Comparison of retinal nerve fiber layer thickness between monocular and alternating exotropia in patients with intermittent exotropia.

PURPOSE: To investigate differences in intraocular structure based on the presence or absence of fixation preference in children with intermittent exotropia (IXT) by comparing the thickness of the retinal nerve fiber layer (RNFL). METHODS: From October 2018 to March 2022, RNFL thickness was retrospectively analyzed using spectral domain optical coherence tomography. Participants had uncorrected visual acuity of 20/20, refractive errors close to emmetropia, and no anisometropia. The patients were divided into monocular and alternating exotropia groups through a cover-uncover test. The average and sectoral thickness of the RNFL in both groups were compared. RESULTS: The average global thickness and average thickness of each of the six sectors of the RNFL did not significantly differ between dominant and non-dominant eyes in the monocular exotropia group and between right and left eyes in the alternating exotropia group. The thickness did not significantly differ between the monocular exotropia group and the right or left eye of the alternating exotropia group. Interocular differences in RNFL thickness were negative in the monocular exotropia group (dominant eye-non-dominant eye) and positive in the alternating exotropia group (right eye-left eye) for the average, inferonasal, and inferior sectors, exhibiting statistically significant between-group differences (p = 0.019, p = 0.003, p = 0.023, respectively). CONCLUSIONS: In children with IXT without obvious refractive error, there was a significant interocular difference in RNFL thickness of the average, inferonasal, and inferior sectors between monocular and alternating exotropia groups. The presence of fixation preference may affect RNFL thickness.

Strong fixation preference in patients with manifest exotropia: Does it matter or not?

PURPOSE: To evaluate the influence of strong fixation preference on clinical and surgical outcomes, in non-amblyopic patients with basic-type intermittent exotropia (IXT). MATERIALS AND METHODS: The records of patients were retrospectively investigated. Non-amblyopic patients with the diagnosis of basic-type IXT were enrolled and divided into two groups according to the presence of strong fixation preference (SFP). Best-corrected visual acuity, refractive errors, deviations in near and distance, convergence patterns, motor fusion, stereopsis were evaluated and compared. Patients who underwent surgery in each group composed subgroups and postoperative deviations, convergence patterns, motor fusion, and stereopsis were compared. RESULTS: Seventy-seven patients were enrolled and divided into two groups according to the presence of SFP: patients with SFP composed Group 1 and patients with alternating fixation composed Group 2. Statistically significant difference was seen between groups in terms of motor fusion (p: 0.02). Other parameters did not differ between groups. Data obtained from patients in subgroups of each group were not statistically different. CONCLUSION: The evaluation of basic-type exotropic patients according to their fixation preference revealed us that motor fusion might be affected by strong fixation preference. We also observed that SFP did not affect surgical success rates, convergence patterns, and stereopsis of exotropic patients.

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

PURPOSE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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 16 years 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.

Contralateral lateral rectus muscle recession in a patient with unilateral exotropic Duane retraction syndrome type II: A case report.

A fixation preference for the affected eye is uncommon in patients with unilateral Duane retraction syndrome (DRS), and surgery on the fellow eye is rarely advocated. We are presenting a case report of a 9-year-old boy with unilateral DRS type II in the left eye who received lateral rectus muscle recession in his right amblyopic eye. The patient was orthophoric and his face turn was gone 6 months postoperatively. Surgery on the fellow amblyopic eye is a good choice for unilateral DRS where the affected eye dominants the fixation, and the satisfactory outcome suggests that alignment in the primary position can correct the face turn effectively despite the muscle duction deficit in the affected eye and further extend the binocular single visual field.

Saccade Strategy in Alternating Exotropia.

Patient with exotropia frequently alternate fixation, looking at something with one eye and then switching their attention to acquire a new target with the other eye. Which eye informs the brain about the location of the new target? To address this issue, we presented targets dichoptically to 16 exotropes that were visible to the fixating eye, the deviated eye, or to both eyes. We then compared the subjects' choice of eye for target acquisition with the organization of their suppression scotomas. There was a correspondence between suppression scotoma maps and the eye used to acquire peripheral targets. In other words, a target perceived via an eye was also fixated by it. These studies reveal how patients with alternating strabismus, despite eye misalignment, manage to localize and fixate efficiently visual targets in their environment.

Is macular pigment optical density really involved in fixation preference?

PURPOSE: To evaluate macular pigment optical density in healthy children and to compare the values with those of strabismic children with respect to fixation preference. METHODS: The study recruited 54 healthy and 41 strabismic children. Two groups were matched in terms of gestational age, birth weight, and body mass index. All participants underwent complete ophthalmological evaluation and macular pigment optical density measurement and filled a self-reported food frequency questionnaire. Strabismic children were categorized according to fixation preference. RESULTS: The mean age was 9.87 ± 2.39 years in healthy children and 9.07 ± 2.07 years in children with strabismus (p = 0.091). Mean macular pigment optical density was 0.23 ± 0.25 in healthy eyes and 0.25 ± 0.27 in non-preferred eyes of strabismic children (p = 0.964). Macular pigment optical density was significantly higher in preferred eyes of strabismic children (0.43 ± 0.34) compared to non-preferred eyes (p = 0.004) and healthy eyes (p = 0.001). There was a difference of macular pigment optical density between both eyes in patients with grades 1, 2, and 3 fixation preference, whereas patients with grade 4 preference had similar macular pigment optical density in both eyes (p = 0.008). There was a statistically significant positive correlation between macular pigment optical density in preferred eyes and body mass index (r = 0.354, p = 0.023). CONCLUSION: Preferred eyes of children with strabismus seem to have higher macular pigment optical density readings. This difference may emerge from the higher tendency of recognizing the flicker stimulus while preferred eye is under testing. Similar macular pigment optical density in healthy and non-preferred eyes and the fact that both lower than preferred eyes remain unexplained. It should be kept in mind that macular pigment optical density results should be carefully interpreted and macular pigment optical density in cases with strabismus should be further investigated.

Induced Tropia Test and Visual Acuity Testing in Nonverbal Children.

The objective of our study was to compare the Cardiff Acuity Card© test (CAC test) (Kay Pictures Ltd) with the induced tropia test (ITT) in nonverbal children for the detection of monocular vision deficit. This is a retrospective case note review of 34 nonverbal children, aged 12-48 months, attending the pediatric ophthalmology clinic at Children's Hospital of Pittsburgh of UPMC between October 2014 and January 2015. 30/34 were included for analysis. Binocular visual acuity and monocular visual acuity were tested at 50cm in 30 and 17 patients, respectively. At 100cm, binocular visual acuity and monocular visual acuity were tested in 16 and 11 patients, respectively. All 30 children had successful induced tropia testing; 21 had no fixation preference and 9 had a fixation preference. Of those that had no difference on monocular visual acuity, five had a fixation preference at 50cm and three at 100cm. Out of 21 that had no fixation preference, 3 had a monocular visual acuity difference, but of only one line. Our study suggests that to obtain as much information as possible without losing the interest or cooperation of the child, it may be more beneficial to perform the CAC test with both eyes open, followed by ITT, before attempting monocular visual acuity testing with the CAC test. Obtaining visual information using ITT was much more attainable compared to monocular CAC testing. The sensitivity using CAC test to find a visual acuity discrepancy is 40% using ITT as the standard, and the specificity is 63%. If one loses the interest of the child after the ITT, at least some information will have been gleaned rather than none about monocular visual behavior. This provides a more complete, attainable approach to gathering visual information.

Is the 15∆ Base in Prism Test Reliable for Detection of Amblyopia in Anisometropic Patients?

PURPOSE: The 15∆ base in prism test (15∆BIPT) introduced by Gobin is often used in The Netherlands to detect fixation preference, especially in young and preverbal children in whom a reliable measurement of the visual acuity (VA) is difficult. It is assumed that the fixation preference detected by the 15∆BIPT can be used to predict the presence of amblyopia. The aim of this retrospective case note review was to investigate the accuracy of the 15∆BIPT in detection of amblyopia in anisometropic patients. METHODS: Four hundred and twelve files of anisometropic patients visiting the orthoptic department of The Rotterdam Eye Hospital were analyzed. Amblyopia was defined as an intraocular difference in VA of 2 or more Snellen lines. The sensitivity, specificity, and positive and negative predictive values of the 15∆BIPT were calculated and the receiver operating characteristic (ROC) curve was plotted. RESULTS: One hundred and fifty-two patients ranging from 3.3-13.1 years of age (median 5.4 years) met the inclusion criteria. One hundred and two patients were diagnosed with amblyopia. Best-corrected median VA of the best eye was 1.0 (range 0.5-1.2) and the worst eye 0.70 (range 0.05-1.2). Sensitivity of the 15∆BIPT (based on detecting amblyopia) was 34.3%. Specificity was 88.0%. The positive predictive value was 85.4% versus a negative predictive value of 39.6%. The area under the ROC curve (AUC) was 0.65 (95% CI 0.56-0.74). CONCLUSION: The low sensitivity, large number of false negatives and the AUC show that the 15∆BIPT can be considered a poor test for detecting amblyopia in anisometropic patients.

Reliability of fixation preference for detecting amblyopia in strabismic patients.

PURPOSE: To evaluate the association between fixation preference (FP) and amblyopia in strabismic patients. METHODS: This study includes 50 patients with horizontal, vertical or mixed strabismus of at least 10 prism diopters. Best-corrected monocular visual acuity (VA) was measured using Snellen E-chart and the presence of amblyopia was determined accordingly; FP was evaluated and graded from 0 to 3. RESULTS: Of 50 patients, including 27 female and 23 male subjects, 29 (58%) patients had FP but 18 (36%) subjects were truly amblyopic. Overall, the sensitivity and specificity of FP for detection of amblyopia was 88.9% and 59.4% respectively. The positive predictive value (PPV) and negative predictive value (NPV) were 55.2% and 90.5% respectively. Sensitivity, PPV and NPV were significantly higher in esotropic as compared to exotropic patients. Strong monocular FP was correlated with more than 3 lines of interocular difference (IOD) in visual acuity (P=0.001). CONCLUSION: Although FP is not an ideal method for diagnosis of strabismic amblyopia, it has high sensitivity, PPV and NPV in esotropic patients and in subjects with more than 3 lines of IOD in VA.