist h. Innervation of EOM’s CN3 (Oculomotor) innervates MR, SR, IR, IO CN4 (Trochlear) innervates SO CN6 (Abducens) innervates LR 4 Anomalies of Binocular Vision II – Strabismus/Amblyopia Diagnosis and Management– YC Tea 3. Objective Diagnostic Testing Methods a. Direct observation to identify an obvious abnormal head position. Head turns suggest MR and LR involvement Chin tipping or raising suggests A–V pattern deviation Head tilt is most often oblique muscle problem Is abnormal head position OCULAR torticollis or CONGENITAL torticollis? i. Patch Test: If it is ocular, patching one eye will eliminate any reason for patient to tilt head to establish binocular vision, so they’ll straighten head up. If it is a skeletal problem, a patch will not make the head tilt go away. b. Version Testing Involves moving the eyes into each diagnostic action field (DAF) and observing for any change in eye position (underacting-UA, overacting-OA) Can add Hirschberg to improve examiner’s sensitivity. (do versions with penlight) Done as command (voluntary) or pursuit (involuntary)? i. Command – patient requested to move eyes into various positions of gaze ii. Pursuit – patient follows a target into different DAFs If patient unable to fixate/follow well, such as infant, move patient’s head, thus putting eyes into DAFs (Dolls Head) Can attempt to quantify the severity of the UA/OA by either of two systems: i. 4+ (representing severe OA) to 4- (representing severe UA) ii. Relative scale of mild, moderate, or severe Red Lens Test -- If you suspect an UA muscle during version testing, the red lens test is helpful as a subjective test to confirm your findings. Refer to SUBJECTIVE diagnostic testing methods section If UA is detected on version testing, follow up with DUCTION testing. 5 Anomalies of Binocular Vision II – Strabismus/Amblyopia Diagnosis and Management– YC Tea c. Duction Testing Move patient’s eye monocularly into DAFs to see if any limitation to muscle action. Can improve sensitivity by adding