Bivariate Contour Ellipse Area Values Research Articles

Visual rehabilitation training in a patient with large central scotoma due to Leber’s hereditary optic neuropathy

Background. Leber’s hereditary optic neuropathy (LHON) is a disease associated with pathogenetic mutations of mitochondrial DNA which affects predominantly young adult males and leads to loss of central vision, low visual acuity and unstable fixation. The purpose of this study was to allow the patient to establish the best possible fixation in the best area of retinal sensitivity in LHON patient with central scotoma. Methods. A 17 years old patient with confirmed mitochondrial LHON 11778G > A mutation was included in the study. The patient underwent 16 visual rehabilitation sessions — two for each of 8 weeks using the training module available in the equipment — MAIA microperimeter. Visual acuity and standrad microperimetry examination were performed before and 8 weeks period of training. To measure the fixation stability with MAIA microperimeter, P1, P2 and Bivariate Contour Ellipse Area (BCEA) parameters were used. Results. Visual acuity of the trained better eye was 0.08 at the baseline versus 0.063 after 8 weeks training. Fixation stability parameter was P1-21%, P2-64% at the first session versus P1-60%, P2-90% at the last session. BCEA values 29.2°˛ before and 14.2°˛ after training, respectively. Conclusions. Visual training via microperimetry could potentially be a method that improves the fixation stability in patients with LHON.

Longitudinal Changes of Fixation Location and Stability Within 12 Months in Stargardt Disease: ProgStar Report No. 12

To investigate the natural history of Stargardt disease (STGD1) using fixation location and fixation stability. Multicenter, international, prospective cohort study. Fixation testing was performed using the Nidek MP-1 microperimeter as part of the prospective, multicenter, natural history study on the Progression of Stargardt disease (ProgStar). A total of 238 patients with ABCA4-related STGD1 were enrolled at baseline (bilateral enrollment in 86.6%) and underwent repeat testing at months 6 and 12. Outcome measures included the distance of the preferred retinal locus from the fovea (PRL) and the bivariate contour ellipse area (BCEA). After 12months of follow-up, the change in the eccentricity of the PRL from the anatomic fovea was-0.0014 degrees (95% confidence interval [CI],-0.27 degrees, 0.27 degrees; P= .99). The deterioration in the stability of fixation as expressed by a larger BCEA encompassing 1 standard deviation of all fixation points was 1.21 degrees squared (deg2) (95% CI,-1.23 deg2, 3.65 deg2; P=.33). Eyes with increases and decreases in PRL eccentricity and/or BCEA values were observed. Our observations point to the complexity of fixation parameters. The association of increasingly eccentric and unstable fixation with longer disease duration that is typically found in cross-sectional studies may be countered within individual patients by poorly understood processes like neuronal adaptation. Nevertheless, fixation parameters may serve as useful secondary outcome parameters in selected cases and for counseling patients to explain changes to their visual functionality.

Metrics and Acquisition Modes for Fixation Stability as a Visual Function Biomarker

PurposeTo compare different metrics and acquisition modes of fixation stability as a new visual function biomarker in a large cohort of patients with ABCA4-related Stargardt disease from the multicenter prospective ProgStar study.MethodsFixation was tested during a separate fixation exam and also dynamically during a sensitivity exam, using fundus-tracking microperimetry (Nidek MP-1). Fixation data were analyzed using the bivariate contour ellipse area (BCEA), the 2/4 degree method, and the Fujii classification.ResultsIn a total of 235 patients, the mean BCEA was larger when measured during the sensitivity exam (418 eyes; 12.5 vs. 4.6 deg2 during the fixation task in 427 eyes). Correlations between the two tests were generally weak. Fixation stability during the sensitivity test was significantly correlated with visual acuity. Comparing the BCEA values and the corresponding Fujii categories for these eyes revealed ranges of overlap where an eye with one defined BCEA value can fall into each of the three Fujii categories.ConclusionsPatients may have limited ability to fixate over defined time periods, which leads to significant differences between shorter and longer measurements of fixation stability. The most appropriate way to use this functional biomarker appears to be using continuous metrics for fixation stability, such as the BCEA, during a macular sensitivity test.

Visual rehabilitation via microperimetry in patients with geographic atrophy: a pilot study

BackgroundAge-related macular degeneration (AMD) is the leading cause of blindness in the western world. As a consequence of AMD, patients develop structural damage that comprises the fovea and subsequently present loss of central vision, low visual acuity and unstable fixation. Contrary to what happens with anti-angiogenic treatment in neovascular AMD, there is currently no definitive treatment to reverse geographic atrophy progression. The aim of this study was to determine the effectiveness of the visual rehabilitation treatment via microperimetry in patients with geographic atrophy.MethodsLongitudinal and prospective study, 18 patients with areas of geographic atrophy in their eye of better visual acuity were included. Macular integrity assessment (Maia) microperimeter (CentreVue, Padova, Italy) was used to diagnose retinal fixation and sensitivity in these patients. Based on these data and using the training module available in the equipment, the patients underwent visual rehabilitation sessions intended to allow the patient to establish the best possible fixation in the best area of retinal sensitivity. To determine the training effectiveness, the following variables were compared before and after: visual acuity in LogMAR scale with ETDRS charts, reading speed with Minnesota Low-Vision Reading Test (MN Read), average sensitivity threshold in microperimetry; P1 and 95% Bivariate Contour Ellipse Area (BCEA) values were used for fixation stability measurement.ResultsMean age was 77 years old (65–92). Visual acuity of the trained eye was on average 0.7 versus 0.6 LogMAR (p = 0.006) before and one week after training. Reading speed, using both eyes, was 47 words per minute (wpm) before training and 69 wpm after training (p = 0.04). Average retinal sensitivity was 14.1 versus 14.6 db (p = 0.4). Fixation stability improved with P1 values of 45% versus 51% (p = 0.05) and 95% BCEA values of 43 versus 25 (p = 0.02) before and after training, respectively.ConclusionsVisual training via microperimetry in patients with age-related macular degeneration is effective in improving fixation stability, reading speed, and visual acuity, measured one week after training is completed.

Fixation Stability and Refractive Error After Cataract Surgery in Highly Myopic Eyes

To analyze the refractive error in highly myopic eyes after cataract surgery and investigate the possible impact of fixation stability on it. Secondary data analysis from a previous prospective study. Clinical data of 98 eyes of 98 consecutive patients with high myopia and 42 eyes of 42 controls, which underwent cataract surgery, were analyzed. Refractive error was calculated 1month after surgery based on both Sanders-Retzlaff-Kraff theoretic (SRK/T) and Holladay 1 formulas. Fixation stability was evaluated using the Macular Integrity Assessment microperimeter system, which assessed the fixation pattern in terms of 63% and 95% of the bivariate contour ellipse area (BCEA). Multiple linear regression analysis was performed to identify independent predictors of postoperative refractive error. The highly myopic cataract group had greater hyperopic refractive errors (P < .001 for both formulas) and larger 63% and 95% BCEA values (P= .033 and P= .034) than the control group. In the highly myopic group, the factors 63% or 95% BCEA were positively correlated with the postoperative refractive error (SRK/T formula, r= 0.383, P < .001 and r= 0.320, P= .002, respectively). Multiple linear regression analysis showed that with the SRK/T formula, postoperative refractive error in highly myopic eyes was significantly correlated with axial length (β= 0.491, P < .001), 63% BCEA (β= 0.181, P= .045), and corneal curvature (β=-0.190, P= .024). The refractive error was no longer associated with corneal curvature after using the Holladay 1 formula. Highly myopic eyes usually had hyperopic refractive errors after cataract surgery. Fixation stability might serve as an important determinant of postoperative refractive errors in this population.

Evaluation of fixation stability using different targets with the MP1 microperimeter.

The aim of this study was to evaluate fixation stability using two different fixation targets with the Nidek MP1 microperimeter. Twenty-nine healthy subjects with a mean age of 26.53 ± 7.35 years and visual acuity ≥0.0 logMAR were enrolled in this study. Fifty-eight eyes of 29 patients without ophthalmic and/or systemic disease underwent a fixation test with the MP1 microperimeter. Fixation stability related to a red cross (central) and/or a red circle (pericentral) target was quantified using either Fujii classification or by calculating the bivariate contour ellipse area (BCEA). For statistical analysis, BCEA values were converted into their logarithms (logBCEA) and all data obtained were analyzed using paired Student's t test. The inclination values of the axis of BCEA were analyzed with Chi squared test. The mean values of logBCEA and the mean values of the major and minor axis of the ellipses related to the cross and the circle fixation target were significantly different (68.2 %, p = 0.00; 95.4 %, p = 0.00; 99.6 %, p = 0.00, respectively) for each BCEA standard deviation. Fixation was significantly less stable for the pericentral fixation target in normal subjects, indicating an advantage for central fixation targets. These results are of particular interest when evaluation of changes in fixation is needed.

Relationship between fixation stability measured with MP‐1 and reading performance

People with visual impairment have reduced reading performance, which is thought to be related to unstable or eccentric fixation. New microperimeters such as the MP-1 offer straightforward analysis of fixation stability. The aim of this study was to investigate the relationship between fixation stability and reading speed in a large cohort of people with diverse causes of visual impairment and to verify the correlation between reading speed and different methods for the quantification of fixation. The better eye of one hundred and twenty subjects was assessed. Fixation values were obtained from the MP-1 microperimeter. Reading speed was evaluated using newspaper text with magnifiers if required. The poorest fixation stability and reading performance was found in people with age-related macular degeneration while the best fixation was in retinitis pigmentosa subjects. A linear relationship was found between reading speed and the proportion of fixations within 2° (r²=0.51, p<0.001) and 4° (r²=0.36, p<0.001). A negative correlation was found between reading speed and all three bivariate contour ellipse areas (BCEA; for log transformation of 1-S.D., 2-S.D. and 3-S.D.: r²=0.39, p<0.001). In a multiple regression model, proportion of points falling within 2° and 4° circle was significantly related to reading speed (r²=0.55, p<0.01; r²=0.43 p<0.01); also BCEAs values were strongly related to reading ability only in patients with central vision loss (r²=0.62, p<0.01 for LogBCEA 68.2%; r²=0.61, p<0.01 for LogBCEA 95.4% and 99.6%) and peripheral defect (r²=0.52, p<0.01 for LogBCEA 68.2%; r²=0.50, p<0.01 for LogBCEA 95.4%; r²=0.49, p<0.01 for LogBCEA 99.6%) but not in combined defect subjects. The study confirms that in people with visual impairment the reduced reading performance is correlated with fixation instability. Moreover, there is a strong relationship between reading speed and both the proportion of fixations falling within 2° and 4° and bivariate contour ellipse area values.

Quantifying Eye Stability During a Fixation Task: A Review of Definitions and Methods

Several definitions, measurements, and implicit meanings of 'fixation stability' have been used in clinical vision research, leading to some confusion. One definition concerns eye movements observed within fixations (i.e., within periods separated by saccades) when observing a point target: drift, microsaccades and physiological tremor all lead to some degree of within-fixation instability. A second definition relates to eye position during multiple fixations (and saccades) when patients fixate a point target. Increased between-fixation variability, combined with within-fixation instability, is known to be associated with poorer visual function in people with retinal disease such as age-related macular degeneration. In this review article, methods of eye stability measurement and quantification are summarised. Two common measures are described in detail: the bivariate contour ellipse area (BCEA) and the within-isolines area. The first measure assumes normality of the underlying positions distribution whereas the second does not. Each of these measures can be applied to two fundamentally different kinds of eye position data collected during a period of target observation. In the first case, mean positions of eye fixations are used to obtain an estimate of between-fixation variability. In the second case, often used in clinical vision research, eye position samples recorded by the eyetracker are used to obtain an estimate that confounds within- and between-fixation variability. We show that these two methods can produce significantly different values of eye stability, especially when reported as BCEA values. Statistical techniques for describing eye stability when the distribution of eye positions is multimodal and not normally distributed are also reviewed.

Fixation Stability: A Comparison between the Nidek MP-1 and the Rodenstock Scanning Laser Ophthalmoscope in Persons with and without Diabetic Maculopathy

Impaired fixation stability is associated with reduced reading speed. In previous research, fixation stability has been assessed using an infrared eye tracker or a confocal scanning laser ophthalmoscope. The new MP-1 microperimeter from Nidek Technologies (Padova, Italy) provides another option for the assessment of fixation. Here the authors compare fixation stability values measured using the MP-1 microperimeter and the Rodenstock scanning laser ophthalmoscope (SLO; Rodenstock GmbH, Munich, Germany) in persons with and without diabetic maculopathy. Sixteen normally sighted volunteers and 21 patients with diabetic maculopathy were recruited. Fixation stability was recorded monocularly on the SLO and the MP-1 in counterbalanced order while participants fixated a red 1 degree cross. Fixation data collected from each instrument were used to calculate a bivariate contour ellipse area (BCEA) that encompassed 68% of fixation points. For control subjects, MP-1 BCEA values were larger than SLO by 0.25 log min arc(2), though the difference was small (10%) and of borderline significance (MP-1, 2.51 log min arc(2); SLO, 2.26 log min arc(2); P = 0.06). In patients with diabetic maculopathy there was no significant difference between MP-1 and SLO values (MP-1, 2.94 log min arc(2); SLO, 2.90 log min arc(2); P = 0.88). No significant difference was found in BCEA values from the SLO and MP-1 in control subjects and patients with diabetic maculopathy. The authors suggest that the similarity between BCEA values, together with the consistent and reliable operation of the MP-1, make it a useful and viable alternative to the SLO in the assessment of fixation.

FIXATION STABILITY MEASUREMENT USING THE MP1 MICROPERIMETER

The Nidek microperimeter (MP1, Nidek Instruments, Italy) is a microperimetry device that also assesses fixation stability. The MP1 does not use the method of quantifying fixation stability by calculating a bivariate contour ellipse area (BCEA). Here we compare the MP1 fixation quantification with the BCEA technique by correlating these values to various parameters of reading known to be related to fixation stability. Twenty-five people with age-related macular disease were assessed. Eye position was recorded using the MP1 during a fixation task. Fixation score and central 2 degrees and central 4 degrees values were obtained from the MP1. Bivariate contour ellipse area values were calculated from raw fixation data. Reading was assessed using MNREAD, Rapid Serial Visual Presentation, and European reading tests. Fixation data could not be collected for two observers. For the other 23 participants, the MP1 fixation scores were very poorly related to reading parameters. In contrast, there was a significant relationship between fixation stability assessed using the BCEA technique and Rapid Serial Visual Presentation reading speed (r = -0.59, P < 0.01), European reading test reading error rate (r = 0.66, P < 0.01), and MNREAD peak reading speed (r = 0.55, P < 0.05). Using the software supplied with the MP1 does not adequately quantify fixation stability in people with age-related macular disease. We recommend that the BCEA technique is used to quantify fixation stability when using the MP1 microperimeter.

Fixation stability using central and pericentral fixation targets in patients with age-related macular degeneration

To determine fixation stability for central and pericentral fixation targets in patients with age-related macular degeneration (AMD). Comparative study. Twelve patients having late-stage AMD involving the fovea and 10 age-matched controls having no other eye diseases and visual acuity better than 20/25. Six different fixation targets (1 degrees cross; 1 degrees filled circle; 1 degrees letter x; small 4-point diamond; large 4-point diamond using dimensions as in a field analyzer; large-crossover whole-image diagonal with open 1 degrees center) were presented on a high-resolution monitor. Before examination, subjects were given verbal instructions to move their eye to see the center of the target best. Fixation stability was measured for the preferred eye, with the fellow eye occluded, using a gaze tracker. Fixation stability was quantified by calculating the bivariate contour ellipse area (BCEA) over 30 seconds for each target. For statistical analysis, BCEA values (minutes of arc2) were converted into their logarithms. The absolute retinal scotoma for the study eye was determined using a scanning laser ophthalmoscope. Bivariate contour ellipse area. Visual acuity in patients (age range, 57-87 years) ranged from 20/32 to 20/600. The lowest BCEA values were found for the 1 degrees letter x in patients (mean, 12052.2%+/-254.0%) and for the 1 degrees cross in normal subjects (mean, 1286.9%+/-47.8%); the highest BCEA values were found for the small 4-point diamond in patients (mean, 23109.5%+/-298.3%) and for the large 4-point diamond in normals (age range, 62-79 years) (mean, 3229.2%+/-105.4%). The difference between the targets was significant for normal subjects (analysis of variance [ANOVA], P<0.01) but not for patients (ANOVA, P>0.05). In normals, BCEA values were significantly lower for central fixation targets than for pericentral fixation targets (P<0.01). Fixation is significantly less stable for pericentral fixation targets in normal subjects, indicating an advantage for central fixation targets. These results are particularly significant for any clinical and experimental testing method that requires the patient to maintain stable fixation.