Transcript Method
BLOCK 1: Clinical Exams •Theme 1: Anamnesis •Theme 2: Material •Theme 3: Visual acuity •Theme 4: Retinoscopy •Theme 5: Subjective •Theme 6: Cover Test •Theme 7: Accomodation Theme 6: Cover test Utility What is a strabismus? What is a phoria? 6 7 15 Material 18 Method 19 Theme 6: Cover test Method 19 Unilateral Cover 20 Description 21 Characterization of strabismus 28 Direction 30 Frequency 36 Magnitude 38 Laterality 45 comitance 49 Theme 6: Cover test Cover – Uncover 53 Description 54 Characterization of strabismus 58 Direction 59 Magnitude 59 comitance 59 Cover – Alternating 64 Theme 6: Cover test Self-evaluation 69 Bibliography 79 Utility The cover test is an optometric test that can prove or disprove the presence of a strabismus or a phoria. The presence or absence of the fusional ability is determined. Utility What is a strabismus We are facing a strabismus when both eyes do fle fre not simultaneously direct their visual axes on object of interest…. What happens when an ocular deviation is axis produced? Utility What is a strabismus When binocular vision exists, the object of interest stimulates both foveas simultaneously, thereby achieving a fusion of the image on a cortical level. fle In this case, what is called a Normal Sensory Correspondence (NSC) exists. fre Utility What is a strabismus Facing an ocular deviation, the following effects could be produced: • diplopia • confusion fle + fre = + = Confusion fle fle + O = + = Diplopia 0 fre Utility What is a strabismus? Facing these possibilities and uncomfortable effects, the visual system can respond by trying to avoid them through: • Abnormal retinal correspondence • Suppresion • Eccentric fixation • Torticollis fle 0 fre Utility What is a strabismus? Abnormal retinal correspondence The fovea of the deviated eye will not correspond with fixating eye, thereby resulting in the binocular function, point “0”. 0 fre fle ARC Utility What is a strabismus? Suppression The image that prevails is that which only pertains to the directing eye. fle 0 fod Utility What is a strabismus? Eccentric fixation It happens when the deviated eye, in a monocular way, prefers to look at the Occluder object of interest with a distinct point of the fovea fle 0 fre Utility What is a strabismus? Torticollis There are different types of strabismus in Habitual position which diplopia and confusion only appear in certain “sight” positions This can make the patient present an inclination of the head in order to maintain, “in a habitual way”, sight in the position of greatest comfort. Ocular deviation Paralysis of the OS from the RE Utility What is a phoria? A phoria is a latent deviation. This deviation becomes apparent after the elimination of the fusion stimulus (occluder, Maddox rod, prisms...) The visual axes of both eyes are directed at the object of interest thanks to the utilization of fusional convergence A phoria at a given distance implies that, at that distance and in that instant, binocular vision exists Utility What is a phoria? fre fle The type of fusional convergence to utilize depends on the type of phoria An endophoria utilizes the negative fusional NFC vergence (NFV) in order to bring both visual axes onto the object of interest. c Utility What is a phoria? fre fle An exophoria utilizes the positive fusional vergence (PFV) in order to bring the visual CFP axes onto the object of interest. c Material • Optotype from distance • Accomodative card • Occluder • Prisms Method By covering one of the two eyes and analyzing what is observed Objective Unilateral Cover Detection of strabismus Cover - Uncover Detection of phorias Alternating Cover Test Evaluation of the totality of the deviation Method By covering one of the two eyes and analyzing what is observed Objective Unilateral Cover Detection of strabismus Cover - Uncover Detection of phorias Alternating Cover Test Evaluation of the totality of the deviation Method Unilateral Cover Detection of strabismus Cover and uncover an eye, observing if in the other eye some movement of fixation is produced fre fle Movement? e Method Unilateral Cover If upon covering the right eye… 1. There is No movement of the left eye fre fle fre fle Hide the left eye e e The absence of movement tells of orthotropia (absence of strabismus) Method Unilateral Cover Detection of strabismus Observe whether movement of the uncovered eye fre fle 1. There is no movement • Possible Orthotropia (there is no strabismus) Movement? 2. There is movement e • Tropia (there is strabismus) Method Unilateral Cover If upon hiding the right eye… 1. There is No movement of the left eye fre Hide the left eye fle fre fle The absence of movement tell of orthotropia (absence of strabismus) e e Method Unilateral Cover If upon covering the right eye… 2. There is movement of the left eye fre fre fle fle Indicates that the left eye was deviated e The presence of movements tells of strabismus e Method Unilateral Cover If upon hiding the right eye… 2. There is movement of the left eye fre fle e fre It indicates that the left eye was deviated fle e Endotropia LE Method Unilateral Cover If upon covering the right eye … 2. There is movement of the left eye fre fle After detecting a strabismus it must be characterized: • Direction • Frequency • Magnitude • Laterality e • comitance Method Unilateral Cover Characterization of the strabismus: • Direction • Frequency • Magnitude • Laterality • Comitance Method Unilateral Cover Characterization of the strabismus: • Direction • Frequency • Magnitude • Laterality • comitance Method Unilateral Cover Characterization of the strabismus: • Direction • Frequency • Magnitude • Laterality • comitance Method Unilateral Cover Characterization of the strabismus Direction If upon covering the right eye, the left eye moves… There is a strabismus Vertical movement... Horizontal movement... upwards Hypotropia Exotropia downwards Hypertropia Endotropia inwards outwards Method Characterization of the strabismus If upon covering the right eye, The left eye moves vertically UPWARDS Direction fre e fle Unilateral Cover Hypotropia LE Method Unilateral Cover Characterization of the strabismus Direction fod e foi If when covering the right eye, the left eye moves vertically UPWARD Hypertropia LE Method Unilateral Cover Characterization of the strabismuc Direction If when covering the right eye,the left eye moves horizontally OUTWARD fre fle e Endotropia LE Method Unilateral Cover Characterization of the strabismus Direction If when covering the right eye, the left eye moves horizontally INWARD fre fle e Exotropia LE Method Unilateral Cover Characterization of the strabismus Characterization of the strabismus: • Direction • Frequency • Magnitude • Laterality • Comitance Frequency Method Unilateral Cover Characterization of the strabismus Frequency Given a concrete distance we can find that.. A strabismus is present Always Constant strabismus Greater probability of Sensory adaptations (amblyopías, eccentric fixations, suppressiones, anomalous correspondence) Sometimes Intermitent strabismus Binocular vision is present sometimes Method Unilateral Cover Characterization of the strabismus: • Direction • Frequency • Magnitude • Laterality • comitance Method Unilateral Cover Characterization of the strabismus Magnitude In order to evaluate the magnitude of the deviation we are going to rely on the alternating cover test with prisms. The alternating cover test consists in passing the occluder from one eye to the other without allowing the possibility of fusion. In this moment we evaluate the type of movement. The placement of the situated prisms in the appropriate position will make the movement cease. The prismatic quantity that makes the movement cease during the alternating cover test tells of the total measurement of the deviation. Method Characterization of the strabismus Unilateral Cover fre Magnitude But what does the prism do? fle When facing an ocular deviation, the deviated eye, when incited to fixate due to the covering of the fixating eye (supposing central fixation), will have to realize movement in order to direct its fovea towards the object of interest. The prism corresponding to the magnitude of the deviation makes it so that the eye does not need to move towards the object of interest since through the prism the image of this object has been situated along the visual axis Method Characterization of the strabismus Unilateral Cover Magnitude But what does the prism do? fre fre fle Movement during the cover test fle Method Characterization of the strabismus Unilateral Cover Magnitude But what does the prism do? fre fle fre fre fle That prism that ceases the Occluder movement provides us with the magnitude of the deviation Occluder fle Method Unilateral Cover Characterization of the strabismus The base of the prism depends of the type of deviation ENDODEVIATIONS: Temporal bases (BT) EXODEVIATIONS: Nasal bases (BN) Magnitude Method Unilateral Cover Characterization of the strabismus Magnitude In vertical deviations, it depends on the eye on which the prism is situated Left HYPOTROPIA: Superior bases (SB) in front of the left eye Inferior bases (IB) in front of the right eye Left HYPERTROPIA: Superior bases (SB) in front of the right eye Inferior bases (IB) in front of the left eye Method Unilateral Cover Characterization of the strabismus: • Direction • Frequency • Magnitude • Laterality • Comitance Method Unilateral Cover Characterization of the strabismus Laterality The strabismic eye can always be the same or it can be both in an alternating pattern The strabismic eye can be… Always the same Unilateral strabismus Greater probability of Sensory adaptations (amblyopias, eccentric fixations, suppressiones, anomalous correspondence) The right or left eye Alternating strabismus Method Unilateral Cover Characterization of the strabisums Always the same Laterality Unilateral strabismus The deviated eye is always the LE Method Unilateral Cover Characterization of the strabismus Laterality Alternating strabismus The deviated eye can be one or the other Method Unilateral Cover Characterization of the strabismus: • Direction • Frequency • Magnitude • Laterality • Comitance Method Unilateral Cover Characterization of the strabismus INcomitance It is a characteristic of the ocular deviations that is related to their etiology. It will be evaluated in various ways: • Quantifying the deviation depending on the vantage point. • Evaluating the existence of limitations in versions or ductions. Method Unilateral Cover Characterization of the strabismus Incomitance Deviation Comitance • Differences inferior to 7D in distinct vantage points Incomitance • Differences superior to 7D in distinct vantage points • There is no limitation in versions or in ductions • There is limitation in versions and/or in ductions Method Unilateral Cover Characterization of the strabismus Incomitance Supra dextroversion Supraversion Supra levoversion Dextroversion Primary position Levoversion Infra dextroversion Infraversion Infra levoversion Method Method Through occlusion and analysis of the observations Objective Unilateral Cover Detection of strabismus Cover - Uncover Detection of phoria Alternating Cover Test Evaluation of the totality of the deviation Method Cover - Uncover Detection of phoria Cover an eye and observe if uncovering it results in movement of any type fre fle Movement? e Method Cover - Uncover Detection of phoria Observe if any movement of the eye that is covered is produced fre fle After the occluder is eliminated the fixation stimulus and the eye are situated in the passive position. The evaluation of the passive position Determines the existence of a phoria. e If when taking away the occluder the covered eye moves, we are facing a phoria. Method Cover - Uncover Detection of phoria If when covering the right eye, it takes a passive position so that when it is uncovered it needs to move in order to fixate, we are faced with a phoria. fre fle e fre fle e The presence of movement reveals a phoria fre fle e Method Cover - Uncover Detection of phoria If the uncovered eye moves, we are faced with a phoria fre fle After detecting a phoria these factors must be characterized: • Direction • Magnitude • Comitance e Method Cover - Uncover Characterization of a phoria: • Direction • Magnitude • Comitance Method Cover - Uncover Characterization of the phoria Direction When covering the right eye, it takes its passive position behind the occluder When uncovering we can find that… It moves in a horizontal sense It does not move upward inward Orthophoria Hypophoria Exophoria downward outward Hyperphoria Endophoria It moves in a vertical sense Method Cover - Uncover Characterization of the phoria If when uncovering the right eye, It moves horizontally… fre fle e outwards Endophoria Direction Method Cover - Uncover Characterization of the phoria If when uncovering the right eye, it moves horizontally… fod foi e inward Exophoria Direction Method Cover - Uncover Characterization of the phoria fre e fle If when uncovering the right eye, it moves vertically… upward Hypophoria Direction Method Cover - Uncover Characterization of the phoria fod e foi If when uncovering the right eye, it moves vertically… downward Hyperphoria Direction Method Method Through occlusion and analysis of the observations Objective Unilateral Cover Detection of strabismus Cover - Uncover Detection of phoria Alternating Cover Test Evaluation of the totality of the deviation Method Method Alternating Cover Test Evaluation of the totality of the deviation Pass the occluder from one eye to the other repeatedly without allowing fusion. Evaluate the existence of movement in the eye that is fixating. fre fle e Movement? Method Method Alternating Cover Test Evaluation of the totality of the deviation Observe if movement of the eye that is uncovered is produced. fre fle After the occluder is eliminated the fixation Stimulus and the eye are situated in passive positions Not allowing fusion to be produced makes the Movement being observed clearer e Phoria and tropia are not differentiated Method Method Evaluation of the totality of the deviation Alternating Cover Test If when passing the occluder from one eye to another the uncovered eye moves… fre fle e fre fle e fre fle e Method Method Alternating Cover Test Evaluation of the totality of the deviation If the uncovered eye moves, the type of deviation* will have to be characterized: fre fle • Direction • Phoria or tropia • Magnitude • Comitance e (*See the characteristics in prior sections) Exercises Self-evaluation Exercises Give a name to the following conditions according to the observations realized during the cover test. Exercises Example 1. Exercises Example 1. Orthotropia Exercises Example 2. Exercises Example 2. Constant Endotropia LE Exercises Example 3. Exercises Ejemplo 3. Constant Exotropia LE Exercises Example 4. Exercises Example 4. Constant Hypotropia LE Bibliography Bibliography Bibliography • Von Noorden GK. Atlas de estrabismos. Madrid: Mosby-Ciagami, 1997 • Caloroso EE, Rouse MW. Tratamiento clínico del estrabismo. Madrid: Ciagami, 1999 • Hugonnier R. Hugonnier S. Estrabismos heteroforias y parálisis oculomotrices. Barcelona: Toray-Masson, 1977 • Prieto-Díaz J, Souza-Dias C. Estrabismo (5ª ed.). Buenos Aires : Ediciones Científicas Argentinas, 2005 • Von Noorden GK , Helveston EM. Estrabismos. Decisiones clínicas. Madrid: Ciagami, 1997 • Borràs MR et al. Visión binocular. Diagnóstico y tratamiento. Barcelona. Ediciones UPC, 1996 • Computer program OSP2