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Purpose: This study aimed to compare the periods for exodrift stabilization and the long‐term surgical outcomes among different surgical methods in intermittent exotropia. Methods: The medical records of 350 patients who had undergone intermittent exotropia correcting surgery [unilateral lateral rectus recession–medial rectus resection (R&R, n = 221), bilateral lateral rectus recession (BLR, n = 51) and unilateral lateral rectus recession (ULR, n = 78)] with a postoperative follow‐up period of 1.5 years or more were retrospectively reviewed. The deviation angles every 6 months after surgery, periods of exodrift stabilization and surgical outcomes were analysed. The period of postoperative exodrift stabilization was defined as when exodrift was no longer significantly different from that at the next visit (p > 0.05). An alignment of 5 PD (prism diopters) esotropia to 10 PD exotropia at a distance and near fixation was considered surgical success. Results: The mean angle of exodeviation was significantly different among surgical procedures at postoperative 1 month (BLR > ULR > R&R, p < 0.001); however, there were no differences among the procedures at 6 months (p = 0.088). The periods of exodrift stabilization were 6 months after ULR, 1 year after BLR and 4.5 years after R&R. The surgical success and reoperation rates did not show significant differences among procedures at the final follow‐up. Conclusion: Patients undergoing R&R showed smaller exodeviation shortly after surgery but required a longer period to stabilize the exodrift. Following ULR, exodeviation was larger in the early postoperative period, but the exodrift was stabilized earlier. Therefore, the long‐term surgical outcomes were similar among ULR, BLR and R&R. [ABSTRACT FROM AUTHOR]

The Korean Intermittent Exotropia Multicenter Study (KIEMS) was a retrospective, cross-sectional and multicenter study for the investigation of intermittent exotropia involved 65 strabismus specialists from 53 institutions in Korea. Purpose of this study was to present ophthalmologic findings of intermittent exotropia from the KIEMS. Consecutive patients with intermittent exotropia of ≥ 8 prism diopters (PD) at distance or near fixation were included. Best-corrected visual acuity, cycloplegic refraction data, angles of deviation at several cardinal positions, ocular dominance, fusion control, oblique muscle function, and binocular sensory outcomes were collected. A total of 5385 participants (2793 females; age 8.2 years) were included. Non-dominant eye was more myopic than the dominant eye (− 0.60 vs. − 0.47 diopters, P < 0.001). Mean exodeviation angles were 23.5 PD at distance and 25.0 PD at near fixation. Basic type (86.2%) was the most, followed by convergence insufficiency (9.4%) and divergence excess (4.4%) types. Alternating ocular dominance and good fusion control were more common at near than at distance fixation. Good stereopsis at 40 cm was observed in 49.3% in Titmus stereo test (≤ 60 arcsec) and in 71.0% in Randot stereo test (≤ 63 arcsec). Intermittent exotropia was mostly diagnosed in childhood and patients with the condition showed relatively good binocular functions. This study may provide objective findings of intermittent exotropia in a most reliable way, given that the study included a large study population and investigated comprehensive ophthalmology examinations. [ABSTRACT FROM AUTHOR]

Here, we compared sensory outcomes between patients with successful motor outcomes and recurrent exotropia after intermittent exotropia surgery. We retrospectively analyzed 303 patients who underwent surgery for intermittent exotropia, divided into two groups: successful motor outcome defined as an alignment between 10 prism diopters (PD) exodeviation and 5PD esodeviation at the final follow-up (Group A, n = 177) and residual or recurrent exotropia defined as exodeviation > 10 PD (Group B, n = 126). Preoperative and postoperative (at final visit) sensory outcomes were compared using the Titmus stereotest and distance Worth 4-dot test. Stereoacuity significantly improved postoperatively in both successful motor outcome group (Group A) and residual or recurrent exotropia group (Group B). However, stereoacuity did not differ between groups preoperatively and postoperatively. On the other hand, fusion rates for the Worth 4-dot test were significantly higher in group A than in group B, preoperatively and postoperatively, and significantly increased postoperatively only in group A. Therefore, the distance Worth 4-dot test may be useful for evaluating postoperative prognosis and preoperative sensory status. [ABSTRACT FROM AUTHOR]

To determine the efficacy of unilateral lateral rectus recession (ULR) for convergence insufficiency-type intermittent exotropia (CI-type IXT), we compared surgical outcomes following ULR and recess‒resect (RR) procedures for CI-type IXT. In this retrospective study, medical records of 57 children who underwent ULR (n = 30) or RR (n = 27) for CI-type IXT of less than 25 PD at distance with a postoperative follow-up of 6 months or more were reviewed. Surgical success was defined as an alignment between 10 PD exodeviation and 5 PD esodeviation at distance and near fixation. The postoperative exodeviation showed no significant difference between the two groups at the last follow-up. A significant reduction in the mean near-distance difference was achieved postoperatively in both groups: from 5.4 PD preoperatively to 2.5 at last follow-up after ULR, and from 8.2 to 2.4 after RR (both p = 0.001). However, this difference between ULR and RR was not statistically significant (p > 0.05). The success rate at the last follow-up was 63.3% for ULR and 70.4% for RR (p = 0.574). ULR was found to be an effective treatment for CI-type IXT, with similar surgical outcomes to RR. [ABSTRACT FROM AUTHOR]

To determine whether intermittent exotropia (IXT) surgery affects contrast sensitivity (CS), this retrospective study evaluated the changes in monocular and binocular CS and the binocular summation ratio (BSR) quantified as the ratio between the values of the binocular and the better monocular CS score (BSR = binocular CS score/better monocular CS score) after surgery for IXT. The subjects were patients who had undergone IXT-correcting surgery with a postoperative follow-up of > 3 months and had pre- and postoperative records of Mars CS test scores. In total, 64 patients (128 eyes) were evaluated. Both the binocular and monocular CS scores of the operated eyes were significantly worse on postoperative 1 day than the preoperative scores, but they were recovered after 1 week. The monocular CS scores of the operated eyes were significantly worse than those of the non-operated eyes until 1 week. There was no significant difference in monocular CS scores between the one-muscle and two-muscle surgeries and in binocular CS scores between the successful alignment and overcorrection groups even on the first day after surgery. The mean BSR was significantly decreased until postoperative month 1, however, recovered to preoperative levels after month 3. In conclusion, IXT-correcting surgery may temporarily worsen the CS, but it is recovered to preoperative levels. Thus, changes in CS in the immediate postoperative period after strabismus surgery should not be of concern. [ABSTRACT FROM AUTHOR]

Purpose: While initial overcorrection after exotropia-correcting surgery is widely accepted for a favorable long-term outcome, some have not advocated such overcorrection in younger children owing to concerns regarding rapid deterioration of bifixation ability. This study aimed to evaluate the relationship between initial overcorrection after intermittent exotropia surgery and the surgical outcome in patients aged <4 years. Methods: In this retrospective study, 391 patients who had undergone surgery for intermittent exotropia were classified into two groups according to the age at surgery: <4 years old (group Y [young], 130 patients) and 4–16 years old (group O [old], 261). The patients were subdivided into three groups according to the angle of deviation at postoperative 1 week: esophoria-tropia (ET) ≥10 prism diopters (PD) (subgroup I), ET 1–9 PD (II), and orthotropia or exophoria-tropia (XT) (III). We compared the surgical outcomes between the two groups and among subgroups; then, we analyzed consecutive esotropia patients. Results: The mean exodeviation was smaller in the order of subgroup I, II, and III at every postoperative visit (p<0.05) in group Y but showed no difference among subgroups after 2 years in group O. Consecutive esotropia occurred at 1 month, postoperatively, in 6.9% and 2.6% of the patients in groups Y and O (p = 0.133), respectively. However, it persisted in two and one patient in groups Y and O, respectively, until the last visit. Conclusion: Early overcorrection after intermittent exotropia surgery was a safe and desirable result in terms of motor outcome in children aged under 4 years, as well as for children aged between 4–16 years. [ABSTRACT FROM AUTHOR]

Background: To measure the amounts of matrix metalloproteinase (MMP)‐2, MMP‐9, tissue inhibitor of metalloproteinase (TIMP)‐1, TIMP‐2 and bone morphogenetic protein (BMP)‐4 in medial rectus muscle (MR) tissue obtained from intermittent exotropia (IXT) patients and to investigate the correlation between each protein amount and the clinical features of IXT including angles of deviation, age at surgery, duration of IXT and postoperative recurrence. Methods: The protein amounts were measured by enzyme‐linked immunosorbent assay (ELISA) in MR collected during surgery for 78 IXT patients. Results: The mean amount of MMP‐2 per mm of resected MR was 0.86 ng, of MMP‐9, 2.72 ng, of TIMP‐1, 1.99 ng, of TIMP‐2, 0.92 ng and of BMP‐4, 0.82 pg. MMP‐2 showed a positive correlation with angle of deviation at distance and at near, age at surgery and duration of IXT (p = 0.000, p = 0.000, p = 0.000, p = 0.022, respectively, Spearman's rank correlation analysis). MMP‐9 showed a positive correlation with angle of deviation at distance and at near (p = 0.001, p = 0.024) and BMP‐4 showed a positive correlation with angle of deviation at distance (p = 0.012). TIMP‐1 showed a negative correlation with angle of deviation at distance and at near (p = 0.003, p = 0.000). Conclusion: In IXT patients, MMPs and BMP‐4 tended to increase and TIMPs to decrease with increasing angle of deviation, greater age at surgery and longer duration of IXT. [ABSTRACT FROM AUTHOR]

Purpose: Most ophthalmologists appear to have no distinct preference between unilateral recess-resect (R&R) and bilateral lateral rectus (BLR) recessions to treat basic-type exotropia. This study aimed to determine whether differences in distance-near discrepancy and resultant exotropia types of recurrent exotropia following surgery for primary basic-type exotropia exist between the two surgical options. Methods: Ninety-three patients with recurrent exotropia following BLR recessions for basic-type exotropia (BLR group) and 95 following R&R for basic-type exotropia (R&R group) were included in this retrospective study. The exotropia types in recurrent exotropia were classified into three types according to distance-near discrepancy: basic, divergence-excess, and convergence-insufficiency. The BLR and R&R groups were compared. Results: After surgery for basic-type exotropia, the type composition changed differently in each group (p < 0.001). The basic-type of primary exotropia was more often maintained in recurrent exotropia in the R&R group than in the BLR group. The incidence of postoperative convergence-insufficiency type exotropia in the BLR group was 28.0% and 8.4% in the R&R group (p = 0.001). Postoperative near stereopsis and fusion control grade of distance deviation did not differ between the two groups (p > 0.05). Conclusions: Convergence-insufficiency type recurrent exotropia occurred more frequently after BLR recessions than after R&R for basic-type exotropia. The high rate of secondary convergence-insufficiency type exotropia after BLR recessions should be considered when clinicians select a surgical option to treat exotropia. [ABSTRACT FROM AUTHOR]

We compare the surgical outcomes of intermittent exotropia of the basic, pseudo-divergence excess (pseudo-DE) and true divergence excess (true DE) types. A study was performed with 342 patients who had undergone surgery for intermittent exotropia of the basic, pseudo-DE or true DE type with a postoperative follow-up period of 6 months or more. The main outcome measures were postoperative angles of deviation at distance and near, and surgical success rates. Surgical success was defined as alignment between exodeviation of 10 PD and esodeviation of 5 PD at distance and near. Additionally, survival curves of recurrence were analyzed by the Kaplan-Meier method. The postoperative angles of deviation at both distance and near in pseudo-DE type were significantly smaller than those in basic type at the final examination (p = 0.003, <0.001). The final surgical success rate in pseudo-DE (70.2%) was better than in basic (46.3%) or true DE (28.6%) (p = 0.003, 0.01). Reoperation for recurrent exotropia was performed in 27% of the basic, 17% of the pseudo-DE, and 35.7% of the true DE cases. According to a survival analysis for recurrence, patients with pseudo-DE showed lower incidence of recurrence than did patients with basic and true DE (p = 0.003, 0.02). In conclusion, the patients with intermittent exotropia of the pseudo-DE type showed better surgical outcomes than those with the basic or true DE type. Pseudo-DE also showed a lower recurrence rate than did the other 2 groups. [ABSTRACT FROM AUTHOR]

Purpose: To analyze changes in corneal topographic measurements and higher-order aberrations (HOAs) after horizontal muscle surgery for exotropia. Design: Retrospective, observational study. Methods: A total of 131 eyes of 121 patients who had undergone surgery for exotropia were included. The eyes with unilateral lateral rectus (ULR) or bilateral lateral rectus (BLR) recession(s) were assigned to group A, and those with unilateral lateral rectus recession & medial rectus resection (R&R) to group B. Corneal topographic measurements and HOAs were compared between the preoperative and postoperative periods using a Placido-dual Scheimpflug analyzer (Galilei 2TM, Ziemer, Port., Switzerland) for each group. Results: In group A, simulated keratometery (sim K) was significantly changed until 3 months postoperatively relative to the preoperative value (postoperative 1 week, p = 0.017; 1 month, p = 0.037; and 3 months, p = 0.023, respectively). All steep K (steep sim K, steep-Kpost, and TCP-steep K) parameters also were significantly changed at postoperative 1 month (p<0.001, p = 0.015, p<0.001, respectively), but not at 3 months. Among the higher-order aberrations, spherical aberration (Z40) and secondary horizontal astigmatism (Z42) at postoperative 1 week had significantly changed from the preoperative values, as had horizontal quadrafoil (Z44) at 1 month. However, in group B, only vertical quadrafoil (Z4-4) showed statistically significant changes, at postoperative 1 and 3 months. None of the other postoperative parameters was significantly different from the corresponding preoperative value. Conclusion: Lateral rectus recession induced changes in both corneal topographic measurements and HOAs, whereas R&R did so only in HOAs. These changes might explain some patients' complaints about poor quality of vision. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate postoperative changes of the intermittent exotropia type as classified by 1-hour monocular occlusion test. Design: Institutional, retrospective study. Methods: We retrospectively reviewed the medical records of 179 patients who had undergone surgery for intermittent exotropia with a postoperative follow-up of 6 months or more. We evaluated the exodeviation obtained before and after 1-hour monocular occlusion preoperatively and again at postoperative 1, 3 and 6 months. Intermittent exotropia was divided into 4 types according to Burian’s classification. The main outcome measure was the distribution of intermittent exotropia type based on 1-hour monocular occlusion in both pre- and postoperative periods. Results: Of the 179 patients, 152 (84.9%) were assigned preoperatively to the basic type, 14 (7.8%) to the pseudo-divergence excess type, and 13 (7.8%) to the convergence insufficiency type. At postoperative 1, 3, and 6 months, the exotropia-type distribution was shifted predominantly to the basic type (p<0.001, p = 0.004, p = 0.029, respectively). Among the preoperative basic-type patients, 96.9% maintained that type postoperatively. However, only 18.2 and 11.1% of the pseudo-divergence excess and convergence insufficiency types maintained the same type. The proportions of the basic type had increased at postoperative 6 months, from 87.8 to 95.7% for bilateral lateral rectus (BLR) recession, from 73.7 to 92.3% for unilateral recess-resect (R&R), and from 88.0 to 95.0% for unilateral lateral rectus (ULR) recession. Conclusion: The type of intermittent exotropia changed mostly to the basic type postoperatively even as classified after 1-hour monocular occlusion. This finding was consistent regardless of the surgical methods (BLR, ULR recession and R&R). [ABSTRACT FROM AUTHOR]

Purpose: To determine whether the inferior oblique (IO) muscle weakening procedure combined with exotropia surgery affects the surgical correction of exotropia. Design: Institutional, retrospective study. Methods: We retrospectively reviewed the medical records of 310 patients who had undergone exotropia-correcting surgery combined with IO weakening (group A, 64 patients) or without IO weakening (group B, 246) with a postoperative follow-up of 6 months or more. The main outcome measures were the postoperative mean angle of horizontal deviation, the success rate, and the overcorrection rate. Surgical success was defined as an alignment between 10 prism diopters (PD) of exodeviation and 5 PD of esodeviation. Results: The postoperative mean angles of exodeviation, throughout the follow-up period, did not significantly differ between the groups. Although the surgical success rate was higher in group B at postoperative 1 month (p = 0.035), there was no statistical difference between the 2 groups from postoperative 6 months.: The final success rates were 56.3 and 51.6% (p = 0.509). The overcorrection rate was significantly higher in group A at postoperative 1, 6 and 24 months (p = 0.017, p = 0.028, p = 0.030, respectively); however, at the final follow-up, there was no overcorrection in either group. Conclusion: The overcorrection rate was higher in group A until postoperative 2 years, even though the mean angles of exodeviation and the success rates did not significantly differ between the 2 groups. Surgeons should be mindful of overcorrection when planning exotropia surgery combined with the IO weakening procedure. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the early postoperative changes of the angle of deviation after surgery for intermittent exotropia.Methods: We retrospectively reviewed the medical records of 114 patients who had been surgically treated for intermittent exotropia and followed-up on postoperatively for 1 month or more. Patients were observed at postoperative 6 h, 1 day, 1 week, and 1 month. The main outcome measure was the change of the angle of deviation during the early postoperative period (from 6 h to 1 day postoperatively).Results: The mean preoperative angle of exodeviation was 26.3 ± 7.6 PD at distance and 25.4 ± 10.3 PD at near. The angle of deviation was −3.3 (esodeviation) ± 7.0 PD at distance and −0.7 ± 7.1 PD at near at postoperative 6 h, and −3.7 ± 6.9 PD and −0.8 ± 6.8 PD at postoperative 1 day. Neither of these sets represented a significant change from 6 h to 1 day postoperatively (p = 0.300 at distance, p = 0.945 at near). However, in 25 patients (21.9%) the angle of deviation changed 5 PD or more from 6 h to 1 day. Among them, ten showed exodrift and 15 esodrift. At postoperative 1 month, the deviations became significantly more exotropic compared with postoperative 1 day (p < 0.001).Conclusions: The mean angle of deviation showed no significant change from 6 h to 1 day postoperatively, but 21.9% of patients showed a change of 5 PD or more in this period. These results should be considered in determining the time and the target angle of adjustment in adjustable strabismus surgery for exotropia. [ABSTRACT FROM AUTHOR]

Background: The aim of this study was to compare the primary surgery and reoperation outcomes of unilateral lateral rectus recession and medial rectus resection (R&R) for intermittent exotropia.Methods: We retrospectively reviewed the medical records of 80 patients, all of whom had undergone unilateral R&R for intermittent exotropia as a primary surgery or reoperation and been followed-up on postoperatively for 6 months or more. The patients were divided into two groups: unilateral R&R as primary surgery (group A, 44 patients) and unilateral R&R as reoperation (group B, 36 patients). The outcome measures were postoperative angle of deviation, surgical success rate, and mean dose-effect ratio (PD/mm, corrected angle of deviation / sum of amount of recession of lateral rectus and of resection of medial rectus). Surgical success was defined as exo- or esodeviation within 8 PD.Results: The mean postoperative follow-up duration was 49.91 ± 14.83 months in group A and 43.17 ± 26.91 months in group B (p = 0.160). The mean angles of deviation at postoperative 1 day were -5.18 PD (overcorrection) in group A and -5.28 PD in group B (p = 0.932). However, there was a significant difference in the mean angle of deviation between the two groups at each visit from postoperative 3 months to final follow-up (p < 0.05): in short, group A had become more exotropic than group B. And the surgical success rate was higher in group B than in group A at each visit from postoperative 12 months to final follow-up (47.7% in group A and 83.3% in group B at final follow-up) (p < 0.05). The mean dose-effect ratio at 6 months after surgery was 1.89 ± 0.58 PD/mm in group A and 2.26 ± 0.32 PD/mm in group B (p = 0.001).Conclusions: Unilateral R&R as reoperation presented better results for the surgical treatment of recurrent exotropia, showing a smaller exodrift pattern and higher surgical success rates compared with R&R as a primary surgery. The mean effect per millimeter (the mean dose-effect ratio, PD/mm) of R&R as reoperation was significantly greater than that of R&R as primary surgery at postoperative 6 months. These results could serve as useful guidelines in the planning of surgical correction for primary and recurrent exotropia. [ABSTRACT FROM AUTHOR]

We evaluated effect of horizontal rectus surgery on sub-A or sub-V pattern intermittent exotropia. We enrolled patients with sub-A or sub-V pattern intermittent exotropia. The sub-A pattern was diagnosed when the eyes diverged less than 10 prism diopters (PD) from upgaze to downgaze, and sub-V pattern when the divergence was 14 PD or less from downgaze to upgaze. Patients had undergone horizontal rectus surgery without vertical transposition of horizontal rectus muscle or oblique muscle weakening. The patients were divided into two groups: sub-A pattern (group A) and sub-V pattern (group V). The outcome measures were change of amount of pattern and rate of collapse of pattern postoperatively. The amount of pattern (vertical incomitance) was amount of difference in exodeviation between upgaze and downgaze. Collapse of pattern was defined as disappearance of difference in exodeviation between upgaze and downgaze. In groups A and V, preoperative amounts of pattern were 4.9 PD and 6.8 PD, respectively. A significant reduction in amount of pattern was observed in both groups throughout the follow-up period (p<0.05). At postoperative 6 months, the amounts of pattern were 1.0 PD and 1.2 PD and the extents of reduction in amount of pattern were 4.4 PD and 5.9 PD. The rates of collapse of pattern at postoperative 6 months were 77.8 and 60.0%, respectively. In the patients with sub-A or sub-V pattern exotropia, horizontal rectus surgery without vertical transposition or oblique muscle weakening can successfully collapse the pattern. [ABSTRACT FROM AUTHOR]

Correction to: I Scientific Reports i https://doi.org/10.1038/s41598-023-28015-2, published online 24 January 2023 The original version of the Article contained errors in the Consortia author list of The Korean Association of Pediatric Ophthalmology and Strabismus (KAPOS), where author names Dong Gyu Choi and Dae Hee Kim were duplicated in the KIEMS writing committee, and Jae Ho Jung, Mi Young Choi, Jeong-Min Hwang, Su Jin Kim, Yeon-hee Lee, Sueng-Han Han and Dong Gyu Choi were duplicated in KIEMS investigators in the KAPOS. The original article can be found online at https://doi.org/10.1038/s41598-023-28015-2. [Extracted from the article]

Background: The aim of this study was to investigate the type of exotropia (XT) based on the distance-near (D/N) difference in recurrent XT after bilateral lateral rectus (BLR) recession to treat intermittent XT (IXT) to look into the possibility of secondary convergence insufficiency (CI)-type strabismus.Methods: A total of 121 patients with recurrent XT after BLR recession for basic-type and divergence excess (DE)-type IXT were retrospectively enrolled at a single institution. The distributions in the XT types were compared according to the D/N difference between primary and recurrent XT.Results: Preoperatively, the population comprised 14 divergence excess (DE) types and 107 basic types. After the BLR recession, the XT-type composition changed to 59 basic types, 33 CI types, and 29 DE types. In one of the 14 preoperatively identified DE-type XT cases, the XT type changed to CI type, it changed to basic type in four cases, and the remaining nine cases showed no change in the DE type. The 107 preoperatively identified basic-type XT cases postoperatively became 55 basic-type, 32 CI-type, and 20 DE-type recurrent XT cases, and their postoperative distance XT control grades and near stereoacuity values did not significantly differ.Conclusion: The XT type composition changed after the BLR recession. The XT types in recurrent XT after BLR recession showed an increasing proportion of CI-type. We suspect that an individual fusion mechanism might also influence the XT-type in recurrent XT in view of the somewhat increased DE-type in recurrent XT. [ABSTRACT FROM AUTHOR]

Purpose To analyse the characteristics of children who had maintained the successful outcome at 2 years after surgery for intermittent exotropia. Methods A retrospective study was performed in 216 patients who had undergone intermittent exotropia surgery and had had at least 2 years of follow-up. Surgical outcomes were grouped, according to the angle of deviation at postoperative 2 years, as success (esophoria/tropia ≤ 5 prism dioptres ( PD) to exophoria/tropia ≤ 10 PD), recurrence (exotropia > 10 PD or reoperation within 2 years) or overcorrection (esophoria/tropia > 5 PD). We investigated various clinical factors for their possible associations with the surgical outcomes. Results Of the 216 patients, 128 (59%) were assigned to the success group, and 84 (39%) to the recurrence group. According to a univariate analysis, surgical method and the angle of deviation at the postoperative day 1 showed statistically significant associations with the surgical outcome for intermittent exotropia. However, in the results of a logistic regression test, the angle of deviation at distance at postoperative day 1 was the only factor showing a significant association (p = 0.023). Conclusions Early postoperative overcorrection was significantly associated with the maintenance of successful surgical outcome of intermittent exotropia at postoperative 2 years. [ABSTRACT FROM AUTHOR]