Field-Dependent Aniseikonia Associated with an Epiretinal Membrane

Additional measures of macular function beyond visual acuity

PURPOSE

Visual function is a complex process in which external visual stimuli are interpreted. Patients with retinal diseases and prolonged follow-up times may experience changes in their visual function that are not detected by the standard visual acuity measure, as they are a result of other alterations in visual function. With the advancement of different methods to evaluate visual function, additional measurements have become available, and further standardization suggests that some methods may be promising for use in clinical trials or routine clinical practice. The objectives of this article are to review these additional measurements and to provide guidance on their application.

METHODS

The Vision Academy's membership of international retinal disease experts reviewed the literature and developed consensus recommendations for the application of additional measures of visual function in routine clinical practice or clinical trials.

RESULTS

Measures such as low-luminance visual acuity, contrast sensitivity, retinal fixation and microperimetry, and reading performance are measures which can complement visual acuity measurements to provide an assessment of overall visual function, including impact on patients' quality of life. Measures such as dark adaptation, color vision testing, binocular vision testing, visual recognition testing, and shape discrimination require further optimization and validation before they can be implemented in everyday clinical practice.

CONCLUSION

Additional measurements of visual function may help identify patients who could benefit from earlier diagnosis, detection of disease progression, and therapeutic intervention. New and additional functional clinical trial endpoints are required to fully understand the early stages of macular disease, its progression, and the response to treatment.

Asymmetric extent of distortion measured using the Watzke-Allen Test in patients with macular hole

Visual dysfunction in patients with macular hole is believed to occur because of cone cell displacement, often measured by the Watzke-Allen test (WAT). However, it is unknown if the horizontal and vertical measurements recorded by WAT reflect the true extent of photoreceptor displacement. This study aimed to measure the extent of photoreceptor displacement in patients with macular hole using WAT and compare the displacement value with the hole diameter measured by optical coherence tomography (OCT). This prospective, observational study at a single tertiary referral center included 43 patients with macular hole. WAT thresholds were assessed for their ability to detect macular hole. The slit was presented vertically and horizontally, and the brightness of the monitor screen was 180 cd/m². Horizontal and vertical WAT thresholds for distortion were measured. Correlations and performance evaluations were assessed by Pearson's correlation analysis and Wilcoxon rank-sum test, respectively, between WAT threshold values and hole diameters. Horizontal and vertical WAT thresholds and diameters were compared using paired t-tests. The mean vertical WAT threshold (1.95° ± 0.87°) was significantly higher than the mean horizontal threshold (1.71° ± 0.73°; P < 0.0001). The mean minimum horizontal hole diameter (303.42 ± 111.16 mm; visual angle, 1.01°) was significantly greater than the mean minimum vertical diameter (264.12 ± 107.88 mm; visual angle, 0.88°; P = 0.0149). The minimum vertical and horizontal macular hole diameters were positively correlated with the vertical and horizontal WAT threshold values (r = 0.514, P < 0.01; r = 0.447, P < 0.01, respectively). The WAT threshold values were greater than the respective minimum macular hole diameters, indicative of cone cells displacement over an area larger than that of the hole. The difference in the extent of vertical and horizontal distortions suggests asymmetric hole formation. Hence, WAT threshold values may help evaluate visual function in patients with macular hole.

Aniseikonia following intravitreal ranibizumab treatment for branch retinal vein occlusion

PURPOSE

To quantify aniseikonia following intravitreal ranibizumab (IVR) in patients with branch retinal vein occlusion (BRVO) and assess the relationship between aniseikonia and retinal microstructure.

STUDY DESIGN

Prospective observational study.

METHODS

This study included 50 patients undergoing IVR treatment for unilateral BRVO. The degree of aniseikonia and best-corrected visual acuity (BCVA) was examined, and retinal microstructure was assessed with optical coherence tomography (OCT) before and 1, 2, 3, 4, 5, and 6 months after treatment. Based on OCT images, we assessed central retinal thickness (CRT), presence of the epiretinal membrane, and serous retinal detachment (SRD), as well as status of the external limiting membrane and ellipsoid zone.

RESULTS

At baseline, mean aniseikonia was - 1.0 ± 2.5%, ranging from - 11.0 to + 6.0%. Nine out of 50 patients had micropsia (18%), one had macropsia (2%), and 40 had no aniseikonia (80%). After 6 months of treatment, mean aniseikonia was - 0.7 ± 1.5%, ranging from - 4.5 to + 3.5%. BCVA significantly improved after treatment (P < 0.001), but aniseikonia did not change (P = 0.73). In patients with BRVO who had micropsia (≤ - 2.0%) at baseline, mean aniseikonia significantly improved from - 4.8 ± 3.3% to - 0.9 ± 1.4% (P < 0.05). Aniseikonia after treatment significantly correlated with BCVA (P < 0.05) and the presence of SRD at baseline (P < 0.05).

CONCLUSION

Majority of eyes with aniseikonia in BRVO had micropsia. The BCVA as well as the micropsia improved following treatment with IVR for BRVO. BCVA and the presence of SRD were predictors of post-treatment aniseikonia.

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.

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.

Anisometropic Amblyopia: Interocular Contrast and Viewing Luminance Effects on Aniseikonia

Purpose

To demonstrate an aniseikonia test for anisometropic amblyopia (ATAA) that uses variable viewing luminance at different interocular contrast levels.

Methods

The test consists of a direct size comparison task based on a computer. The subject is asked to adjust the size of a dichoptically dissociated paired square target. One square was always presented at 100% contrast to the amblyopic eye/nondominant eye, whereas its counterpart was presented to the fellow eye at six contrast levels. Measurements were performed at two luminance backgrounds: (1) a white square on a black background (WoB) and (2) a black square on a white background (BoW). To test the feasibility of this approach, 16 patients with anisometropic amblyopia and 23 normal controls were recruited.

Results

The Aniseikonia Index (AI) calculated from the ATAA increased when the difference in the interocular contrast increased in both the patients with anisometropic amblyopia and controls under BoW and WoB conditions. The mean AI differed dramatically between the BoW and WoB conditions in patients with amblyopia but not in normal subjects.

Conclusions

Our model predicted interocular differences in contrast to the measurement of aniseikonia. Execution of the AI in individuals with amblyopia should consider that their responses to different luminance viewing conditions could be asymmetric.

Translational Relevance

The ATAA has the potential to optimize optical correction for the management of aniseikonia in individuals with anisometropic amblyopia.

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.

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.

Associations of aniseikonia with metamorphopsia and retinal displacements after epiretinal membrane surgery

PurposeTo determine the correlation of the degree of aniseikonia with the retinal displacements and metamorphopsia in patients that have undergone successful epiretinal membrane (ERM) surgery.MethodsSubjects were 28 eyes with an ERM in 28 patients. The New Aniseikonia Test (NAT) and M-CHARTS were used to quantify the degree of preoperative and postoperative aniseikonia and metamorphopsia. We also evaluated the distance between the intersections of 2 sets of retinal vessels situated vertically or horizontally by using spectral-domain optical coherence tomography (SD-OCT) images in 28 patients.ResultsThe vertical score of M-CHARTS (MV) was not significantly improved, but the horizontal score of M-CHARTS (MH) was significantly improved at 1 week, 1 month, and 3 months postoperatively. The preoperative NAT score was significantly correlated with the preoperative MH. The NAT score at 3 months was significantly correlated with the MH at 3 months and the MV at 3 months. The preoperative NAT score was significantly correlated with the ratio of the vertical retinal displacement at 1 month and at 3 months after surgery. However, the NAT scores did not improve significantly at any postoperative times.ConclusionsThe degree of aniseikonia was significantly correlated with the degree of metamorphopsia and the tangential displacement of the retina after ERM surgery. Aniseikonia is difficult to improve and metamorphopsia may be a more sensitive parameter to detect the functional recovery after successful ERM surgery.

Aniseikonia following pneumatic retinopexy for rhegmatogenous retinal detachment

PURPOSE

To evaluate the characteristics of aniseikonia in patients with rhegmatogenous retinal detachment (RD) after pneumatic retinopexy.

DESIGN

Prospective, interventional case series study.

METHODS

Thirty patients who had undergone pneumatic retinopexy as the initial procedure for rhegmatogenous retinal detachment were selected for this study. The principal outcomes included visual acuity, postoperative aniseikonia measured by the New Aniseikonia Test, anatomical success, and measurement of central retinal thickness using optical coherence topography (OCT). These outcomes were measured postoperatively at 3, 6, and 12 months.

RESULTS

The median patient age was 37 years (range, 13-57 years), with 17 cases of macula-off RD and 13 cases of macula-on RD. All of these patients achieved anatomical success, proven by OCT after surgical repair. Three months after pneumatic retinopexy, 18 patients (60.0%) developed micropsic aniseikonia and aniseikonia was diagnosed in 15 patients (88.2%) in the macula-off RD group, leaving 2 patients (11.8%) unaffected. In the macula-on RD group, 3 patients (23.1%) were found to have aniseikonia, while 10 patients (76.9%) were unaffected. The presence of aniseikonia was strongly linked to the difference in central retinal thickness, between the operated eye and the fellow eye, measured at 12 months postoperatively.

CONCLUSION

Aniseikonia after pneumatic retinopexy for rhegmatogenous RD may be related to the preoperative macular status. Macula-off RD patients had a higher incidence of aniseikonia, compared to macula-on RD patients, following retina reattachment. There was a moderate to high correlation between the grading of aniseikonia and the difference in central retinal thickness.

Use of Bangerter filters with adults having intractable diplopia

PURPOSE

The aim of this study was to describe the use of Bangerter filters in adults having intractable diplopia.

METHODS/CASE REPORTS

A series of adults having intractable diplopia caused by either cyclotorsion, retinal disease, monocular diplopia, or rapid alternating fixation who were treated with Bangerter filters is reported. Detailed case reports on 4 of the 10 patients are included.

CONCLUSION

Bangerter filters can be used to mitigate diplopia that cannot be eliminated with either prism, modification of the spectacle prescription, vision therapy, or extraocular muscle surgery. The weakest density filter that eliminates the diplopia should be prescribed. Prospective studies reporting the long-term efficacy and quality of life with the filters are needed.

The evaluation of two new computer-based tests for measurement of Aniseikonia

PURPOSE

To evaluate the accuracy and repeatability of size lens induced aniseikonia measurement with the Aniseikonia Inspector Version 1 and a newer customized version of the Aniseikonia Inspector, Version 2.

METHODS

Aniseikonia was measured on 27 subjects with both versions of the Aniseikonia Inspector in normal room illumination. Measurements of induced aniseikonia were made using size lenses in a randomized order. Twenty-five subjects were further tested in the dark using target sizes of equal visual angle for both tests. Repeatability of the intrinsic aniseikonia measurement was assessed on five subjects using randomized testing order for instrument and light and dark measurements.

RESULTS

In normal illumination, the mean slopes for plots of induced aniseikonia vs. size lens magnification for Version 1 were 0.883 and 0.838 for the vertical and horizontal meridians, respectively. For Version 2, the corresponding slopes were 1.162 and 1.043. In the dark and using targets of the same size for both tests, the slopes for Version 1 were 1.038 in the vertical meridian and 0.866 in the horizontal meridian whereas for Version 2, the slopes were 1.195 in the vertical meridian and 1.127 in the horizontal meridian. The amount of underestimation or overestimation within any given testing condition showed considerable intersubject variation. Version 1 was more repeatable than 2, particularly in the vertical meridian.

CONCLUSIONS

On average, the most accurate and repeatable measurement of aniseikonia was found with Version 1 in the vertical meridian in the dark. Measurement of aniseikonia in the horizontal meridian appears to be less reliable. Version 2 overestimates size lens-induced aniseikonia under all testing conditions. Intersubject variation in slopes of induced aniseikonia vs. size lens magnification should be further addressed.

Comparison of aniseikonia as measured by the aniseikonia inspector and the space eikonometer

PURPOSE

The purpose of this study was to compare the new, computerized Aniseikonia Inspector with the Space Eikonometer for the measurement of aniseikonia.

METHODS

Eighteen subjects, ages 21 to 61 years, with normal binocular vision and normal visual acuity had aniseikonia measured with both the Aniseikonia Inspector Version I and the Space Eikonometer. Aniseikonia was measured first with the subjects' habitual refractive correction and then with afocal size lenses of 1%, 2%, and 3.5% added in random order before the right and left eyes. Measurements were taken initially with the Aniseikonia Inspector and on a subsequent day with the Space Eikonometer.

RESULTS

For the Space Eikonometer, the slopes of the lines for the relationship between the measured aniseikonia and the induced magnification differences in the vertical and horizontal meridians are not significantly different from 1.0. For the Aniseikonia Inspector, the slopes of the lines in the vertical and the horizontal meridians are less than and significantly different from 1.0. On average, the Aniseikonia Inspector underestimates the magnitude of induced aniseikonia, predicting only 68% and 61% of the overall size lens magnification in the vertical and horizontal meridians, respectively. The corresponding values of the Space Eikonometer in the vertical and horizontal meridians are 99% and 93%. Variability is greater with the Space Eikonometer than the Aniseikonia Inspector.

CONCLUSION

The Space Eikonometer appears to be measuring the induced aniseikonia appropriately, whereas the Aniseikonia Inspector underestimates the amount of aniseikonia. However, the Space Eikonometer shows greater measurement variability. Modification of the Aniseikonia Inspector or the testing conditions should be pursued in future studies.