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PubMed1986

Effect of aniseikonia on binocular function.

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.

Adult↗
PubMed1981

Aniseikonia for near vision with unilateral aphakia corrected by intraocular lenses.

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).

Accommodation, Ocular↗
PubMed1992

Aniseikonia and stereoacuity in pseudophakic patients. Unilateral and bilateral cases.

PURPOSE: To evaluate the efficacy of intraocular lens (IOL) implant procedures, analyzing visual function of the operated eyes and the resulting binocular vision. METHOD: The authors measured aniseikonia and stereoacuity in patients with both bilateral and unilateral posterior chamber intraocular lenses (PC IOLs). The aniseikonia was measured with the New Aniseikonia Test; the stereoacuity was evaluated with the Titmus Stereotest. RESULTS: In 41 patients with bilateral PC IOLs, aniseikonia measured with the New Aniseikonia Test ranged from 0% to 4% (mean, 0.76%; standard deviation = 1.04%). The average stereoacuity evaluated with the Titmus test was 7.68 circles (less than 60 seconds; range, greater than 800 to 40 seconds of arc), with 36 of 41 patients (87.8%) showing a stereoacuity less than or equal to 100 seconds of arc. In 37 patients with unilateral PC IOLs, the aniseikonia ranged from 0% to 6% (mean, 0.97%; standard deviation = 1.13%). Their stereoacuity also ranged from greater than 800 to 40 seconds (mean, 7.67 circles) (less than 60 seconds). In this group, 34 of 37 (91.8%) patients showed a stereoacuity less than or equal to 100 seconds of arc. CONCLUSION: Although the problem of aniseikonia still remains, a significant number of patients attain good binocular function after unilateral and bilateral PC IOL implantation.

Adult↗
PubMed1989

The influence of aniseikonia on the VEP by random-dot stereogram.

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%.

Adult↗
PubMed1988

Binocular function in unilateral aphakia. Correlation with aniseikonia and stereoacuity.

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.

Adolescent↗
PubMed2004

Induced aniseikonia diminishes binocular contrast sensitivity and binocular summation.

PURPOSE: To study the effect on binocular contrast sensitivity and binocular summation of aniseikonia induced by size (afocal) lenses. METHODS: In 18 young emmetropic observers, the monocular and binocular contrast sensitivity function was measured under normal conditions and after inducing different degrees of aniseikonia (2%, 3%, and 5% and for 6 observers, 8%) in the right eye. The spatial frequencies tested were 2.4, 3.7, 6.0, 9.2, 12, 15, 20, and 24 cpd. RESULTS: The results reveal a significant decline in binocular contrast sensitivity and binocular summation for 5% aniseikonia, this decline being more pronounced for intermediate and high spatial frequencies. CONCLUSIONS: These results, together with others on different binocular functions, show the importance of aniseikonia in binocular vision. On this basis, we recommend that aniseikonia be considered in surgical processes such as cataract and refractive surgery, whereby aniseikonia could be induced and binocular performance subsequently diminished.

Adolescent↗
PubMed2007

Validity and repeatability of a new test for aniseikonia.

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 reliability was estimated by the Bland-Altman statistical method. RESULTS: The results showed that the AI underestimated aniseikonia and that the underestimation was greater in the horizontal than in the vertical direction. The reliability was low, with biases that were clinically insignificant, but the 95% limits of agreement were around +/-2%. The behavior of the test was similar in both groups of subjects. CONCLUSIONS: The reliability of the AI is only moderate, and professionals are therefore warned to use the results of this test with caution.

Adult↗
PubMedDate not supplied

Management of aniseikonia after intraocular lens implantation or refractive surgery.

BACKGROUND: Aniseikonia is a difference in perceived image size in the two eyes resulting in asthenopic symptoms and distortions of binocular space perception. This is a complication of refractive and implant surgery in patients with binocular vision. While many individuals adapt readily to modest aniseikonic errors, quite a number do not. METHOD AND RESULTS: Few instruments exist to adequately test for aniseikonia. A means is described to determine if aniseikonia exists and a series of simple steps is suggested to minimize aniseikonia induced by refractive surgery or by surgery for removal of cataract and intraocular lens insertion. Also, using the proposed protocol, it is possible to determine if existing image size differences resulting from prior and/or induced aniseikonia are predominantly refractive or axial. A case report is presented. CONCLUSIONS: The techniques described are not costly, provide no risk, take little time, and resolve or meaningfully reduce aniseikonia in many patients having non-extreme errors of this type.

Aniseikonia↗
PubMed1999

Aniseikonia quantification: error rate of rule of thumb estimation.

PURPOSE: To find the error rate in quantifying aniseikonia by using "Rule of Thumb" estimation in comparison with proven space eikonometry. METHODS: Study 1: 24 adult pseudophakic individuals were measured for anisometropia, and astigmatic interocular difference. Rule of Thumb quantification for prescription was calculated and compared with aniseikonia measurement by the classical Essilor Projection Space Eikonometer. Study 2: parallel analysis was performed on 62 consecutive phakic patients from our strabismus clinic group. RESULTS: Frequency of error: For Group 1 (24 cases): 5 ( or 21 %) were equal (i.e., 1% or less difference); 16 (or 67% ) were greater (more than 1% different); and 3 (13%) were less by Rule of Thumb calculation in comparison to aniseikonia determined on the Essilor eikonometer. For Group 2 (62 cases): 45 (or 73%) were equal (1% or less); 10 (or 16%) were greater; and 7 (or 11%) were lower in the Rule of Thumb calculations in comparison to Essilor eikonometry. Magnitude of error: In Group 1, in 10/24 (29%) aniseikonia by Rule of Thumb estimation was 100% or more greater than by space eikonometry, and in 6 of those ten by 200% or more. In Group 2, in 4/62 (6%) aniseikonia by Rule of Thumb estimation was 200% or more greater than by space eikonometry. CONCLUSION: The frequency and magnitude of apparent clinical errors of Rule of Thumb estimation is disturbingly large. This problem is greatly magnified by the time and effort and cost of prescribing and executing an aniseikonic correction for a patient. The higher the refractive error, the greater the anisometropia, and the worse the errors in Rule of Thumb estimation of aniseikonia. Accurate eikonometric methods and devices should be employed in all cases where such measurements can be made. Rule of thumb estimations should be limited to cases where such subjective testing and measurement cannot be performed, as in infants after unilateral cataract surgery.

Adult↗
PubMed1992

[Aniseikonia of central serous chorioretinopathy].

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".

Adult↗
PubMed1999

Diplopia secondary to aniseikonia associated with macular disease.

OBJECTIVE: To provide an explanation for diplopia and the inability to fuse in some patients with macular disease. METHODS: We identified 7 patients from our practices who had binocular diplopia concurrent with epiretinal membranes or vitreomacular traction. A review of the medical records of all patients was performed. In addition to complete ophthalmologic and orthoptic examinations, evaluation of aniseikonia using the Awaya New Aniseikonia Tests (Handaya Co Ltd, Tokyo, Japan) was performed on all patients. RESULTS: All patients were referred for troublesome diplopia. Six of the patients had epiretinal membranes and 1 had vitreomacular traction. All 7 patients had aniseikonia, ranging from 5% to 18%. In 5 of the patients the image in the involved eye was larger, and in the other 2 patients it was smaller than in the fellow eye. All patients had concomitant small-angle strabismus and at least initially did not fuse when the deviation was offset with a prism. Response to optical management and retinal surgery was variable. CONCLUSIONS: Aniseikonia caused by separation or compression of photoreceptors can be a contributing factor to the existence of diplopia and the inability to fuse in patients with macular disease. Concomitant small-angle strabismus and the inability to fuse with prisms may lead the clinician to the incorrect diagnosis of central disruption of fusion. Surgical intervention does not necessarily improve the aniseikonia.

Adult↗
PubMed1981

Aniseikonia in patients with a unilateral artificial lens, measured with Aulhorn's phase difference haploscope.

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.

Aged↗
PubMed1993

Residual aniseikonia among patients fitted with one or two intraocular lenses (pseudophakic corrections)

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.

Aniseikonia↗
PubMed2006

The validity and repeatability of the New Aniseikonia Test.

PURPOSE: Aniseikonia has been traditionally measured using the New Aniseikonia Test (NAT) based on red/green anaglyphs. This study was designed to establish whether the NAT is a valid and reliable test. METHODS: The NAT was tested on three groups of subjects: a control group (n = 45) and two groups of participants at risk of experiencing aniseikonia, those with anisometropia greater than or equal to 1.00 D (n = 29) and those with bilateral pseudophakia (n = 26). The validity of the test was established by comparing the measured aniseikonia with that simulated with size lenses in a double-blind study. Repeatability was evaluated by comparing the results obtained at two different time points. RESULTS: Our results indicate that the NAT underestimates aniseikonia and more so in the horizontal than in the vertical direction. Repeatability was poor, although biases were clinically insignificant. However, the 95% limits of agreement were around +/-2%. The behavior of the test was similar in the three groups of subjects. CONCLUSIONS: We conclude that the repeatability of the NAT is not very high and recommend that clinicians be cautious when interpreting the results of this test.

Adult↗
PubMedDate not supplied

Effect of aniseikonia on fusion.

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.

Aniseikonia↗
PubMedDate not supplied

Elimination of aniseikonia in monocular aphakia with a contact lens-spectacle combination.

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%.

Aniseikonia↗
PubMed1999

Stereoacuity and aniseikonia after unilateral and bilateral implantation of the Array refractive multifocal intraocular lens.

PURPOSE: To evaluate stereoacuity and aniseikonia in eyes with unilateral and bilateral implantation of the Allergan Array refractive multifocal intraocular lens (MIOL). SETTING: Department of Ophthalmology, University Hospital, Kiel, Germany. METHODS: This study comprised 31 patients with a unilateral MIOL and a phakic fellow eye and 29 patients with bilateral MIOLs. In all pseudophakic eyes, an Array MIOL had been implanted between 1991 and 1994 during a prospective clinical trial. In the present study, patients were re-examined. Near and distance visual acuity were tested; binocular functions were assessed using Bagolini lenses, the Worth 4-dot test, the Lang random-dot test, and the Titmus fly chart. Aniseikonia was evaluated using Aulhorn's phase-difference haploscope. Mean follow-up was 43 months in both groups. RESULTS: After unilateral implantation 87.1% of patients and after bilateral implantation 93.1% of patients correctly perceived the stereograms of the Lang random-dot test. The mean subjective height of the measured Titmus fly was 4.2 cm after unilateral and 4.3 cm after bilateral implantation. The stereoacuity tests revealed no statistically significant differences between the groups. Distance and near aniseikonia were significantly less after bilateral than after unilateral implantation. CONCLUSION: Despite the simultaneous formation of multiple retinal images, the Array MIOL allowed good binocular vision including random-dot stereopsis. Functional aniseikonia developed but did not interfere with normal binocular vision.

Aged↗
PubMed1986

[Significance of aniseikonia following implantation of posterior chamber lenses].

Posterior chamber lenses with angled haptics were implanted in one eye of each of 53 patients with senile cataract. Dioptric aniseikonia was calculated between 1 month and 24 months after surgery (with Gruber's and Huber's computer program) on the basis of most recently obtained values (bulb axis length, depth of the anterior chamber, lens thickness, necessary refraction), and compared with subjective measurements taken with the phase difference haploscope. The agreement between the calculated and subjective aniseikonia was greatest when tested in a vertical meridian. However, it was not possible to predict any correlation between dioptric and subjective aniseikonia with confidence. On the basis of the test results it seems justified to aim for a minimal refractive error in the pseudophakic eye of about +/- 0.5 D in patients with hypermetropia or myopia up to 4 D, even if subjective aniseikonias of over 10% can be proved. The latter manifest great meridional differences and hardly interfere with binocular single vision.

Adult↗