斜视与屈光不正英文课件.ppt

Fujian Provincial Hospital Wenjie Wu MD., PhD.Chapter 15 StrabismusAny Deviation From Perfect Ocular AlignmentDefinitions  Conjugate movement: Movement of the eyes in the same direction at the same time. Ductions: Monocular rotations with no consideration of the position of the other eye.abductionInfraduction （Depression ）Supraduction （Elevation）adduction Fusion: Formation of one image from the two images seen simultaneously by the two eyes. Motor Fusion: Adjustments made by the brain in innervation of extraocular muscles in order to bring both eyes into bifoveal and torsional alignment. Sensory Fusion: Integration in the visual sensory areas of the brain of images seen with the two eyes into one picture.Definitions Definitions  Heterophoria(phoria): Latent deviation of the eyes held straight by binocular fusion. Esophoria Exophoria Hyperphoria Hpophoria Heterotropia (Tropia) Strabismus: Manifest deviation of the eyes that cannot be controlled by binocular fusion. Esotropia Exotropia Hypertropia HypotropiaDefinitions  Orthophoria: The absence of any tendency of either eye to deviate when fusion is suspended. Seldom Primary deviation: The deviation measured with the normal eye fixing and the eye with the paretic muscle deviating. Prism diopter: A unit of angular measurement used to characterize ocular deviation. A 1-diopter prism deflects a ray of light toward the base of the prism by 1 centimeter at 1 meter. One degree of arc equals approximately 1.7∆.Definitions  Secondary deviation: The deviation measured with the paretic eye fixing and the normal eye deviating. Torsion: Rotation of the eye about its anteroposterior axis Intorsion(Incycloduction): Rotation of the 12 O’clock meridian of the eye toward the midline of the head. Exorsion(Excycloduction): Rotation of the 12 O’clock meridian of the eye away from the midline of the head. Vergences(Disjunctive movements): Movement of the two eyes in opposite direction . Convergence: The eyes turn inward. Divergence: The eyes turn outward.Definitions Physiology Individual Muscle Function Motor AspectsMotor Aspects Field of Action Physiology Synergistic & Antagonistic Muscles Synergistic muscles are those that those that have the same field of action.  Muscles synergistic for one function may be antagonistic for anther.PhysiologyMotor Aspects Yoke Muscles: The pair of agonist muscles with the same primary action.PhysiologyMotor Aspects Binocular Vision: Objects imaged on the two foveas. Because of the different vantage point in space of each eye (For one object only), the image in each eye is actually slightly different from that in the other. Sensory fusion and stereopsis are the two different physiologic processes that are responsible for binocular vision.PhysiologySensory Aspects Sensory Fusion & Stereopsis Sensory fusion is the process whereby dissimilarities between the two images are not appreciated. IN the process of fusion, the direction values of these points can be modified.  Fusion is possible because subtle differences between the two images are ignored, and stereopsis, or binocular depth perception, occurs because of the cerebral integration of these two slightly dissimilar images.Physiology Sensory Aspects Sensory Changes in StrabismusUp to age 7 or 8, the brain usually develops responses to abnormal binocular vision that may not occur if the onset of strabismus in later.  DiplopiaThe foveal image is localized straight ahead, while the peripheral image of the same object in the other eye is localized in some other direction. Thus, the same object is seen in two places (diplopia) Suppression  Amblyopia Anomalous Retinal CorrespondencePhysiology Sensory Aspects Suppression Under binocular viewing conditions, the images seen by one eye become predominant and those seen by the other eye are not perceived (suppression). Suppression takes the form of a scotoma in the deviating eye only under binocular viewings. AmblyopiaProlonged abnormal visual experience in a child under the age of 7 years may lead to amblyopia (reduced visual acuity in the absence of detectable organic disease in one eye). Anomalous Retinal CorrespondencePhysiology Sensory AspectsAnomalous Retinal CorrespondenceAnomalous retinal correspondence is a sensory adaptation that occurs in strabismus under binocular viewing conditions. Heterotropia leads to suppression in the non-fixating eye and a shift in the visual direction of the deviated eye. This shift in visual direction offsets the amount of motor deviation and prevents the perception of diplopia. Stereopsis remains abnormal.Eccentric FixationIn eyes with sufficiently severe amblyopia, an extrafoveal retinal area may be used for fixation under monocular viewing conditions. It is always associated with severe amblyopia and unstable fixation. Gross eccentric fixation can be readily identified clinically by occluding the do。