Fixation Preference Testing Research Articles

Is Fixation Preference a Potential Indicator of Macular Function in Children?

Objectives:Fixation preference testing is widely used to detect amblyopia, particularly in preverbal children. Pattern electroretinogram (pERG) is an electrophysiological test which is a sensitive indicator of macular function. The aim of this study was to investigate the relationship between fixation preference and macular function on pERG in children with strabismus.Materials and Methods:The study included 11 children with strabismus. All underwent ophthalmological examination including fixation preference by binocular fixation pattern test, best corrected visual acuity (BCVA) assessment, and pERG.Results:The mean age of the patients was 10.09±1.18 years. All patients had unilateral fixation. The mean BCVA was 0.85±0.17 in preferred and 0.48±0.19 in non-preferred eyes (p=0.003). The mean p50 amplitude was 6.07±2.06 μV in preferred and 5.29±2.20 μV in non-preferred eyes (p=0.203), and the mean N95 amplitude was 8.27±2.86 μV and 8.03±3.24 μV respectively (p=0.594). BCVA was correlated with p50 and N95 amplitudes in the non-preferred eyes (p=0.023 and p=0.014). Interocular BCVA difference was correlated with interocular P50 amplitude difference (r=0.688, p=0.019).Conclusion:Although amblyopia is typically considered a cortical phenomenon, future larger studies are needed to investigate the relationship between fixation preference and macular electrophysiological function.

Fixation preference test: reliability for the detection of amblyopia in patients with strabismus and interexaminer agreement.

The purpose of this study was to analyze the reliability of the fixation preference test (FPT) in the detection of amblyopia, and to determine interexaminer agreement. Eighty patients whose visual acuity could be tested objectively and had a horizontal misalignment of more than 10 prism diopters were enrolled. The best corrected visual acuity (BCVA) and orthoptic findings were all recorded. Non-preferred eye in primary position and fixation preference grade were assessed independently by two masked experienced examiners. The primary outcome measures were reliability of FPT in terms of its correlation with BCVA and interexaminer agreement. There was no significant correlation between fixation preference grades and interocular visual acuity difference as well as the type and amount of deviation, the presence of fusion, stereopsis, anisometropia, and previous strabismus surgery for none of the examiners (p>0.05 for all). Sensitivity was 52.0% for examiner 1 and 54.0% for examiner 2 while specificity was 50.0 and 46.7%, respectively. Interexaminer agreement was 76.7% (p<0.001) for all patients. FPT is widely used in children particularly when the visual acuity cannot be determined in an objective manner. The test may not be accurate and reliable in the detection of amblyopia and also in predicting the visual acuity difference between both eyes, even though it was found to show a high degree of agreement between examiners. In conclusion, it should be kept in mind that the reliability of FPT may be limited and the results should be interpreted with caution and be supported by other tests.

Reliability and interexaminer agreement for induced tropia test: is normal always normal?

The purpose of this study was to evaluate the reliability of the fixation preference testing with 10 and 20 diopter prisms (Δ) in children without strabismus in order to extrapolate its utility to preverbal children and to determine interexaminer agreement. Fourty children (24 girls, 16 boys) aged between 5 and 16years with normal ophthalmological examination except refractive errors were included in the study. The visual acuity, refractive errors, and orthoptic findings were recorded. The base-down prism fixation test was performed by two experienced examiners with 10Δ and 20Δ. The presence of corrective movement was recorded as positive result separately for each eye. Best-corrected visual acuity was 1.0 bilaterally for all patients. All patients had binocular single vision and stereopsis. First examiner noted bilateral fixation movement in 65% patients with 10Δ and in 57.5% with 20Δ, second examiner in 50% with 10Δ, and in 37.5% with 20Δ. Interexaminer agreement was 42.5% for 10Δ and 54.5% for 20Δ (p<0.01). Both examiners observed the fixation movement to be less frequent in older children. The fixation movement can be absent or seen asymmetrically even in children with equal visual acuity and binocular vision. The rate of fixation movement seemed to be reduced with age possibly due to increased concentration and cooperation of the child. In addition, there was a remarkable interexaminer variability in both tests. It should be borne in mind that the findings of prism-guided fixation preference tests may be misleading in preverbal children.

False positive amblyopia prediction during fixation preference testing of strabismic patients (“pseudoamblyopia”) correlates with ocular dominance

False positive amblyopia prediction during fixation preference testing of strabismic patients (“pseudoamblyopia”) correlates with ocular dominance

False amblyopia prediction in strabismic patients by fixation preference testing correlates with contralateral ocular dominance

Binocular fixation preference testing is commonly used to predict strabismic amblyopia in preverbal children. However, false positives can occur and can lead to unnecessary patching treatment. We explored potential causes for this phenomenon. In this prospective cohort study (2013-2014) of consecutive verbal strabismic patients without incomitance or decreased vision other than strabismic amblyopia, binocular fixation preference testing was graded from 1 (strong preference) to 4 (free alteration), with grade 1 or 2 considered predictive of amblyopia and the examiner masked to visual acuity. These results were compared to the presence/absence of true strabismic amblyopia. Ocular dominance and hand dominance were assessed, and previous patching history was documented. Of 114 enrolled subjects (mean age, 7.9 years; range, 3.4-22.4; 63 males), 98 (86%) had esotropia and 16 (14%) had exotropia (mean primary position horizontal strabismus, 27.9(Δ); range, 8(Δ)-70(Δ), with only one <10(Δ)). For the 39 false positives (34%), the fixating eye correlated with ipsilateral ocular dominance (79.5%; P < 0.0001 [χ(2)]) but not with hand dominance or recent patching history. Positive predictive value was poor (45.8%; 95% CI, 34.0%-58.0%), but negative predictive value was high (97.6%; 95% CI, 87.4%-99.6%). Subgroup analysis revealed no significant correlations with degree or type of strabismus. False positives during binocular fixation preference testing of strabismic patients are common and likely due to contralateral ocular dominance. The test is more useful for predicting the absence rather than the presence of strabismic amblyopia.

Screening, confirming, and treating amblyopia based on binocularity.

Screening, confirming, and treating amblyopia based on binocularity.

Comparação do teste modificado de fixação preferencial com o convencional em pacientes com estrabismo

To compare the accuracy of the fixation preference test performed with the patient touching and looking at the fixation target, to the conventional method test done with the patient only looking at it. A pilot transversal and prospective study was done with 40 strabismic patients with deviations greater than 10 prism diopters, from 7 to 30 years old. The modified test had a sensitivity of 93% (IC 95%=68.53 - 98.73%) and specificity of 77% (IC 95%=57.95 - 88.97%); while the conventional test had a sensitivity of 93% (IC 95%=68.53 - 98.73%) and a specificity of 46% (IC 95%=28.76 - 64.54%). Our results suggest that the modification of the fixation preference test by asking the patient to touch the fixation target might reduce the number of false positive results of the test.

The accuracy of binocular fixation preference for the diagnosis of strabismic amblyopia

To determine the accuracy of different scales of the binocular fixation preference test and 10(Delta) fixation test in diagnosing amblyopia in patients with strabismus. A prospective and masked diagnostic study was undertaken. We compared 3 binocular fixation preference test scales with interocular Early Treatment Diabetic Retinopathy Study (ETDRS) acuity differences. The 10(Delta) fixation test was used for patients with strabismus <10(Delta). Sensitivity, specificity, and likelihood ratios for amblyopia with an interocular difference of >or=2 lines were determined. Intra- and interexaminer agreements were measured. The study included 221 literate strabismic patients. The accuracy of the binocular fixation preference test was similar for all scales, with no advantage in combining them (Cronbach's alpha = 0.99). The sensitivity and specificity of binocular fixation preference among patients with strabismus >or=10(Delta) were 72.8% (95% CI, 59.7%-83.6%) and 77.6% (95% CI, 66.6%-86.3%), respectively; among patients with deviations <10(Delta), these were 89.6% (95% CI, 72.6%-97.8%) and 64.2% (95% CI, 44.0%-81.3%), respectively. The 10(Delta) fixation test did not alter this accuracy. Likelihood ratios were stronger for extreme grades of the binocular fixation preference test; however, in intermediate grades, they only changed by approximately 15% of the pretest probability of amblyopia. Intra- and interexaminer agreements were 76% (95% CI, 51%-100%) and 73% (95% CI, 48%-97%), respectively. The binocular fixation preference test is more useful for diagnosing amblyopia when the results indicate either a very strong preference or no fixation preference. The intermediate grades of the test were less accurate in our study, accounting for most of the false positives and negatives results.

Evaluation of central, steady, maintained fixation grading for predicting inter-eye visual acuity difference to diagnose and treat amblyopia in strabismic patients

Background:Diagnosis of amblyopia in preverbal strabismic patients is frequently made by binocular fixation preference (BFP) testing. The reports on reliability of BFP are equivocal. This study evaluated the reliability of BFP testing in patients with horizontal strabismus.Materials and Methods:This prospective observational study included patients with manifest, horizontal, comitant deviation >10 prism diopter (PD). Inter-eye acuity difference (IEAD) was calculated by converting Snellen visual acuity to logMAR and was compared with BFP testing. The fixation behavior of the non-preferred eye was evaluated by a single investigator as central or uncentral, steady or unsteady and maintained or unmaintained. Amblyopia was defined as the IEAD of >0.2 logMAR.Results:Of total 61 patients 36 were females and 36 had convergent squint, mean age 9.8 years. The correlation of BFP testing with IEAD was good for esotropia and exotropia. The sensitivity, specificity, positive and negative predictive value of central, steady, maintained (CSM) grading was 93%, 78%, 79%, and 93% respectively. Sensitivity and negative predictive values were higher in children aged four to nine years and anisometropia >1 diopter. The correlation between IEAD and lower grades of BFP testing was poor.Conclusions:CSM grading for BFP testing is useful for the detection of strabismic amblyopia but not useful to differentiate the depth of the amblyopia.

Fixation Preference and Visual Acuity Testing in a Population-based Cohort of Preschool Children with Amblyopia Risk Factors

To compare the clinical assessment of fixation preference (FP) to visual acuity (VA) in a population-based sample of preschool children with amblyopia risk factors. Evaluation of diagnostic test in a population-based study. 243 children with anisometropia and/or strabismus, aged 30 to 72 months, living in Los Angeles County, CA [corrected] Before measuring VA, FP testing was performed at near and usually without correction, using the binocular fixation pattern in children with strabismus >10 prism diopters (Delta), or the induced tropia test for children with strabismus <or=10Delta or without strabismus. We determined the sensitivity and specificity of FP testing for predicting unilateral amblyopia, defined by optotype VA, among children with amblyopia risk factors. Grade of FP. Sensitivity of FP testing for amblyopia among children with anisometropia was 20% (9/44) and specificity was 94% (102/109). Among strabismic children, sensitivity was 69% (9/13; worse in children 30-47 than 48-72 months old) and specificity was 79% (70/89), with similar findings for esotropia and exotropia. The ability of FP testing to correctly identify amblyopia in preschool children with amblyopia risk factors is poor. Clinicians should be wary of using FP as a surrogate measure of interocular difference in VA in young children. The authors have no proprietary or commercial interest in any materials discussed in this article.

Lack of Concordance between Fixation Preference and HOTV Optotype Visual Acuity in Preschool Children: The Baltimore Pediatric Eye Disease Study

To compare the results of fixation preference testing and standardized visual acuity testing in white and black children aged 30 through 71 months. Cross-sectional study. The Baltimore Pediatric Eye Disease Study is a population-based evaluation of the prevalence of vision disorders in children aged 6 through 71 months in Baltimore, Maryland, United States. A total 1714 children 30 through 71 months of age were eligible for inclusion in this report, with 1435 (83.7%) testable by both fixation preference and Amblyopia Treatment Study (ATS) visual acuity testing protocol. The vision of all children 30 through 71 months of age was tested using both the ATS visual acuity testing protocol (using single HOTV symbols with surround bars) and fixation preference testing (FPT). The ability of fixation preference testing to identify children with clinically important interocular differences (IOD) in visual acuity (i.e., two or more logarithm of minimum angle of resolution units of difference or more). Fifty-three children had 2 or more lines of IOD in visual acuity. Seven of them were graded as having momentary or no fixation (sensitivity = 13.2%; 95% confidence interval [CI], 5.3-27.2]), whereas 45 were graded as normal by FPT. In all 7 of the cases of poor FPT, the better-seeing eye was preferred. Low sensitivity and high specificity for detecting an IOD of 2 lines or more with FPT were seen for both white (33.3% sensitivity; 95% CI, 9.5-57.2; 99.6% specificity; 95% CI, 98.7-100) and black (6.5% sensitivity; 95% CI, 0.6, 23.2; 99.3% specificity; 95% CI, 98.3-99.8) children. When assessing FPT performance for 3 or more lines of IOD, only 5 of the 20 children (sensitivity, 25%; 95% CI, 6.0-44.0) had FPT grades of momentary or no fixation. Fixation preference testing, when used as part of a population-based research project, does not identify accurately preschool children with 2 lines or more of IOD in presenting visual acuity. The clinical value of this test is poor and its use for diagnosis and monitoring interventions should be reconsidered.

Results of ocular dominance testing depend on assessment method

We developed a near ocular dominance test modeled after the distance hole-in-the-card test and assessed both test-retest reliability of four tests of ocular dominance and agreement between tests. Forty-six subjects aged 18 to 78 years with visual acuity 20/40 or better in each eye were enrolled from a primary care practice. All subjects had normal eye examinations, with the exception of refractive error, and were examined in their habitual correction. Subjects were tested twice each with the distance hole-in-the-card test, new near hole-in-the-card test, near convergence test, and the Pediatric Eye Disease Investigator Group fixation preference test. There was excellent test-retest reliability for each ocular dominance test. Nevertheless, there was only moderate to slight agreement between each possible pairing of tests. Results of ocular dominance tests vary depending on both the testing distance and the specific activity performed as part of the testing procedure.

Estimation of strabismic amblyopia by small-sized concentric gratings in preverbal children

Evaluate the ability to assess strabismic amblyopia of small-sized Concentric Gratings in comparison with classic linear gratings preferential looking test. Thirty-three preverbal children (age 6-30 months) with esotropia were tested for monocular visual acuity, using small-sized Concentric Gratings (target size 1.6, in 1/3 octave steps) and the Teller Acuity Cards. A fixation preference testing score was also obtained. In 17 of these children, 1-3 years later, after treatment of amblyopia and strabismus, fixation preference testing score, and visual acuity with Teller Acuity Cards, Concentric Gratings, and Glasgow Acuity Cards were measured. In 24 additional verbal untreated strabismic children (age 39-48 months), the same procedures were used. Correlations between interocular acuity difference of each preferential looking test and the Glasgow Acuity Cards were compared. Correlations between interocular acuity difference of each preferential looking procedure and fixation preference testing score were also compared. Concentric Gratings procedure was correlated significantly better than Teller Acuity Cards with fixation preference testing score (0.7 and 0.49, respectively), in the preverbal group (P=0.04). In treated verbal children, correlation of Concentric Gratings and Glasgow Acuity Cards (0.90) was stronger (P=0.06) than correlation of Teller Acuity Cards and Glasgow Acuity Cards (0.64). In untreated verbal children, correlation of Concentric Gratings and Glasgow Acuity Cards (0.89) was stronger (P=0.045) than correlation of Teller Acuity Cards and Glasgow Acuity Cards (0.67). The small-sized Concentric Gratings procedure improves detection and estimation of amblyopia depth in strabismus when compared with classic linear gratings.

Association Between Fixation Preference Testing and Strabismic Pseudoamblyopia

Fixation preference testing is the mainstay of clinical diagnosis of strabismic amblyopia in preverbal children and infants. The purpose of this study is to evaluate the strength of the association between fixation preference and strabismic amblyopia. Eighty patients (3 to 8.3 years) with manifest strabismus and the capability to cooperate with a Snellen acuity test were prospectively examined. Thirty patients were diagnosed as having partially accommodative esotropia, 15 as having congenital esotropia, 15 as having primary acquired esotropia, 15 as having congenital exotropia, and 5 as having hypertropia. Visual acuity levels were measured using a Snellen E-chart. Fixation preference was evaluated and graded from 0 (free alternation) to 3 (strong uniocular fixation). At the end, we compared visual acuity and the grade of fixation preference. Amblyopia was defined as a difference of two or more Snellen lines between the two eyes. Sixty patients (75%) had strong uniocular fixation (grade 3). Of these patients, 50 (85%) had no amblyopia and only 10 had deep amblyopia. Ten patients (12.5%) had moderate fixation (grades 1 and 2). Of these patients, five (50%) had no amblyopia and five had moderate amblyopia. Ten patients (12.5%) had free alternation (grade 0). These patients had equal vision. Treatment of strabismic amblyopia on the basis that the sound eye will show strong fixation preference can be hazardous. Fixation preference could be a severe form of eye dominance, and better methods for testing visual acuity in preverbal children are required.

The Multi-Ethnic Pediatric Eye Disease Study: Design and Methods

Purpose: To summarize the study design of the Multi-Ethnic Pediatric Eye Disease Study (MEPEDS). Methods: The objectives of the MEPEDS are to: (1) estimate age- and ethnicity-specific prevalence of strabismus, amblyopia, and refractive error; (2) evaluate the association of selected risk factors with these ocular disorders; and (3) evaluate the association of ocular conditions on limitations in health-related functional status in a population-based sample of 12,000 children aged 6–72 months from four ethnic groups—African-American, Asian-American, Hispanics/Latinos and non-Hispanic White. Each eligible child undergoes an eye examination, which includes an interview with his/her parent. The interview includes an assessment of demographic, behavioral, biological, and ocular risk factors and health-related functional status. The examination includes fixation preference testing, visual acuity, stereoacuity, axial length measurement, cycloplegic refraction, keratometry, eye alignment, and anterior and posterior segment examination.

The course of moderate amblyopia treated with atropine in children: experience of the amblyopia treatment study

Purpose To * The Writing Committee listed in the Appendix served as author for the Pediatric Eye Disease Investigator Group. A listing of the investigators who participated in the study appears in the Appendix. assess the course of the response to atropine treatment of moderate amblyopia and to assess factors predictive of the treatment response in children 3 years old to younger than 7 years old. Design Multicenter, randomized clinical trial comparing atropine and patching (one of the amblyopia treatment studies). Methods A total of 195 children 3 years old to younger than 7 years of age with amblyopia in the range of 20/40 to 20/100 from the atropine treatment arm of this trial were enrolled and included in this analysis. At baseline, daily topical atropine was prescribed for the sound eye. During follow-up, a plano spectacle lens was prescribed for the sound eye for patients whose amblyopia had not been successfully treated with atropine alone. Follow-up examinations were performed at 5 weeks, 16 weeks, and 6 months. The primary outcome measure was visual acuity in the amblyopic eye at 6 months. Results Mean visual acuity improved from baseline by 1.3 lines after 5 weeks of treatment, by 2.4 lines after 16 weeks, and by 2.8 lines at 6 months. Visual acuity of 20/30 or better and/or 3 or more lines of improvement from baseline was achieved by 75% of the patients. Improvement occurred over the entire range of baseline acuities (20/40 to 20/100) and was not related to patient age ( P = .36). Among the 134 patients improving 3 or more lines from baseline, 7% achieved their maximum improvement by 5 weeks and 46% by 16 weeks. Among the 55 patients who did not respond adequately to atropine alone and were prescribed a plano lens for the sound eye, the mean improvement before the use of the plano lens was 1.0 lines, compared with 1.6 lines after prescribing the plano lens ( P = .11). None of the demographic or clinical factors assessed was predictive of the response to treatment. A shift in fixation preference at/near from the atropinized sound eye to the amblyopic eye was not required for the amblyopic eye to improve; amblyopic eye acuity improved 3 or more lines in 29 (60%) of the 48 patients who were found to be using the atropinized sound eye on fixation preference testing. A 2 or more line decrease in sound eye visual acuity occurred more frequently when a plano lens was prescribed in addition to atropine (7 of 43, 16%) compared with treatment with atropine alone (4 of 123, 3%; P = .01). Conclusions A beneficial effect of atropine is present throughout the age range of 3 years old to younger than 7 years old, and with an acuity range of 20/40 to 20/100. A shift in near fixation to the amblyopic eye is not essential for atropine to be effective in all cases. Sound eye acuity should be monitored when a plano spectacle lens is prescribed for the sound eye to augment the treatment effect of atropine.

The reliability of grading the fixation preference test for the assessment of interocular visual acuity differences in patients with strabismus

Purpose: The purpose of this study is to test the reliability of the grading system of standard fixation preference testing compared with the logarithmic scale of the minimum angle of resolution (logMAR) interocular visual acuity difference of patients with manifest strabismus and to test the strength of association between the interocular visual acuity difference and the grade of alternation. Methods: A total of 111 strabismic patients with large angle heterotropias (> 10 PD) were included in this study. The visual acuities of these patients were determined using the Snellen's, tumbling E, or Lea visual acuity charts as appropriate for the child's age and ability to cooperate. The results were converted to their logarithmic equivalents of minimum angle of resolution or recognition. Fixation preference was graded from 0 to 4 and was evaluated by observing the time-period through which fixation was maintained with the nonpreferred eye. Results: The median value of interocular visual acuity difference for grade 4 was determined as 0.0, grade 3 as 0.097, grade 2 as 0.17, grade 1 as 0.3, and grade 0 as 0.8. The grade of fixation preference was found to be inversely related to the logMAR interocular visual acuity difference (P <.0001). There was a significant difference between every fixation grade except grade 1 and grade 2 (P <.005). Conclusions: The grades used in fixation preference testing correlate with the logMAR visual acuity differences in strabismic amblyopic patients. However, the grading system does not imply a linear function in terms of visual acuity difference. The difference between the logMAR values of patients with grade 0 and 1 are more profound compared with other grades. (J AAPOS 2002;6:191-4)

The Effect of Fixation Target on Fixation Preference Testing

Purpose:The purpose of this study is to determine whether the outcome of fixation preference testing in amblyopia is affected by the type of fixation target.Methods:Fifty patients with a history of amblyopia, either treated or untreated, and 30 normal patients were studied. Standard fixation preference testing was performed in patients with manifest strabismus of at least 10Δ, and induced tropia testing with a 12Δ vertical prism was used in all others. Each patient was tested with three different targets: a light, a wiggle-stick, and a large toy. Outcomes were compared to determine the agreement between the different targets and the sensitivity of each.Results:A high rate of sensitivity was achieved using each of the targets, regardless of the depth of amblyopia. The rates of exact agreement between the different targets were 66–78%. Close agreement was found in 80–86% of patients. The strength of fixation preference did not correlate with the magnitude of interocular acuity difference. Specificity in normal patients was 100% with all targets.Discussion:Sensitivity and specificity of fixation preference testing do not appear to be significantly influenced by the type of fixation target employed. Because fixation preference tends to be quite strong in amblyopia, regardless of the actual difference in interocular acuity, it may be a more reliable technique for diagnosis of amblyopia than for assessment of severity or monitoring of treatment.

Lack of Alternation in Strabismic Patients without Amblyopia

The binocular fixation preference test may fail to differentiate amblyopia from fixation preference. This occurs most frequently in certain patients with anomalous retinal correspondence in whom an...

Reliability of fixation preference testing in diagnosing amblyopia.

We evaluated the sensitivity and specificity of standard fixation preference testing and the 10-prism diopter (PD) fixation test in 427 patients. Standard fixation preference testing showed good sensitivity and specificity for than 10 PD. Patients with small angle tropias, however, had a high false-positive rate, with 40% of nonamblyopic patients inappropriately responding with strong fixation preference. The 10-PD fixation test reduced this high false-positive rate and showed only 1.5% false-positive results. Unfortunately, this shift to equal fixation preference was also seen in some patients with amblyopia, as five of 19 patients with three or more lines difference alternated fixation with the 10-PD fixation test. Retesting disclosed that, although these children would briefly alternate to the amblyopic eye while viewing a stationary target, they would not hold fixation with the amblyopic eye through smooth pursuit. Our conclusion is that standard fixation preference testing can be used to diagnose moderate to severe amblyopia in patients with tropias greater than 10 PD. Patients with small angle deviations or straight eyes should be examined with the 10-PD fixation test, with the criterion for equal vision being the ability to hold fixation well with either eye through smooth pursuit.