Effects of induced aniseikonia on binocular visual acuity.

CLINICAL RELEVANCE: Binocular visual acuity is an important index of functional performance. Optometrists need to know how binocular visual acuity is affected by aniseikonia, and whether reduced binocular visual acuity is a marker for aniseikonia. BACKGROUND: Aniseikonia, the perception of unequal image sizes between the eyes, can occur spontaneously or can be induced after different types of eye surgery, or trauma. It is known to affect binocular vision, but there are no prior studies about how it affects visual acuity. METHODS: Visual acuity was measured for 10 healthy well-corrected participants aged 18-21 years of age. Aniseikonia of up to 20% was induced in one of two ways: (1) size lenses, which provided minification of field of view in one eye of each participant and (2) polaroid filters, which allowed vectographic viewing of optotypes on a 3D computer monitor. The best corrected acuity was measured on conventional logarithmic progression format vision charts and isolated optotypes, under both induced aniseikonia conditions. RESULTS: Induced aniseikonia caused binocular visual acuity thresholds to increase by small but statistically significant amounts, with the largest deficit being 0.06 logMAR for 20% size differences between the eyes. Binocular visual acuity was worse than monocular visual acuity for aniseikonia of 9% and greater. Acuity measured with the vectographic presentation gave slightly higher thresholds (by 0.01 logMAR) than for those viewed with size lenses. Acuity measured with charts gave slightly higher thresholds (by 0.02 logMAR) than with isolated letters. CONCLUSION: An acuity change of 0.06 logMAR is small and may be missed in a clinical examination. Therefore, visual acuity cannot be used as a marker of aniseikonia in clinical settings. Even with very marked induced aniseikonia, binocular visual acuity remained well within standards for licen*c*sing of drivers.

Measurement of Aniseikonia Tolerance in Binocular Fusion.

SIGNIFICANCE: The determination of aniseikonia tolerance may aid in developing optimal treatment plans for cataract surgery, refractive surgery, and refractive correction with glasses and contact lenses. PURPOSE: This study aimed to measure aniseikonia tolerance. METHODS: We included 33 patients (mean age ± standard deviation, 28.9 ± 6.4 years; male/female, 12:21) with anisometropia ≤1.0 D and best spectacle-corrected visual acuity of 20/20 or more in both eyes, with no ophthalmologic disease other than refractive errors and no history of ocular surgery. The exclusion criteria were anisometropia >1.0 D, axial length difference >0.5 mm, corneal refractive power difference >0.5 D, astigmatism >3.0 D, stereoacuity threshold >100 arcsec according to the Titmus Stereo Test, and >0% aniseikonia according to the New Aniseikonia Test. Aniseikonia tolerance was assessed using Eyemark Hello, a haploscope using gaze detection technology. Although the optotype of one eye was enlarged or reduced at a speed of 2%/s, the patients were instructed to press a button on the controller to indicate blurring, flickering, and diplopia. The value at which the patient responded was considered the aniseikonia tolerance value and assessed thrice per eye, five times if the values were highly variable, and then averaged. RESULTS: The mean aniseikonia tolerance was approximately 3%; the median value was approximately 2% (range, 1.0 to 11.5%; dominant eye, 3.3 ± 2.6%; nondominant eye, 2.9 ± 1.8%). No significant difference in aniseikonia tolerance between the dominant and nondominant eyes was observed for the enlarged optotypes. No case showed changes in the ocular alignment before discomfort occurred. No significant correlation was observed between aniseikonia tolerance and anisometropia, axial length difference, corneal power difference, and ocular deviation. CONCLUSIONS: Aniseikonia should be maintained at <2% for a comfortable visual environment. Aniseikonia tolerance may be an important indicator for cataract surgery, refractive surgery, and spectacle correction.

Prediction of ocular magnification and aniseikonia after cataract surgery.

BACKGROUND: Ocular magnification and aniseikonia after cataract surgery has been widely ignored in modern cataract surgery. The purpose of this study was to analyse ocular magnification and inter-individual differences in a normal cataract population with a focus on monovision. METHODS: From a large dataset containing biometric measurements (IOLMaster 700) of both eyes of 9734 patients prior to cataract surgery, eyes were indexed randomly as primary (P) and secondary (S). Intraocular lens power (IOLP) was derived for the HofferQ, Haigis and Castrop formulae for emmetropia for P and emmetropia or myopia (-0.5 to -2 dpt) for S to simulate monovision. Based on the pseudophakic eye model in addition to these formulae, ocular magnification was extracted using matrix algebra (refraction and translation matrices and a system matrix describing the optical property of the entire spectacle corrected or uncorrected eye). RESULTS: With emmetropia for P and S the IOLP differences (S-P) showed a standard deviation of 0.162/0.156/0.157 dpt and ocular magnification differences yielded a standard deviation of 0.0414/0.0405/0.0408 mm/mrad for the HofferQ/Haigis/Castrop setting. Simulating monovision, the myopic eye (S) showed a systematically smaller mean absolute spectacle corrected ocular magnification than the emmetropic eye (-0.0351/-0.0340/-0.0336, respectively, relative magnification around 2%). If myopia in the S eye remains uncorrected, the reduction of ocular magnification is much smaller (around 0.2-0.3%). CONCLUSION: Vergence formulae for IOLP calculation sometimes implicitly define a pseudophakic eye model which can be directly used to predict ocular magnification after cataract surgery. Despite a strong similarity of both eyes, ocular magnification does not fully match between eyes and the prediction of ocular magnification and aniseikonia might be relevant to avoid eikonic problems in the pseudophakic eye.

Measuring aniseikonia and investigating neuroplasticity and image factors in amblyopia (MAGNIFY): study protocol for a randomised clinical trial.

BACKGROUND: Aniseikonia represents a potential barrier to neuroplasticity which may limit visual outcomes in children with anisometropic amblyopia. Full correction of refractive error is the first step in standard amblyopia treatment, which corrects for image focus but neglects image size differences. METHODS: The MAGNIFY study is a double-masked, randomised clinical trial investigating the effectiveness of aniseikonia correcting lenses in children at first diagnosis of significant anisometropia. We hypothesis that aniseikonia correction lenses will improve image clarity and reduce the retinal size differences producing better visual acuity and stereoacuity improvements after 15 weeks of optical treatment for children with anisometropia. Eligible children will be randomly allocated to the treatment group (aniseikonia-correcting spectacle lenses) or control group (standard spectacle lenses). Visual acuity and binocular functions will be assessed every 5 weeks during the 15-week optical treatment phase according to standard amblyopia treatment protocol. DISCUSSION: It is possible that correcting aniseikonia along with anisometropia at first diagnosis will promote binocularity as well as increase spectacle adherence by reducing visual discomfort, improving optical treatment outcomes. This could then reduce the need for additional amblyopia treatment such as patching or atropine, reducing the burden on hospital eye departments and potentially improving visual outcomes for children with amblyopia. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry (ANZCTR) ACTRN12620000061932 . Registered on 24 January 2020. Protocol 15th November 2019, version one.

The effects of optically and digitally simulated aniseikonia on stereopsis.

PURPOSE: To simulate both lens-induced and screen-induced aniseikonia, and to assess its influence on stereopsis. Additionally, to determine if screen-based size differences could neutralise the effects of lens-induced aniseikonia. METHOD: A four-circle (4-C) paradigm was developed, where one circle appears in front or behind the others because of crossed or uncrossed disparity. This stereotest was used for three investigations: (1) Comparison with the McGill modified random dot stereogram (RDS), with anisometropia introduced with +2 D spheres and cylinders, and with aniseikonia introduced with 6% overall and 6% meridional (×180, ×90) magnifiers before the right eye; (2) Comparison of lens-induced and screen-induced 6% overall and meridional magnifications and (3) Determining if lens and screen effects neutralised, by opposing 6% lens-induced magnification to the right eye with screen-inducements of either 6% left eye magnification or 6% right eye minification. A pilot study of the effect of masking versus not masking the surround was also conducted. RESULTS: The 4-C test gave higher stereo-thresholds than the RDS test by 0.5 ± 0.2 log units across both anisometropic and aniseikonic conditions. However, variations in power, meridian and magnification affected the two tests similarly. The pilot study indicated that surround masking improved neutralisation of screen and lens effects. With masking, lens-induced and screen-induced magnifications increased stereo-thresholds similarly. With lens and screen effects opposed, for most participants stereo-thresholds returned to baseline for overall and ×180 magnifications, but not for ×90 magnification. Only three of seven participants showed good compensation for ×90 magnification. CONCLUSIONS: Effects of lens-induced aniseikonia on stereopsis cannot always be successfully simulated with a screen-based method. The ability to neutralise refractive aniseikonia using a computer-based method, which is the basis of digital clinical measurement, was reasonably successful for overall and ×180 meridional aniseikonia, but not very successful for ×90 aniseikonia.

Aniseikonia and visual functions with optical correction and after refractive surgery in axial anisometropia.

PURPOSE: To evaluate differences in the subjective aniseikonia and stereoacuity in patients with axial anisometropia after full correction of the refractive error with spectacles, contact lenses, and refractive surgery. METHODS: A prospective study was performed in Cairo University Hospitals on 20 patients with axial anisometropia caused by unilateral myopia > 5 D with > 4 D inter-ocular difference in spherical equivalent who were suitable candidates for excimer laser ablation (LASIK) or implantable collamer lens implantation (ICL). All patients had measurement of best-corrected visual acuity (BCVA), fusion, stereoacuity, and magnitude of aniseikonia with spectacles, contact lenses, and after surgery. RESULTS: The mean age at time of surgery was 25.7 ± 3.1 years. There were no statistically significant differences in the BCVA or stereoacuity with spectacles, contact lenses, or after refractive surgery. Microkonia < 5%) was perceived with spectacles in 8 patients (40%) and remained unchanged in 7 of these 8 patients with contact lenses. Following LASIK (n = 11), there was an induced macrokonia < 2% in 4 patients (36%), persistent microkonia of 3% in 1 patient (9%), and no change in image size in 6 (55%) patients. Following ICL implantation (n = 9), there was a perceived macrokonia of 2% in 4 patients (44%), disappearance of microkonia in 1 patient (11%) and no change in 4 patients (44%). CONCLUSIONS: Differences in BCVA, stereoacuity, and aniseikonia after correction of anisometropia by glasses, contact lens and surgery are both clinically and statistically insignificant. Retinal or neural adaptation might have a role in correction for differences in image size.

[Simple method to estimate object to image magnification and aniseikonia following cataract surgery]. / Einfaches Verfahren zur Abschätzung des postoperativen Abbildungsmaßstabs und der Aniseikonie bei der Kataraktoperation.

BACKGROUND AND PURPOSE: Aniseikonia as one of the major risk factors for asthenopic problems is mostly overlooked in modern cataract surgery. The purpose of this study was to develop a simple calculation scheme for clinicians to predict the object to image magnification in a pseudophakic eye with biometric data. METHODS: The calculation scheme for object to image magnification in the pseudophakic eye is based on a vergence calculation of the lens power with theoretical optical formulae. From the biometric data, which are typically derived from both eyes during lens power calculation, the vergences in front of and behind the 3 or 4 refractive surfaces of the pseudophakic eye model are used to predict the magnification for objects at infinity or objects located at a finite measurement distance (e.g. 5 m). RESULTS: With a formula-based lens power calculation a pseudophakic eye model is set up with 3 or 4 refractive surfaces (postoperative spectacle refraction; thick cornea described by anterior surface or thick cornea characterized by anterior and posterior surfaces; intraocular lens). The vergence in front of and behind each refractive surface is derived by means of linear Gaussian optics. The quotient of the product of all vergences in front of the surfaces and the product of all vergences behind the respective surfaces describes the object to image magnification of the eye. A comparison of the object to image magnification of both eyes yields the retinal image size disparity or aniseikonia. This calculation strategy is shown in a step-by-step approach exemplarily for the Haigis and Hoffer­Q formulae (3 surfaces) and the Castrop formula (4 surfaces). CONCLUSION: If during planning and lens power calculation biometry is performed for both eyes, ocular magnification of both eyes can be easily derived with this calculation scheme and aniseikonia can be extracted from a comparison of magnification of both eyes. Such a simple prediction should be established as a standard for precataract biometry and lens power calculation for early detection and avoidance of asthenopic complaints after cataract surgery.

Meridional aniseikonia-causes, symptoms, and therapies.

BACKGROUND: The term aniseikonia refers to the two eyes' appreciating different image sizes when viewing the same object. Meridional aniseikonia can occasionally cause significant distortion of the binocular spatial sense in perceptive patients. METHODS: The medical records of 3 adult patients who complained of binocular spatial distortion consistent with meridional aniseikonia were reviewed retrospectively. Detailed descriptions of symptoms, ocular findings, and management are reported. RESULTS: Each patient had undergone a refraction-altering surgical procedure, and each complained of binocular spatial distortion characterized by a trapezoidal view of square or rectangular shapes. Each patient improved following management of the astigmatic correction. CONCLUSIONS: Patients requiring a new astigmatic correction following cataract or corneal surgery may complain of binocular spatial distortion caused by meridional aniseikonia.

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.

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.

Preoperative aniseikonia is a prognostic factor for postoperative stereopsis in patients with unilateral epiretinal membrane.

PURPOSE: To investigate stereopsis and other visual functions in patients with unilateral epiretinal membrane (ERM) and to identify vision-related parameters affecting stereopsis. METHODS: This prospective study included 63 consecutive patients who were scheduled to undergo vitrectomy for unilateral idiopathic ERM. We examined stereopsis (Titmus Stereo Test, TST; TNO stereotest, TNO), best-corrected visual acuity (BCVA), letter contrast sensitivity, severity of metamorphopsia, and degree of aniseikonia preoperatively and 6 months postoperatively. RESULTS: Preoperatively, we observed significant correlation between TST scores and other vision-related parameters except severity of metamorphopsia and between TNO score and all the vision-related parameters. Multiple regression analysis showed that preoperative TST and TNO scores were significantly associated with the degree of aniseikonia (both P < 0.01). ERM surgery significantly improved stereopsis, BCVA, contrast sensitivity, and metamorphopsia, but not aniseikonia. Postoperatively, TST was significantly associated with BCVA, and TNO showed association with BCVA and aniseikonia. Postoperative TST and TNO scores showed significant correlation with preoperative aniseikonia (P < 0.005 and P < 0.001, respectively). CONCLUSIONS: Impairment of stereopsis in patients with unilateral ERM was considered to be due to retinally induced aniseikonia. Aniseikonia did not improve by surgery, and preoperative aniseikonia can be a prognostic factor for postoperative stereopsis.

CORRELATION BETWEEN MACULAR MICROSTRUCTURES AND ANISEIKONIA AFTER IDIOPATHIC EPIRETINAL MEMBRANE REMOVAL.

PURPOSE: To analyze the correlation between preoperative measurements of macular microstructures and aniseikonia after epiretinal membrane removal. METHODS: This retrospective study included 32 eyes of 32 patients who underwent epiretinal membrane surgery and were followed up for 12 months. Spectral-domain optical coherence tomography was used to measure the thicknesses of the ganglion cell layer-inner plexiform layer, inner nuclear layer (INL), and outer retinal layer in macular microstructures. The new aniseikonia test was used to measure vertical and horizontal aniseikonia scores. RESULTS: There was a significant decrease in central macular thickness and ganglion cell layer-inner plexiform layer thickness at 6 and 12 months postoperatively (all P < 0.001). Vertical aniseikonia scores, horizontal aniseikonia scores, and INL and outer retinal layer thicknesses did not show significant changes. Vertical aniseikonia scores and horizontal aniseikonia scores were significantly associated with INL thicknesses of each meridian at each follow-up time point (all P < 0.05). Preoperative vertical and horizontal INL thicknesses were correlated with vertical aniseikonia scores and horizontal aniseikonia scores at 12 months postoperatively (P = 0.014 and P = 0.002, respectively). CONCLUSION: Aniseikonia values did not change after epiretinal membrane removal and were associated with INL thickness before and after surgery. Thus, preoperative INL thickness could be used as a predictor of surgical prognosis in epiretinal membrane patients.

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.

Aniseikonia and anisometropia: implications for suppression and amblyopia.

Aniseikonia is a difference in the perceived size or shape of images between eyes, and can arise from a variety of physiological, neurological, retinal, and optical causes. Aniseikonia is associated with anisometropia, as both anisometropia itself and the optical correction for anisometropia can cause aniseikonia. Image size differences above one to three per cent can be clinically symptomatic. Common symptoms include asthenopia, headache and diplopia in vertical gaze. Size differences of three and more impair binocular visual functions such as binocular summation and stereopsis. Above five per cent of aniseikonia, binocular inhibition or suppression tend to occur to prevent diplopia and confusion. Aniseikonia can be measured using a range of techniques and can be corrected or reduced by prescribing contact lenses or specially designed spectacle lenses. Subjective testing of aniseikonia is the only way to accurately measure the overall perceived amount of aniseikonia. However, currently it is not routinely assessed in most clinical settings. At least two-thirds of patients with amblyopia have anisometropia, thus we may expect aniseikonia to be common in patients with anisometropic amblyopia. However, aniseikonia may not be experienced by the patient under normal binocular viewing conditions if the image from the amblyopic eye is of poor quality or is too strongly suppressed for image size differences to be recognised. This lack of binocular simultaneous perception in amblyopia may also prevent the measurement of aniseikonia, as most common techniques require direct comparisons of images seen by each eye. Current guidelines for the treatment of amblyopia advocate full correction of anisometropia to equalise image clarity, but do not address aniseikonia. Significant image size differences between eyes may lead to suppression and abnormal binocular adaptations. It is possible that correcting anisometropia and aniseikonia simultaneously, particularly at the initial diagnosis of anisometropia, would reduce the need to develop suppression and improve treatment outcomes for anisometropic amblyopia.

Relationship between the morphology of the foveal avascular zone and the degree of aniseikonia before and after vitrectomy in patients with unilateral epiretinal membrane.

PURPOSE: Persistent metamorphopsia, particularly aniseikonia, is a troublesome problem which may occur after epiretinal membrane (ERM) surgery. To clarify if the preoperative foveal avascular zone (FAZ) morphology can be used as a predictor of postoperative residual aniseikonia, the morphological changes in the FAZ and the degree of aniseikonia between before and 12 months after vitrectomy for epiretinal membrane (ERM) were measured and analyzed. METHODS: Thirty patients, each with a unilateral idiopathic ERM, who underwent treatment between September 2016 and March 2017 were enrolled for this prospective case series study. Best-corrected visual acuity (BCVA), the degree of aniseikonia, central foveal thickness (CFT), FAZ area (FAZa), perimeter (FAZp), and circularity in ERM eyes were examined before and 1, 3, 6 and 12 months after surgery. The fellow eye without an ERM was also examined and used as the control. The interocular ratios of the CFT, FAZa, and FAZp in ERM eyes with those in control eyes were also calculated. Multiple regression analysis was performed on preoperative parameters that were found to be significantly correlated with the 12-month aniseikonia in univariate analyses. RESULTS: The BCVA in the ERM eyes was significantly improved at 1 month after surgery (P < .0001) The degree of aniseikonia was significantly reduced only after 12 months (P = .004). The CFT had decreased significantly by 3 months after the surgery and continued decreasing thereafter (P < .0001). Both FAZa and FAZp were significantly smaller in the ERM eyes than in the control eyes throughout the study period (P < .0001 and P < .0001, respectively), with no change in either parameter over the study period. Correlation analyses revealed that the degree of aniseikonia was significantly correlated with pre- and postoperative CFT, CFT ratio, FAZa, FAZa ratio, FAZp, and FAZp ratio. Within preoperative OCT parameters, FAZa ratio remained significant after multiple regression analysis was performed (P < .0001). CONCLUSIONS: Aniseikonia changed little over the long term following ERM surgery. Preoperative FAZ area ratio was identified as a significant predictor of postoperative 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.

POSTOPERATIVE CHANGES AND PROGNOSTIC FACTORS OF VISUAL ACUITY, METAMORPHOPSIA, AND ANISEIKONIA AFTER VITRECTOMY FOR EPIRETINAL MEMBRANE.

PURPOSE: To investigate postoperative changes and prognostic factors of visual impairment after vitrectomy for unilateral epiretinal membrane. METHODS: A prospective observational study on 45 eyes from 45 patients with unilateral idiopathic epiretinal membrane who underwent vitrectomy. Visual parameters (best-corrected visual acuity, metamorphopsia using M-CHARTS, and aniseikonia using the New Aniseikonia Test) and spectral domain optical coherence tomography parameters (macular retinal layer thickness and microstructure of the outer retina) were measured preoperatively and 6 and 12 months postoperatively. Statistical analyses included linear mixed-effects models for the longitudinal changes and prognostic factors of visual parameters. RESULTS: Best-corrected visual acuity and horizontal metamorphopsia improved significantly from 6 months after surgery (P < 0.001), whereas aniseikonia decreased significantly only at 12 months (P = 0.015). Vertical metamorphopsia remained unchanged. Preoperative inner nuclear layer thickness was significantly correlated with preoperative metamorphopsia. Besides baseline values, best-corrected visual acuity had no significant prognostic factors, but preoperative ellipsoid zone disruption had a negative direction of association with postoperative metamorphopsia (coefficients: -0.37 and -0.62, P = 0.015 and 0.006 for horizontal and vertical metamorphopsia, respectively), and preoperative horizontal metamorphopsia had a positive direction of association with postoperative aniseikonia (coefficient: 1.77, P = 0.002). CONCLUSION: After vitrectomy, postoperative changes and prognostic factors for unilateral epiretinal membrane differed for best-corrected visual acuity, metamorphopsia, and aniseikonia.

Prevalence and Associations of Central-Peripheral Rivalry-Type Diplopia in Patients With Epiretinal Membrane.

Importance: The prevalence and clinical associations of patients with epiretinal membrane (ERM) who develop central-peripheral rivalry (CPR)­type diplopia are unknown. Objectives: To determine the prevalence of CPR-type diplopia in retinal disease clinic patients with ERM and to determine clinical findings associated with CPR-type diplopia. Design, Setting and Participants: A prospective cross-sectional study of 31 patients with ERM from retinal disease clinics to determine the prevalence of CPR-type diplopia. A retrospective case cohort of 25 additional patients with ERM, selected from adult strabismus clinics, was added (total = 56) to determine clinical associations with CPR-type diplopia. All data were collected between June 2014 and November 2016; prospective cohort data were collected from June 2016 to November 2016. Main Outcomes and Measures: The presence of diplopia was determined by patient history and diplopia questionnaire responses. Visual acuity and ocular alignment were recorded. Metamorphopsia was documented qualitatively by evaluation of the door frame and Amsler grid and measured quantitatively using M-charts and D-charts. Aniseikonia was determined by subjective description and results of the Awaya new aniseikonia test. Retinal misregistration testing consisted of optotype-frame test and synoptophore; CPR-type diplopia was defined as diplopia associated with evidence of retinal misregistration when other causes did not fully explain diplopia. Outcomes were as follows: prevalence of CPR-type diplopia in patients with ERM seen in retinal disease clinics, and whether or not clinical findings differed between patients with ERM and CPR-type diplopia vs patients with ERM without CPR-type diplopia. Results: Of the 31 patients with ERM seen in retinal disease clinics, 16 were women and 15 were men; the mean (SD) age was 69 (10) years. The prevalence of any diplopia was 23% (7 of 31; 95% CI, 10% to 41%), with CPR-type diplopia present in 16% (5 of 31; 95% CI, 5% to 34%). For analysis of associations, 12 of 56 patients (21%) had CPR-type diplopia and 37 (66%) had no diplopia. Seven of the 56 patients were excluded for other types of diplopia. Patients with CPR-type diplopia had better worse-eye visual acuity (mean difference, −0.23; 95% CI, −0.37 to −0.09 logMAR, P = .003), and more severe quantitative metamorphopsia (mean M-score difference 0.6; 95% CI, 0.05 to 1.1, P = .01) than patients without diplopia, but similar aniseikonia (Awaya new aniseikonia test; mean difference 0.6%; 95% CI, −2.9% to 4.0%, P = .33) and similar evidence of retinal misregistration (100% vs 73%; P = .09) by any test. Conclusions and Relevance: Our findings suggest that CPR-type diplopia is not uncommon in patients with ERM. On average, patients with CPR-type diplopia have better visual acuity and more metamorphopsia than those without CPR-type diplopia, but there is considerable individual variability. Aniseikonia and retinal misregistration are similar between patients with ERM associated with CPR-type diplopia and those without CPR-type diplopia. Retinal misregistration with coexistent metamorphopsia appears necessary but is not sufficient for CPR-type diplopia.

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.

Evaluation of newly-developed aniseikonia testing method based on space eikonometry.

BACKGROUND: We have developed a new aniseikonia testing method based on the space eikonometry (ATSE) principle. The purpose of this study was to compare aniseikonia obtained by the ATSE to that of the conventional new aniseikonia tests (NAT), which is commonly used in Japan. METHODS: Thirty normal subjects (mean age: 22.8 years) without ocular disease except for refractive errors were studied. All of the subjects had normal binocular single vision with stereopsis. We excluded subjects with refractive errors greater than 1.00 D cylinder or anisometropia (spherical equivalent) greater than 1.00 D. We simulated overall aniseikonia of five and 10 per cent with afocal size lenses (HOYA, Tokyo, Japan) placed in the optical path of the fully corrected right eye. We measured aniseikonia three times with either the ATSE or NAT and the averages were used for the statistical analyses. RESULTS: The mean and standard deviation (SD) of aniseikonia determined by the ATSE was 5.1 ± 0.8 per cent with the five per cent afocal lens and 10.1 ± 0.8 per cent with the 10 per cent afocal lens. Aniseikonia was 2.8 ± 1.3 per cent with the five per cent afocal lens and 6.0 ± 2.5 per cent with the 10 per cent afocal lens by the NAT. The mean error was + two per cent of the theoretical value by the ATSE and -42 per cent by the NAT for both afocal lenses. CONCLUSION: We recommend the use of the new ATSE for quantitative determination of aniseikonia, as it is more accurate than the NAT.