Maintenance of normal fusion in intermittent exotropia

Abstract

To evaluate the reliability of the Bagolini filter bar and striated lenses for measuring the fusion maintenance score, which is the ability of participants with intermittent exotropia to maintain normal sensorimotor fusion. Methods: Thirty-two Chinese participants aged 7-20 years with intermittent exotropia (excluding the convergence insufficiency type) were enrolled in this prospective study. At the eligibility screening, visual acuity, cover test and assessment of the office control score were performed. At study visit 1, eligible participants underwent negative and positive fusional vergence tests at far and near, eye dominance test and the fusion maintenance test. All eligible participants returned for study visit 2 on the same day (2-4 h later) and the testing was repeated. The primary outcome measure was the intra-class correlation coefficient of the fusion maintenance score between the two study visits. Results: The intra-class correlation coefficient of the fusion maintenance score was 0.84, indicating good reliability. There was no significant difference (mean difference = 0.05, p = 0.95) between the fusion maintenance scores for the first (5.62) and second study visits (5.57). The coefficient of repeatability and the smallest detectable change for the fusion maintenance scores were 7.6 and 6.3, respectively. The fusion maintenance score was significantly associated with the distance (Spearman correlation À0.57, p < 0.001) and near (Spearman correlation À0.4, p = 0.02) office control scores. Conclusion: These data demonstrate that the fusion maintenance score is a reliable tool to evaluate sensorimotor fusion in intermittent exotropia. These results suggest that the fusion maintenance score may be a useful outcome measure in future clinical trials to evaluate the effectiveness of treatments for intermittent exotropia.

Analysis of Improvement Time and Influencing Factors of Diplopia after Intermittent Exotropia in Children

“…Intermittent exotropia, which is between exotropia and constant exotropia, is regarded as a medium-high exotropia, which turns into dominant exotropia after distraction, fatigue, and close reading for a long time, accounting for about 80% of exotropia [ 17 ]. Many scholars are discussing the etiology and pathogenesis of strabismus; there are probably several major factors, one of which is anatomical factors, and various developmental abnormalities of extraocular muscles, including congenital abnormalities, microstructural abnormalities, abnormalities of muscle attachment points [ 17 ]. All kinds of anomalies accumulate, aggravate, and become strabismus for a long time.…”

Reliability of step vergence method for assessing fusional vergence in intermittent exotropia

“…Most coefficients of repeatability in the present study are more than double those of Antona et al 29 This large difference can be attributed to a number of factors. First, other outcome measures (level of control, 31 stereoacuity, 32 angle of deviation 33 and fusion maintenance score 8 ) have been shown to have a great deal of variability in intermittent exotropia. Complicating matters was the large percentage (57%) of participants who decompensated at the beginning of the test in all or some of the measurements, yielding a zero value for the test according to our protocol.…”

“…Given the limitation of the step vergence method in clinical research, there is a substantial need to investigate other clinical tests of fusional vergence (e.g., neutralizing the angle of deviation before using the step vergence method, the smooth vergence method using a phoropter or a synoptophore) and to report their repeatability. Alternatively, one could use the fusion maintenance score to evaluate the ability to maintain normal sensorimotor fusion 8 …”

“…The following tests were performed in this sequence: negative and positive fusional vergence test at distance and near, eye dominance and fusion maintenance score. Data on the fusion maintenance score are presented in a separate report 8 …”

“…A recent report suggested that four clinical outcome measures (control score, near stereoacuity, quality of life score and the angle of deviation) should be reported in surgical studies of intermittent exotropia. 7 Other parameters have also been proposed, and these include, but are not limited to the fusion maintenance score, 8 distance stereopsis, 9,10 vergence, [9][10][11][12][13][14][15] near point of convergence, 10,11 accommodative function 9,[12][13][14] and suppression. 10,11 Treatment of intermittent exotropia includes surgical and nonsurgical options (watchful observation, 16 patching, 16 prisms, 17 overminus lenses 18 and vision therapy/orthoptics 19,20 ).…”