Astigmatic changes after horizontal rectus muscle surgery in intermittent exotropia

Refractive Changes After Horizontal Strabismus Surgery

PURPOSE

To investigate the changes in refractive status after surgery in patients with horizontal strabismus and high refractive error.

METHODS

This was a prospective study of patients with horizontal strabismus and high refractive error. The patients were divided into a horizontal rectus recession group (group 1) and a horizontal rectus recession combined with horizontal rectus resection group (group 2). The postoperative follow-up duration was 3 months. The refractive status of the patients was evaluated at each postoperative examination, and the refractive changes in the two groups were compared.

RESULTS

The spherical equivalent in group 1 changed by -0.26 D at 3 months postoperatively relative to the preoperative value (p = 0.078), indicating gradual progression toward myopia over time, but the difference was not significant; however, the postoperative cylinder in group 1 significantly increased by 0.34 D at 3 months postoperatively relative to the preoperative value (p = 0.03). The spherical equivalent in group 2 also indicated progression toward myopia; compared with the preoperative value, the spherical equivalent significantly decreased by -0.28 D (p = 0.019) at 1 month postoperatively and decreased by -0.21 D at 3 months postoperatively. The regression line drawn among the points also indicated a progression in the spherical equivalent toward myopia. In group 2, the cylinder increased by 0.30 D (p = 0.004) from the preoperative level at 1 month postoperatively, peaked, then decreased by 3 months postoperatively.

CONCLUSIONS

Patients with high refractive error who undergo horizontal strabismus correction will experience myopic shift. Patients who undergo rectus recession surgery should be fully informed of the possibility of changes in astigmatism preoperatively. For patients who undergo horizontal rectus recession combined with horizontal rectus resection, it is not recommended that glasses be changed within 1 month after surgery.

Corneal tomography changes following major (6 mm) medial rectus muscle recession: a prospective cohort study using Pentacam®

INTRODUCTION

The aim of this study is to evaluate changes in corneal astigmatism, axial anterior corneal curvature, as well as changes in the anterior chamber depth and central corneal thickness, 2 months following the unilateral recession of medial rectus muscle in children.

METHODS

Thirty-three children with esotropia were prospectively evaluated following unilateral medial rectus muscle recession, using Pentacam®. Comparisons were made between the operated and fellow unoperated eyes, pre, and postoperatively. The assessment was made for changes in the radius of axial curvature on major meridians at 3 and 3.5 mm from the optical corneal center in the mid-peripheral zone. Astigmatism changes of the anterior and posterior corneal surface were calculated using vector analysis software (astigMATIC®). ANOVA model was used to examine the interaction between age or central corneal thickness and postoperative changes in anterior and posterior surface corneal astigmatism.

RESULTS

In the intervention group, changes in anterior and posterior corneal surface astigmatism were statistically significant, with a mean increase of 0.59Dx92 and 0.08Dx91, respectively. In the mid-peripheral corneal zone, there is an increase in the radius of anterior corneal axial curvature more evident nasally 3.5 mm from the corneal center on the horizontal meridian, with corresponding decrease superiorly and inferiorly at 3 and 3.5 mm from the corneal center on the vertical meridian.

DISCUSSION

The changes in total astigmatism of the operated eyes are mainly attributed to the anterior corneal surface. These changes are associated with flattening in the 180 meridian of the cornea, leading to a shift to "with-the-rule" astigmatism.

Evaluation of aberrometry changes following strabismus surgery in patients with horizontal strabismus

BACKGROUND

The aim is to investigate the change in aberrations following strabismus surgery in patients with horizontal strabismus.

MATERIALS AND METHODS

This prospective study included patients who underwent surgery for horizontal strabismus. The patients were assessed preoperatively and 1 month and 3 months after the surgery, in terms of logMAR best-corrected visual acuity, eye deviation, spherical equivalent refractive error, tomographic and aberrometric corneal changes. Corneal tomography was performed using Orbscan II device. Wavefront analyses were performed using Bausch and Lomb Zywave II.

RESULTS

A total of 25 patients (48 eyes) with exotropia or esotropia were entered in this study. Mean values of exotropia in the distance and near deviations were reported as 31.42 ± 7.13 and 28.82 ± 6.96 prism diopters (PD), respectively. Mean scores of esotropia in the distance and near deviations were 25.22 ± 5.41 and 30.45 ± 9.4 PD, respectively. Evaluation of irregularity in 5 mm zone, horizontal coma, spherical aberration changes, and root mean square of higher-order aberrations (HOAs) in 6 mm, and HOA w/o Z 400 changes showed that there was a significant difference before the intervention and 1 month after the surgery (P < 0.05). However, no difference was observed in the aforementioned variables before and 3 months after the intervention (P > 0.05).

CONCLUSIONS

Results of the present study indicated a transient increase in HOAs and corneal irregularity following strabismus surgery on horizontal eye muscles that returned to the baseline after 3 months.

Myopic progression in school-aged children with moderate intermittent exotropia

Objective

It is still controversial whether intermittent exotropia (IXT) affects myopic progression during the critical period of visual development. This study retrospectively analyzed the long-term myopic changes and the impact of IXT surgery on myopic progression in school-aged children with moderate IXT.

Methods

The medical records of 65 children from 5 to 13 years old with or without IXT between 2015 and 2021 were retrospectively reviewed. Patients whose spherical equivalent refraction (SER) were less than -3.00 diopter (D) were included and divided into three groups: IXT surgery group (Group A), which comprised 22 IXT patients who received IXT surgery, IXT observation group (Group B), which comprises 19 IXT patients who only received long-term observational follow-up; and normal control group (Group C), which comprised 24 normal controls without IXT. The main outcome measurement was the rate of myopic progression, which was defined as the mean myopic shift in SER per year.

Results

The 3- and 5-years long-term follow-up rates of myopic progression were -0.47 ± 0.28 D per year and -0.48 ± 0.23 D per year respectively in Group B, and those were significantly slower than that in Group C (-0.73 ± 0.32 D per year and -0.76 ± 0.19 D per year respectively). However, there was no significant difference in the rate of myopic progression between Group A and B or between Group A and C.

Conclusion

Moderate IXT may have lower rate of myopic progression in school-aged children. Whether IXT surgery influence the rate of myopic progression still needs further study.

Correlation between bilateral lateral rectus muscle recession and myopic progression in children with intermittent exotropia

Although several studies have reported about the relationship between the surgical correction of intermittent exotropia and myopic progression, it remains unclear, unlike the relationship between esotropia and hyperopia. Thus, this retrospective case control study evaluated the impact of bilateral lateral rectus recession in intermittent exotropia on myopic progression. This study included 388 patients with intermittent exotropia. The refractive errors and degree of exodeviation at each follow up period were analyzed. The rate of myopic progression was -0.46 ± 0.62 diopter (D)/year in patients who underwent surgery and -0.58 ± 0.78 D/year in patients who did not, with no significant difference between them (p = 0.254). Patients who had recurrences of more than 10 prism diopters were compared with patients who did not have. The rate of myopic progression was -0.57 ± 0.72 D/year in the recurrent group and -0.44 ± 0.61 D/year in the non-recurrent group, with no significant difference between them (p = 0.237). Patients with fast myopic progression had more recurrence than patients with slow progression (p = 0.042). Moreover, recurrence had a positive correlation with fast myopic progression (OR = 2.537, p = 0.021). Conclusively, the surgical correction of intermittent exotropia did not influence myopic progression.

Refractive changes after strabismus surgery in patients with intermittent exotropia

OBJECTIVES

To evaluate the long-term refractive changes after horizontal muscle surgery in patients with intermittent exotropia and investigate the correlation between changes in the postoperative refractive error and clinical factors.

METHODS

We retrospectively reviewed the clinical data of patients aged < 15 years who underwent unilateral strabismus surgery (lateral rectus recession and medial rectus resection [RR, n = 47], lateral rectus recession and medial rectus plication [RP, n = 81], or lateral rectus recession [LRc, n = 68]). Preoperative and postoperative refractive errors up to four years after surgery were recorded. A mixed model was applied to compare the refractive error between the operated and fellow eyes and identify the factors associated with postoperative refractive changes.

RESULTS

The mean age at surgery was 7.5±2.4years, and girls accounted for 56.1% of the study population. There was no significant difference in the change in the spherical equivalent of refractive error between both eyes throughout the postoperative period. In contrast, the operated eyes consistently and significantly showed higher cylindrical power in with-the-rule astigmatism by 0.25D than in fellow eyes. Age, sex, and preoperative refractive error were not correlated with changes in postoperative astigmatism. Meanwhile, the type of surgery showed a significant interaction with the astigmatism changes. RP had less effect on the changes in astigmatism than RR and LRc (p = 0.001 and p = 0.022, respectively).

CONCLUSIONS

Horizontal muscle surgery has no long-term effect on the change in the spherical equivalent. However, mild with-the-rule astigmatism is induced and sustained after surgery, and the type of surgery affects the postoperative change of astigmatism.

Corneal Astigmatic and Refractive Changes after Rectus Muscle Surgery

Objective:In the present study, we investigated the postoperative astigmatic and refractive changes in patients with rectus muscle strabismus surgery. Materials and methods:Ninety-three eyes of 51 patients who underwent strabismus surgery at Amir- Almomenin Hospital, Rasht, Iran, were enrolled. The ocular measurements before surgery as well as one month, three and six months postoperatively included cycloplegic refraction, the degree of near and far deviation, mean corneal power, mean keratometry, spherical equivalent (SE) and the change of astigmatism cylinder (measured using power vector analysis). All data were analyzed using SPSS software, version 21. Results:The mean age of participants was 18.31±14.58 years. A similar myopic shift was observed in all deviation groups. The mean SE values differed according to the type of surgery one month and three months postoperatively, with maximum change being seen in medial rectus (MR) recess + inferior oblique (IO) myectomy and in MR recess and lateral rectus (LR) recess six months after surgery. The change in mean J0 remained significant six months postoperatively only in MR recess surgery and in medial and lateral rectus recess groups based on topography (both P<0.001). The postoperative J0 and J45 differed according to the type of surgery (PP<0.001 and 0.007, respectively). The mean keratometry was different before-after LR recess (the minimum change), MR recess and MR recess + IO myectomy groups (the maximum change; PP<0.05). Conclusion:Refractive error toward myopic shift and with-the-rule (WTR) astigmatism are common after strabismus surgery on the rectus muscles, most of which sustain until six months postoperatively.

Analysis of the Changes and Possible Reasons in Aberrations before and after Surgery in Patients with Concomitant Exotropia

Objective. The objective is to observe the changes in aberrations before and after surgery in patients with common horizontal strabismus and to analyze the possible reasons for the changes. Methods. Forty eyes of 40 cases with concomitant exotropia who underwent strabismus correction at the Ophthalmology Department of Nantong University Hospital from October 2020 to July 2021 were included in this study, all of whom underwent unilateral lateral rectus recession combined with a medial rectus resection in the same eye. Aberration parameters were measured 1 day before surgery and 1 week, 1 month, 3 months, and 6 months after surgery. Differences in the indicators at each time period were compared by analysis of variance (ANOVA) of repeated measures data for a single factor, and data were analyzed using SPSS 25.0 statistical application software. Results. 5 mm pupil diameter: the preoperative and postoperative RMS of total aberration showed statistically significant difference ( $P<0.01$ ). Postoperation test (Bonferroni method) and preoperative comparison at each period after surgery showed statistically significant differences between 6 months after surgery ( $P=0.002$ ) and preoperative comparison. The preoperative and postoperative comparison of RMS in LOAs was statistically significant ( $P<0.01$ ); postoperative test (Bonferroni method) and preoperative comparison showed that there were statistically significant differences between 1 week ( $P=0.033$ ) and 6 months ( $P=0.002$ ) after operation. The difference of RMS of defocus before and after operation was statistically significant ( $P<0.01$ ); postoperation test (Bonferroni method) and preoperative comparison showed that there was statistically significant difference between 6 months after operation ( $P=0.007$ ) and preoperative comparison. There was statistically significant difference in preoperative and postoperative RMS of HOAs ( $P=0.013$ ). Postoperative test (Bonferroni method) and preoperative comparison showed that there was statistically significant difference 6 months after surgery ( $P=0.03$ ). The RMS of secondary astigmatism showed a statistically significant difference before and after operation ( $P=0.001$ ), and the postoperation test (Bonferroni method) showed a statistically significant difference 6 months after operation ( $P=0.002$ ). In 5 mm pupil diameter, the preoperative and postoperative RMS of total aberration showed statistically significant difference ( $P<0.01$ ), postoperative test (Bonferroni method) was used to compare each period after surgery with that before surgery, and there were statistically significant differences between 1 week after surgery ( $P=0.034$ ), 3 months after surgery ( $P=0.033$ ), and 6 months after surgery ( $P=0.003$ ). The preoperative and postoperative comparison of RMS in LOAs was statistically significant ( $P<0.01$ ), postoperative test (Bonferroni method) was used to compare each period after surgery with that before surgery, and there were statistically significant differences between 1 week after surgery ( $P=0.04$ ), 3 months after surgery ( $P=0.034$ ), and 6 months after surgery ( $P=0.004$ ). The difference of RMS of defocus before and after surgery was statistically significant ( $P=0.002$ ), and the comparison between postoperation test (Bonferroni method) and preoperation showed that the difference was statistically significant 6 months after surgery ( $P=0.027$ ). The RMS of astigmatism showed statistically significant difference before and after operation ( $P=0.002$ ), and the postoperation test (Bonferroni method) showed statistically significant difference between 6 months after operation ( $P=0.009$ ) and before operation. Conclusion. We found that horizontal rectus surgery had a transient effect on LOAs and almost no effect on HOAs. Long-term follow-up is recommended after strabismus surgery to observe eye position and binocular visual function. Because of the high prevalence of strabismus in adolescents, long-term observation of the eye axis and aberration is recommended.

Long-term astigmatism changes following horizontal muscle recession: a prospective cohort study

Strabismus surgery may cause refractive changes, particularly in astigmatism. The aim of this study is to evaluate those changes in astigmatism two and 12 months following unilateral recession of horizontal rectus muscles in children. The authors prospectively evaluated 66 children with esotropia or exotropia, that would undergo a unilateral recession strabismus surgery. Comparisons were made between the 66 eyes that would undergo strabismus surgery and the fellow unoperated 66 eyes of the same children. The 66 eyes that would undergo strabismus surgery were divided into medial (38 eyes) and lateral (28 eyes) rectus muscle subgroups, and further, into subgroups based on the astigmatism axis preoperatively (with-the-rule astigmatism: 35 eyes, no astigmatism: 20 eyes, oblique astigmatism: 10 eyes, against-the-rule astigmatism: 1 eye). All patients were examined one day preoperatively, and then, two and 12 months postoperatively. Paired tests were conducted, and the significant level was set to 0.05 or was adjusted for subgroups. Mean age of children included was 6.73 years (SD = 3.19). Mean astigmatism values preoperatively, 2 and 12 months postoperatively were 0.92D (SD = 0.95), 1.45D (SD = 1.04) and 1.50D (SD = 1.10), respectively, for the eyes that underwent strabismus surgery. A statistically significant mean increase of 0.58D in astigmatism values in the eyes that underwent strabismus surgery was observed 12 months postoperatively (p < .005). Astigmatism values in the eyes that did not undergo strabismus surgery did not statistically significantly change during the observation period. The increase of the absolute values of astigmatism in medial and lateral rectus muscle subgroups was similar, 0.59D (SD = 0.10) and 0.57D (SD = 0.11), respectively. For the eyes that had with-the-rule astigmatism and no astigmatism preoperatively, a statistically significant increase was shown 12 months postoperatively (0.64D and 0.66D respectively) (p < .005). Changes in astigmatism were observed in the eyes which underwent recession of horizontal rectus muscles compared to the fellow eyes, which did not undergo any intervention. An increase in cylindrical power was noted in the eyes that had with-the-rule and no astigmatism prior to surgery. This increase may be interpreted by the decreased tension of the recessed rectus muscle following strabismus surgery. Decreased forces, caused by the recessed horizontal rectus muscle, acting on the sclera on 180-degree meridian may lead to corneal flattening on this particular meridian and consequently, a corneal steepening on the 90-degree meridian. These changes seem to be stable during the first 12 postoperative months.

Dioptric power and refractive behaviour: a review of methods and applications

Myopia is a global healthcare concern and effective analyses of dioptric power are important in evaluating potential treatments involving surgery, orthokeratology, drugs such as low-dose (0.05%) atropine and gene therapy. This paper considers issues of concern when analysing refractive state such as data normality, transformations, outliers and anisometropia. A brief review of methods for analysing and representing dioptric power is included but the emphasis is on the optimal approach to understanding refractive state (and its variation) in addressing pertinent clinical and research questions.

Although there have been significant improvements in the analysis of refractive state, areas for critical consideration remain and the use of power matrices as opposed to power vectors is one such area. Another is effective identification of outliers in refractive data. The type of multivariate distribution present with samples of dioptric power is often not considered. Similarly, transformations of samples (of dioptric power) towards normality and the effects of such transformations are not thoroughly explored. These areas (outliers, normality and transformations) need further investigation for greater efficacy and proper inferences regarding refractive error. Although power vectors are better known, power matrices are accentuated herein due to potential advantages for statistical analyses of dioptric power such as greater simplicity, completeness, and improved facility for quantitative and graphical representation of refractive state.

Alterations of lower- and higher-order aberrations after unilateral horizontal rectus muscle surgery in children with intermittent exotropia: A retrospective cross-sectional study

Background

This retrospective, cross-sectional study investigated changes in corneal lower- and higher-order aberrations that cause visual disturbance after lateral rectus recession and medial rectus resection in children.

Methods

Eighty-five eyes of 85 patients (44 boys; 8.64±2.88 years) who underwent lateral rectus recession and medial rectus resection to correct intermittent exotropia were assessed. The Galilei G4 Dual Scheimpflug Analyzer was used for wavefront analysis. Risk factors (age, sex, amount of surgery, preoperative axial length, preoperative intraocular pressure) were determined. Outcome measures included simulated and ray-tracing mode keratometry with secondary defocus, oblique, and vertical astigmatism (for lower-order aberrations) and the root mean square, 3^rd-order vertical and horizontal coma, oblique and horizontal trefoil, 4^th-order spherical aberration, oblique and vertical secondary astigmatism, and oblique and vertical quadrafoil (2^nd‒8^th sums) (for higher-order aberrations).

Results

Myopic with-the-rule changes in low-order aberrations and increases in simulated and ray-tracing mode keratometry during the 3 months following lateral rectus recession and medial rectus resection were attributed to muscle healing and stability changes. High-order aberrations altered in the week following surgery almost returned to normal within 3 months. Axial length, the amount of surgery, age, and sex affected astigmatism due to differences in patients’ scleral states.

Conclusions

Clinicians should consider changes in high-order aberrations of young individuals who underwent lateral rectus recession and medial rectus resection and may not be able to verbalize changes in vision.

Morphological change of the posterior pole following the horizontal strabismus surgery with swept source optical coherence tomography

Extraocular muscle movement during strabismus surgery causes changes in eyeball shape. Because extraocular muscle insertion is in front of the equator, it is thought that changes due to strabismus surgery mainly occur in the anterior segment. However, changes in the posterior segment of eye may also occur, which may also result in changes in refractive error after strabismus surgery. Using a 3-dimensional reconstruction technique (en face imaging) of the swept source optical coherence tomography, we determined and quantitatively measured the posterior polar change. The deepest interface between Bruch's membrane and the choroid could be identified as the deepest point of the eyeball (DPE), and the location of the DPE relative to the optic disc and the fovea was measured. After lateral rectus muscle recession, the DPE moved away from the fovea, but after medial rectus muscle recession, the DPE moved toward the fovea. The amount of DPE movement differed by age and preoperative refractive error. Our findings suggest that the positional shift of the rectus muscle in horizontal strabismus surgery causes a structural change in the posterior segment of the eye, and the postoperative refractive changes may be related to this shift.

Changes in astigmatism after horizontal muscle recession strabismus surgery: A retrospective cohort study

Purpose:

The aim of this study was to evaluate the changes in astigmatism after unilateral recession of horizontal rectus muscles in pediatric patients.

Methods:

The authors retrospectively evaluated the medical history of 52 children with esotropia or exotropia, that underwent a unilateral recession strabismus surgery. The intervention group consisted of the 52 eyes that underwent strabismus surgery, and the control group consisted of the other 52 fellow unoperated eyes of the same participants. The intervention group was divided into medial and lateral rectus muscle subgroups, and four subgroups based on the astigmatism axis preoperatively (A: with-the-rule astigmatism, B: no astigmatism, C: intermediate meridians, D: against-the-rule astigmatism). All patients were examined one day preoperatively, and then, six weeks postoperatively. Paired tests were conducted, and the significant level was set to 0.05 or was adjusted for subgroups.

Results:

A mean difference 0.43 D of astigmatism (95% CI: 0.27, 0.59) was observed after the surgery between intervention and control group (P < 0.001). Astigmatism change (postoperative - preoperative) in subgroup A was 0.50 D (P < 0.001) and in subgroup B was 0.75 D (P < 0.001). Moreover, astigmatism changes of 0.50 D were found in both lateral (P < 0.001) and medial rectus muscle group (P = 0.002).

Conclusion:

Strabismus surgery appears to be associated with alterations in astigmatism, and in particular increase in cylindrical power in the eyes that had with-the-rule astigmatism or no astigmatism preoperatively. Those changes should be considered when planning the operation, to avoid transforming clinically non-significant astigmatism into clinically significant.

Analysis of astigmatism outcomes after horizontal rectus muscle surgery in patients with intermittent exotropia

This study examined the factors affecting corneal curvature change after lateral rectus recession and medial rectus resection surgery in patients with intermittent exotropia. This was a retrospective cross-sectional study in intermittent exotropia patients who underwent rectus resection surgery. The study involved 41 male and 42 female patients (mean age: 9.55 ± 5.03 years, range: 3-28 years). Corneal astigmatism analysis was performed using the Galilei G4 Dual Scheimpflug Analyzer. The values of simulated and ray tracing corneal keratometry (K) of astigmatism, including axis changes, were determined preoperatively and at 1 week and 3 months postoperatively. The factors found to affect corneal curvature change were sex, extent of surgery, and axial length. Simulated and ray tracing changes were significant preoperatively and at 1 week and 3 months after rectus resection surgery (p < 0.05); however, there were no differences in astigmatism (D) at any time. The spherical equivalent had a myopic change after rectus resection surgery with cycloplegic refraction, and in ray tracing mode, flat K was decreased at 1 week from baseline and increased 3 months later. Steep, mean K, and axis increased continuously from baseline to 1 week and 3 months. Astigmatism, in contrast, was increased at 1 week, but decreased at 3 months, with no return to baseline. Univariable linear regression analyses showed that the extent of surgery had an effect on flat K change and that sex had an effect on steep K and axis. Additionally, axial length affected steep K and astigmatism, while age had no effect on any variable. Ray tracing values were significantly different from simulated values. In ray tracing mode, rectus resection surgery may result in astigmatism shifted toward with-the-rule, and myopic changes may be caused by differences in thickness and flexibility of the sclera. Notably, age did not affect any variable.

Interocular difference associated with myopic progression following unilateral lateral rectus recession in early school-aged children

PURPOSE

To compare refractive changes in operated eyes and fellow unoperated eyes following unilateral lateral rectus recession in early school-aged children.

STUDY DESIGN

A retrospective case control study.

METHODS

The medical records of children under ten years of age with intermittent exotropia who underwent unilateral lateral recession surgery were reviewed. The operated eyes were reviewed and the fellow unoperated eyes were used as control. The rate of myopic progression was calculated by spherical equivalent (SE) changes per year, and by the rate of refractive growth (RRG) equation.

RESULTS

SE showed a myopic shift one week after surgery and in the following months, from -1.43 ± 1.84 diopters (D) at 1 week post operation to -1.57 ± 2.22 D at one year and, finally -2.95 ± 2.97 D at the average 4.62 years following surgery. However, the SE shift was not significantly different from the unoperated eye. The low myopia group (under -3.0 D) showed a significantly higher myopic change in the operated eye until one year post operation (p = 0.022). The average myopic shift ratio was -0.53 ± 0.46 D yearly in the operated eye.

CONCLUSIONS

This study presents data of a large series of refractive changes secondary to lateral rectus recession, and of long-term myopia progression in Korean population.

Astigmatismus

Der Astigmatismus ist der weltweit häufigste Refraktionsfehler vor Hypermetropie und Myopie. Man unterscheidet den äußeren vom inneren Astigmatismus. Der äußere Astigmatismus kann weiter in „mit der Regel“, „gegen die Regel“ und „schräg“ unterteilt werden. Die Summierung des äußeren und inneren Astigmatismus ergibt den refraktiven Zylinder. Astigmatismus wurde lange als zweidimensionales Phänomen gesehen, doch erst die dreidimensionale Betrachtung hat den Blick auf bestehende Analyseverfahren (Topo- und Tomographie) erweitert. Die Vektoranalyse nach Alpins ist hierbei eine bekannte Methode zur Therapieplanung. Zur Therapie des Astigmatismus stehen konservative Optionen wie Brille oder torische Kontaktlinse sowie unterschiedlichste chirurgische Verfahren wie photorefraktive Keratektomie, Femtosekundenlaser-assistierte Keratotomie, Laser-in-situ-Keratomileusis, „small-incision lenticule extraction“ und die Implantation torischer Intraokularlinsen zur Verfügung.

Transient Increase of Wavefront Aberrations after Horizontal Rectus Muscle Surgery in Exotropia

Aims: Wavefront aberration (WA) has become one of the important indicators for measuring the visual quality. Whether strabismus surgery affects the WA remain controversial. This study aims to investigate the postoperative alterations of WA in patients who underwent horizontal rectus muscle surgery.Methods: A total of 34 patients were enrolled and divided into two groups: bilateral lateral rectus recession (BLR) group and unilateral lateral rectus recession and medial rectus resection (R&R) group. The WA was examined 1 day before surgery, 3 days, and 6 weeks after surgery using the iTrace Visual Function Analyzer (Tracey Technologies).Results: Significant increases in total WA, lower-order aberration (LOA) and higher-order aberration (HOA) of both groups were detected in 3 days after surgery (P < 0.05), while no significant differences in 6 weeks after surgery. Significant increases in astigmatism, secondary astigmatism, and trefoil of both groups were detected in 3 days after surgery (P < 0.05), while no significant differences in individual order of LOA and HOA in 6 weeks postoperatively. Z₂², Z₃³, and Z₄² of both groups increased significantly 3 days after surgery (P < 0.05) and returned to baseline level 6 weeks after surgery, while the rest Zernike coefficients remained the same postoperatively. When comparing the differences between the two groups, there were no statistically significant differences in these parameters between baseline and each follow-up visit postoperatively.Conclusions: The increase of WA restored to pre-operative level in 6 weeks after surgery, indicating the influences of horizontal rectus muscle surgery to WA were transient and reversible.

Torsional Changes After Vertical Transposition of Horizontal Recti in V-pattern Exotropia Without Oblique Dysfunction

PURPOSE

To evaluate pattern collapse and torsional changes following vertical transposition of horizontal recti in patients with V-pattern exotropia and no oblique dysfunction.

METHODS

A prospective study was performed on patients who had V-pattern exotropia and no oblique dysfunction. Lateral recti were transposed upward half-tendon width in V-pattern of 25 prism diopters (PD) or less (n = 14) and full-tendon width in V-pattern of greater than 25 PD (n = 10). Amblyopic patients had unilateral lateral rectus recession with upward transposition and medial rectus resection with downward transposition (n = 8). Ductions, versions, pattern strabismus, disc foveal angle, and astigmatic axis were analyzed before and 6 months after surgery.

RESULTS

In the 32 patients (21 females), the mean age was 8.25 ± 1.23 years. Only amblyopic patients showed preoperative fundus extorsion (mean disc foveal angle = 16.9°, P < .01). Mean pattern collapse was 13.1 ± 3.8 PD with half-tendon transposition, 35.6 ± 13.7 PD with full-tendon transposition, and 13.8 ± 7.9 PD in the unilateral group. Pattern collapse increased gradually so that pattern normalization occurred after 6 months in most patients. There was a statistically significant correlation between the preoperative V-pattern and the magnitude of pattern collapse after surgery (r = 0.80, P < .01). There were no significant changes in the mean disc foveal angle (< 0.5°) or axis of astigmatism (< 0.5°) in all three groups.

CONCLUSIONS

Vertical transposition of horizontal muscles can correct V-pattern exotropia, although the effect might not be immediate. Torsional changes are minimal. Amblyopic patients with V-pattern exotropia showed a preoperative extorsion that did not change after surgery. [J Pediatr Ophthalmol Strabismus. 2019;56(2):107-115.].

[Astigmatism]

Astigmatism is the most frequent refractive error worldwide followed by hyperopia and myopia. Internal astigmatism has to be differentiated from external astigmatism. Furthermore, external astigmatism can be divided into "with the rule", "against the rule" and "oblique". The summation of internal and external astigmatism results in the refractive cylinder. Astigmatism has for a long time been regarded as a two-dimensional phenomenon; however, only a three-dimensional consideration expanded the view on existing analytical methods (topography and tomography). Alpins' vector analysis is a commonly used method for treatment planning. Multiple options exist for treatment of astigmatism with conservative approaches, such as eyeglasses or toric contact lenses as well as various surgical procedures, such as photorefractive keratectomy, femtosecond laser-assisted keratotomy, laser in-situ keratomileusis, small incision lenticule extraction and toric intraocular lens implantation.

Changes in refractive error and axial length after horizontal muscle surgery for strabismus

PURPOSE

To investigate changes in refractive error following horizontal muscle surgery and to analyze the relationship between these changes and axial length.

METHODS

Patients with intermittent exotropia who underwent bilateral lateral rectus recession (LR group) or unilateral lateral rectus recession with medial rectus resection (RR group) were investigated prospectively. The patients were followed for at least 3 months postoperatively; refractive error, axial length, mean corneal astigmatism, anterior chamber depth, corneal thickness, and intraocular pressure were evaluated at each examination. Postoperative changes in both groups were compared.

RESULTS

A total of 64 eyes of 47 patients were included-34 eyes in the LR group and 30 eyes in the RR group. In both groups refractive error, axial length, and mean corneal astigmatism significantly increased 1 day postoperatively, although the changes in all three parameters returned to their preoperative values within 1 month of surgery and remained stable thereafter for the duration of the follow-up period. There was a negative correlation between changes in axial length and refractive error toward myopia in the 64 eyes on postoperative day 1 (partial correlation coefficient r = -0.637; P < 0.001). Changes in refractive error and axial length were significantly larger in the RR than in the LR group 1 day postoperatively (P < 0.001 and P < 0.001, resp.).

CONCLUSIONS

Horizontal muscle surgery induces a transient myopic shift. This is thought to be due to axial length elongation as well as changes in corneal astigmatism.

A paired comparison study on refractive changes after strabismus surgery

PURPOSE

To quantify refractive changes following horizontal lateral rectus recession and medial rectus resection surgery and to investigate the causes of these changes.

METHODS

The medical records of patients who underwent unilateral horizontal lateral rectus recession and medial rectus resection for exotropia by a single surgeon over a period of 14 years were reviewed retrospectively. Using vector analysis, refractive changes in operated eyes (cases) were compared to changes in the sound eyes (controls). The main outcome measures were differences in mean change of refractive parameters and the proportion of clinically significant changes.

RESULTS

A total of 31 subjects (median age, 13.6 years; interquartile range, 8.8-19.8 years) were included. A significantly higher magnitude of refractive changes was observed in the operated eyes (P = 0.001). In addition, the proportion of cases with clinically significant change in sphere or cylinder was significantly higher in the operated eyes compared to the sound eyes (48% vs 10% [OR = 2.31, P = 0.002] and 32% vs 10% [OR = 5.0, P = 0.039], resp.).

CONCLUSIONS

Horizontal strabismus surgery is associated with refractive changes that might be of clinical significance. Pediatric ophthalmologists should consider re-refraction 1 month postoperatively.

Refractive Changes Induced by Strabismus Corrective Surgery in Adults

Purpose. To investigate refractive changes after strabismus correction procedures among adults. Methods. Retrospective chart review of adult patients who had horizontal recti muscles surgery with preoperative and postoperative cycloplegic refraction measurements. The preoperative refraction was mathematically subtracted from the postoperative refraction, and the induced refractive changes were statistically analyzed. Vector analysis was used to examine the magnitude of the toric change. The proportion of clinically significant refractive change was evaluated as well. Results. Thirty-one eyes from 22 subjects met the criteria and were included in the final analysis. A significant postoperative refractive change of the spherical equivalent towards myopia and a change of the astigmatism in the with-the-rule direction were observed. In a subset of 9 cases a third cycloplegic refraction measurement demonstrated stable refraction compared to the 1-month postoperative measurement. In 10 cases of single eye surgery, significant refractive changes were observed only in the operated side when compared to the sound eye. The induced surgical refractive change was of clinical significance (≥0.5 D) in 11 eyes of 9 patients (40.9% of patients). Conclusions. Refractive changes are a significant side effect of horizontal strabismus corrective surgery among adults. Therefore, patients should be informed about it prior to surgery and should be rerefracted in the postoperative period.

Comparison of Astigmatism Induced by Combined Inferior Oblique Anterior Transposition Procedure and Lateral Rectus Recession Alone

PURPOSE

The purpose of this study is to compare the magnitude and axis of astigmatism induced by a combined inferior oblique (IO) anterior transposition procedure with lateral rectus (LR) recession versus LR recession alone.

METHODS

Forty-six patients were retrospectively analyzed. The subjects were divided into two groups: those having concurrent inferior oblique muscle overaction (IOOA) and intermittent exotropia (group 1, 20 patients) and those having only intermittent exotropia as a control (group 2, 26 patients). Group 1 underwent combined anterior transposition of IO with LR recession and group 2 underwent LR recession alone. Induced astigmatism was defined as the difference between preoperative and postoperative astigmatism using double-angle vector analysis. Cylinder power, axis of induced astigmatism, and spherical equivalent were analyzed at 1 week, 1 month, and 3 months after surgery.

RESULTS

Larger changes in the axis of induced astigmatism were observed in group 1, with 4.5° incyclotorsion, than in group 2 at 1 week after surgery (axis, 84.5° vs. 91°; p < 0.001). However, there was no statistically significant inter-group difference thereafter. Relaxation and rapid regression in the incyclotorsion of induced astigmatism were observed over-time. Spherical equivalent significantly decreased postoperatively at 1 month in both groups, indicating a myopic shift (p = 0.011 for group 1 and p = 0.019 for group 2) but did not show significant differences at 3 months after surgery (p = 0.107 for group 1 and p = 0.760 for group 2).

CONCLUSIONS

Combined IO anterior transposition procedures caused an increased change in the axis of induced astigmatism, including temporary incyclotorsion, during the first week after surgery. However, this significant difference was not maintained thereafter. Thus, combined IO surgery with LR recession does not seem to produce a sustained astigmatic change, which can be a potential risk factor of postoperative amblyopia or diplopia compared with LR recession alone.

Is Inferior Oblique Overaction Associated With Astigmatism?

PURPOSE

To study the relationship between inferior oblique muscle overaction and astigmatism, and to explore any change in astigmatism after surgery.

METHODS

This was a retrospective chart review of patients undergoing strabismus surgery. Demographic data collected included age, diagnosis, preoperative refraction, presence of inferior oblique overaction, surgery performed, and postoperative refraction. Patients were divided into three groups: those having only horizontal strabismus without inferior oblique overaction (no inferior oblique group) as a control group, those having bilateral inferior oblique overaction (bilateral inferior oblique group), and those having unilateral inferior oblique overaction (unilateral inferior oblique group). Right eyes of the bilateral inferior oblique and no inferior oblique groups were chosen for analysis, whereas the eye with inferior oblique overaction was included in the unilateral cases. Refractions were converted to power vector coordinates for comparison. Statistical analysis was performed to compare the power vectors among groups using the no inferior oblique group as controls and to explore any postoperative change in astigmatism.

RESULTS

One hundred eighteen patients undergoing strabismus surgery were included (60 males and 58 females; mean age: 11.31 ± 10.59 years). Patients were divided into three groups: those having only horizontal strabismus without inferior oblique overaction (no inferior oblique group; 60 patients) as controls, those having bilateral inferior oblique overaction (bilateral inferior oblique group; 41 patients), and those having unilateral inferior oblique overaction (unilateral inferior oblique group; 17 patients). Preoperatively, there were no differences in astigmatism when comparing eyes with and without inferior oblique overaction. Postoperatively, both the no inferior oblique group and the bilateral inferior oblique group equally showed an increase in with-the-rule cylinder power (P = .02 and .01, respectively).

CONCLUSIONS

Inferior oblique muscle overaction did not result in an increased prevalence of astigmatism along the axis of the overacting muscle.

Comparison of surgically induced astigmatism in patients with horizontal rectus muscle recession

AIM

To compare surgically induced astigmatism (SIA) following horizontal rectus muscle recession surgery between suspension recession with both the "hang-back" technique and conventional recession technique.

METHODS

Totally, 48 eyes of 24 patients who had undergone horizontal rectus muscle recession surgery were reviewed retrospectively. The patients were divided into two groups. Twelve patients were operated on by the hang-back technique (Group 1), and 12 by the conventional recession technique (Group 2). SIA was calculated on the 1(st) wk, 1(st) and in the 3(rd) mo after surgery using the SIA calculator.

RESULTS

SIA was statistically higher in the Group 1 all postoperative follow-up. SIA was the highest in the 1(st) wk, and decreased gradually in both groups.

CONCLUSION

The suspension recession technique induced much more SIA than the conventional recession technique. This difference also continued in the following visits. Therefore, the refractive power should be checked postoperatively in order to avoid refractive amblyopia. Conventional recession surgery should be the preferred method so as to minimize the postoperative refractive changes in patients with amblyopia.

The impact of intermittent exotropia and surgery for intermittent exotropia on myopic progression among early school-aged children with myopia

AIM

To investigate the relationship between myopic progression and intermittent exotropia, and the impact of surgery for exotropia on myopic progression in early school-aged children (from 7 years to 12 years of age).

METHODS

Medical records of early school-aged patients with myopia were reviewed. Patients were divided into three groups; (A) Patients with intermittent exotropia and myopia at presentation and who underwent bilateral lateral rectus muscle recession for exotropia when 7-12 years old; (B) Patients with intermittent exotropia and myopia at presentation and who were merely observed for exotropia; and (C) Patients with myopia and straight ocular alignment. Main outcome measurements were the simple rate of myopic progression per year, the preoperative and postoperative rates of refractive growth with regards to the logarithmic age model in Group A, and the rate of high myopia development at the end of the early school period.

RESULTS

The rates of myopic progression were -0.43±0.14 dioptre (D) per year in Group A, -0.49±0.17 D/year in Group B and -0.42±0.24 D/year in Group C. There was no significant difference in the rate of myopic progression among three groups. There was no significant intergroup difference in the preoperative and postoperative rates of refractive growth in Group A. There were no significant intergroup differences in the rates of high myopia development among three groups.

CONCLUSIONS

Whether patients with intermittent exotropia underwent surgical correction for intermittent exotropia did not influence the rate of myopic progression. There was no significant difference in the rate of myopic progression between patients with accompanying intermittent exotropia and myopia and those with myopia alone.

Surgically induced astigmatism following medial rectus recession: short-term and long-term outcomes

PURPOSE

The current study aimed to investigate short- and long-term postoperative ocular refractive effects of medial rectus recession on the involved eye and to describe the detectable effects in detail by the results of vector analysis.

METHODS

Data of patients in whom medial rectus recession was performed between 2010 and 2012 were retrospectively evaluated. The study included 52 eyes of 32 patients. Patients with a history of previous ocular surgery, congenital or progressive corneal disease, familial or acquired posterior segment disease, glaucoma, a history of ocular trauma, or any neurological or systemic disease were excluded. Best-corrected and uncorrected visual acuities and refraction examination findings of the patients were recorded before the surgery and at the postoperative first month and first year. A vector analysis program was used to analyze surgically induced astigmatism.

RESULTS

Significant myopic shift and astigmatic change were determined in the spherical equivalent refraction in the early postoperative period (first month); however, these changes disappeared in the long term (at the postoperative first year). A positive correlation was not observed between the amount of surgical recession and the results of ophthalmic examination at the postoperative first month and first year.

CONCLUSIONS

Only postoperative first month spherical equivalent showed a positive correlation with the amount of surgical recession; however, this correlation disappeared at the postoperative first year.