Comparison of surgical outcomes between bilateral recession and unilateral recession-resection in moderate-angle intermittent exotropia

Symmetric versus asymmetric surgery for the treatment of intermittent exotropia with equal dominance

PURPOSE

Long-term surgical outcomes were compared between bilateral lateral rectus recession (BLR) and unilateral lateral rectus recession combined with medial rectus resection in the same eye (R&R) for therapy of basic type intermittent exotropia (IXT) with equal dominance.

METHODS

Two hundred and sixty-eight subjects (3-11 years old) with basic IXT with equal dominance who underwent BLR or R&R surgery were enrolled to this study, and with a minimum follow-up period of 18 months. One hundred and fourteen patients underwent BLR surgery and 144 underwent R&R surgery at a single centre. Surgical outcomes between groups were compared. Surgery results were divided into 3 categories: undercorrection/recurrence (exotropia/phoriaå 10PD), success(esotropia/phoria ≤5PD to exotropia/phoria≤10PD), and overcorrection (esotropia/phoriaå 5 PD) according to postoperative deviation angle.

RESULTS

No statistical difference was detected between BLR group and R&R group at all intervals with the exception of the last examination, demonstrating a higher success rate and a lower recurrence rate in the BLR group than R&R group at last visit (P = 0.04). Additionally, the BLR group demonstrated a smaller exodrift than the R&R group at distance and near fixation (P = 0.01; P = 0.03). Stereoacuity and exotropia control showed overall improvement following both surgeries, and this improvement had no statistical difference between groups(P > 0.05).

CONCLUSIONS

BLR showed better long-term results than R&R in the treatment of basic type intermittent exotropia with equal dominance given its low recurrence rate. Both BLR and R&R surgeries could improve stereoacuity function and exotropia control, and to same extents.

Comitant strabismus etiology: extraocular muscle integrity and central nervous system involvement-a narrative review

Strabismus is not a condition in itself but the consequence of an underlying problem. Eye misalignment can be caused by disease, injury, and/or abnormalities in any of the structures and processes involved in visual perception and oculomotor control, from the extraocular muscles and their innervations to the oculomotor and visual processing areas in the brain. A small percentage of all strabismus cases are the consequence of well-described genetic syndromes, acquired insult, or disease affecting the extraocular muscles (EOMs) or their innervations. We will refer to them as strabismus of peripheral origin since their etiology lies in the peripheral nervous system. However, in most strabismus cases, that is comitant, non-restrictive, non-paralytic strabismus, the EOMs and their innervations function properly. These cases are not related to specific syndromes and their precise causes remain poorly understood. They are generally believed to be caused by deficits in the central neural pathways involved in visual perception and oculomotor control. Therefore, we will refer to them as central strabismus. The goal of this narrative review is to discuss the possible causes behind this particular type of eye misalignment and to raise awareness among eyecare professionals about the important role the central nervous system plays in strabismus etiology, and the subsequent implications regarding its treatment. A non-systematic search was conducted using PubMed, Medline, Cochrane, and Google Scholar databases with the keywords "origins," "causes," and "etiology" combined with "strabismus." A snowball approach was also used to find relevant references. In the following article, we will first describe EOM integrity in central strabismus; next, we will address numerous reasons that support the idea of central nervous system (CNS) involvement in the origin of the deviation, followed by listing several possible central causes of the ocular misalignment. Finally, we will discuss the implications CNS etiology has on strabismus treatment.

Effects of orthoptic therapy in children with intermittent exotropia after surgery: study protocol for a randomized controlled trial

Background

Intermittent exotropia (IXT) is the most common type of exotropia in China. Surgery is usually required to align the eye deviation to maintain or obtain better binocular visual function. However, there is a high rate of exodrift or recurrence in surgically treated patients. Orthoptic therapy is sometimes recommended for IXT patients after surgery. However, there is a lack of high-quality randomized controlled trials to prove that orthoptic therapy could be an effective supplement to surgical treatment for IXT patients. The main purpose of this study is to test the clinical effectiveness of orthoptic therapy in long-term stabilization of postoperative IXT patient. This report describes the design and methodology of the Intermittent Exotropia Postoperative Treatment Clinical Trial, which is the first large-sample, blank-controlled, randomized clinical trial.

Methods

A total of 136 IXT patients (aged 7 to 17 years) will be enrolled and assigned to the orthoptic therapy group or blank control group according to a simple randomization scheme. Patients in the orthoptic therapy group will receive at least 2 months of orthoptic therapy, such as anti-suppression, vergence, and accommodation training. Patients in the blank control group will receive only refractive correction. All enrolled patients will need regular follow-up observation until 24 months after surgery. The primary outcome will be the proportion of participants meeting suboptimal surgical outcomes in this 24-month follow-up, which is defined as (1) exodeviation of 10 prism diopters (PD) at distance or near using the simultaneous prism and cover test (SPCT) or (2) loss of 2 or more octaves of stereoacuity from baseline, at any masked follow-up visit examination. The secondary outcomes will be the exodeviation at distance and near using the simultaneous prism and alternate cover test (PACT), magnitude of fusional convergence, stereoacuity, and accommodation. Measurements will be taken at baseline and at the 6-, 12-, 18-, and 24-month follow-ups.

Discussion

To the best of our knowledge, this will be the first prospective, randomized controlled study of orthoptic training in IXT patients after surgery. The aim of this work is to confirm the efficacy of orthoptic therapy in reducing the proportion of recurrence among IXT patients after surgery and improving binocular vision function.

Trial registration

Chinese Clinical Trial Registry ChiCTR1900026891. Registered on 25 October 2019.

Dose-Response of Primary Bilateral Medial Rectus Resection in Infantile Exotropia

PURPOSE

To evaluate the dose-response relationship for primary bilateral medial rectus resection in children with exotropia, based on outcomes with this procedure.

METHODS

Dose-response at both distance and near were calculated as prism diopters correction per millimeter (PD/mm) of rectus resection. All surgeries were performed under general anesthesia through a fornix incision, using doubled-armed 6-0 polyglactin sutures. The resection amount ranged from 5 to 8 mm in each eye, according to the surgical dosage based on the largest angle of preoperative deviation.

RESULTS

The mean surgical dose-response for all procedures was 2.83 ± 1.03 PD/mm of resection at distance and near. The overall success rate was 53% at the final examination after a mean follow-up of 21.9 months. Patients with moderate angles (25 to 45 PD) had a higher success rate than those with 50 PD or greater deviation.

CONCLUSIONS

Primary bilateral medial rectus resection should be considered as a surgical alternative in childhood exotropia, particularly for moderate and constant deviations. [J Pediatr Ophthalmol Strabismus. 2022;59(1):24-27.].

Long term surgical outcomes of unilateral recession-resection versus bilateral lateral rectus recession in basic-type intermittent exotropia in children

The long-term results of surgical treatment of intermittent exotropia (X(T)) according to the type of surgery are controversial. We conducted a retrospective cohort study to compare the long-term results between unilateral recession-resection (RR) and bilateral lateral rectus recession (BLR) with an average follow-up of 9.5 years in children with basic-type X(T). Patients with basic-type X(T), who underwent RR (RR group) or BLR (BLR group) and were followed-up for more than 5 years postoperatively, were analyzed. Of the 560 patients, 363 patients received BLR and 197 patients underwent RR. There was no significant difference in the success rates between the two groups until postoperative 3 years. At an average of 9.5 ± 2.6 years after surgery, the success rate of the RR group was significantly higher than that of the BLR group starting from the fourth post-operative year until the last follow-up examination (64.5% vs 43.3%, P < 0.001). By multivariate analysis, preoperative hyperopia of more than + 2.00 diopters, younger age of onset, younger age at surgery, larger exodeviation at near than at distance of > 5 prism diopters, and the type of surgery (BLR) were risk factors of recurrence. In conclusion, RR was more successful than BLR with a lower recurrence rate in the long-term follow-up of patients with basic-type X(T).

Short-Term Near Stereoacuity Improvements Following Favorable Surgical Alignment in Exotropic and Esotropic Patients

PURPOSE

Surgical treatment for strabismus is to promote binocular vision, and the study is to evaluate the effect of surgical realignment on near stereopsis in exotropic and esotropic patients.

METHODS

The records of patients who underwent strabismus surgery were retrospectively reviewed. Visual acuity, ocular deviations, fusion control, ocular motility, strabismus subtype and duration, surgery procedures, and stereopsis at before and at one month after surgery were collected. RMANOVA was performed to analyze stereopsis improvement by surgery. A logistic analysis was used to investigate the factors for stereopsis improvement.

RESULTS

143 exotropic and 40 esotropic patients were enrolled. The stereopsis was not significantly improved in patients with exotropia (p > .05), but not in esotropic patients (p < .01). Small degree of near deviation (β = 0.01), without vertical surgery (β = 0.11), and the high pre-surgery Titmus (β = -0.44) were related factors for stereopsis improvement in exotropia patients; male (β = 0.21) and the high pre-surgery Titmus (β = -0.36) were related factors for stereopsis improvement in esotropia patients.

CONCLUSION

The loss of stereopsis was significantly restored by surgery in esotropia patients and the extent of stereopsis recovery by surgery depends on the deviation at near distance, vertical surgery, and pre-surgery stereopsis in exotropes and on sex and pre-surgery Titmus in esotropes.

Effect of inferior oblique muscle belly transposition on versions and vertical alignment in primary position

PURPOSE

To evaluate the effect of inferior oblique muscle belly transposition (IOBT) on vertical deviation (VD) in primary position and inferior oblique overaction (IOOA).

METHODS

Twenty-eight patients who underwent unilateral IOBT for mild hypertropia (≤ 10^△) due to unilateral IOOA were included. Surgical results regarding the correction of hypertropia, IOOA, and fovea disc angle (FDA) were analyzed and compared between groups A (VD ≤ 5^△) and B (5^△ < VD ≤ 10^△).

RESULTS

IOBT showed an overall reduction of 5.86^△ (± 2.24^△) of primary position VD, a mean correction of 1.00 (± 0.27) of IOOA, and an average change of 1.83° (± 3.02°) of FDA. The surgical success rate of IOBT for VD correction and IOOA elimination in all patients was 68% and 71%, respectively. The correction of VD was correlated with preoperative VD significantly (r = 0.86, p < 0.001). Consistently, IOBT demonstrated comparable efficacy in reduction of VD between group A and group B (p = 0.507). Furthermore, the two groups were comparable in the success rates for correcting VD and IOOA (both p > 0.05). None of the patients developed consecutive hypotropia, postoperative contralateral IOOA, or anti-elevation syndrome postoperatively.

CONCLUSIONS

IOBT achieved satisfactory outcomes in patients with mild primary position VD (≤ 10^△) that is associated with unilateral IOOA, without any risk of overcorrection of VD and contralateral IOOA for a follow-up period of up to 12 months. This procedure is considered effective and safe alternative for weakening the IO in patients with appropriate surgical indications.

An artificial intelligence platform for the diagnosis and surgical planning of strabismus using corneal light-reflection photos

Background

Strabismus affects approximately 0.8–6.8% of the world’s population and can lead to abnormal visual function. However, Strabismus screening and measurement are laborious and require professional training. This study aimed to develop an artificial intelligence (AI) platform based on corneal light-reflection photos for the diagnosis of strabismus and to provide preoperative advice.

Methods

An AI platform consisting of three deep learning (DL) systems for strabismus diagnosis, angle evaluation, and operation plannings based on corneal light-reflection photos was trained and retrospectively validated using a retrospective development data set obtained between Jan 1, 2014, and Dec 31, 2018. Corneal light-reflection photos were collected to train the DL systems for strabismus screening and deviation evaluations in the horizontal strabismus while concatenated images (each composed of two photos representing different gaze states) were procured to train the DL system for operative advice regarding exotropia. The AI platform was further prospectively validated using a prospective development data set captured between Sep 1, 2019, and Jun 10, 2020.

Results

In total, 5,797 and 571 photos were included in the retrospective and prospectively development data sets, respectively. In the retrospective test sets, the screening system detected strabismus with a sensitivity of 99.1% [95% confidence interval (95% CI), 98.1–99.7%], a specificity of 98.3% (95% CI, 94.6–99.5%), and an AUC of 0.998 (95% CI, 0.993–1.000, P<0.001). Compared to the angle measured by the perimeter arc, the deviation evaluation system achieved a level of accuracy of ±6.6º (95% LoA) with a small bias of 1.0º. Compared to the real design, the operation advice system provided advice regarding the target angle within ±5.5º (95% LoA). Regarding strabismus in the prospective test set, the AUC was 0.980. The platform achieved a level of accuracy of ±7.0º (95% LoA) in the deviation evaluation and ±6.1º (95% LoA) in the target angle suggestion.

Conclusions

The AI platform based on corneal light-reflection photos can provide reliable references for strabismus diagnosis, angle evaluation, and surgical plannings.

The stability of horizontal ocular alignment of triad exotropia after one-step triple surgery

PURPOSE

A-pattern exotropia, superior oblique muscle overaction, and dissociated vertical deviation may coexist and are referred to as triad exotropia. The present study evaluated the postoperative stability of horizontal ocular alignment of triad exotropia and possible prognostic factors.

METHODS

Medical records of patients with triad exotropia who had one-step triple surgery of superior oblique muscle weakening, superior rectus muscle recession, and lateral rectus muscle recession were reviewed. The horizontal alignment and postoperative drift of triad exotropia were analyzed and compared with constant exotropia.

RESULTS

The triad exotropia showed a mean of 7.7^△ (± 8.5^△) eso-drift, while the constant exotropia was (3.5^△ ± 3.4^△) exo-drift. Multiple linear regression analysis showed that the degree of superior oblique muscle overaction after surgery (P = 0.011) was the only factor associated with horizontal drift. Patients with superior oblique muscle underaction showed larger eso-drift when compared to patients without superior oblique muscle underaction (- 18.0^△ ± 11.1^△ vs. - 5.1^△ ± 5.7^△; P = 0.024). The final success rates of the triad exotropia and constant exotropia groups were 53.3% and 69.2%, respectively, and the overcorrection rates were 26.7% and 2.6% (P = 0.035).

CONCLUSIONS

An overall trend of eso-drift in primary position occurred in triad exotropia after triple surgery up to a follow-up of 25 months. Patients presenting superior oblique muscle underaction after surgery seemed to have large angles of eso-drift, which might be taken into account in surgical planning and follow-up.