Gains beyond cosmesis: Recovery of fusion and stereopsis in adults with longstanding strabismus following successful surgical realignment

Strabismus Surgery for Psychosocial Reasons-A Literature Review

Introduction

Strabismus surgery may be undertaken for visual benefit, to improve or eliminate diplopia symptoms, or to restore or improve binocular single vision (BSV). In patients without visual symptoms or expected visual benefit, strabismus surgery may still be undertaken if the presence of strabismus causes the patient psychosocial symptoms. To evaluate strabismus surgery undertaken for psychosocial reasons, evidence of postoperative outcomes in this specific cohort is needed.

Methods

A systematic search of the literature was conducted (1946-2023) to identify evidence where postoperative outcomes were reported for adult patients (age 18 years and above) who had undergone strabismus surgery for psychosocial reasons.

Results

Sixty-nine papers were included in the literature review. Most sources of evidence included patients within heterogeneous cohorts of strabismus surgery outcomes, with a range of symptoms and differing surgical aims.

Discussion

In adults who underwent strabismus surgery for psychosocial reasons, improved postoperative ocular alignment and/or improved health related quality of life (HRQoL) were common. Strabismus surgery outcomes appeared to be measured satisfactorily at three months postoperatively. Additional surgical outcomes, including an expanded field of vision, unexpected BSV, improved binocular summation, improved task performance and improved eye movements have been reported, but not fully investigated. There was a lack of consensus on how postoperative success should be defined and measured. A core outcome set for strabismus has been suggested and there is potential to add to the available evidence by investigating which outcome measures are most relevant to those with strabismus and psychosocial symptoms. There is a growing need for robust evidence in this specific subgroup of patients due to a lack of evidence specifically reporting postoperative outcomes in adults with strabismus and psychosocial symptoms.

Measures and variability with age of low contrast acuity and near stereoacuity in children

CLINICAL RELEVANCE

Low contrast acuity (LCA) and near stereoacuity (NS) testing are integral to the comprehensive assessment of sensory visual function in children. However, routine ophthalmological evaluations seldom take these measures into consideration. Additionally, there is limited literature regarding the normative values of these parameters in children.

BACKGROUND

This study investigated LCA and NS measures and their variability in children with normal visual acuity. The aim was to provide a benchmark for distinguishing normal measures from abnormal ones.

METHODS

A prospective observational study was conducted in primary and secondary schools across North India. The participants numbered 240 children, aged between 3 and 15 years. They were split into 12 smaller groups of 20 participants in each age group. Only participants with normal monocular uncorrected visual acuity, no refractive error, normal birth history, and no systemic ailments, were recruited. All the participants underwent a complete ophthalmic examination and non-cycloplegic retinoscopy. LCA was measured, using the low contrast Lea number chart at three metres. NS was measured using the Randot® stereo test at 40 cm.

RESULTS

The percentages of males and females, were found to be 55%, and 45%, respectively (p = 0.093). The mean NS was found to be 38.7 ± 11.5 arcsecs in the 3-9-year age group, and 26.7 ± 5.6 arcsecs in the 9-15-year age group (p-value <0.001). The mean NS showed an increasing trend up to 9 years of age. The mean LCA was 64.4 ± 20.1 in the age group of 3-8 years, and 76.38 ± 11.39 in the age group of 8-15 years (p-value <0.001). Considerable variability was noted in the LCA in the younger age group (p-value = 0.000).

CONCLUSIONS

LCA and NS mature gradually during childhood. LCA stabilises after the age of 8, while NS stabilises after the age of 9.

Factors Influencing Stereopsis Outcomes in Adults Following Strabismus Surgery

Objectives

The aim of the study was to evaluate binocular vision after adult strabismus surgery and to investigate the predictive factors on improvement stereoacuity.

Methods

Patients aged upper from 16 years who underwent strabismus surgery in our hospital reviewed retrospectively. Age, existence of amblyopia, pre-operative and postoperatively fusion ability, stereoacuity, and deviation angle were recorded. Patients were divided into two groups according to final stereoacuity; 200 sn/arc and lower: Good stereopsis (Group 1), upper 200 sn/arc: Poor stereopsis (Group 2). Characteristics were compared between groups.

Results

A total of 49 patients, who were 16-56 years of age, were included in the study. The mean follow-up time was 37.8 months (range 12-72 months). Of patients, 26 had improvement in stereopsis scores after surgery (53.0%). Group 1 includes 200 sn/arc and lower (n=18, 36.7%) and Group 2 includes higher than 200 sn/arc (n=31, 63.3%). The presence of amblyopia and higher refraction error was frequent significantly in Group 2 (p=0.01 and p=0.02, respectively). The existence of fusion postoperatively was significantly frequent in Group 1 (p=0.02). Type of strabismus and the amount of deviation angle were not found in a relationship with good stereopsis.

Conclusion

In adults, surgical correction of horizontal deviation improves stereoacuity. Having no amblyopia, having fusion after surgery, and low refraction error are predictive for the improvement in stereoacuity.

Factors Determining Improvement in Stereopsis and Binocularity After Good Postoperative Alignment in Patients With Childhood-Onset Strabismus

Introduction: The purpose of the present study was to determine the factors that affect the outcome of strabismus surgery in terms of improvement in stereopsis and binocularity.

Methods: Data were collected prospectively from patients with childhood-onset, concomitant, constant strabismus greater than 30 prism diopters (PD) with postoperative alignment within 10 PD. Pre- and postoperative stereopsis and binocularity testing were performed using the Titmus fly test, random dot test, Bagolini striated glass test, and Worth four dot test at one, four, and 12 weeks postoperatively.

Results: A total of 73 patients (55% males and 45% females) who underwent surgery at our center were studied. The mean age at the time of surgery was 16 ± 7.7 years (range: 5-35 years). We found that factors such as age of strabismus onset, type of deviation, and amblyopia had a statistically significant influence on the postoperative surgical outcome. A statistically insignificant relationship was noted with gender, refractive error, and duration of strabismus. Patients who had strabismus after six months of age noticed a significant improvement in stereopsis (p-value = 0.000) than those who had strabismus before six months of age (p-value = 0.660). Further, there was a statistically significant improvement in patients having exotropia (p-value = 0.018) or combined horizontal and vertical deviations (p-value = 0.000), but there was no significant improvement in patients with esotropia (p-value = 0.180). Moreover, non-amblyopes had a significantly better postoperative stereopsis than amblyopes (p-value = 0.006). Although there was no association between preoperative deviation and improvement in stereopsis (p-value = 0.081), patients having preoperative deviation in the range of 31-45 PD had a statistically significant improvement in stereopsis (p-value = 0.000). There was no significant difference between postoperative residual deviation and final stereopsis (p-value > 0.05). All the results were the same for both the Titmus test and the random dot test. Binocular fusion was observed in 34 subjects, and uniocular suppression was noted in 38 subjects preoperatively. It was observed that only one patient gained binocular single vision postoperatively.

Conclusion: The presence of amblyopia, esotropia, early onset of strabismus (within six months of age), and a larger preoperative deviation (>45 PD) were associated with poorer stereopsis. In patients with horizontal strabismus, the coexistence of vertical deviation had a positive impact on the postoperative stereopsis. Gender, refractive error, and duration of strabismus did not influence the final stereopsis in our study.

Predictive factors of stereopsis outcomes following strabismus surgery

Purpose:

To determine the predictive factors of post-operative stereopsis in patients with strabismus.

Method:

In this retrospective study, records of patients who received surgical treatment for strabismus were reviewed. All types of strabismus were included. Pre- and post-treatment stereoacuity were measured using the Titmus Stereo Fly test, and predictive factors of stereopsis were evaluated.

Results:

A total of 194 patients (132 females and 62 males) with a mean age of 14.8 ± 8.4 years were included. There was a statistically significant improvement in stereopsis following surgery (p value < 0.001). Patients with a higher amount of deviation at baseline had poorer stereopsis on the final examination (p value < 0.001). Stereopsis improvement was more prominent in the pure horizontal strabismus group, compared to combined horizontal and vertical deviations. Baseline and the final stereopsis were higher in the “exotropia” group as compared to the “esotropia” group (p value = 0.003 and 0.0155, respectively); however, the within group change of stereopsis was not significantly different between these two groups (p value = 0.144). Post surgical residual deviation was associated with a poorer stereopsis (p value = 0.002, r = 0.251). A longer duration of strabismus before surgery was associated with poorer final stereopsis levels (p value = 0.026). The presence of amblyopia before surgery was associated with poorer stereopsis on last examination (p value < 0.001 for both correlations).

Conclusion:

Based on the result of this study, final stereopsis after strabismus surgery could be affected by the type, duration, and the amount of deviation before surgery, amblyopia, and post operative ocular deviation.

A dichoptic feedback-based oculomotor training method to manipulate interocular alignment

Strabismus is a prevalent impairment of binocular alignment that is associated with a spectrum of perceptual deficits and social disadvantages. Current treatments for strabismus involve ocular alignment through surgical or optical methods and may include vision therapy exercises. In the present study, we explore the potential of real-time dichoptic visual feedback that may be used to quantify and manipulate interocular alignment. A gaze-contingent ring was presented independently to each eye of 11 normally-sighted observers as they fixated a target dot presented only to their dominant eye. Their task was to center the rings within 2° of the target for at least 1 s, with feedback provided by the sizes of the rings. By offsetting the ring in the non-dominant eye temporally or nasally, this task required convergence or divergence, respectively, of the non-dominant eye. Eight of 11 observers attained 5° asymmetric convergence and 3 of 11 attained 3° asymmetric divergence. The results suggest that real-time gaze-contingent feedback may be used to quantify and transiently simulate strabismus and holds promise as a method to augment existing therapies for oculomotor alignment disorders.

Does successful surgical correction of childhood large angle exotropia in adults make any difference to binocularity and quality of life?

Background/Aim: Strabismus surgery could achieve motor alignment and improve health-related quality of life (HRQOL) in adults with large angle exotropia, but whether it could improve binocularity and whether the binocularity is associated with HRQOL are unknown. The aim of this study is to evaluate the binocularity and HRQOL following successful surgical correction of childhood large angle exotropia in adults. Methods: Consecutive adults with childhood large angle exotropia (≥90 prism diopters) who underwent strabismus surgery in the Department of Ophthalmology and Vision Science, Eye and ENT Hospital, Shanghai Medical School, Fudan University were enrolled. Static and dynamic stereopsis tests were performed before surgery and 1 month after surgery. At the same time, Adult Strabismus-20 (AS-20), and Amblyopia and Strabismus questionnaire (A&SQ) were investigated. Results: A total of 29 adults achieved successful alignment: 18 intermittent exotropes (IXT) and 11 constant exotropes (CXT). One month after surgery, stereopsis was demonstrated better in all types of tests (p < .05 for all comparisons). Twelve patients gained normal stereopsis. More patients in IXT group gained normal stereopsis than in CXT group (x² = 7.62 p = .008). All HRQOL scores showed statistically significant improvement after surgery (p < .05 for all comparisons). IXT group had more changes of the composite score (t = 2.24, p = .03) and the functional score (t = 2.92, p = .007) of AS-20, and the functional score (t = 3.06, p= .005) of A&SQ than CXT group. Only the change of the functional score of A&SQ was demonstrated a statistically significant correlation with the normal stereopsis (t = 2.67, p = .02). Conclusions: The stereopsis and HRQOL in adults with childhood large angle exotropia can be improved after successful surgical correction. More patients in IXT group gained normal stereopsis correlated with better functional aspects of HRQOL.

Outcomes of undercorrection in surgical management and binocular vision gained of adult intermittent exotropia

Purpose

To study the surgical outcomes of intended undercorrection on adult intermittent exotropia (X(T)) performed to avoid postopertively overcorrected diplopia.

Patients and methods

A retrospective chart review was conducted for adult patients (age ≥18 years) with X(T) ≥15 prism diopter (PD) who underwent strabismus surgery by a single surgeon. Inclusion criteria were 1) corrected VA ≥20/40 in either eye; 2) monocular occlusion at least 30 minutes before deviation measurement; 3) difference of ≤10 PD between near and distance deviation; 4) absence of significant A or V pattern or vertical deviation; 5) lateral rectus recession and medial rectus resection procedure were performed unilaterally; and 6) intended surgical number for deviation correction was aimed at 5 PD undercorrection.

Results

Of 234 patients who met the inclusion criteria, 122 were women (52.14%). Average age at the time of surgery was 27.56 years (range, 18–42 years). A total number of 197 patients (84.19%) had postoperative exodeviation under 10 PD. Twenty five (10.68%) and 12 patients (5.13%) had postoperative exodeviation within 10–15 PD and >15 PD, respectively. All patients who had postoperative exodeviation >15 PD exhibited initial deviation of ≥40 PD and had undergone re-operation. In 74 patients (46.25%) out of 160 who had no binocular vision in orthoptic examination before surgery, fusion or stereopsis was gained after good alignment. No postoperative diplopia was found in this study.

Conclusion

Intended undercorrection in surgical management of adult X(T) showed good functional and cosmetic outcomes. No procedure resulted in consecutive esodeviation or persistent diplopia. Fusion or stereopsis could be gained after successful surgical alignment. Our recommendations are as follows: 5 PD undercorrection if deviation is <40 PD and regular correction if deviation is ≥40 PD.

The fast exodrift after the first surgical treatment of exotropia and its correlation with surgical outcome of second surgery

Background

To compare the rate of exodrift after a second surgery for recurrent exotropia, in patients grouped to fast versus slow exodrift after their first surgery. To determine whether there is a correlation with surgical outcome, and to evaluate the factors associated with fast exodrift.

Methods

Patients with recurrent intermittent exotropia, who underwent contralateral lateral rectus recession and medial rectus resection as the second surgery and were followed up for 24 months postoperatively between January 1991 and January 2013, were reviewed retrospectively. The patients were divided into two groups according to the rate of exodrift after the first surgery: Group F, patients exhibiting fast exodrift after the first surgery (> 10 prism diopters [PD] before postoperative month 6); and Group S, patients exhibiting slow exodrift after the first surgery (≤10 PD before postoperative month 6). The difference in the clinical course over the 24 months after the second surgery between the two groups and factors associated with fast exodrift were analyzed.

Results

In total, 106 patients with recurrent exotropia were enrolled in this study. Of these, 68 (64.2%) and 38 (35.8%) patients were included in group F and S, respectively. Group F showed more exodrift compared with groups S over the 24-month postoperative period; however, there was no significant difference in the clinical course between the two groups during that time (p = 0.54, repeated-measure ANOVA). In logistic analysis, immediate postoperative deviation after the first surgery was associated with fast exodrift (p <  0.001).

Conclusion

Although patients with recurrent exotropia had shown fast exodrift after the first surgery, no significant difference in the surgical outcome was observed after the second surgery according to the rate of exodrift after the first surgery.

Straightening the Eyes Doesn't Rebalance the Brain

Surgery to align the two eyes is commonly used in treating strabismus. However, the role of strabismic surgery on patients' binocular visual processing is not yet fully understood. In this study, we asked two questions: (1) Does realigning the eyes by strabismic surgery produce an immediate benefit to patients' sensory eye balance? (2) If not, is there a subsequent period of "alignment adaptation" akin to refractive adaptation where sensory benefits to binocular function accrue? Seventeen patients with strabismus (mean age: 17.06 ± 5.16 years old) participated in our experiment. All participants had normal or corrected to normal visual acuity (LogMAR < 0.10) in the two eyes. We quantitatively measured their sensory eye balance before and after surgery using a binocular phase combination paradigm. For the seven patients whose sensory eye balance was measured before surgery, we found no significant change [t₍₆₎ = -0.92; p = 0.39] in the sensory eye balance measured 0.5-1 months after the surgery, indicating that the surgical re-alignment didn't by itself produce any immediate benefit for sensory eye balance. To answer the second question, we measured 16 patients' sensory eye balance at around 5-12 months after their eyes had been surgically re-aligned and compared this with our measurements 0.5-1 months after surgery. We found no significant change [t₍₁₅₎ = -0.89; p = 0.39] in sensory eye balance 5-12 months after the surgery. These results suggest that strabismic surgery while being necessary is not itself sufficient for re-establishing balanced sensory eye dominance.

Gain beyond cosmesis: demonstration of psychosocial and functional gains following successful strabismus surgery using the adult strabismus questionnaire adult strabismus 20

Background:

Strabismus adversely affects psychosocial and functional aspects; while its correction impacts positively.

Aim:

The aim was to evaluate the gains in scores: Overall scores (OASs), psychosocial subscale scores (PSSs) and functional subscale scores (FSSs) following successful surgical alignment.

Settings and Design:

We evaluated changed scores in the adult strabismus 20 (AS-20) questionnaire, administered before and after successful surgery.

Materials and Methods:

Thirty adults horizontal strabismics, were administered the AS-20, at baseline, and at 6-week and 3-month. Group-wise analysis was carried out based on gender, strabismus type (esotropia [ET] or exotropia [XT]), back-ground and amblyopia.

Statistical Analysis:

We used Wilcoxon, and Mann-Whitney U-tests. Significance was set at P ≤ 0.05.

Results:

At baseline, there were no significant differences within the groups, except that those with amblyopia significantly scored less than nonamblyopes in OAS (median scores: 53.8 vs. 71.3; P = 0.009) and FSS (56.3 vs. 85.3; P = 0.009). OAS, PSS and FSS showed significant gains at 6-week and 3-month (all Wilcoxon P < 0.001). Compared with males, females showed significantly more gain at 3-month (OAS: 37.9 vs. 28.7; P = 0.02), on account of PSS gain (49.6 vs. 37.5; P = 0.01). The ET performed better than XT only on the FSS at 6-week (28.7 vs. 15.0; P = 0.02). Vis-à-vis the nonamblyopes, the amblyopes showed significantly more benefit at 6-week alone (OAS: 18.7 vs. 28.7; P = 0.04), largely due to gains in PSS.

Conclusions:

Successful strabismus surgery has demonstrated significant gains in psychosocial, functional and overall functions. There is some evidence that gains may be more in females; with a trend to better outcomes in ET and amblyopes up to 6-week.

Predictors of stereoacuity outcome in visually mature subjects with exotropia

The purpose of this study was to determine the predictors of stereoacuity outcome in visually mature subjects with exotropia following surgical correction. Visually mature subjects who were surgically aligned and had been tested for stereoacuity in the postoperative period were studied retrospectively. Subjects were grouped with respect to their responses to Titmus or TNO stereotests. Characteristics such as amblyopia, anisometropia, and characteristics of the exodeviation such as time of onset, duration, intermittency, presence of an A or V pattern, distance-near disparity, coexisting vertical deviation, and inferior oblique overaction, were compared between the groups. One hundred and four visually mature subjects with exotropia met the inclusion criteria. Stereoacuity was achieved in 77% of the study group and only 9% of these could achieve fine stereoacuity. Negative stereoacuity was more frequently associated with larger deviation angles, higher anisometropia, inferior oblique overaction, pattern strabismus, coexisting vertical strabismus, and distance-near disparity, but not at a statistically significant level. The optimal cutoff for strabismus duration was 20 years for a positive stereoacuity outcome. Any-level visual acuity difference was found to decrease the chance for positive stereoacuity significantly. The odds ratios for the stereoacuity positivity were 4.05 for strabismus duration <20 years, 7.9 for strabismus onset >1 year of age, 3.79 for weaker eye visual acuity >20/25 and 9.85 for intermittency of strabismus. Intermittence of exotropia was the strongest predictor for positive stereoacuity. Exotropia onset after 1 year of age, absence of any-level visual acuity difference, and strabismus duration <20 years were the other predictors with decreasing power.

Sensory eye balance in surgically corrected intermittent exotropes with normal stereopsis

Surgery to align a deviated or strabismic eye is often done for both functional as well as cosmetic reasons. Although amblyopia is often an impediment to regaining full binocularity in strabismics in general, intermittent exotropes, because their deviation is intermittent, have no amblyopia and some degree of stereopsis. Binocular function, including a balanced ocular dominance, could be expected to be normal after surgical correction if normal levels of stereopsis and visual acuity are postsurgically achieved. Here we used a binocular phase combination paradigm to quantitatively assess the ocular dominance in a group of surgically corrected intermittent exotropes who have normal stereo and visual acuity as defined clinically. Interestingly, we found significant interocular imbalance (balance point < 0.9) in most of the surgically treated patients (8 out 10) but in none of the controls. We conclude that the two eyes may still have a residual sensory imbalance in surgically corrected strabismus even if stereopsis is within normal limits. Our study opens the possibility that a further treatment aimed at re-balancing the ocular dominance might be necessary in surgically treated intermittent exotropia to provide more efficient binocular processing in the long term.

The effect of amblyopia treatment on stereoacuity

PURPOSE

To explore how stereoacuity changes in patients while they are being treated for amblyopia.

METHODS

The Monitored Occlusion Treatment for Amblyopia Study (MOTAS) comprised 3 distinct phases. In the first phase, baseline, assessments of visual function were made to confirm the initial visual and binocular visual deficit. The second phase, refractive adaptation, now commonly termed "optical treatment," was an 18-week period of spectacle wear with measurements of logMAR visual acuity and stereoacuity with the Frisby test at weeks 0, 6, 12, and 18. In the third phase, occlusion, participants were prescribed 6 hours of patching per day.

RESULTS

A total of 85 children were enrolled (mean age, 5.1 ± 1.5 years). In 21 children amblyopia was associated with anisometropia; in 29, with strabismus; and in 35, with both. At study entry, poor stereoacuity was associated with poor visual acuity (P < 0.001) in the amblyopic eye and greater angle of strabismus (P < 0.001). Of 66 participants, 25 (38%) who received refractive adaptation and 19 (29%) who received occlusion improved by at least one octave in stereoacuity, exceeding test-retest variability. Overall, 38 (45%) improved one or more octaves across both treatment phases. Unmeasureable stereoacuity was observed in 56 participants (66%) at study entry and in 37 (43%) at study exit.

CONCLUSIONS

Stereoacuity improved for almost one half of the study participants. Improvement was observed in both treatment phases. Factors associated with poor or nil stereoacuity at study entry and exit were poor visual acuity of the amblyopic eye and large-angle strabismus.