Relationships between fusional convergence, suppression depth, and exotropia control in intermittent exotropia.

Purpose: To assess the correlation between the contribution rates of fusional convergence from the dominant and non-dominant eye and suppression depth and exotropia control. Study design: Cross-sectional prospective study. Methods: The fusional convergence of 25 participants with intermittent exotropia (mean age 10.8 ± 3.4; range 6-18 years) was measured with an eye-tracking system. The contribution rate was defined based on the amplitude of fusional convergence during refusion relative to the exo-deviation angle. The suppression depth was assessed, and exotropia control was evaluated using the intermittent exotropia Office Control Score. We analyzed the correlations between the contribution rate from the dominant and non-dominant eyes and the suppression depth or control score. Results: There was a negative correlation between the dominant eye's contribution rate and the suppression depth in both eyes (r = -0.85, 95% confidence interval [CI]: -0.97 to - 0.20 in the fixated dominant eye and r = -0.91, 95%CI: -0.95 to - 0.40 in the fixated non-dominant eye). There was a negative correlation between the dominant eye's contribution rate and the control score at a 4-meter distance (r = -0.53, 95%CI: -0.76 to - 0.17). Conclusion: Suppression in intermittent exotropia patients could affect the fusional convergence in the dominant eye.

Saccade Analysis in Patients With Orbital-Wall Fractures Without Diplopia.

PURPOSE: This study aimed to analyze saccades in patients with orbital-wall fractures with little or no ocular motor impairment. METHODS: We included 7 eyes of 7 patients with unoperated orbital-wall fractures (3 cases of orbital-floor fractures and 4 cases of medial orbital-wall fractures) with mild or no diplopia who presented to our hospital between August 2019 and March 2021. Eye movements were assessed at the first visit and after 1 month using the Hess area ratio according to the Hess screen test, binocular single vision (BSV) scores (total 59 points) obtained using Goldman perimetry, and maximum velocity and amplitude of saccades within 15 degrees obtained using an eye tracker system. RESULTS: Hess area ratio and BSV scores at the first visit and after 1 month were 88.6±8.2% and 97.4±3.6% and 49.6±8.5 points and 53.5±6.6 points, respectively, with no significant change (Hess area ratio, P =0.06; BSV, P =0.44). Next, the authors compared the velocity and amplitude of the saccades between the first visit and 1 month later and found no significant changes in any of the 4 directions (adduction, abduction, upgaze, and downgaze). Similarly, no significant differences were observed between the velocity and amplitude of the saccades between the injured and noninjured eyes, both at the first visit and after 1 month. CONCLUSIONS: In patients with orbital-wall fractures with little or no eye movement impairment, eye tracker-based saccade analysis showed that the saccade velocity and amplitude did not change during the natural course of healing of the fracture.

Utility of a cheiroscope to test for simultaneous perception and sensory fusion.

CLINICAL RELEVANCE: The synoptophore has been used clinically to assess simultaneous perception and sensory fusion in strabismic patients; however, due to suppression or the visual condition of patients with normal stereopsis, a synoptophore does not always detect simultaneous perception or sensory fusion. A cheiroscope may be a better alternative. BACKGROUND: The aim of this work was ro determine whether a cheiroscope could be useful for examining simultaneous perception and sensory fusion in strabismus patients. METHODS: Thirty-three patients with strabismus who could undergo cheiroscopic tracing were categorised into two groups: the intermittent exotropia group (XT; n = 19; mean age 9.8 ± 5.6 yrs, range 5-23 yrs) and the esotropia group (ET; n = 14; mean age 10.2 ± 6.0 yrs, range 4-23 yrs). Two sizes of square line drawings (20° and 6°) were used for the cheiroscopic tracing. The cheiroscopic tracing results were compared with those of synoptophore testing for simultaneous perception and sensory fusion. RESULTS: The rate of cheiroscopic tracing of detecting sensory fusion was significantly higher than that of the synoptophore. With the synoptophore, simultaneous perception was detected in 89.5% and 85.7% of the XT and ET patients, and sensory fusion was detected in 73.7% and 71.4%, respectively. The synoptophore identified 11 patients who had no simultaneous perception or sensory fusion. Among them, eight patients were associated with suppression and two patients were 4 years old. CONCLUSION: Cheiroscopic tracing is useful for determining the presence of simultaneous perception and sensory fusion if they are not detected by a synoptophore due to age < 5 years or suppression.

Changes in saccadic eye movement and smooth pursuit gain in patients with acquired comitant esotropia after strabismus surgery.

This study investigates the change in horizontal saccadic eye movement and smooth pursuit in patients with acquired comitant esotropia (ACE), before and after strabismus surgery. The horizontal saccades and pursuit in 11 patients with ACE were recorded using a video eye-tracker under binocular viewing before and after strabismus surgery. Participants were instructed to fixate on the new target as rapidly as possible when it randomly appeared at either 18.3° rightward or 18.3° leftward. For smooth pursuit, participants were asked to track, as accurately as possible, a step-ramp target moving at ±6.1°/s. The asymmetry of adduction-abduction and the binocular coordination in gains of saccade and pursuit were compared between the pre- and post-surgical data. The asymmetry of adduction-abduction saccade gain in each eye after surgery tended to be smaller than that before surgery. The binocular coordination of saccade showed significant improvement after surgery in only the non-dominant eye direction. Adduction-abduction asymmetry in the smooth pursuit gain in each eye after surgery tended to be smaller than before surgery. After surgery, the binocular coordination of pursuit was improved significantly in both directions. In patients with ACE, binocular coordination of saccade and smooth pursuit was poor. Binocular coordination of saccade and pursuit seems to be improved due to the improvement in ocular deviation angle and binocular visual function after surgery.

Correlation of saccade amplitude during refusion with the fusional convergence amplitude in patients with intermittent exotropia.

In patients with intermittent exotropia (IXT), to investigate the correlation between fusional convergence amplitude and saccade during refusion, as well as the differences in saccade caused by suppression.We measured the fusional convergence amplitude using a synoptophore. Suppression was assessed in 15 patients with IXT (mean age 18.1 ± 11.0 yrs, range 8-54 yrs) having diplopia during exotropia. We performed the cover-uncover test and recorded the saccade during the shift from exotropia to binocular fixation using an eye-tracking system. We analyzed the correlation between the fusional convergence amplitude on the one hand and the saccade peak velocity (PV), the saccade amplitude, and the saccade amplitude of the fusion on the other. We also investigated the difference of those saccade variables between patients with and without suppression.In 15 patients with IXT, the median fusional convergence amplitude was 14 (range 0-60) °, and suppression was confirmed in 11 patients. When the cover was removed from the dominant eye, the fusional convergence amplitude showed a positive correlation with the saccade PV and the amplitude in non-dominant eye (r = 0.570, p = 0.042 and r = 0.669, p = 0.012, respectively). The mean saccade PV, the mean saccade amplitude and the mean saccade amplitude of the fusion were not significantly different with the presence or the absence of the suppression.The fusional convergence amplitude was correlated with saccade in patients with IXT. The saccade during refusion can thus be used to quantitatively evaluate sensory and/or motor fusion.

Evaluation of saccadic velocity in patients with orbital floor fracture before and after surgery.

Saccadic eye movement plays an important role in the rapid movement of the eyes to visual targets; however, it has not been fully investigated in patients with an orbital floor fracture. Thus, this study investigated saccadic eye movement before and after surgery in patients with an orbital floor fracture. The saccadic peak velocity (PV) was recorded using an eye-tracking device before and after surgery in nine eyes of nine patients with an orbital floor fracture. The type of fracture was a depressed fragment fracture in all cases, and there was no trap-door fracture. Ocular motility and diplopia were evaluated by the Hess area ratio (HAR%) and the scoring of binocular single vision (BSV). The preoperative HAR% and those at 1 month post-surgery and the final post-surgery observation were 62 ± 6%, 83 ± 11%, and 91 ± 8%, respectively. The preoperative, 1 month post-surgery, and final observation post-surgery BSV scores were 34 ± 18, 46 ± 8, and 50 ± 8 points, respectively. The postoperative HAR% and BSV were significantly improved at the final post-surgery observation (p < .05 each). The saccadic PVs of adduction, abduction, and downgaze before and after surgery were not significantly different in both the non-injured eyes and the injured eyes. However, the upgaze saccadic PVs at 1 month and the final post-surgery observation in the injured eyes were significantly increased (p < .05 each). The saccadic PV may be useful to evaluate detailed and precise extraocular muscle function before and after surgery for orbital floor fractures.

Longitudinal changes in binocular coordination of smooth pursuit in patients with intermittent exotropia after strabismus surgery.

PURPOSE: To observe the change in horizontal smooth pursuit in patients with intermittent exotropia before and after strabismus surgery. METHODS: The smooth pursuit of patients with intermittent exotropia was recorded using a video eye-tracker before and 1 week, and 1, 3, and 6 months after strabismus surgery. Subjects were asked to track a step-ramp target moving at ±6.1°/sec horizontally as accurately as possible under binocular viewing. The differences in gain (eye velocity divided by target velocity) and amplitude of smooth pursuit between right and left eyes before and after surgery were compared. RESULTS: A total of 9 patients (mean age, 22.2 ± 13.9 years) were included. Mean preoperative ocular alignment at near was 59.1Δ ± 34.7Δ. The difference in gain between the left and right eyes before surgery was 0.23 ± 0.1; in amplitude, 3.0° ± 3.7°. These values were improved at 1 week after surgery (gain, 0.08 ± 0.06; amplitude, 0.9° ± 0.65°) and continued to improve for 6 months after surgery; however, ocular alignment at near reverted from 5.9Δ ± 10.5Δ to 18.9Δ ± 17.5Δ by 6 months after surgery. CONCLUSIONS: In this small patient cohort, surgical correction of ocular alignment improved binocular coordination of smooth pursuit in intermittent exotropia. In the long term, the improvement of the binocular coordination of smooth pursuit tended to remain, although the eye position partially reverted to the presurgical state.

Horizontal Saccadic Velocity in Patients with Exotropia before and after Unilateral Resection and Recession Surgery.

PURPOSE: The effects of strabismus surgery on eye movement are not known in detail, as few studies have compared saccade velocities before and after strabismus surgery. In this study, horizontal saccades were recorded using an eye-tracker in patients with only exotropia to compare the peak velocities (PVs), before and after undergoing strabismus surgery of the same type (unilateral resection and recession). METHODS: Horizontal saccades of monocular vision were recorded using an eye-tracking device in 18 patients with exotropia and 20 normal subjects. All patients were examined using the same method after strabismus surgery. RESULTS: The PVs of adduction and abduction in the patients were higher than those in the normal subjects (in dominant eye, P=0.032 for adduction and P=0.049 for abduction; in nondominant eye, P=0.016 for adduction and P=0.037 for abduction). Following the surgery, the PVs of abduction of the surgical eye (nondominant eye) decreased to the level of the normal subjects (P=0.016). However, there were no correlations between changes in the PVs and the extent of surgery (resection and recession). CONCLUSION: Strabismus surgery normalized the patient's increased PV in the operated eye for abduction of horizontal saccade. Not only peripheral (extraocular muscle) but also central sensory-motor mechanisms may be involved in the changes in PV of horizontal saccades, both of which could result from the improvement of the primary eye position.

Fixation stability of the upward gaze in patients with myasthenia gravis: an eye-tracker study.

OBJECTIVE: To quantify fixation stability of the upward gaze in patients with myasthenia gravis (MG) using an eye tracker. METHODS AND ANALYSIS: In this study, 21 normal subjects, 5 patients with MG with diplopia, 5 patients with MG without diplopia and 6 patients with superior oblique (SO) palsy were included. Subjects fixated on a target in the upward direction for 1 min. The horizontal (X) and vertical (Y) eye positions were recorded using an eye tracker. Fixation stability was first quantified using the bivariate contour ellipse areas (BCEA) of fixation points as an index of whole stability. Then, the SDs of the X and Y eye positions (SDX and SDY, respectively) were quantified as indices of directional stability, with the data divided into three 20 s fractions to detect temporal fixation fluctuation. RESULTS: BCEAs were larger in patients with MG (both with and without diplopia) than normal subjects and patients with SO palsy, without significant differences among the three 20 s fractions. Compared with normal subjects, SDXs were larger only in patients with MG with diplopia; SDYs were larger in both patients with MG with and without diplopia. In addition, SDYs in patients with MG with diplopia were larger than those in patients with MG without diplopia and patients with SO palsy. Furthermore, a significant difference among the three 20 s fractions was detected for SDYs in patients with MG with diplopia. CONCLUSION: Patients with MG, especially those with diplopia, exhibit fixation instability in the upward gaze. Non-invasive quantification of fixation stability with an eye tracker is useful for precisely identifying MG-specific fatigue characteristics. TRIAL REGISTRATION NUMBER: UMIN000023468; pre-results.