ASTENOPIA ADALAH PDF
)enyebab utama astenopia adalah kelelahan pada ciliary dan extraoculer otot akibat akomodasi penglihatan jarak dekat dalam 5aktu lama” *aktor penyebab. enyebab utama astenopia adalah kelelahan pada. ciliary. dan. extraoculer. otot akibat akomodasi penglihatan jarak dekat dalam 5aktu lama”. Translator English – Spanish. astenopía. millions of speakers Translator English – Portuguese. astenopia. millions of speakers.
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Translated from Greek aniseikonia means “unequal images”. It is a binocular condition, so the image in one eye is perceived as different in size compared to the image in the other eye. Two different types of aniseikonia can be differentiated: Static aniseikonia or aniseikonia in short means that in a static situation where the eyes are gazing in a certain direction, the perceived peripheral images are different in size see Fig.
Dynamic aniseikonia or optically induced anisophoria means that the eyes have to rotate a different amount to gaze i. This is especially difficult for eye rotations in the vertical direction. Click on image to enlarge. In the remainder of this web-page we will speak of aniseikonia and anisophoria instead of static aniseikonia and dynamic aniseikonia.
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Aniseikonia will be the target parameter to be measured and corrected. By contrast, anisophoria can more or less been determined from the prescription and is a parameter that needs to asenopia kept within bounds when correcting the aniseikonia.
A niseikonia values by definition represent how much the right eye should be magnified or minified to cancel the aniseikonia.
With optically-induced aniseikonia i. This ellipse describes the aniseikonia asfenopia all directions. It consists of an overall aniseikonia and a meridional aniseikonia. The overall part describes the minimum closest to zero aniseikonia aastenopia the meridional part describes the direction-dependent part of the aniseikonia usually induced by the cylinder part of the prescription. In the case of retinally-induced aniseikonia, the aniseikonia most likely varies with field angles we call this field-dependent aniseikonia.
The field angle is defined as the angle between the gaze direction and the direction of a peripheral point see Fig. With field-dependent aniseikonia, one cannot speak of the aniseikonia anymore, since the aniseikonia varies depending on from which location on the retina the aniseikonia is determined. For more information on field-dependent aniseikonia, see our article: First objects in the outside world are imaged with a certain optical magnification minification on the retina.
Next, adala retinal receptors sample the retinal image into ‘pixels’. Finally, this information is processed by the brain. Aniseikonia could basically arise if there is a difference between the eyes in any of the three steps depicted in Fig.
Optically-induced aniseikonia patients might be anisometropespseudophakesand refractive surgery patients. Retinally-induced aniseikonia patients are those patients in which the retina may be compressed or stretched due to an ocular condition or surgery. Due to the compression or stretching, an image projected onto the retina will be sampled by either a greater pr lesser number of receptors, causing the perceived image to appear bigger or smaller macropsia or micropsia.
There may also be a more random local distortion, called metamorphopsia. Retinally-induced aniseikonia patients are for example patients with an epiretinal membrane macular puckera retinal detachmenta macular holemacular edemaor a retinoschisis. We astwnopia not found any cortically-induced aniseikonia patients in the literature.
Bannon and Triller 2 reported a list of characteristic aniseikonia symptoms based on a study with patients see Table 1. Burian 3 published a similar list presenting the symptoms the patients most frequently complained about. His main categories were I. Sometimes sensitive individuals are suspected to have symptoms with less aniseikonia 9but it is well possible that these symptoms are caused by optically-induced anisophoria and not aniseikonia.
The topic of clinically significant aniseikonia values warrants further research. It is unclear what the contribution to aniseikonic symptoms is of aniseikonia versus anisophoria. In case of retinally-induced field-dependent aniseikonia, it is also unclear which field angles and field directions are causing the most symptoms. These rules are based on Knapp’s law, which deals with an image size difference as projected onto the retina in anisometropia i.
Eye care professionals using these rules will base treatment on the patient’s prescription and perhaps the difference in corneal curvature or eye length between the eyes. However, in the more recent literature it has been well established that even in anisometropia, the retinal receptor distribution may also play a role, and therefore these rules of thumb should not be used. Instead the aniseikonia should be measured. There are basically two methods to test for aniseikonia: Table 2 compares the space eikonometer with the three commercially available direct comparison tests: Because it is the most complete product for aniseikonia management, we will now discuss the aniseikonia test of the Aniseikonia Inspector, version 3.
The patient looks through red-green glasses adalwh the computer screen, which gives a series of test images see Fig. For each test image the patient’s task is to identify which of the two I-shaped bars is perceived as larger a forced choice procedure. Note that because of the red-green glasses, one eye sees only the left I-bar and the other eye sees only the right I-bar.
If all images of a series have been presented, the data can be plotted in a ‘psychometric curve’ aadalah Fig. Using a maximum likelihood mathematical method, the aniseikonia value can be obtained from this data. This is also very useful when the patient self-administers the test and the results are analyzed elsewhere. Raw aniseikonia test data.
Each data point represents the result of one presentation as for example shown in Fig. The transition where the left I-bar is perceived as larger to where the right I-bar is perceived as larger is the patient’s aniseikonia. If a fixation disparity is present which might occur especially in the horizontal directionthe aniseikonia test is more difficult to do because the two I-bars will not be symmetrically aligned next to each other.
In software it is easy to compensate for a fixation disparity by shifting the I-bars relative to each other see for example Fig 3b.
So when a patient with a certain vertical fixation disparity looks at Fig. The aniseikonia testing discussed above has all been ‘objective’ testing. However, an eye care provider serious about aniseikonia management should also have a set of size lenses for subjective testing. Size lenses are lenses without refractive power the image stays sharpbut with an optical magnification.
They may provide the patient with a sense of what it would be like to have a certain aniseikonia correction. Of course, no patient is happy about that ‘solution’, and it should only be a last resort.
Aniseikonia and its accompanying aniseikonic symptoms can often be reduced by changing the magnification properties of the auxiliary optics of the patient. There are basically 4 possible optical solutions, each with its own advantages and disadvantages. Depending on the patient’s case optically or retinally induced aniseikonia, refractive errors of the eyes, amount of aniseikonia to be corrected, whether contact lenses are an option, importance of cosmetics, etc.
Below 4 possible optical solutions will be discussed assuming the amount of aniseikonia has been measured. Even though it is best practice to measure the aniseikonia before designing and prescribing a specialized correction see section on testing aniseikonianot all eye care providers may have testing equipment.
In case of optically-induced aniseikonia such as associated with anisometropia, the eye care provider could first examine if contact lenses would improve the vision comfort enough.
Contact lenses fully eliminate any optically induced anisophoria dynamic aniseikonia and often lessen the static aniseikonia. Alternatively to contact lenses, the Shaw TM spectacle atsenopia could be tried. These are specifically aimed at reducing the optically induced anisophoria and may also reduce the aniseikonia. How much and if the aniseikonia will be reduced can only be known though by measuring the aniseikonia asalah. Optical solution 1 contact lenses only If a patient tolerates the use of contact lenses, the first option that should be investigated calculated after the measurement of aniseikonia is what the remaining aniseikonia would be if all of the patient’s prescription were put into contact lenses.
Especially with anisometropia it has been shown that contact lenses often but not always give less aniseikonia than regular spectacle lenses. If this solution happens to work, then there only astenpia to be advantages.
This solution does not compromise the visual acuityit is cosmetically very acceptable, there is no anisophoria contact lenses move with eye rotations, so do not induce any prism effects with eye rotationsand it is relatively low cost. To get a subjective experience of how much this solution would improve the vision comfort, the patient should look first through some trial contact lenses. Optical solution 2 aatenopia only, good VA This is adallah classic aniseikonia correction.
This solution does not compromise the central visual acuity. Because of the changes in shape of the spectacle lenses, adaah cosmetics of the glasses might be compromised depending on the amount of aniseikonia to be corrected.
In optically-induced aniseikonia both aniseikonia and anisophoria are often reduced at the same time. In retinally-induced aniseikonia a correction of the aniseikonia may often result in the introduction of anisophoria, so a balance needs to be found between how much aniseikonia is corrected and how much zdalah is introduced. The amount of introduced anisophoria for this solution may be less though than that of solutions 3 and 4. The cost of these spectacle lenses might be a little higher than standard spectacle lenses, because of the non-standard thickness and curvature of the lenses.
Optical solution 3 glasses only, compromised VA In this solution, the optical magnification change aralah accomplished by altering the refractive power of one of the spectacle lenses. As a consequence the image is blurred in one eye, reducing the effective visual acuity in that eye. Since the other eye is supposed to have a good visual acuity, the overall binocular visual acuity should not be affected too much.
However, the blurring may cause visual discomfort for example, if the blurred eye is strongly dominant. Also, the patient’s eye care professional will need to determine if a decoupling of the central vision due to the blurring in one astenopla is likely to cause, for example, eye alignment astdnopia.
If the refractive power change results in an overcorrection some plus-power addedthen the glasses may become useful as monovision glasses one eye sees sharp at far, and one eye sees astenopka at near.
The spectacle lenses used for this solution can be standard spectacle lenses, so the cosmetics as well as the cost are favorable compared to solution 2.
The resulting amount of anisophoria will depend mainly on the final refractive power difference between the two spectacle lenses for astwnopia aniseikonia, this will often mean that the amount of anisophoria will increase. The anisophoria may be less or more than that of solution 4, depending on the refractive state of the eyes and the aniseikonic correction necessary.
To get a subjective experience of how much and if this solution would approximately improve the vision comfort, the adaalah could be fitted with a trial frame with adlah trial lenses. Optical solution 4 contact – glasses combination This astenoia is similar to solution 3, but now one contact lens is added to restore the compromised visual acuity.
The cosmetics will be good, as standard spectacle lenses can be used. The cost will go up some, because now both glasses and a contact lens are used at the same time.
The anisophoria may be less or more than that of solution 3, depending on the refractive state of the eyes and the aniseikonic correction necessary.
For an isometrope the two eyes appr.
To get a subjective experience of how much and if this solution would approximately improve the vision comfort, the patient should be fitted with a trial frame with standard trial lenses and a trial contact lens. In the case of field dependent aniseikonia associated with retinally-induced aniseikoniathe astebopia cannot be fully corrected by optical means, because an optical correction is approximately field in dependent.