Cover Test PPO2_2024 (1).pptx

COVER TEST Ariette Acevedo, O.D. PPO2 DEFINITIONS Tropia: a manifest deviation of the visual axes of the two eyes, occurring when stimuli to fusion is operating. ⚬ Also known as heterotropia, strabismus or squint Phoria: a latent deviation of the visual axes of the two eyes, brought on by eliminatin...

COVER TEST Ariette Acevedo, O.D. PPO2 DEFINITIONS Tropia: a manifest deviation of the visual axes of the two eyes, occurring when stimuli to fusion is operating. ⚬ Also known as heterotropia, strabismus or squint Phoria: a latent deviation of the visual axes of the two eyes, brought on by eliminating all stimuli of fusion. ⚬ Heterophoria Cover test: clinical test in which one eye is covered, by means of an occluder, in order to determine the presence of a latent or manifest deviation. STRABISMUS SYMPTOMS Diplopia: perception of one object that projects upon two different noncorresponding retinal areas. ⚬ This causes a reduction of reading, driving and vocational skills Visual confusion: the simultaneous perception of dissimilar objects that project upon corresponding retinal points. ⚬ Can result from newly acquired strabismus or from a change in the angle of strabismus in adults who had childhood strabismus ￭ Example: a patient may complain of trouble driving due to seeing a car crossing over the STRABISMUS SYMPTOMS In adults the sudden onset of strabismus may be related to a neurological condition such as a brain tumor, head trauma, stroke or myasthenia gravis. ⚬ May also be caused by microvascular conditions such as diabetes or hypertension ⚬ Diplopia may also develop in an adult who had childhood strabismus If sudden onset strabismus presents, diplopia is going to be a symptom If longstanding or present from childhood, suppression may have developed, and no diplopia may be reported STRABISMUS EVALUATION Case history is key ⚬ HPI: onset, nature of misalignment, trauma history ⚬ PMH: gestational, birth and developmental history ￭ Gestational age at birth, type of birth, complications during pregnancy or during birth, NICU or incubator use ⚬ ROS: recent viral syndrome, fever, malaise, headaches, nausea, neurological changes, head tilt, weight loss, growth defect ⚬ POH: ocular and visual ￭ LEE, ocular diagnosis, refractive correction, ect… ⚬ FOH: strabismus, refractive error ⚬ General physical: neurological findings ⚬ Ocular exam: VAs, Hirschberg, Cover Test, EOMs, Bruckner and pupillary responses STRABISMUS EVALUATION History ⚬ Onset ￭ Recent or longstanding ⚬ Age of onset ￭ Presented since infancy or as child was older ⚬ Present all the time or sometimes ￭ Constant or Intermittent ⚬ At distance, near or both ⚬ Presents in one eye or both ￭ Unilateral or Alternating ⚬ Presents constantly or only when tired and inattentive ⚬ Any trauma or physical stress associations ⚬ Birth and developmental history ￭ Birth age, crawled, walked, talked ⚬ Family history of strabismus ⚬ Medical conditions ￭ Headaches, Vertigo CLASSIFICATION OF DEVIATION Unilateral vs Alternating: ⚬ Unilateral tropia: a deviation that is manifest in only one eye ⚬ Alternating tropia: a deviation which can be manifested in either eye Constant vs Intermittent: ⚬ Constant tropia: a deviation occurring all the time ⚬ Intermittent tropia: a deviation that is not always present ￭ Sometimes may be manifested as a phoria, other times as a tropia Comitancy: ⚬ Concomitant tropia: a deviation in which the angle of deviation is the same in all directions of gaze or less than 5PD between gazes ⚬ Incomitant tropia: a deviation in which the angle of deviation is not CLASSIFICATION OF DEVIATION Periodic tropia: a deviation that occurs at only one testing distance ⚬ Near or distance Paralytic tropia: a deviation that occurs due to the paralysis of a nerve or a muscle ⚬ Oculomotor paresis, Abducens paresis, Trochlear paresis DIRECTION OF DEVIATION No movement: Ortho (ɸ) Lateral/Horizontal ⚬ Outward deviation: Exo (tropia or phoria) ￭ Measure with BI prism ⚬ Inward deviation: Eso (tropia or phoria) ￭ Measure with BO prism Vertical ⚬ Upward deviation: Hyper (tropia or phoria) ￭ Measure with BD prism ⚬ Downward deviation: Hypo (tropia or phoria) ￭ Measure with BU prism ⚬ When evaluating vertical deviations, a seesaw movement will be seen ￭ https://www.youtube.com/watch?v=oVBmBzsbHGA Combined: ⚬ Lateral and vertical movement ⚬ Cyclodeviations Exotropia (XT): a tropia in which the visual axis of one eye deviates outward Esotropia (ET): a tropia in which the visual axis of one eye deviates inward Hypertropia: a tropia in which the visual axis of one eye deviates upward Hypotropia: a tropia in which the visual axis of one eye deviates EVALUATION: TROPIA VS PHORIA Tropia: manifest deviation when stimuli to fusion is operating ⚬ AKA: heterotropia, strabismus Phoria: latent deviation, brought by eliminating all stimuli to fusion ⚬ Heterophoria, dissociated phoria Pseudostrabism us Strabismus Latent Deviation (Heterophoria) Concomitant Manifest Deviation (Heterotropia) Incomitant COVER TEST Provides an objective magnitude of the deviation Deviations may be: ⚬ Latent (Phorias) ⚬ Manifest (Strabismus-Tropia) Cover Test: ⚬ Unilateral CT ⚬ Alternate CT Must evaluate: ⚬ Presence or absence of deviation ⚬ Direction of deviation ￭ ￭ ￭ Horizontal Vertical Torsional ⚬ Magnitude of the deviation COVER TEST For both UCT and ACT Full room illumination Target: one line above best VA of the worst eye with habitual SRx Performed with correction if the patient wears correction ⚬ But can be performed with and without correction to compare Distance UCT/ACT is performed at 6m and near at 40cm Position yourself at eye level with the patient, but not obstructing line of sight UNILATERAL COVER TEST Used to determine the presence of tropias or manifest deviations Each eye is covered, but binocular fixation is allowed Any deviation of the uncovered eye indicates the presence of a tropia Observe the eye that is not covered PROCEDURE FOR UNILATERAL COVER TEST For UCT: ⚬ While patient is fixating the target, ask them to keep it clear ⚬ With occluder cover the OD and observe the OS for any movement ￭ Repeat multiple times, covering the eye for 1-2 seconds then uncovering the eye ⚬ After, cover the OS and observe the OD for any ALTERNATING COVER TEST Used to determine phoria or latent deviation Both eyes are alternately covered by means of the occluder The occluder is moved quickly, to avoid fusion ⚬ Must move over the nose avoiding fusion Observe the eye when it is uncovered PROCEDURE FOR ALTERNATING COVER TEST For ACT: ⚬ While patient is fixating the target, ask them to keep it clear. ⚬ Occlude the OD, observe the OS after 1-2 seconds move occluder to OS and observe OD ￭ Do not allow for fusion to take place, move the occluder fast between eyes ⚬ Repeat multiple times at a consistent pace and observe for movement of both eyes. DIRECTION AND MAGNITUDE With unilateral cover test you determine the presence or absence of a tropia With an alternating cover test you identify the presence of a phoria, direction and magnitude of deviation For all patients you have to perform UCT and ACT Tropias have to be identified by laterality, direction and magnitude Phorias have to be identified by direction and magnitude ⚬ No laterality PRISMS When a prism is place in front of the eye, the retinal image is shifted towards the base of the prism. ⚬ The perceived image moves towards the apex of the prism This image jump causes the eye to move in the direction of the apex of the prism, to allow for foveal NEUTRALIZATION WITH PRISM Always orient the prism with the apex in the direction of the deviation ⚬ Eso deviation: BO ⚬ Exo deviation: BI ⚬ Hyper deviation: BU ⚬ Hypo deviation: BD Identify the fixating or dominant eye and place the prism over the deviated or non-fixating eye While doing ACT, continue to increase the prism magnitude until no movement is seen ⚬ Make a mental note of this PD Continue adding prism until you see a reversal (the 1ˢᵗ opposite movement) NEUTRALIZATION WITH PRISM Example: ⚬ While performing UCT the patient presented with an exotropia in OD constant, OS is the fixating eye ￭ Using BI in OD to measure, increased in magnitude until no movement is seen at 10BI ￭ Continue adding prisms until reversal is seen at 12BI Eye starts to move outward for the first time ￭ 11Δ Right Exotropia (RXT) ORTHOPHORIA If when evaluated the patient appears to be ortho, you have to induce the phoria, since there could be a latent phoria Add BI prisms until you notice movement and then do the same with the BO prisms ⚬ Example: with correction at distance ACT: ortho ￭ BI induction: first movement 4BI ￭ BO induction: first movement 4 BO ￭ 4BI -4BO = 0/2 (true orthophoria) ⚬ Example 2: ACT ortho ￭ BI: first movement 6BI ￭ BO: first movement 4 BO ￭ RECORDING ABBREVIATIONS XT: Exotropia ET: Esotropia HT: Hypertropia ⚬ Only the hyper eye is recorded R: OD L: OS A: Alternating (T): Intermittent T: Distance T’: Near XP: Exophoria EP: Esophoria ɸ: Ortho cc: with correction sc: without correction RECORDING COVER TEST RESULTS A tropia/strabismus has to be identified by at least: ⚬ Direction + frequency + deviated eye + magnitude + testing distance ⚬ Examples: ￭ 20Δ RET (Right 20PD constant esotropia at distance) ￭ 22Δ RE(T)’ (Right 22PD intermittent esotropia at near) ￭ 20Δ AXT (20PD alternating Phorias are identified by the direction and magnitude and testing distance ⚬ THEY DO NOT HAVE LATERALITY, THEY ARE NOT MEASURED SEPERATELY ⚬ Examples: ￭ 8XP/12XP’ ￭ ɸ/3XP’ ￭ 4EP/6EP’ RECORDINGS Examples ⚬ CT ⚬ CT ⚬ CT ⚬ CT ⚬ CT ⚬ CT ⚬ CT cc Ortho at D and N sc constant 30Δ AXT D and N (this is comitant) cc constant 45PD RXT; 45PD RXT’ sc 20 PD RXT with 10 PD RHT at D and N sc 15Δ AET; 30Δ AET’ cc 20 PD RXT ; 10 PD RXT’ (these last 2 are non-comitant) sc 8PD RE(T) D and N (25% times tested) EXPECTED FINDINGS 1Δ XP ± 2Δ at distance 3Δ XP ± 3Δ at near Presbyopes tend to have larger XP at near ⚬ It is expected to increase in exophoria as we increase in age ⚬ Also expected to have less convergence HIRSCHBERG TEST Used to identify strabismus when other precise methods cannot be used ⚬ Screening tool Equipment: penlight or transilluminator and occluder Examiner must be directly behind the penlight observing the patient at eye level ⚬ Keep patients attentions with toy or parent can help Dim room illumination Direct the light into the patient’s eyes from a distance of 30-100cm Corneal Light Reflections - YouTube HIRSCHBERG TEST Procedure: ⚬ Instruct the patient to look at the light ⚬ Occlude the OS and observe the location of the corneal reflex in OD ￭ Center, Nasal, Temporal ⚬ Repeat with OD occluded ⚬ Remove the occluder and observe the location of the corneal reflex with both eyes open ⚬ Compare the corneal reflex when one eye is fixating vs when both eyes are fixating ￭ If the reflex is in the same relative position in each eye: No strabismus ￭ If the reflex are not in the same relative position: the patient has strabismus HIRSCHBERG When the corneal light reflex (CLR) is nasal to the center of the pupil, it is assigned a positive (+) value When the CLR is temporal to the center of the pupil, it is a assigned a negative value (-) Expected: +0.5mm CLR in both eyes EXAMPLE When evaluating notice if the CLR is in the same relative position on each pupil If they are not equal, the patient might have strabismus HIRSCHBERG VS KRIMSKY Hirschberg: penlight is held directly in front of the patient and the corneal light reflexes are observed. ⚬ Any asymmetry indicates the direction and magnitude of an eye turn, depending upon the position of the reflexes. ⚬ It is estimated in mm. ￭ 1mm of corneal reflex displacement = deviation of 22Δ Krimsky: uses prisms to move the deviated reflex back to the expected position as a means of Prisms: ⚬ Eso deviation: BO prism ⚬ Exo deviation: BI Prism ⚬ Hyper deviation: BD Prism ⚬ Hypo deviation: BU Prism BRUCKNER TEST Fixation screening test for: ⚬ Strabismus, anisometropia, and media opacities in infants and young children Use ophthalmoscope at 1m away Observe the red reflexes in both eyes and compare the brightness between the two eyes ⚬ Equal: binocular fixation ⚬ Not equal: ￭ Darker reflex: fixating eye ￭ Brighter reflex: non-fixating eye PRACTICE Simulator: ⚬ https://aao-resources-enformehosting.s3.amazonaws.com/res ources/Pediatrics_Center/Strabismus-Simulator/index.html Video: ⚬ https://webeye.ophth.uiowa.edu/eyeforum/video/basic-cover-t est.htm