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Heterophoria
Heterophoria is an eye condition in which the directions that the eyes are pointing at rest position, when ''not'' performing binocular fusion, are not the same as each other, or, "not straight". This condition can be esophoria, where the eyes tend to cross inward in the absence of fusion; exophoria, in which they diverge; or hyperphoria, in which one eye points up or down relative to the other. Phorias are known as 'latent squint' because the tendency of the eyes to deviate is kept latent by fusion. A person with two normal eyes has single vision (usually) because of the combined use of the sensory and motor systems. The motor system acts to point both eyes at the target of interest; any offset is detected visually (and the motor system corrects it). Heterophoria only occurs during dissociation of the left eye and right eye, when fusion of the eyes is absent. If you cover one eye (e.g. with your hand) you remove the sensory information about the eye's position in the orbit. Wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asymptomatic
In medicine, any disease is classified asymptomatic if a patient tests as carrier for a disease or infection but experiences no symptoms. Whenever a medical condition fails to show noticeable symptoms after a diagnosis it might be considered asymptomatic. Infections of this kind are usually called subclinical infections. Diseases such as mental illnesses or psychosomatic conditions are considered subclinical if they present some individual symptoms but not all those normally required for a clinical diagnosis. The term clinically silent is also found. Producing only a few, mild symptoms, disease is paucisymptomatic. Symptoms appearing later, after an asymptomatic incubation period, mean a pre-symptomatic period has existed. Importance Knowing that a condition is asymptomatic is important because: * It may develop symptoms later and only then require treatment. * It may resolve itself or become benign. * It may be contagious, and the contribution of asymptomatic and pre-symptom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fixation Disparity
Fixation disparity is a tendency of the eyes to drift in the direction of the heterophoria. While the heterophoria refers to a fusion-free vergence state, the fixation disparity refers to a small misalignment of the visual axes when both eyes are open in an observer with normal fusion and binocular vision. The misalignment may be vertical, horizontal or both. The misalignment (a few minutes of arc) is much smaller than that of strabismus. While strabismus prevents binocular vision, fixation disparity keeps binocular vision, however it may reduce a patient's level of stereopsis. A patient may or may not have fixation disparity and a patient may have a different fixation disparity at distance than near. Observers with a fixation disparity are more likely to report eye strain in demanding visual tasks; therefore, tests of fixation disparity belong to the diagnostic tools used by eye care professionals: remediation includes vision therapy, prism eye glasses, or visual ergonomics at the w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vergence
A vergence is the simultaneous movement of both eyes in opposite directions to obtain or maintain single binocular vision. When a creature with binocular vision looks at an object, the eyes must rotate around a vertical axis so that the projection of the image is in the centre of the retina in both eyes. To look at an object closer by, the eyes rotate towards each other (convergence), while for an object farther away they rotate away from each other (divergence). Exaggerated convergence is called ''cross eyed viewing'' (focusing on the nose for example). When looking into the distance, the eyes diverge until parallel, effectively fixating the same point at infinity (or very far away). Vergence movements are closely connected to accommodation of the eye. Under normal visual conditions, looking at an object at a different distance will automatically cause changes in both vergence and accommodation, sometimes known as the '' accommodation-convergence reflex''. When under non-typi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optometry
Optometry is a specialized health care profession that involves examining the eyes and related structures for defects or abnormalities. Optometrists are health care professionals who typically provide comprehensive primary eye care. In the United States and Canada, optometrists are those that hold a Doctor of Optometry degree. They are trained and licensed to practice medicine for eye related conditions, in addition to providing refractive (optical) eye care. In the United Kingdom, optometrists may also practice medicine (and provide refractive care) for eye related conditions. The Doctor of Optometry title can also be used in the UK for those that hold the postgraduate O.D. degree. Within their scope of practice, optometrists are considered physicians and bill medical insurance(s) (example: Medicare) accordingly. Moreover, many participate in academic research for eye related conditions and disease. Optometrists are the only health care professionals with a first professiona ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ophthalmology
Ophthalmology ( ) is a surgical subspecialty within medicine that deals with the diagnosis and treatment of eye disorders. An ophthalmologist is a physician who undergoes subspecialty training in medical and surgical eye care. Following a medical degree, a doctor specialising in ophthalmology must pursue additional postgraduate residency training specific to that field. This may include a one-year integrated internship that involves more general medical training in other fields such as internal medicine or general surgery. Following residency, additional specialty training (or fellowship) may be sought in a particular aspect of eye pathology. Ophthalmologists prescribe medications to treat eye diseases, implement laser therapy, and perform surgery when needed. Ophthalmologists provide both primary and specialty eye care - medical and surgical. Most ophthalmologists participate in academic research on eye diseases at some point in their training and many include research as par ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Esophoria
Esophoria is an eye condition involving inward deviation of the eye, usually due to extra-ocular muscle imbalance. It is a type of heterophoria. Cause Causes include: * Refractive errors * Divergence insufficiency * Convergence excess; this can be due to nerve, muscle, congenital or mechanical anomalies. Unlike esotropia Esotropia is a form of strabismus in which one or both eyes turns inward. The condition can be constantly present, or occur intermittently, and can give the affected individual a "cross-eyed" appearance. It is the opposite of exotropia and usual ..., fusion is possible and therefore diplopia is uncommon. References External links {{Eye pathology Disorders of ocular muscles, binocular movement, accommodation and refraction ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exophoria
Exophoria is a form of heterophoria in which there is a tendency of the eyes to deviate outward. During examination, when the eyes are dissociated, the visual axes will appear to diverge away from one another. The axis deviation in exophoria is usually mild compared with that of exotropia. Cause Exophoria can be caused by several factors, which include: *Refractive errors – distance and near deviation approximately equal. *Divergence excess - exodeviation is more than 15 dioptres greater for distance than near deviation. *Convergence insufficiency – near exodeviation greater than distance deviation. These can be due to nerve, muscle, or congenital problems, or due to mechanical anomalies. Unlike exotropia, fusion is possible in this condition, causing diplopia to be uncommon. Diagnosis Prevalence Exophoria is particularly common in infancy and childhood A child (plural, : children) is a human being between the stages of childbirth, birth and puberty, or betwee ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orthophoria
Orthophoria is a condition of binocular fixation in which the lines of vision meet at the object toward which they are directed, and considered as a normal condition of balance of the ocular muscles of the two eyes. The condition opposite of Orthophoria, is called heterophoria Heterophoria is an eye condition in which the directions that the eyes are pointing at rest position, when ''not'' performing binocular fusion, are not the same as each other, or, "not straight". This condition can be esophoria, where the eyes ten .... References Ophthalmology Vision {{eye-disease-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fusional Vergence
Fusional vergence is the movement of both eyes that enables the fusion of monocular images producing binocular vision In biology, binocular vision is a type of vision in which an animal has two eyes capable of facing the same direction to perceive a single three-dimensional image of its surroundings. Binocular vision does not typically refer to vision where an .... It is especially important when a person has heterophoria. Premotor cells for fusional vergence are located in the mesencephalon near the oculomotor nucleus. References Eye {{eye-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Strabismus
Strabismus is a vision disorder in which the eyes do not properly align with each other when looking at an object. The eye that is focused on an object can alternate. The condition may be present occasionally or constantly. If present during a large part of childhood, it may result in amblyopia, or lazy eyes, and loss of depth perception. If onset is during adulthood, it is more likely to result in double vision. Strabismus can occur due to muscle dysfunction, farsightedness, problems in the brain, trauma or infections. Risk factors include premature birth, cerebral palsy and a family history of the condition. Types include esotropia, where the eyes are crossed ("cross eyed"); exotropia, where the eyes diverge ("lazy eyed" or "wall eyed"); and hypertropia or hypotropia where they are vertically misaligned. They can also be classified by whether the problem is present in all directions a person looks (comitant) or varies by direction (incomitant). Diagnosis may be made by obser ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heterotropia
Strabismus is a vision disorder in which the eyes do not properly align with each other when looking at an object. The eye that is focused on an object can alternate. The condition may be present occasionally or constantly. If present during a large part of childhood, it may result in amblyopia, or lazy eyes, and loss of depth perception. If onset is during adulthood, it is more likely to result in double vision. Strabismus can occur due to muscle dysfunction, farsightedness, problems in the brain, trauma or infections. Risk factors include premature birth, cerebral palsy and a family history of the condition. Types include esotropia, where the eyes are crossed ("cross eyed"); exotropia, where the eyes diverge ("lazy eyed" or "wall eyed"); and hypertropia or hypotropia where they are vertically misaligned. They can also be classified by whether the problem is present in all directions a person looks (comitant) or varies by direction (incomitant). Diagnosis may be made by obs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cover Test
A cover test or ''cover-uncover test'' is an objective determination of the presence and amount of ocular deviation. It is typically performed by orthoptists, ophthalmologists and optometrists during eye examinations. The two primary types of cover tests are: * the alternating cover test * the unilateral cover test (or the cover-uncover test). The test involves having the patient focusing on both a distance as well as near object at different times during the examination. A cover is placed over an eye for a short moment then removed while observing both eyes for movement. The misaligned eye will deviate inwards or outwards. The process is repeated on both eyes and then with the child focusing on a distant object. The cover test is used to determine both the type of ocular deviation and measure the amount of deviation. The two primary types of ocular deviations are the tropia and the phoria. A tropia is a misalignment of the two eyes when a patient is looking with both eyes uncov ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
