Effect of Horizontal Strabismus Surgery on the Refractive Status

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.

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.

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.

Unilateral transient high myopization after pediatric strabismus surgery: Observation by anterior segment optical coherence tomography

PURPOSE

To describe an unusual case of unilateral transient high myopization after pediatric strabismus surgery.

OBSERVATIONS

A 6-year-old girl with intermittent exotropia had undergone strabismus surgery and experienced a transient decrease in best-corrected visual acuity (BCVA, from 20/20 to 20/33) with high myopization (from +0.25 D to -9.00 D). Slit-lamp microscopy showed anterior chamber inflammation and a narrow angle only in the affected eye. Anterior segment optical coherence tomography (AS-OCT) revealed ciliary body detachment, a narrow angle, a shallow anterior chamber, and an anteroposterior elongation of the crystalline lens in the affected eye. Her symptoms of blurry vision and high myopization improved 8 weeks postoperatively. AS-OCT revealed the resolution of the ciliary body detachment, an open angle, and a deep anterior chamber, with normalization of the anteroposterior length of the crystalline lens. Her BCVA recovered to 20/20 with spherical equivalence of 0 D.

CONCLUSIONS AND IMPORTANCE

We reported on an extremely rare case of unilateral transient high myopization following strabismus surgery, which was resolved without additional surgery. This myopization was probably caused due to ciliary body inflammation.

Changes in refractive status of amblyopic patients with partially refractive esotropia

PURPOSE

To investigate the changes in refractive status of amblyopic patients with partially refractive esotropia (PAET).

MATERIALS AND METHODS

Amblyopic patients with PAET were enrolled. Non-amblyopic patients with full refractive accommodative esotropia (RAET) were included in the study as a control group. Preoperative and postoperative best-corrected visual acuity (BCVA), spherical equivalent (SE), astigmatism, stereoacuity, and deviations at near and distance were evaluated and statistically compared within the study group. Mean BCVA, SE, astigmatism were compared between the two groups.

RESULTS

The patient and the control groups were composed of 58 eyes of 29 patients per group. There were statistically significant differences between pre- and postoperative mean astigmatism and SE between the patient and control groups. The mean astigmatism was higher in amblyopic eyes when compared with the eyes in the control group (P:0.009). During the follow-up period, changes in SE and astigmatism were not different between groups.

CONCLUSION

The mean SE and astigmatism were changed in both amblyopic patients with PAET and non-amblyopic patients with RAET during the follow-up period. This suggested that neither amblyopia nor strabismus surgery has an effect on refractive status in patients with PAET.

Do rectus muscle parameters vary between emmetropes and myopes?

PURPOSE

This study investigated the thickness, area, and insertion site of the medial (MR) and lateral (LR) rectus muscles in individuals with emmetropia and different degrees of myopia.

METHODS

Swept-source optical coherence tomography images of the MR and LR muscles in 80 participants including emmetropes (spherical equivalent refractive error [SER] ±0.50 D, N = 14) and myopes (≤ -0.75 D, N = 66), were analysed. Custom-designed, semi-automated software was used to measure parameters such as insertion distance from limbus, muscle thickness at every 1 mm interval to 3 mm periphery and muscle area from insertion site to 3 mm.

RESULTS

The median (Q1, Q3) SER error and axial length were -6.00 D (-13.25, -2.12) and 25.78 mm (23.78, 28.61), respectively. The MR was significantly thinner (mean ± SE: 137.7 ± 8.9 vs. 159.7 ± 8.9 µm, p < 0.01) and occupied less area than the LR (0.35 ± 0.01 vs. 0.42 ± 0.01 mm² , respectively, p < 0.01). The thickness of the MR gradually increased from the insertion site to a 3 mm peripheral eccentric location (106.5 3.8 µm at 1 mm, 135.5 ± 4.5 µm at 2 mm and 156.1 ± 5.9 µm at 3 mm, p < 0.01). The overall median thickness of the MR was significantly less in myopes (129 µm [111.5, 152.2]) than emmetropes (158.1 [134.3, 167.7] µm, p = 0.03). However, no such trend was seen in the LR muscle. Muscle area and insertion distance were not different between emmetropes and myopes in both horizontal rectus muscles.

CONCLUSION

Unlike the LR, the parameters of the MR (thin and occupying less area) show significant association with myopia. While the key finding of this study indicates the possible association of MR parameters with myopia, the clinical relevance of this finding and its role in myopiogenesis/progression needs to be investigated further.

The incidence and clinical outcome of complications in 4,000 consecutive strabismus operations

PURPOSE

To test the validity of the British Ophthalmic Surveillance Unit (BOSU) study's incidence figure of severe complications following strabismus surgery and to determine the incidence, type, risk factors, and outcome of all strabismus surgery complications at a single institution.

METHODS

A prospective audit of consecutive strabismus operations performed by consultants or trainees was carried out between 2011 and 2016 at Moorfields Eye Hospital NHS Foundation Trust. Patient diagnosis, age, sex, surgical details, complications, and outcome were recorded from hospital records. We classified complications as minor, moderate, or severe. The outcome was graded using the Bradbury and Taylor grading system (I to IV), with a poor or very poor outcome meaning loss of corrected visual acuity or unexpected primary position diplopia.

RESULTS

A total of 4,076 consecutive strabismus operations were performed during the study period. There were 46 (1.13%) complications, of which 28 (0.69%) were minor, 7 (0.17%) were moderate, and 9 (0.22%) were severe. Only 1 patient (0.02%) had a poor visual outcome. Two patients had nonocular postoperative complications (0.05%).

CONCLUSIONS

In this large, prospective series, we found the rate of severe complications of strabismus surgery to be 1 in 455 cases. Our results validate the findings of the BOSU study.

Effect of strabismus surgery on ocular axial length, anterior chamber depth, and intraocular pressure

We evaluated changes in ocular axial length (AL), anterior chamber depth (ACD), and intraocular pressure (IOP) after strabismus surgery by comparing the operated and fellow eyes in patients undergoing unilateral strabismus surgery.This was a prospective study including patients who underwent unilateral strabismus surgery for exotropia alone or exotropia with unilateral superior oblique palsy. The AL and ACD using IOLMaster biometer and the IOP using non-contact tonometry were measured 1 day prior to surgery and 1 week, 1 month, and 3 months postoperatively.Fourteen female and 22 male patients (mean age: 8.2 years) were included in the study. In the operated eye, the mean AL increased significantly from 23.99 mm preoperatively to 24.08 mm 1 week postoperatively (P < .001), and although the mean ACD decreased in this time, the decrease was not statistically significant. The mean IOP of the operated eye increased from 17.08 mmHg preoperatively to 20.31 mmHg at 1 week postoperatively (P = .01), as did the IOP of the fellow eye (P = .03). However, the AL and IOP of the operated eyes decreased by 1 month postoperatively. There were no significant differences in the AL, ACD, and IOP between operated and fellow eyes by 3 months postoperatively.Strabismus surgery caused significant AL elongation in the operated eye and IOP elevation in both the operated and fellow eyes immediately after surgery. However, both ocular changes were transient. The AL, ACD, and IOP did not exhibit any significant differences between operated and fellow eyes 3 months postoperatively.

Refractive changes following corrective surgery for thyroid-related orbitopathy

Thyroid-related orbitopathy (TRO) is a common and recognizable manifestation of Graves' disease, caused by an increase in orbital fat volume, increased extraocular muscle diameter, and fibrosis. Together, within the bony confines of the orbit, these changes might alter the shape and position of the globe, potentially inducing refractive shifts. These refractive changes may then be affected by corrective surgical interventions for TRO such as orbital decompression and strabismus surgery. We studied refractive changes in patients with TRO who underwent strabismus surgery with or without orbital decompression. Manifest refraction was performed preoperatively and postoperatively in 33 patients who met inclusion criteria. Statistically significant postoperative refractive changes were found for cylinder, axis, and spherical equivalent.

Long-Term Changes in Refractive Error and Clinical Evaluation in Partially Accommodative Esotropia after Surgery

We investigate the changes in refractive error and clinical evaluation in partially accommodative esotropia(PAET) after surgery. A total of 68 patients PAET who received at least 2 years of follow-up after surgery were enrolled in this study. We performed a retrospective study in patients who underwent unilateral or bilateral medial rectus recession for a non-accommodative component of PAET between January 2005 and March 2013. Patients were divided into groups according to the presence of dominancy (dominant, non-dominant, alternative eye), and presence of amblyopia (amblyopic, fellow, normal eye). Changes and changing pattern in SE refractive error were analyzed in all patients and compared between groups. Patients were divided into two groups, those weaned off of hyperopic glasses and those who continued using them, then factors that significantly influenced the continued use of glasses were analyzed. The changes and changing pattern in SE refractive error according to time after operation and presence of amblyopia or dominancy. The mean length of follow-up was 4.89±1.74 years after surgery and the mean change in SE refractive error rate per year was -0.284±0.411 diopters (D). The pattern of changes in the mean SE refractive error for those with dominant, non-dominant, and alternative eyes was not significantly different (p = 0.292). The pattern of changes in the mean SE refractive error for those with amblyopic, fellow, and normal eyes was significantly different (p = 0.0002). Patients were successfully weaned off of hyperopic glasses at an average age of 9.41±2.74 years. The average SE refractive error in the group weaned off of hyperopic glasses was significantly lower than that in the group maintained on hyperopic glasses (p = 0.0002). The change of SE refractive error in amblyopic eyes decreased less than that in fellow or normal eyes, which may be correlated with the presence of amblyopia. Patients with a smaller esodeviated angle without hyperopic correction, a lower degree of hyperopia, and who were older at the time of disease onset were discontinued from hyperopic glasses sooner after surgery.