Sample records for aniseikonia

  1. Aniseikonia associated with epiretinal membranes


    Ugarte, M.; Williamson, T H


    Aims: To determine whether the computerised version of the new aniseikonia test (NAT) is a valid, reliable method to measure aniseikonia and establish whether aniseikonia occurs in patients with epiretinal membranes (ERM) with preserved good visual acuity.

  2. Contemporary management of aniseikonia. (United States)

    Achiron, L R; Witkin, N; Primo, S; Broocker, G


    The diagnosis and management of aniseikonia has become a lost art. Refractive surgery and intraocular lens implantation has created a new patient population of anisometropia. Measurement of aniseikonia through instrumentation such as the space eikonometer is not readily available. Therefore, estimating the degree of aniseikonia based on the dioptral differences between the two eyes may be the most practical approach. The optical principles of spectacle magnification can be translated by the prescribing eye doctor to reduce ocular image disparity. Contemporary lens designs, such as hi-index and aspherics, allow the practitioner to modify shape and power factors to achieve higher levels of aniseikonic correction in a cosmetically fashionable pair of spectacles.

  3. Effect of aniseikonia on fusion. (United States)

    Sharma, P; Prakash, P


    Physiological aniseikonia is the basis of stereopsis but beyond certain limits it becomes an obstacle to fusion. It is not well established as to how much aniseikonia can be tolerated by the fusional mechanism. Different tests under different testing conditions have given a wide range of variation. On the synoptophore we had observed tolerance upto 35% aniseikonia in some cases. Under more physiological conditions on a polaroid dissociation stereoprojector we observed lesser baseline fusional vergences but tolerance in about 70% of the cases upto 30% aniseikonia while 25% could tolerate even 35% aniseikonia. However we realise that these indicate the maximal potential and not the symptom free tolerable limits.

  4. Effect of aniseikonia on fusion

    Directory of Open Access Journals (Sweden)

    Sharma Pradeep


    Full Text Available Physiological aniseikonia is the basis of stereopsis but beyond certain limits it becomes an obstacle to fusion. It is not well established as to how much aniseikonia can be tolerated by the fusional mechanism. Different tests under different testing conditions have given a wide range of variation. On the synoptophore we had observed tolerance upto 35% aniseikonia in some cases. Under more physiological conditions on a polaroid dissociation stereoprojector we observed lesser baseline fusional vergences but tolerance in about 70% of the cases upto 30% aniseikonia while 25% could tolerate even 35% aniseikonia. However we realise that these indicate the maximal potential and not the symptom free tolerable limits.

  5. Predicting aniseikonia in anisometropia. (United States)

    Ryan, V I


    In estimating the amount of aniseikonia that may be present in any given case of anisometropia, it is usual to apply the "rule of thumb" approach. The "rule" states that for each diopter of anisometropia, the amount of aniseikonia to be expected is 1 1/2 to 2 percent. The rule is based upon an average value computed for theoretical amounts of aniseikonia in many possible situations that can occur, some of which have little likelihood of being found in everyday clinical practice. Applied to many cases of anisometropia that are common, the rule leads to extreme overstimates and is grossly misleading, often resulting in the mishandling of patients. In this paper, a number of typical cases are dealt with in the refutation of the use of "the rule."

  6. Differences in tests of aniseikonia. (United States)

    McCormack, G; Peli, E; Stone, P


    The New Aniseikonia Test (NAT), a hand-held direct-comparison test using red/green anaglyphs, has several potential advantages as a screener. We compared the validity of the NAT to that of the Space Eikonometer in three experiments: (1) aniseikonia was induced by calibrated size lenses in a double-blind study of 15 normal subjects; (2) habitual aniseikonia was measured with both instruments in four patients; and (3) eight of the normal subjects were retested with a computer-video simulation of the NAT. The NAT underestimated induced aniseikonia by a factor of 3 in the normal subjects and underestimated habitual aniseikonia in four patients. The Space Eikonometer correctly measured the magnitude of induced aniseikonia in the normal subjects. The simulation test did not show underestimation in the eight normal subjects. We could not attribute the NAT's underestimation of aniseikonia to the red/green anaglyph method, printing error, psychophysical method, or the direct-comparison test format. We speculate that the NAT induces a different sensory fusion response to aniseikonia than do the other tests, and that this altered sensory fusion response diminishes measured aniseikonia. We conclude that the NAT is not a valid measure of aniseikonia.

  7. Effect of aniseikonia on fusion


    Sharma Pradeep; Prakash Prem


    Physiological aniseikonia is the basis of stereopsis but beyond certain limits it becomes an obstacle to fusion. It is not well established as to how much aniseikonia can be tolerated by the fusional mechanism. Different tests under different testing conditions have given a wide range of variation. On the synoptophore we had observed tolerance upto 35% aniseikonia in some cases. Under more physiological conditions on a polaroid dissociation stereoprojector we observed lesser baseline f...

  8. Electrophysiological detection of aniseikonia. (United States)

    Lovasik, J V; Robertson, K M


    Steady-state and transient Visually Evoked Responses (VERs) were used to verify a paradoxical aniseikonic condition in an anisometropic patient. Testing on the Remole multimeridional horopter apparatus indicated that a 2% overall magnification was required for the more hyperopic eye to eliminate ocular image size differences. A special lens correction for the patient's aniseikonia resulted in a very significant improvement in visual comfort and binocular function.

  9. [Aniseikonia of central serous chorioretinopathy]. (United States)

    Hisada, H; Awaya, S


    Central serous chorioretinopathy (CRS) is one of the typical diseases that accompany micropsia. However very little is known about micropsia of CRS, because of the difficulty to measure "aniseikonia" in terms of micropsia. Aniseikonia in 65 cases of CRS was measured quantitatively by Awaya's New Aniseikonia Tests (NAT). The tests were performed at two different distances of 40 cm (visual angle: 6 degrees) and 20 cm (12 degrees) and under 4 meridians of the halfmoon on NAT, horizontal, 45 degrees, vertical and 135 degrees, respectively. The mean value of aniseikonia under each testing condition was as follows: 6 degrees horizontal -3.13%, 45 degrees -2.56%, vertical -2.13%, 135 degrees -2.57%, 12 degrees; horizontal -1.38%, 45 degrees -1.69%, vertical -1.84%, 135 degrees -1.50%. At 6 degrees aniseikonia is larger in the horizontal meridian than in the vertical with statistical significance (t-test, p less than 0.05), while at 12 degrees aniseikonia is smaller than at 6 degrees and shows no particular tendency in terms of meridian. The phenomenon observed at 6 degrees may be what is called "oriented metamorphopsia".

  10. Effect of induced aniseikonia on fixation performance. (United States)

    Remole, A


    The purpose of the study was to determine to what extent induced aniseikonia affects fixation performance. Aniseikonia was induced in the vertical meridian only, whereas fixation alignment was monitored in the horizontal meridian. A previously developed technique based on the dependency of border enhancement bandwidth on fixation eccentricity was used to monitor deviations from central fixation during fusion. Stress on the fusion mechanism was supplied by controlled increments of forced horizontal vergence. It was found that deviation from central fixation in the horizontal meridian generally increases with increasing amounts of vertical aniseikonia. The effect is particularly pronounced for small amounts of aniseikonia.

  11. [Fusion amplitude and aniseikonia. Experimental studies of aniseikonia tolerance in unilateral aphakia]. (United States)

    Pittke, E C


    The fusion amplitude of image pairs with aniseikonia was measured using the synoptophore. Aniseikonia was produced in five subjects by alteration of slide drawings. The subject's right eye was in cycloplegia after paralysis with cycloplegic eye drops. To compare these measurements with aniseikonic pictures to those using the same image pairs without aniseikonia the fusion amplitude achieved was expressed as a percentage of the aniseikonia-free fusion amplitude. The relation between aniseikonia, eccentricity of the image borders and percent fusion amplitude was described using a mathematical approach. The experimental results reveal that a minimal increase in overall aniseikonia with greater eccentricities (greater than 5 degrees) leads to a rapid decrease in the fusion amplitude and the occurrence of diplopia. The aniseikonia tolerance level of images with greater eccentricities achieved experimentally and theoretically are in good agreement with results found in unilaterally aphakic patients.

  12. Effect of aniseikonia on binocular function. (United States)

    Katsumi, O; Tanino, T; Hirose, T


    The pattern reversal visual evoked response (VER) was recorded under conditions of artificially unbalanced visual input between two eyes, an aniseikonia induced by size lenses that alter the perceived retinal image size without changing refraction. At 3.0% aniseikonia binocular summation started to decrease, and at 5.0% aniseikonia there was no significant binocular summation. In higher aniseikonia (8.0-10.0%), binocular inhibition replaced binocular summation. The phase difference between binocular and monocular VER was largest at zero aniseikonia. When aniseikonia exceeded 5.0%, there was no significant phase difference between the two recording conditions. These results suggested that the binocular system can compensate for up to a 3.0% difference in perceived retinal image size (aniseikonia), but in higher aniseikonia the binocular system can no longer compensate for the difference and binocular inhibition takes place. These findings agree with previously reported subjective and psychophysical results. The authors suggest that this objective method of evaluation using the pattern reversal VER may be helpful in pediatric ophthalmology when subjective methods are of limited use.

  13. Validity and repeatability of a new test for aniseikonia


    Antona Peñalba, Beatriz; Barra Lázaro, Francisco; Barrio de Santos, Ana Rosa; González Díaz-Obregón, Enrique; Sánchez Pérez, Isabel


    PURPOSE. The Aniseikonia Inspector 1.1 (AI) is a new software product to measure aniseikonia using red-green anaglyphs. The purpose of this study was to test whether the AI is a valid and reliable test. METHODS. There were two groups of sample subjects: one at risk of aniseikonia, with anisometropia greater than or equal to 1.00 D (n = 29), and a control group (n = 45). The validity was studied by comparing the measured aniseikonia with the aniseikonia simulated with size lenses. The reli...

  14. Anisophoria and aniseikonia. Part I. The relation between optical anisophoria and aniseikonia. (United States)

    Remole, A


    Part I of this publication demonstrates and explains the close relation between aniseikonia and anisophoria induced by spectacles. It discusses the clinical implications of this relation by discussing certain aspects of aniseikonia theory, prismatic effects during oblique gaze through spectacles as for reading, and a simple formula that presents a comprehensive description of all prismatic effects and prismatic differences produced by a pair of spectacles. It also describes an easy method of specifying iseikonic lenses, as well as some conventional methods of measuring aniseikonia and anisophoria. Part II will deal with the correction and management of anisophoria when induced together with aniseikonia. Parts I and II, together, will convey a new approach toward the management of anisophoric spectacle corrections.

  15. Binocular function in unilateral aphakia. Correlation with aniseikonia and stereoacuity. (United States)

    Katsumi, O; Miyanaga, Y; Hirose, T; Okuno, H; Asaoka, I


    Aniseikonia and stereoacuity were measured in patients with unilateral aphakia, most of whom were postoperative senile cataract cases. The New Aniseikonia test was used to evaluate aniseikonia and the Titmus Stereotest to measure stereoacuity. Ninety cases were studied, 57 (63.3%) of which had intraocular lens (IOL) implants; 27 (30%) had extended-wear soft contact lenses; and six (6.7%) had spectacle lenses. In the IOL group, aniseikonia averaged 2.8%, and 39 patients (68.4%) had good stereoacuity. In the contact lens group, aniseikonia averaged 4.6%, and 11 (40.7%) had good stereoacuity. In the spectacle lens group, aniseikonia averaged 17.8%; none of the patients had good stereoacuity. The authors concluded that in cases with unilateral aphakia, correction with an IOL implant is superior to the other alternatives in achieving good binocular function.

  16. [Aniseikonia reduces binocular summation in the VECP]. (United States)

    Krause, K; Gerding, H; Timmermann, M; Kauffmann, T


    The binocular summation effect of human VECP (increase in amplitude from about 4.0 microV to about 5.4 microV) was proved and optimized in 32 subjects. Stimulus parameters: TV steady-state pattern reversal (7.0 Hz); pattern size 1 degree; stimulus contrast 5% (higher stimulus contrasts reduced considerably the selectivity of the binocular summation effect); 96 sweeps averaging (Nicolet Compaq Four); position of electrodes: 10% and 30% above Protuberantia occipitalis externa of nasioninion distance. Aniseikonia of 7 to 52% was generated by means of small Galilei telescopes. Because of comparatively large interindividual variance within the series of subjects, no decrease in binocular VECP amplitude could be demonstrated at an aniseikonia less than 52%. On one woman subject, a significant reduction in amplitude (5% level) at 14%, 26% and 52% aniseikonia was apparent, but not at 7%. Thus, for this subject, it was possible to correlate the results with the clinically known limits of toleration for aniseikonia. This result was confirmed by more than 60% of the subjects in the test group.

  17. The control of aniseikonia after intraocular lens implantation. (United States)

    Hillman, J S; Hawkswell, A


    This paper reports a study of postoperative refraction and eikonometry of 50 patients who had unilateral cataract extraction with implantation of a pupil-supported intraocular lens. The mean postoperative aniseikonia (+/- SD) was 1.97 (+/- 1.82). A statistically significant relationship was shown between anisometropia and aniseikonia. Despite aniseikonia of up to 7.8 per cent there were no diplopia problems as the visual system exhibits a high degree of tolerance. It is concluded that aniseikonia can be controlled to within clinically acceptable limits by the simple calculation of intraocular lens power for isometropia.

  18. Aniseikonia in patients with a unilateral artificial lens, measured with Aulhorn's phase difference haploscope. (United States)

    Miyake, S; Awaya, S; Miyake, K


    Aniseikonia was measured in unilaterally pseudophakic patients using Aulhorn's phase difference haploscope. Mean values of aniseikonia were 1.5% horizontally and 2.0% vertically without correction, and 2.1% horizontally and 2.3% vertically with correction. With spectacle correction, the greater the dioptric difference between two eyes, the greater the amount of aniseikonia. In either case, patients tolerated these amounts of aniseikonia according to our criteria of aniseikonia tolerance.

  19. Reduced aniseikonia in axial anisometropia with contact lens correction. (United States)

    Winn, B; Ackerley, R G; Brown, C A; Murray, F K; Prais, J; St John, M F


    Aniseikonia, although present in isometropia, is associated principally with anisometropia and is widely thought to be the result of differences in the retinal image size presented to each eye. This assumes that equating retinal image size results in congruous cortical images. To test this assumption 1 refractive and 17 axial anisometropic subjects were examined to determine the aniseikonia present when corrected with spectacles and contact lenses. Contrary to many previous predictions, based upon Knapp's Law, the presence of equal retinal images resulted in larger aniseikonias than observed when the eyes were presented with unequal retinal images. This suggests that non-optical components have a significant role in the production of the cortical image, and this therefore requires a shift in the way the management of anisometropia is considered clinically. Contact lens correction maintains the aniseikonia at a minimum level in axial as well as refractive anisometropia and offers the clinician an acceptable practical alternative when prescribing for these patients.

  20. Aniseikonia and Foveal Microstructure after Retinal Detachment Surgery. (United States)

    Okamoto, Fumiki; Sugiura, Yoshimi; Okamoto, Yoshifumi; Hiraoka, Takahiro; Oshika, Tetsuro


    Purpose:To quantify aniseikonia after successful surgical repair of rhegmatogenous retinal detachment (RD), and to investigate the relationship between the severity of postoperative aniseikonia and retinal microstructures as well as clinical parameters. Methods:The study included 106 eyes of 106 patients, without any history of ocular disease/surgery and less than 2 diopters of anisometropia, who had undergone successful retinal reattachment surgery. Aniseikonia was measured with New Aniseikonia Test and foveal microstructure was assessed with the spectral-domain optical coherence tomography at 6 months postoperatively. Results:Twenty-eight of 106 patients (26%) had micropsia, 17 patients (16%) had macropsia, and 61 patients (58%) had no aniseikonia. The mean absolute value of aniseikonia was 2.3 ± 2.9% (range; -12.5% - +12.0%). Of 57 eyes with macula-on RD, 3 had micropsia and 12 had macropsia. Of 49 eyes with macula-off RD, 25 had micropsia and 5 had macropsia. Eyes with micropsia mostly exhibited persistent or transient cystoid macular edema, subretinal fluid, hyperreflective or disruption of IS/OS line, while most of the eyes with macropsia presented epiretinal membrane. Stepwise multiple regression analysis revealed that postoperative best-corrected visual acuity and the area of RD were significantly relevant to the mean absolute value of aniseikonia. Conclusions:These results suggested that about half of patients with successful repair of RD had aniseikonia. Eyes with macula-off RD tended to show micropsia, while those with macula-on RD mostly presented macropsia. Micropsia and macropsia were primarily caused by respective specific abnormal structures at the foveal region.

  1. Residual aniseikonia among patients fitted with one or two intraocular lenses (pseudophakic corrections) (United States)

    Lakshminarayanan, V; Enoch, J M; Knowles, R A


    In the presence of one or two intraocular lenses (IOL's; pseudophakic corrections) or in the presence of naturally occurring or developmental anisometropia (due to a tumescent cataract) some induced or residual refractive aniseikonia is usually encountered. We wish to call this problem to the attention of the optometric practitioner. We provide a discussion of the resultant aniseikonia and simple rules of thumb for management of such patients with refractive aniseikonia. Aniseikonia in these patients may be less important than once had been suggested, but certainly it is more significant than it is currently being considered. Use of personal computers to calculate this aniseikonia makes appropriate correction relatively easy and readily applicable.

  2. The influence of aniseikonia on the VEP by random-dot stereogram. (United States)

    Oguchi, Y; Mashima, Y


    Static random-dot stereograms were employed to evaluate the unequal input between two eyes, both objectively by VEP and psychophysically. In subjects with normal binocular function, different levels of artificial aniseikonia (from 2% to 15%) were established by placing several levels of size lenses in front of one eye. Binocular summation in amplitude in the VEP was observed below 5% aniseikonia, and the binocular inhibition took place above 5% aniseikonia. Psychophysically, perception of stereopsis could be maintained between 3% and 5% aniseikonia, but disappeared above 5% aniseikonia. Electrophysiological findings of binocular interaction caused by aniseikonia corresponded to the psychophysical findings, and stereoscopic perception was obtained only in the case of binocular summation in the VEP. In the present study, the amount of tolerable aniseikonia in order to maintain stereopsis was considered to be below 5%.

  3. Aniseikonia and fixation performance: effect of retinal stimulus location. (United States)

    Remole, A


    It has been shown previously that induced aniseikonia amplifies any latent fixation eccentricity associated with binocular fusion stress. This study determines if the retinal location of the stimulus plays a part in this effect. The stimulus consisted of a vertical border formed by the juxtaposition of two fields of unequal luminances and a line segment parallel to the border whose distance from the border can be varied. At the same time, the border allowed the application of a previously tested method of measuring fixation eccentricity, based on the border-enhancement response. It was found that the fixation eccentricity produced by aniseikonia is maximal for the smallest distance of the variable target from the border but unaffected by the larger distances tested. It was concluded that the retinal location of the stimulus has an important influence on the response to aniseikonia.

  4. [Functional aniseikonia: clinical study of 110 cases (author's transl)]. (United States)

    Reboud, F N; Vola, J L; Berard, P V


    A clinical study was conducted in 110 cases of subjective aniseikonia, a syndrome that is often neglected. After in practice summarizing the different distortions composing the phenomenon of aniseikonia, a description of the prototype apparatus used for the experiments is given: it is eikonometric stereo-projector the originality of which lies in the measuring system, constituted by the projected stereograms. Three parameters were studied: depth-perception, peerception threshold of anseiikonic disparity, and value of the found aniseikonia. The results are presented in relation to 3 groups of subjects: 14 emmetropic, 32 isometropic, and 64 anisometropic, 32 isometropic, and 64 anisometropic patients, including 24 monocular aphakic. The author shows the advantage of contact lens correction in the last cases: with an average of 3.5 p. cent, the found aniseikonia was always inferior to 6 p. cent and to the theorectical levels currently accepted. Finally, the phenomenon of "cortical malleability" arises in the adaptation of the patient to his optical correction and could regularly and progressively be increased.

  5. Elimination of aniseikonia in monocular aphakia with a contact lens-spectacle combination. (United States)

    Schechter, R J


    Correction of monocular aphakia with contact lenses generally results in aniseikonia in the range of 7--9%; with correction by intraocular lenses, aniseikonia is approximately 2%. We present a new method of correcting aniseikonia in monocular aphakics using a contact lens-spectacle combination. A formula is derived wherein the contact lens is deliberately overcorrected; this overcorrection is then neutralized by the appropriate spectacle lens, to be worn over the contact lens. Calculated results with this system over a wide range of possible situations consistently results in an aniseikonia of 0.1%.

  6. [Contribution of contact lenses to the reduction of aniseikonia in myopic patients after unilateral cataract operations (author's transl)]. (United States)

    Kreis-Gosselin, F; Prevost, G; Bonnac, P


    The most rapid method for determining the best mode of optical compensation in myopic patients following cataract operations was studied, by employing a graphic method for calculating theoretical aniseikonia and measuring subjective aniseikonia with a new stereo-projector. Several examples of the method chosen are given, this involving optical equipment--glasses, lens, myopisation--aniseikonia being reduced to a maximum.

  7. Aniseikonia for near vision with unilateral aphakia corrected by intraocular lenses. (United States)

    Ivashina, A I


    1. Our methods for calculation of aniseikonia for near vision allow one to determine it in every patient with an intraocular lens. 2. With an eye with an artificial lens there is a correlation between the amount of accommodation used by the phakic eye and aniseikonia changes subject to the distance from the object. Calculations for aniseikonia for near vision in 43 patients showed that with accommodation used by the normal eye aniseikonia was increased by 3.0% to 7.8% as compared with aniseikonia for distance. With accommodation of the phakic eye lacking, aniseikonia for near vision did not differ much from its value for distance. 3. Calculations for aniseikonia for near vision showed the advantage of intraocular lens implantation for obtaining iso-iconia for distance or tolerable aniseikonia not more than 2.5% to 3.0%. 4. For obtaining iso-iconia for near vision it is necessary to correct the phakic eye to switch off its accommodation partially or completely (with emmetropia, correction +2.0D for near vision).

  8. Impact of induced aniseikonia on stereopsis with random-dot stereogram. (United States)

    Jiménez, J R; Ponce, A; del Barco, L Jiménez; Díaz, J A; Pérez-Ocón, F


    In this work, we evaluate the impact of induced aniseikonia on stereopsis. For this, we determined the disparity range (maximum disparity), a parameter related to the size of the physical region that can be perceived stereoscopically. A significant decline in the disparity range was detected with aniseikonia induced by size lenses of 3% for five of the seven observers tested; 5% was necessary for the other two observers. The data indicate the influence of aniseikonia in stereopsis and the need to minimize such impact. These results may be useful in surgical processes such as the correction of pseudophakic patients and refractive surgery in which aniseikonia can be induced to alter the binocular function of the patient.

  9. Aniseikonia Tests: The Role of Viewing Mode, Response Bias, and Size–Color Illusions


    García-Pérez, Miguel A.; Peli, Eli


    PURPOSE To identify the factors responsible for the poor validity of the most common aniseikonia tests, which involve size comparisons of red-green stimuli presented haploscopically. METHODS Aniseikonia was induced by afocal size lenses placed before one eye. Observers compared the sizes of semicircles presented haploscopically via color filters. The main factor under study was viewing mode (free viewing versus short presentations under central fixation). To eliminate response bia...

  10. Aniseikonia Tests: The Role of Viewing Mode, Response Bias, and Size–Color Illusions (United States)

    García-Pérez, Miguel A.; Peli, Eli


    Purpose: To identify the factors responsible for the poor validity of the most common aniseikonia tests, which involve size comparisons of red–green stimuli presented haploscopically. Methods: Aniseikonia was induced by afocal size lenses placed before one eye. Observers compared the sizes of semicircles presented haploscopically via color filters. The main factor under study was viewing mode (free viewing versus short presentations under central fixation). To eliminate response bias, a three-response format allowed observers to respond if the left, the right, or neither semicircle appeared larger than the other. To control decisional (criterion) bias, measurements were taken with the lens-magnified stimulus placed on the left and on the right. To control for size–color illusions, measurements were made with color filters in both arrangements before the eyes and under binocular vision (without color filters). Results: Free viewing resulted in a systematic underestimation of lens-induced aniseikonia that was absent with short presentations. Significant size–color illusions and decisional biases were found that would be mistaken for aniseikonia unless appropriate action is taken. Conclusions: To improve their validity, aniseikonia tests should use short presentations and include control conditions to prevent contamination from decisional/response biases. If anaglyphs are used, presence of size–color illusions must be checked for. Translational relevance: We identified optimal conditions for administration of aniseikonia tests and appropriate action for differential diagnosis of aniseikonia in the presence of response biases or size–color illusions. Our study has clinical implications for aniseikonia management. PMID:26101722

  11. Amount of aniseikonia compatible with fine binocular vision: some old and new concepts. (United States)

    Campos, E C; Enoch, J M


    Random Dot Stereograms (RDS) are useful, but are sometimes misleading in assessing the degree of binocular cooperation in the presence of aniseikonia. RDS may give positive results up to 15% aniseikonia, whereas a fine central binocularity is not possible with more than 5% image-size difference. It is suggested that stereopsis may not be the only parameter to test; stress is given to the importance of peripheral motor fusion in maintaining the eye alignment.

  12. Measuring aniseikonia using scattering filters to simulate cataract (United States)

    Wilson, Jason


    The relationship between anisometropia and aniseikonia (ANK) is not well understood. Ametropic cataract patients provide a unique opportunity to study this relationship after undergoing emmetropizing lens extraction. Because light scatter may affect ANK measurement in cataract patients, its effect should also be evaluated. The Basic Aniseikonia Test (BAT) was evaluated using afocal size lenses to produce specific changes in retinal height. Several light scattering devices were then evaluated to determine which produced effects most similar to cataract. Contrast sensitivity and visual acuity (VA) losses were measured with each device and compared to those reported in cataract. After determining the most appropriate light scattering device, twenty healthy patients with normal visual function were recruited to perform the BAT using the filters to simulate cataract. Cataract patients were recruited from Vision America and the University of Alabama at Birmingham School of Optometry. Patients between 20 and 75 years of age with at least 20/80 VA in each eye, ≥ 2D ametropia, and normal binocular function were recruited. Stereopsis and ANK were tested and each patient completed a symptom questionnaire. ANK measurements using afocal size lenses indicated that the BAT underestimates ANK, although the effect was minimal for vertical targets and darkened surroundings, as previously reported. Based on VA and contrast sensitivity loss, Vistech scattering filters produced changes most similar to cataract. Results of the BAT using Vistech filters demonstrated that a moderate cataract but not a mild cataract may affect the ANK measurement. ANK measurements on cataract patients indicated that those with ≥ 2 D ametropia in each eye may suffer from induced ANK after the first cataract extraction. With upcoming healthcare reform, unilateral cataract extraction may be covered, but not necessarily bilateral, depending on patient VA in each eye. However, a questionnaire about symptoms

  13. [Strabogenesis in case of low hypermetropia, in addition a simple comparison test to detect aniseikonia (author's transl)]. (United States)

    Kettesy, A


    Author attempts to explain the rise of infantile convergent squint, when the hypermetropia is less than 3,5 diopter. In such cases the low hypermetropia is relative in the sense of Donders, because a sometimes isometropic aniseikonia prevents the fusion. To examine the aniseikonia he recommands a very simple procedure, the comparison test, carried out joined to the cover test.

  14. Effects of aniseikonia, anisometropia, accommodation, retinal illuminance, and pupil size on stereopsis. (United States)

    Lovasik, J V; Szymkiw, M


    The sensitivity of clinical measures of stereoacuity in the detection of interocular differences in retinal images was examined in 50 adults with normal binocularity. Interocular differences in retinal image size (aniseikonia), clarity (anisometropia) and brightness, as well as differences in absolute and relative pupil size (anisocoria) were created in small steps over a large range to determine their effect on threshold levels of stereopsis. Their effect on stereoacuity was measured in both contour (Titmus test) and random dot (Randot test) stereograms. Stereoacuity measured by both types of stereograms decreased in a curvilinear manner for aniseikonic and anisometropic test conditions. Monocular blur caused a more rapid decrease in stereoacuity than induced aniseikonia. Stereoacuity measured by the contour stereogram decreased about 1.8 times faster than that measured by the random dot stereogram during induced aniseikonia and anisometropia. This differential sensitivity suggests that the Titmus test would detect small interocular differences in retinal images more effectively than the Randot test in clinical screening procedures for vision abnormalities. However, both tests can miss clinically significant amounts of aniseikonia and anisometropia, and fail to differentiate the cause of reduced stereopsis. Interocular differences in retinal image brightness and pupil size within a normal physiologic range did not reduce stereopsis to clinically unacceptable levels.

  15. Effect of lens induced aniseikonia on stereopsis%无焦放大镜诱导的不等像对立体视功能的影响

    Institute of Scientific and Technical Information of China (English)

    康峥; 高祥璐; 张艳龙


    Objective To study the effect of lens induced aniseikonia on stereopsis with size lenses.Methods A prospective randomized block design was used.Two percent,3%,5%,8%and 10% of aniseikonia were induced by various lens magnification in front of the right eyes of 45 subjects.Stereopsis was then tested utilizing the Stereo Fly Test and Digital Stereoscopic Test Charts (DSTC) under normal binocular vision and induced aniseikonia.The effect of induced aniseikonia on stereopsis then was analyzed based on the data collected.The data was analyzed by Friedman's M test,Spearman rank correlation,Wilcoxon rank sum test and Kruskal-Wallis H test.Results Stereopsis was significantly affected by induced aniseikonia [FLY (x2=210.113,P<0.01,DSTC (x2=162.237,P<0.01]; stereopsis was measurably reduced by 2% aniseikonia,and drastically reduced when aniseikonia was more than 5%.The decline in stereoacuity was positively correlated with induced aniseikonia [FLY (rs=0.776,P=0.000),DSTC (rs=0.626,P=0.000)].Conclusion Stereopsis and other aspects of binocular function are impaired if aniseikonia reaches 2%.An aniseikonia test should be performed more frequently in clinical settings.%目的 研究无焦放大镜诱导下的不等像对立体视功能的影响.方法 前瞻性随机区组设计实验研究.通过在被检者右眼前放置无焦放大镜,人工诱导2%、3%、5%、8%、10%不等像.用FLY立体视测试图和数字化随机点立体图(DSTC)分别测试在正常双眼视情况下及在2%、3%、5%、8%、10%诱导性不等像条件下的立体视锐度,分析诱导性不等像对立体视功能的影响.采用多组相关样本的秩和检验Friedman检验和Spearman秩相关,两组独立样本的Wilcoxon秩和检验,多组独立样本Kruskal Wallis秩和检验进行分析.结果 诱导性不等像对立体视功能具有显著性影响[FLY(x2=210.113,P<0.01),DSTC(x2=162.237,P<0.01)];当不等像为2%时立体视功能

  16. Aniseikonia, metamorphopsia and perceived entoptic pattern: some effects of a macular epiretinal membrane, and the subsequent spontaneous separation of the membrane. (United States)

    Enoch, J M; Schwartz, A; Chang, D; Hirose, H


    Following cryo surgery for retinal hole repair, visual effects in the senior author's eyes were caused by an epiretinal membrane. Subjectively, metamorphopsia was noted, and entoptically perceived radial striae were observed centred near fixation. After subsequent cataract surgery, metamorphopsia was not detectable. Several months later, the centre of the striate entoptic pattern was observed to be centered several degrees from fixation. Concurrently, loss of contrast in the central visual field was noted. In time, both the entoptic pattern and the contrast effects became less visible (contrast improved much faster). The epiretinal membrane had spontaneously separated from the fovea. Repeated measurements of aniseikonia were obtained before cataract surgery, and after cataract surgery both prior to, and after the separation of the epiretinal membrane. Inferences are drawn.

  17. The design and application of an aniseikonia test based on synoptophore%一种同视机不等像检查图的研制与应用

    Institute of Scientific and Technical Information of China (English)

    康峥; 高祥璐; 张艳龙


    Objective To design a subjective aniseikonia test using the synoptophore and to evaluate the validity and repeatability of the tests for further use in clinical practice.Methods It was a repeat measurement design.Two graphs were designed based on the ratio of similar triangles.The differences in size,between subjective images for each eye were measured with the synoptophore.The validity of the test was evaluated by comparing the difference between the measured aniseikonia and the theoretical aniseikonia simulated by different power lenses, and the repeatability was evaluated by comparing the results obtained at two different time points with an interval of 24 hours.The data were analyzed by linear regression analysis and analysis of covariance. Results The regression coefficient of the overall regression equation was 0.908 for tbe two different time points,which was lower than the theoretical value (the theoretical value is 1).There was no statistically significant difference between the results of the two different time points.Conclusion The validity and repeatability of this aniseikonia test is relatively high.However,further clinical study should be carried out to test its use in the clinic.%目的 设计一种基于同视机的不等像检测画片,并检验其在临床应用中的有效性和可靠性.方法 前瞻性重复测量设计实验研究.根据相似三角形相似比的原理设计两张同视机不等像测量画片,用来检测主观不等像值.通过比较实际测量的不等像和无焦放大镜诱导的不等像理论来研究该画片的可靠性,比较间隔24 h的两次测量结果来研究该画片的可重复性.实验数据采用直线回归分析和协方差分析进行统计学分析.结果 两次测量结果总的回归系数0.908,比理论值l低;两次测量结果间差异无统计学意义.结论 该同视机不等像检查图具有较高的可靠性和可重复性.但其在临床中的检验效果,还需要做进一步的临床研究.

  18. 新型计算机不等像检测软件的研制及试用%Application and study of a new aniseikonia test based on the computer

    Institute of Scientific and Technical Information of China (English)

    徐进; 胡聪; 胡卓颖


    目的设计计算机不等像检测方法(aniseikonia test based on computer,ATBC),克服旧图片式不等像检查法的位置线索,提高精度.方法 (1)自制计算机不等像检查软件,在显示屏上绘制可以单屏显示,通过红绿眼镜分视检查;亦可在同视机分视下双屏显示检查的十字和圆两图形,十字图形可调节大小并能自动报告两图形比例;(2)检查正常32例;(3)左右移动同视机(改变屏幕到角膜顶点的距离),人为改变左右眼视网膜上像的大小,然后测试双屏ATBC并与理论计算结果相比较.结果双屏ATBC测试的结果与理论值差异无显著性(P>0.05).单屏与双屏ATBC检查结果差异无显著性(P>0.05).结论 ATBC能够较好的反映双眼影像的真实比值,且不存在位置线索,具有较高的精确度.

  19. [Study and application of "binocular aniseikonia test chart"]. (United States)

    Liu, A N; Yan, S M


    With the help of this chart, the image incongruity of simultaneous perception, fusion and stereoscopic vision can be precisely determined. It can objectively evaluate the binocular visual function and possesses important significance for the diagnosis and treatment of anisometropia, amblyopia, strabismus and visual fatigue.

  20. Saccade amplitude disconjugacy induced by aniseikonia: role of monocular depth cues. (United States)

    Pia Bucci, M; Kapoula, Z; Eggert, T


    The conjugacy of saccades is rapidly modified if the images are made unequal for the two eyes. Disconjugacy persists even in the absence of disparity which indicates learning. Binocular visual disparity is a major cue to depth and is believed to drive the disconjugacy of saccades to aniseikonic images. The goal of the present study was to test whether monocular depth cues can also influence the disconjugacy of saccades. Three experiments were performed in which subjects were exposed for 15-20 min to a 10% image size inequality. Three different images were used: a grid that contained a single monocular depth cue strongly indicating a frontoparallel plane; a random-dot pattern that contained a less prominent monocular depth cue (absence of texture gradient) which also indicates the frontoparallel plane; and a complex image with several overlapping geometric forms that contained a variety of monocular depth cues. Saccades became disconjugate in all three experiments. The disconjugacy was larger and more persistent for the experiment using the random-dot pattern that had the least prominent monocular depth cues. The complex image which had a large variety of monocular depth cues produced the most variable and less persistent disconjugacy. We conclude that the monocular depth cues modulate the disconjugacy of saccades stimulated by the disparity of aniseikonic images.

  1. Compendium of U.S. Army Visual Medical Fitness Standards (United States)


    service. Table 15 Visual standards for retention -- Category Standard Aniseikonia Correctable with iseikonic lenses Dipiopia, Intermittent and in zone...Table 16 Visual standards for mobilization Category Standard Aniseikonia Correctable with iseikonic lenses Diplopia, Intermittent and in zone

  2. The Prevalence of Aphakia in the Civil Airman Population (United States)


    of vision; enlarged visual image (30% magnification); aniseikonia in monocular aphakia; and prismatic and aberrational effects that require head rather...intraocular lenses include: freedom from patient handling, normal peripheral vision, minimal aniseikonia , and rapid return of binocular vision (10

  3. 人工晶体眼的不等像双眼视临床分析%Aniseikonia and binocular vision in pseudophakia patients

    Institute of Scientific and Technical Information of China (English)

    邓大明; 冯波; 林振德; 麦光焕; 林小铭


    目的 了解探讨白内障超声乳化摘除联合折叠型人工晶体囊袋内植入术后患者的双眼单视功能,以及人工晶体植入术后对双眼影像不等的影响、患者保持双眼单视功能所允许的像差程度和范围.方法 随机抽取了术后视力在0.7以上的29例白内障超声乳化摘除联合折叠型人工晶体囊袋内植入术后患者,年龄41~74岁,按双侧或单侧人工晶体眼分成A、B两组;术后一周应用刘蔼年编检测患者的双眼单视功能和双眼影像不等的程度,并分别与正常眼以及两组之间进行比较.结果 除B组3例患者没有立体视外,其余患者均有Ⅲ级双眼单视功能.且两组间的各级影像不等像差值无统计学差异(P>0.05).与正常眼相比,A和B组的Ⅰ级同时视和Ⅱ级融合功能的双眼影像不等像差值均无统计学差异(P>0.05),Ⅲ级立体视功能的双眼影像不等值与正常对照有显著性差异(P<0.01),可能因3例单侧人工晶体无立体视有关.结论 白内障超声乳化摘除联合囊袋内植入的人工晶体,除了获得良好的视力恢复外,并获得正常的Ⅲ级双眼单视功能,不引起Ⅲ级视功能的像差异常改变,是极理想的手术方式.

  4. Aniseikonia in unilateral pseudophakia and its magnification change%假晶体眼的放大率与不等像

    Institute of Scientific and Technical Information of China (English)

    刘晓玲; 金成鹏



  5. Psychophysical Criteria for Visual Simulation Systems. (United States)


    differences ( aniseikonia ) encompass a variety of visual display problems in which the images to the two eyes differ. These disparities are categorized...displacements is treated in the discussion of binocular image rotation. The topic of unequal magnification ( aniseikonia ), which has been the subject of much...The specific functional relationships needinq quantification were the following: 1. The effect of Horizontal Aniseikonia on Target Detection and

  6. Stereo Reconstruction Study (United States)


    geometric explanation of the percepts obtained with uniform and oblique meridional aniseikonia . The authors utilize the geometric theory to construct a...uniform aniseikonia . .1________ Payhcelon and Neuropheiolmo §7.1.6 213 Hogben, Juleoz and Rose 1976 Hogben, J.H., Bela Julesz, and John Ross, "Short

  7. Perception of Depth with Stereoscopic Combat Displays. (United States)


    phorias and aniseikonia contributed to visual fatigue in * observers of stereo displays though this proposition has never been put to test. In future...experiments, individuals with slight, but measurable, eye muscle imbalances or aniseikonia -should be compared with normals across various viewing sy

  8. Perception of Spatial Features with Stereoscopic Displays. (United States)


    aniseikonia (differences in retinal image size in the two eyes) are of little significance because only monocular perception of the display is required for...perception as a result of such factors as aniseikonia , uncor- rected refractive errors, or phorias results in reduced stereopsis. However, because

  9. Effects of defocus and aniseikonia by anisometropia on stereoacuity%实验性屈光参差产生的视网膜像模糊和不等像视对立体视影响的研究

    Institute of Scientific and Technical Information of China (English)

    徐进; 胡聪



  10. The Importance of the Relationship Between The Position of the Correcting Lens Principal Planes (H'1-H'2) and Principal Planes (H1-H2) of the Optical Eye System – Aphakic Correction


    Vojniković, Božo; Njirić, Sanja


    In the clinical refraction of the eye, aniseikonia and anisometropia are inevitably used terms. Image formation and its retinal size is the function of the power of the dioptric eye system. However, the correcting lens in front of the eye and the eye optical system represent a unique optical afocal system, in which the distance between correcting lens and corneal vertex is of utmost importance, since it determines the size (together with appropriate correcting lens) of the retinal image. In t...

  11. [Features of the electronic eikonometer for the study of binocular function]. (United States)

    Bourdy, C


    After presenting the components of this electronic eikonometer (device schematic and organizational chart) for the analysis and measurement of perceptive effects of binocular disparity, we review the specifics (tests with incorporated magnifications seen in polarized light) and the advantages of this device as compared to existing eikonometers (absence of any intermediary optical system). We provide a list of available tests in the test library and their parametric characteristics: Ogle Spatial Test for Aniseikonia, Fixation Disparity Test: binocular nonius, and Linear and Random stereoscopic tests. We develop a methodology adapted to each type of test and the manipulations to be performed by the operators and observers. We then provide some results of examinations performed with this eikonometer for a sample of observers equipped with glasses, contact lenses or implants. We propose an analysis of these various perceptive effects from experimental and theoretical studies: association between Depth, Disparity and Fusion; brief review of theoretical studies by automatic matrix calculus of retinal image size for various types of eyes: emmetropic and isometropic eyes based on various dioptric elements from Gullstrand's eye, axial anisometropia, anisometropia of conformation, aphakia resulting from these various eyes. We demonstrate the role of these studies in the analysis of subjective measurements of aniseikonia and for the choice of best correction: variations in amplitude and sign of the monocular components of the fixation disparity as a function of the viewing distance, Complexity of depth perception, according to the test used. Considering the evolution of the technology used for the realization of this prototype, we propose that this eikonometer be updated, in particular by using high-resolution flat screens, which would allow improvement and enrichment of the test library (definition, contrast and size of the observed images).

  12. [Electronic eikonometer: Measurement tests displayed on stereoscopic screen]. (United States)

    Bourdy, C; James, Y


    We propose the presentation on a stereoscopic screen of the electronic eikonometer tests intended for analysis and measurement of perceptual effects of binocular disparity. These tests, so-called "built-in magnification tests" are constructed according to the same principle as those of preceding eikonometers (disparity variation parameters being included in each test presentation, which allows, for test observation and measurements during the examination, the removing of any intermediate optical system). The images of these tests are presented separately to each eye, according to active or passive stereoscopic screen technology: (1) Ogle Spatial Test to measure aniseikonia; (2) Fixation Disparity test: binocular nonius; (3) retinal correspondence test evaluated by nonius horopter; (4) stereoscopic test using Julesz' random-dot stereograms (RDS). All of these tests, with their variable parameters included, are preprogrammed by means of an associated mini-computer. This new system (a single screen for the presentation of tests for the right eye and left eye) will be much simpler to reproduce and install for all practitioners interested in the functional exploration of binocular vision. We develop the suitable methodology adapted to each type of examination, as well as manipulations to be performed by the operator. We then recall the possibilities for reducing aniseikonia thanks to some theoretical studies previously performed by matrix calculation of the size of the retinal images for different types of eye (emmetropia, axial or conformation anisometropia, aphakia) and for different means of correction (glasses, contact lenses, implants). Software for achieving these different tests is available, on request, at this address:

  13. Anisometropia and stereopsis%屈光参差与立体视觉

    Institute of Scientific and Technical Information of China (English)

    吴微微; 彭秀军


    屈光参差是指两眼屈光度的程度和(或)性质有一定的差别,其主要相关原因是由于双眼眼轴长度发育不平衡。立体视觉是人类和高等动物所特有的一项高级视功能,同时也是人类从事多种工作及日常生活中必备的一种重要功能。屈光参差引起的视网膜像模糊和不等像视是影响立体视觉的主要原因。屈光参差矫正方法不同,对立体视觉的影响也是不同的。%Anisometropia means a certain difference between two eyes in the degree of diopter and ( or ) the nature of diopter.The main associated reason is due to the eyes ocular axial length development imbalance. However, stereopsis is the highest visual function of human beings and higher animals, which is necessary for working people in daily life. The main reason of effecting on binocularity is retinal image blur and aniseikonia caused by uncorrected anisometropia. Different methods of anisometropia correction have different effects on stereo vision.

  14. Neuromuscular plasticity and rehabilitation of the ocular near response. (United States)

    Schor, Clifton M


    The near response is composed of cross-coupled interactions between convergence and other distance-related oculomotor responses including accommodation, vertical vergence, and cyclovergence. The cross-coupling interactions are analogous to the body postural reflexes that maintain balance. Near-response couplings guide involuntary motor responses during voluntary shifts of distance and direction of gaze without feedback from defocus or retinal-image disparity. They optimize the disparity stimulus for stereoscopic depth perception and can be modified by optically induced sensory demands placed on binocular vision. In natural viewing conditions, the near response is determined by passive orbital mechanics and active-adaptable tonic components. For example, the normal coupling of vertical vergence with convergence in tertiary gaze is partly a byproduct of passive orbital mechanics. Both, adapted changes of vertical vergence in response to anisophoria, produced by unequal ocular magnification (aniseikonia), and adapted changes in the orientation of Listing's plane in response to torsional disparities can be achieved by a combination of passive orbital mechanics and neural adjustments for the control of the vertical vergence and cyclovergence. Adaptive adjustments are coupled with gaze direction, convergence angle, and head tilt. Several adaptation studies suggest that it is possible to achieve non-linear changes in the coupling of both vertical vergence and cyclovergence with gaze direction. This coupling can be achieved with changes in neural control signals of ocular elevator muscles that are cross-coupled with both convergence and direction of tertiary gaze. These linear and non-linear coupling interactions can be adapted to compensate for (1) anisophoria induced by spectacle corrections for anisometropia, (2) accommodative esotropia, (3) convergence excess and insufficiency, and (4) non-concomitant deviations with ocular torticollis associated with trochlear palsy

  15. Intraocular lens exchange for high myopia in pseudophakic children. (United States)

    Kraus, C L; Trivedi, R H; Wilson, M E


    PurposeThe purpose of this study was to examine the preoperative factors and postoperative outcomes following intraocular lens (IOL) exchange for high myopia in pseudophakic children.MethodsThe medical records of all patients undergoing IOL exchange for high myopia were retrospectively reviewed.ResultsA total of 15 eyes were identified that had undergone an IOL exchange for myopic shift. Average age of cataract extraction (CE) was 5.4 months. In all, 10/15 had a unilateral cataract. IOL exchange usually occurred at an average of 6 years following cataract surgery. The average spherical equivalent (SE) of the refractive error at that time was -9.6 D. Following IOL exchange, SE was -1.3 D. A two-line reduction in best-corrected visual acuity was observed in 1/13 of our patients for whom pre- and post-exchange data were available. The average axial length (AL) of the eye undergoing the IOL exchange was 24.0 mm, average AL in the non-operative eye was 22.1 mm. On average, the operative eyes grew 4.4 mm and the non-operative eyes 3.02 mm. No adverse events were seen in the operative eyes.ConclusionYounger age at the time of CE creates a greater likelihood of AL elongation and predisposes a child to myopic shift. IOL exchange should be considered an option to reduce anisometropia and associated aniseikonia to improve visual outcomes. Successful visual rehabilitation and predictable post-exchange refractions were seen with our patients.