Measuring aniseikonia tolerance range for stereoacuity - a tool for the refractive surgeon.

OBJECTIVE: No method exists to measure aniseikonia tolerance in stereoacuity. The brain can compensate for 2%-3% aniseikonia (i.e. 2-3 dioptres of anisometropia) without impairing stereoacuity; however, a substantial proportion of anisometropic patients experience problems caused by disruptions of sensory fusion due to surgically induced aniseikonia. We hypothesized that individual differences in tolerance to aniseikonia exist and sought to develop a method to measure aniseikonia tolerance. METHODS: A total of 21 eye-healthy phakic individuals older than 50 years of age and 11 patients awaiting clear lens extraction were included. Patients were tested with best corrected near and distance visual acuity, cover/uncover test, eye dominance test, stereoacuity threshold (TNO test), slit lamp examination and ocular coherence tomography. The stereoacuity threshold was determined with aniseikonia induced by different size lenses ranging from 1% to 9% magnification of both eyes in increments of 1%. The aniseikonia tolerance range (ATR) was defined as the percentage aniseikonia in which the stereoacuity threshold was maintained. RESULTS: We examined 32 patients with a median age of 65 (95% CI: 62-66 years), CDVA better than 6/7.5 (0.1 logMAR), and median near visual acuity better than 6/6 (0.0 logMAR). The median stereoacuity threshold was 60 arcsec (maximum 30, minimum 120). We observed large inter-individual differences in ATR: 6/31 (19%) participants had an ATR of ≤1%, 1/31 (3%) had an ATR of 1-5%, 7/31 (22%) had an ATR of 5-10%, and 17/31 (54%) had an ATR of >10%. CONCLUSION: We present a reliable method for measuring the amount of aniseikonia that a person can tolerate without impairing stereopsis. We report large inter-individual differences in tolerance of aniseikonia.

Comparison of blur and magnification effects on stereopsis: overall and meridional, monocularly- and binocularly-induced.

PURPOSE: To determine whether monocularly- and binocularly-induced spherical and meridional blur and aniseikonia had similar effects on stereopsis thresholds. METHODS: Twelve participants with normal binocular vision viewed McGill modified random dot stereograms to determine stereoacuities in a four-alternative forced-choice procedure. Astigmatism was induced by placing trial lenses in front of the eyes. Twenty-three conditions were used, consisting of zero (no lens), +1 D and +2 D spheres and cylinders at axes 180, 45 and 90 in front of the right eye, and the following binocular combinations of both lens powers: R × 180/L × 180, R × 45/L × 45, R × 90/L × 90, R sphere/L sphere, R × 180/L × 90, R × 45/L × 135, R × 90/L × 180. Aniseikonia was induced by placing magnifying lenses in front of the eyes. Twenty-three conditions were used, consisting of zero, 6% and 12% overall magnification and both magnifications at axes 180, 45 and 90 in front of the right eye only, and the following binocular combinations using 3% and 6% lenses: R × 90/L × 90, R × 45/L × 45, R × 180/L × 180, R overall/L overall, R × 90/L × 180, R × 45/L × 135, and R × 180/L × 90. RESULTS: Stereopsis losses for binocular blur effects with parallel axes (non-anisometropic) were the same as for monocular blur effects of the same axes, and these were strongly dependent on axis (spherical blur and ×90 had the greatest effects). Binocular blur effects with orthogonal axes had greater effects than with parallel axes, with the axis combination of the former having no effect (e.g. R × 90/L × 180 was similar to R × 45/L × 135). For induced aniseikonia, splitting the magnifications between the eyes improved stereopsis slightly, and the effects were not dependent on axis. CONCLUSION: Binocular blur affects stereopsis similarly to monocular meridional blur if axes in the two eyes are parallel, whereas the effect is greater if the axes are orthogonal. In meridional aniseikonia, splitting magnification between the right and left lenses produces a small improvement in stereopsis that is independent of axis direction and right/left combination.

Field-wide Quantification of Aniseikonia Using Dichoptic Localization.

SIGNIFICANCE: We validated a novel paradigm to measure aniseikonia across the visual field and used a mathematical approach that is able to describe the magnitude and shape of aniseikonia in a concise, clinically meaningful fashion. PURPOSE: The measurement of aniseikonia has been performed clinically for more than half a century; however, amalgamation of field-wide local variations in binocular spatial localization into clinically applicable global metrics has yet to be attempted. Thus, the goal of the current study was twofold: first, to measure field-wide aniseikonia and second, to compare how local and global metrics each capture optically induced aniseikonia. METHODS: Twelve visually normal observers performed a dichoptic localization task at 24 locations in the visual field. This was done in four conditions: (A) while wearing red-green filters, (B) while wearing green-red filters, (C) while wearing a monocular 5% overall size lens, and (D) while wearing a monocular 6% meridional size lens. The physical settings at perceptual equality were then used to compute both local (relative magnification) and global (coefficients for Zernike terms) descriptors of aniseikonia. RESULTS: The comparison of each lens condition to the baseline condition confirmed predicted shifts in both the sign and magnitude of aniseikonia at both the local and global levels; however, the intraobserver levels of precision were moderate, and systematic underestimations were present across all locations in conditions C and D. CONCLUSIONS: Local and global analyses derived from dichoptic localization data were both able to capture optically induced changes in binocular spatial perception; however, solutions that address the diagnostic and therapeutic challenges associated with this paradigm are needed before clinical implementation can proceed.

Comparative analysis of metamorphopsia and aniseikonia after vitrectomy for epiretinal membrane, macular hole, or rhegmatogenous retinal detachment.

This study investigated postoperative changes in metamorphopsia and aniseikonia in eyes that underwent vitrectomy for epiretinal membrane (ERM), macular hole (MH), or rhegmatogenous retinal detachment (RRD). In total, 166 eyes were included from 166 patients with ERM, MH, or RRD who underwent primary vitrectomy. Metamorphopsia and aniseikonia were quantified by M-CHARTS and the New Aniseikonia Test (NAT). Best-corrected visual acuity (BCVA), M-CHARTS, NAT assessments, and OCT examination were performed at 1, 3, and 6 months postoperatively. Of the 166 eyes, 65 had ERM, 21 had MH, 42 had macula-off RRD, and 38 had macula-on RRD. BCVA improved significantly between 1 and 6 months postoperatively in eyes with ERM, MH, and macula-off RRD (P = 0.0057, P = 0.0065, and P = 0.0021, respectively). M-CHARTS scores at 1 month postoperatively significantly decreased in eyes with ERM (P = 0.0034) and tended to decrease in eyes with MH (P = 0.068). NAT scores did not change between baseline and 1 month postoperatively in eyes with ERM or MH. Between 1 and 6 months postoperatively, M-CHARTS and NAT scores significantly decreased in eyes with macula-off RRD (P = 0.0064 and P = 0.0009, respectively), but not in eyes with ERM, MH, or macula-on RRD. At 6 months postoperatively, significant metamorphopsia was evident in 33.3% of eyes with ERM, 29.2% of eyes with MH, and 35.7% of eyes with macula-off RRD; 61.5% of eyes with ERM showed macropsia and 52.3% of eyes with macula-off RRD showed micropsia. In eyes with ERM, more central retinal thickness (CRT) correlated with postoperative BCVA, and deep retinal folds on enface OCT image correlated with postoperative metamorphopsia. In eyes with macula-off RRD, less CRT correlated with postoperative BCVA, and tended to correlate with postoperative micropsia. Macular morphologies could contribute to differences in postoperative visual acuity, metamorphopsia, and aniseikonia.

Effects of simulated anisometropia and aniseikonia on stereopsis.

PURPOSE: Stereopsis depends on horizontally disparate retinal images but otherwise concordance between eyes. Here we investigate the effect of spherical and meridional simulated anisometropia and aniseikonia on stereopsis thresholds. The aims were to determine effects of meridian, magnitude and the relative effects of the two conditions. METHODS: Ten participants with normal binocular vision viewed McGill modified random dot stereograms through synchronised shutter glasses. Stereoacuities were determined using a four-alternative forced-choice procedure. To induce anisometropia, trial lenses of varying power and axes were placed in front of right eyes. Seventeen combinations were used: zero (no lens) and both positive and negative, 1 and 2 D powers, at 45, 90 and 180 axes; spherical lenses were also tested. To induce aniseikonia 17 magnification power and axis combinations were used. This included zero (no lens), and 3%, 6%, 9% and 12% at axes 45, 90 and 180; overall magnifications were also tested. RESULTS: For induced anisometropia, stereopsis loss increased as cylindrical axis rotated from 180° to 90°, at which the loss was similar to that for spherical blur. For example, for 2 D meridional anisometropia threshold increased from 1.53 log sec arc (i.e. 34 sec arc) for x 180 to 1.89 log sec arc (78 sec arc) for x 90. Anisometropia induced with either positive or negative lenses had similar detrimental effects on stereopsis. Unlike anisometropia, the stereopsis loss with induced meridional aniseikonia was not affected by axis and was about 64% of that for overall aniseikonia of the same amount. Approximately, each 1 D of induced anisometropia had the same effect on threshold as did each 6% of induced aniseikonia. CONCLUSION: The axes of meridional anisometropia but not aniseikonia affected stereopsis. This suggests differences in the way that monocular blur (anisometropia) and interocular shape differences (aniseikonia) are processed during the production of stereopsis.

The relationship between clinical measures of aniseikonia and stereoacuity before and after LASIK / Relación entre las mediciones clínicas de aniseiconía y estereoagudeza antes y después de la cirugía LASIK

PURPOSE: To determine the significance of changes and and inter-relationships between three markers of binocular function (aniseikonia, distance and near stereoacuity) following unremarkable LASIK at 3 and 6 months postoperatively. METHODS: All patients underwent LASIK using the Schwind Amaris 750S and the flaps were created using Intralase 150 kHz. Patients were I, monocular myopes II, binocular myopes III, binocular hyperopes IV, binocular astigmats V, anisometropes and VI, matched age and gender control (n = 20 in each group except III where n = 18). Aniseikonia (Awaya test), distance and near stereoacuity (Randot tests) were measured before surgery, and at 3 and 6 months after surgery. At all times data were collected under constant conditions and analyzed using appropriate non-parametric statistical tests. RESULTS: The following statistically significant changes were found after applying the Bonferroni correction (p ≤ 0.001); aniseikonia reduced (groups I, III, IV, V), stereoacuity improved at distance (groups I, III-V) and near (groups I, V). Inter-group differences in aniseikonia distance and near stereoacuity were significant preoperatively, but not postoperatively. In groups I, IV and V, the changes in aniseikonia and stereoacuity (near and distance) were significantly correlated with the preoperative value. Aniseikonia was significantly correlated with distance and near stereoacuity preoperatively but not postoperatively. CONCLUSION: Binocular function improved in all groups after LASIK except in binocular myopes. In general, binocular function was still low compared with the control group at six months postoperatively. It is unclear why binocular function improved in the binocular astigmats

OBJETIVO: Determinar la significancia de cualquier cambio, así como las interrelaciones entre tres marcadores de la función binocular (aniseiconía, estereoagudeza de lejos y de cerca) tras LASIK sin complicaciones a los 3 y 6 meses postoperatorios. MÉTODOS: A todos los pacientes se les realizó cirugía LASIK con el laser Schwind Amaris 750S, creándose los flaps con Intralase 150 kHz. Los grupos de pacientes fueron: I miopes monoculares, II miopes binoculares, III hipermétropes binoculares, IV astígmatas binoculares, V anisométropes y VI controles equivalentes en edad y género (n = 20 en cada grupo, exceptuando III donde n = 18). Se midió la aniseiconía (prueba de Awaya), la estereoagudeza de lejos y de cerca (pruebas Randot) durante el preoperatorio, y a los 3 y 6 meses posteriores a la cirugía. En todo momento se recabaron los datos en condiciones constantes, analizándose los mismos con pruebas estadísticas no paramétricas adecuadas. RESULTADOS: Se encontraron los siguientes cambios estadísticamente significativos tras aplicar la corrección de Bonferroni (p ≤ 0,001); se redujo la aniseiconía (grupos I, III, IV, V), y mejoró la estereoagudeza de lejos (grupos I, III-V) y de cerca (grupos I, V). Las diferencias inter-grupo en cuanto a aniseiconía de lejos y de cerca y la estereoagudeza de cerca fueron significativas en el preoperatorio, pero no en el postoperatorio. En los grupos I, IV y V, los cambios en cuanto a aniseiconía y estereoagudeza (de cerca y de lejos) guardaron una correlación significativa con el valor preoperatorio. La aniseiconía guardó una correlación significativa con la estereoagudeza de lejos y de cerca en el preoperatorio, pero no el postoperatorio. CONCLUSIÓN: La función binocular mejoró en todos los grupos tras la cirugía LASIK, excepto en la miopía binocular. En general, la función binocular fue aún baja al compararse con el grupo control a los seis meses postoperatorios. No queda claro por qué la función binocular mejoró en el astigmatismo binocular

The relationship between clinical measures of aniseikonia and stereoacuity before and after LASIK.

PURPOSE: To determine the significance of changes and and inter-relationships between three markers of binocular function (aniseikonia, distance and near stereoacuity) following unremarkable LASIK at 3 and 6 months postoperatively. METHODS: All patients underwent LASIK using the Schwind Amaris 750S and the flaps were created using Intralase 150 kHz. Patients were I, monocular myopes II, binocular myopes III, binocular hyperopes IV, binocular astigmats V, anisometropes and VI, matched age and gender control (n = 20 in each group except III where n = 18). Aniseikonia (Awaya test), distance and near stereoacuity (Randot tests) were measured before surgery, and at 3 and 6 months after surgery. At all times data were collected under constant conditions and analyzed using appropriate non-parametric statistical tests. RESULTS: The following statistically significant changes were found after applying the Bonferroni correction (p ≤ 0.001); aniseikonia reduced (groups I, III, IV, V), stereoacuity improved at distance (groups I, III-V) and near (groups I, V). Inter-group differences in aniseikonia distance and near stereoacuity were significant preoperatively, but not postoperatively. In groups I, IV and V, the changes in aniseikonia and stereoacuity (near and distance) were significantly correlated with the preoperative value. Aniseikonia was significantly correlated with distance and near stereoacuity preoperatively but not postoperatively. CONCLUSION: Binocular function improved in all groups after LASIK except in binocular myopes. In general, binocular function was still low compared with the control group at six months postoperatively. It is unclear why binocular function improved in the binocular astigmats.

Changes in aniseikonia of an axial anisometrope at various stages of orthokeratology lens wear.

PURPOSE: To report a case of reduced aniseikonia in a myopic axial anisometrope during orthokeratology (OK) lens wear. CASE REPORT: A 19-year-old female university student with myopic anisometropia presented for an OK lens fitting consultation. At baseline, perceptual interocular image size difference or aniseikonia of 1.45% was found, with a smaller image seen by the right eye compared to the left eye. The patient was fitted with a pair of OK lenses and interocular image size differences, subjective refraction and corneal topography were measured after 7, 14 and 47 days of overnight lens wear. Hyperopic shifts in central refraction and corresponding flattening of the central cornea was measured during OK treatment. Aniseikonia reduced after OK wear with the most significant change measured from baseline to day 7. Aniseikonia recorded after 7, 14 and 47 nights of lens wear was 0.05%, 0.35% and 0.85%, respectively. Although minimum differences in refractive error between eyes was reached after 47 days of OK, aniseikonia was greater than that measured after 7 and 14 days of OK. CONCLUSION: This case report demonstrates reduction in aniseikonia with OK lens wear in a myopic patient with axial anisometropia, although this effect was not sustained beyond 1 week of lens wear. As the impact of corneal curvature changes on aniseikonia is not well understood, future studies on the impact of OK on aniseikonia and associated asthenopia is required.

Topical Review: Retinally Induced Aniseikonia.

SIGNIFICANCE: We review retinally induced aniseikonia, an underrecognized condition resulting from common retinal conditions that has a significant effect on quality of life. Optometrists can influence the timing of surgical intervention to mitigate the damage from delaying surgical intervention in patients whose other findings do not meet a surgeon's treatment threshold.Aniseikonia due to optical differences between the eyes occurs in 1 to 3.5% of the population and can hinder the quality of binocular vision. The less noted retinally induced aniseikonia is due to mechanical distortion and displacement of the retinal photoreceptors and occurs with disorders such as epiretinal membrane, reattached retinal detachment, macular hole, and macular edema. Despite that it was first reported in 1950 and its incidence continues to rise in the aging population, many eye care practitioners are unaware of this condition, which can persist or even be exacerbated after treatment as a contributing cause of binocular vision symptoms. The purpose of this report is to allow more eye care practitioners to become familiar with retinally induced aniseikonia. The review of the literature includes demographics and epidemiology, etiology, pathogenesis, diagnosis, results of treatment, prognosis, and case examples.

Changes in aniseikonia and influencing-factors following successful macula-off retinal detachment surgery.

This study investigated the changes in the severity of aniseikonia after surgery for macula-off retinal detachment (RD), and the relationship between aniseikonia and retinal microstructures. The study included 26 eyes of 26 patients undergoing RD surgery. Visual acuity was measured preoperatively, and at 3, 6, and 12 months postoperatively. Degree of aniseikonia and OCT images were obtained at 3, 6, and 12 months postoperatively. The aniseikonia values (mean ± standard deviation) at 3, 6, and 12 months postoperatively were -5.3 ± 4.2%, -4.4 ± 4.4%, and -3.1 ± 3.2%, respectively. Significant improvement was observed from 3 to 12 months postoperatively (P = 0.001). Twelve months postoperatively, 14 eyes had micropsia, 1 eye had macropsia, and 11 eyes were free of aniseikonia. Stepwise multiple regression analyses revealed that the severity of aniseikonia at 12 months postoperatively was significantly associated with postoperative development of cystoid macular edema (CME) and epiretinal membrane (ERM), as well as area of preoperative RD. In conclusion, although aniseikonia was gradually relieved after RD surgery during a 1-year follow-up period, approximately half of patients had aniseikonia and almost all of them had micropsia. Aniseikonia was associated with presence of postoperative CME, ERM, and area of preoperative RD.

Dynamics of the accommodative response under artificially-induced aniseikonia.

Aniseikonia has demonstrated to deteriorate the binocular function, however its impact on the accommodative response remains unknown. The present study aimed to analyze the effects of artificially-induced aniseikonia, using afocal magnifiers, on the dynamics of the accommodative response. The magnitude and variability of the accommodative response were objectively measured in 20 young healthy subjects by a binocular open-field autorefractometer. Participants observed a static stimulus for 90 s, under seven degrees of aniseikonia (0%, 1%, 3%, 5%, 8%, 10% and 12%), and at three distances (500 cm, 40 cm and 20 cm). Complementarily, near stereoacuity, and perceived levels of fatigue and visual discomfort were assessed. The degree of induced aniseikonia was associated with the magnitude of the accommodative response (p < 0.001, ηp2 = 0.329), obtaining a statistically significant reduced accommodative lag for the induced aniseikonia conditions of 8%, 10% and 12% in comparison to the control condition at 40 cm (p-corrected = 0.019, <0.001 and 0.013, respectively) and at 20 cm (p-corrected < 0.001, <0.001 and 0.003, respectively). However, the degree of induced aniseikonia did not reveal any effect on the variability of accommodation (p > 0.05). We also found a decline in near stereoacuity and an increment of visual symptomatology when inducing aniseikonia (p < 0.05). Our data evidenced that greater degrees of induced aniseikonia cause a heightened accommodative response. These preliminary findings may be of relevance for patients undergoing cataract or refractive surgery procedures in which aniseikonia can be induced.

Aniseikonia: A 21st Century Look.

Purpose: Aniseikonia, an appreciation of image size differences between the eyes, can produce symptoms in patients, ranging from headaches to loss of fusion. The purpose of this research was to take a 21st century look at aniseikonia. Methods: Kellogg Eye Center patient records were evaluated for measurable aniseikonia in patients tested with the Aniseikonia Helper, a tablet-based application. Anaglyph slides for the synoptophore were developed to test the limits of induced aniseikonia on stereopsis and fusion. A survey was developed to determine how frequently members of the American Association of Certified Orthoptists (AACO) examine and treat patients with aniseikonia.Results: The prevalence of measurable aniseikonia in this cohort was 7.8%. Moderate amounts of induced aniseikonia, 4% induced image size disparity, disrupt fusion and can cause a loss of stereopsis. Eighty percent of responding AACO members see patients with aniseikonia and among those, 25% see them on a monthly basis. Treatment options, other than wearing contact lenses, are limited to occlusion or fogging techniques. Conclusions: Aniseikonia remains a frequent complaint among patients. The ophthalmologic community needs to use the best methods for measuring aniseikonia and to develop better methods for treating aniseikonia.

Comparison of visual acuity, metamorphopsia, and aniseikonia in patients with an idiopathic epiretinal membrane.

PURPOSE: The clinical course of reduced visual acuity, metamorphopsia, and aniseikonia are dissimilar in patients with an epiretinal membrane (ERM). We measured and compared the best-corrected visual acuity (BCVA), metamorphopsia, and aniseikonia of patients with ERM. METHODS: We measured metamorphopsia and aniseikonia horizontally as well as vertically with the M-CHART (MH and MV) and New Aniseikonia Test (NATH and NATV) in 61 patients with unilateral idiopathic ERM. We compared the BCVA with the other values. Comparisons between the MH and the NATV and between the MV and the NATH were performed, because the MH assesses vertical metamorphopsia, and the MV, horizontal metamorphopsia. RESULTS: BCVA was not significantly correlated with the other values (MH vs BCVA: P = .69; MV vs BCVA: P = .114; NATH vs BCVA: P = .656; NATV vs BCVA: P = .935). The MH and NATV magnitudes were significantly correlated, but the correlation coefficient was small (P = .007, r = 0.343); no significant correlation was found between the MV and NATH magnitudes (P = .065). We found patients with aniseikonia, but no metamorphopsia (n = 6), and more patients with metamorphopsia, but no aniseikonia (n = 11). Only 23 patients had coincident directions of metamorphopsia and aniseikonia. CONCLUSIONS: The magnitudes of metamorphopsia and aniseikonia were not closely correlated and their directions did not coincide in most patients. Neither the M-CHARTS nor the NAT measurements correlated with the BCVA. Quantitative testing of metamorphopsia and aniseikonia in addition to that for BCVA is necessary to assess visual function in patients with ERM.

Aniseikonia in various retinal disorders.

PURPOSE: The purpose was to quantify and compare the severity of aniseikonia in patients undergoing vitrectomy for various retinal disorders. METHODS: We studied 357 patients with retinal disorders including epiretinal membrane (ERM), macular hole (MH), cystoid macular edema with branch / central retinal vein occlusion (BRVO-CME / CRVO-CME), diabetic macular edema (DME), macula-off rhegmatogenous retinal detachment (M-off RD), and macula-on RD (M-on RD) as well as 31 normal controls. The amount of aniseikonia was measured using the New Aniseikonia Test preoperatively and at 6 months postoperatively. RESULTS: Of all patients, 59% presented aniseikonia. Preoperative and postoperative mean aniseikonia were 4.0 ± 4.1% and 3.0 ± 3.6%, respectively. In particular, 68% of patients with ERM had macropsia, and approximately half of MH, RVO-CME, DME, and M-off RD patients had micropsia. Preoperative aniseikonia was significantly severe in ERM than in other disorders. Vitrectomy improved aniseikonia only in MH, while visual acuity was improved in all disorders except CRVO-CME. CONCLUSION: More than half of the patients showed aniseikonia preoperatively. A majority of ERM patients exhibited macropsia, whereas MH, RVO-CME, DME, and macula-off RD patients presented micropsia. The aniseikonia score was greatest in ERM patients. In most retinal disorders, surgery significantly improved visual acuity, but not aniseikonia.

RESTORATION OF RETINALLY INDUCED ANISEIKONIA IN PATIENTS WITH EPIRETINAL MEMBRANE AFTER EARLY VITRECTOMY.

PURPOSE: To evaluate changes in aniseikonia in patients with unilateral epiretinal membrane after surgery. METHODS: This prospective study included 24 patients with unilateral idiopathic epiretinal membrane who underwent vitrectomy. Best-corrected visual acuity and aniseikonia were measured using the Aniseikonia Inspector 3 (Optical Diagnostics, Culemborg, The Netherlands) preoperatively and 6 months postoperatively. Aniseikonia was measured in vertical and horizontal directions. RESULTS: Mean age at surgery was 64.2 ± 9.3 years, and mean symptom duration was 12.9 ± 11.4 months. Mean changes in aniseikonia after surgery were 41.0 ± 31.4% reduction in the vertical direction and 41.6 ± 30.8% reduction in the horizontal direction (both P < 0.001). The remaining aniseikonia after surgery correlated with symptom duration (r = 0.565, P = 0.006, and r = 0.812, P < 0.001, for vertical and horizontal directions, respectively). The good preoperative best-corrected visual acuity group showed better improvement of aniseikonia than did the poor preoperative group (P = 0.046 and P = 0.025 for vertical and horizontal directions, respectively). CONCLUSION: Greater improvement of aniseikonia after epiretinal membrane peeling was achieved in patients with better preoperative best-corrected visual acuity and shorter symptom durations. Early vitrectomy helped to reduce aniseikonia in patients with epiretinal membrane.

Aniseikonia induced by cataract surgery and its effect on binocular vision.

PURPOSE: This study measured aniseikonia before and after the first and second cataract surgeries in ametropic adults. The relationship of aniseikonia to anisometropia and its effect on stereopsis, ocular alignment, and clinical symptoms were determined. METHODS: Seventeen patients scheduled to have bilateral cataract surgery with 2 diopters or more ametropia participated. Patients were evaluated before cataract surgery and 4 weeks (±1 week) after the first and second surgery. Visual acuity, refractive error, aniseikonia, stereopsis, ocular alignment, and visual symptoms were determined at each visit. RESULTS: Aniseikonia increased after the first cataract surgery. The increase in aniseikonia occurred in concert with increased anisometropia and resulted in poorer stereopsis overall. Aniseikonia and anisometropia 1 month (±1 week) after the second cataract surgery returned to near baseline and were associated with better stereopsis. The amount of aniseikonia showed substantial variance and could not be predicted by the amount of induced anisometropia. Changes in ocular alignment were minimal. Statistically significant changes in patient symptoms between study visits were infrequent. CONCLUSIONS: Aniseikonia induced by cataract surgery may not be a substantial problem for ametropic adults with normal binocular vision, at least in the short term.

[Stereo Vision Deterioration by Artificially Induced Aniseikonia]. / Zhorsení prostorového videní umele navozenou aniseikonií.

UNLABELLED: Main purpose of this study was to evaluate effect of aniseikonia on the stereo vision. We had together 90 subjects without eye pathology with or without habitual correction. Five of them were excluded due to important anisometropia or bad visual acuity (V < 0.5 on worse eye). All 85 subjects every in 4 cases (without size lens, with size lens on OD 1, 3 and 5 %) undergone measuring of their stereoscopy parallax. This was evaluated by Random dot stereo test. The level for stereoscopy vision was set bellow 60 arc seconds. This criterion was not achieved naturally by 6 subjects, so final number of all cases was 316 (100 %). As a whole 48 subjects (15.2 %) fail after using the test with size lens on OD 1, 3 or 5 %. All 268 cases (84.8 %) had not impaired stereoscopy parallax with size lens over chosen critical level. KEY WORDS: size lens, anisometropia, aniseikonia, heterophoria, stereoscopy vision.

Time course of changes in aniseikonia and foveal microstructure after vitrectomy for epiretinal membrane.

PURPOSE: To quantify aniseikonia in patients undergoing vitrectomy for epiretinal membrane (ERM) and to investigate the relationship between the aniseikonia and the foveal microstructure by spectral-domain (SD) optical coherence tomography (OCT). DESIGN: Prospective, consecutive, interventional case series. SUBJECTS: This study included 44 eyes of 44 patients undergoing vitrectomy for idiopathic ERM. METHODS: We examined visual acuity and aniseikonia using the New Aniseikonia Test and SD-OCT before and 3 and 6 months after surgery. On the basis of the obtained OCT image, we divided the 1.0 × 1.0-mm area centered on the fovea into 9 sections at 0.25-mm intervals and quantified the following parameters using an image-processing program: central foveal thickness and mean thickness of the ganglion cell layer, inner nuclear layer (INL), and outer retinal layer (outer nuclear layer + outer plexiform layer). The status of the photoreceptor inner segment/outer segment junction, external limiting membrane, and cone outer segment tips also was evaluated. MAIN OUTCOME MEASURES: Amount of aniseikonia 6 months after surgery. RESULTS: Of 44 patients, 39 (89%) had macropsia, 1 (2%) had micropsia, and 4 (9%) had no aniseikonia preoperatively. Mean preoperative aniseikonia was 6.2% ± 4.5%. Vitrectomy significantly improved visual acuity in patients with ERM but did not change the amount of aniseikonia. Multiple regression analysis revealed that preoperative aniseikonia at 6 months was significantly related to preoperative INL thickness, whereas postoperative aniseikonia at 6 months was associated with postoperative INL thickness at 6 months. Preoperative INL thickness was found to be of significant prognostic value for postoperative aniseikonia at 6 months. CONCLUSIONS: Most of the patients with ERM had macropsia. Aniseikonia was not reduced after surgery. The amount of aniseikonia was associated with INL thickness.