Horizontal Rectus Muscles Research Articles

Agreement between intraoperative measurements and optical coherence tomography of the limbus-insertion distance of the extraocular muscles

Objective To assess the agreement between intraoperative measurements of the limbus-insertion distance of the extraocular muscles with those measured by spectral domain optical coherence tomography. Methods An analysis was made of a total of 67 muscles of 21 patients with strabismus. The limbus-insertion distance of the horizontal rectus muscles were measured using pre-operative SD-OCT and intra-operatively in 2 ways: (1) direct, after a conjunctival dissection in patients who underwent surgery, or (2) transconjunctival in patients who were treated with botulinum toxin, or in those who were not going to be operated. The intraclass correlation coefficient and Bland–Altman plots were calculated to determine the concordance between the 2 methods. Results The mean age was 45.9 ± 20.9 years (range 16 to 85), with 52% being women. The percentage of identification by direct intraoperative measurement was 95.6% (22/23), by transconjunctival intraoperative measurement 90.9% (40/44), and by OCT 85% (57/67), with 22 muscles finally being analyzed for the agreement study between direct intraoperative measurement and OCT measurements, and 35 muscles for the agreement between transconjuctival intraoperative measurement and OCT. The intraclass correlation coefficient showed good agreement with OCT and direct intraoperative measurements (0.931; 95% confidence interval (95% CI): 0.839–0.972; P < .001), and with transconjunctival intraoperative measurements (0.889; 95% CI: 0.790–0.942; P < .001). Conclusions The SD-OCT is an effective technique to measure the distance from the insertion of the horizontal rectus muscles to the limbus, with a high agreement with intraoperative measurements being demonstrated.

Longitudinal Evaluation of Eye Misalignment and Eye Movements Following Surgical Correction of Strabismus in Monkeys.

PurposeStrabismus correction surgery is well documented in both the literature and practice with varying levels of success and permanence. Our goal was to characterize longitudinal changes in eye alignment and eye movements following strabismus correction surgery in a monkey model for developmental strabismus.MethodsWe studied two juvenile rhesus monkeys with exotropia previously induced via an optical prism-rearing paradigm in infancy. Eye misalignment was corrected via a resection–recession surgery of the horizontal rectus muscles of one eye. Binocular search coils were used to collect eye movement data during smooth-pursuit, saccades, and fixation tasks before surgical treatment, immediately after surgery, and through 6 months after treatment.ResultsBoth animals showed an immediate ∼70% reduction in misalignment as a consequence of surgery that regressed to a 20%–40% improvement by 6 months after treatment. Significant changes were observed in saccade and smooth-pursuit gain of the nonviewing eye after surgery, which also reverted to presurgical values by 6 months. A temporary improvement in fixation stability of the nonviewing eye was observed after surgery; naso-temporal (N/T) asymmetry of monocular smooth-pursuit remained unchanged.ConclusionsSurgical realignment is followed by plastic changes that often lead to reversal of surgery effects. Immediate improvement in misalignment and changes in eye movement gains are likely a result of contractility changes at the level of the extraocular muscle, whereas longer-term effects are likely a combination of neural and muscle adaptation.

Bilateral absence of the inferior rectus muscle presenting with pseudoptosis: treatment of a novel presentation

Isolated bilateral absence of the inferior rectus muscle is a rare congenital anomaly. The usual presentation of this disorder involvesapparent ocular deviations and abnormal head posture from an early age. A 45-year-old woman presented with a bilateral ptosis and lower scleral show. She had a limitation of infraduction in both eyes but was orthophoric in the primary position and had a normal head posture. Ocular motility testing and imaging confirmed a diagnosis of bilateral absence of the inferior rectus muscle; the ptosis was assumed to be a pseudoptosis. The inferior half of the horizontal rectus muscles was transposed inferiorly in both eyes. Postoperatively there was marked improvement of the bilateral ptosis and lower scleral show.

Comparison of postoperative vertical drift in patients with thyroid eye disease with hypotropia: Vertical rectus muscle recession vs combined horizontal rectus muscle recession

Comparison of postoperative vertical drift in patients with thyroid eye disease with hypotropia: Vertical rectus muscle recession vs combined horizontal rectus muscle recession

Concordancia de la distancia desde la inserción hasta el limbo de los músculos rectos entre la medida intraoperatoria y con tomografía de coherencia óptica

ObjectiveTo assess the agreement between intraoperative measurements of the limbus-insertion distance of the extraocular muscles with those measured by spectral domain optical coherence tomography. MethodsAn analysis was made of a total of 67 muscles of 21 patients with strabismus. The limbus-insertion distance of the horizontal rectus muscles were measured using pre-operative SD-OCT and intra-operatively in 2 ways: 1) direct, after a conjunctival dissection in patients who underwent surgery, or 2) transconjunctival in patients who were treated with botulinum toxin, or in those who were not going to be operated. The intraclass correlation coefficient and Bland-Altman plots were calculated to determine the concordance between the 2 methods. ResultsThe mean age was 45.9 ±20.9 years (range 16 to 85), with 52% being women.The percentage of identification by direct intraoperative measurement was 95.6% (22/23), by transconjunctival intraoperative measurement 90.9% (40/44), and by OCT 85% (57/67), with 22 muscles finally being analysed for the agreement study between direct intraoperative measurement and OCT measurements, and 35 muscles for the agreement between transconjuctival intraoperative measurement and OCT. The intraclass correlation coefficient showed good agreement with OCT and direct intraoperative measurements (0.931; 95% confidence interval (95% CI): 0.839–0.972; P<.001), and with transconjunctival intraoperative measurements (0.889; 95% CI: 0.790–0.942; P<.001). ConclusionsThe SD-OCT is an effective technique to measure the distance from the insertion of the horizontal rectus muscles to the limbus, with a high agreement with intraoperative measurements being demonstrated.

Spectral domain optical coherence tomography to assess the insertion of extraocular rectus muscles

To determine the distance of the horizontal rectus muscle insertion to the limbus using spectral domain optical coherence tomography (SD-OCT) and to evaluate whether results are correlated with sex, age, or axial length. The right eyes of healthy, white subjects were imaged with SD-OCT. Subjects' sex and age were recorded, and axial length was measured using an optical biometer. The distance from the horizontal rectus insertion to the limbus was measured. The intraclass correlation coefficient (ICC) was used to assess the reproducibility of the measurements with a subset of images. A multivariate model was adjusted to analyze whether sex, age, and axial length was correlated with insertion distance. A total of 187 right eyes were included. Mean participant age was 43.7±22.1years (range, 6-85). Of the 187 patients, 129 were female; 25 were children. Mean axial length was 23.9±1.6mm (range, 20.4-29.3). Mean rectus insertion distance to the limbus was 6.47±0.52mm (range, 5.2-7.6mm) for the lateral rectus muscle and 5.22±0.51mm (range, 4.1-6.1mm) for the medial rectus muscle. ICC was >0.87 for intra- and interobserver reproducibility. The insertion-limbus distance was correlated with sex, being greater in males (P=0.040 for the lateral rectus muscle; P=0.036 for medial rectus muscle). There was no correlation between this distance and axial length or age (P>0.156). In this study cohort, the insertion distance of the horizontal rectus muscles to the limbus on SD-OCT was greater in males than females; however, age and axial length were not correlated with insertion distance.

Anterior Segment Optical Coherence Tomography of the Horizontal and Vertical Extraocular Muscles With Measurement of the Insertion to Limbus Distance.

To assess the possibility of determining the insertion distance from the limbus of horizontal and vertical extraocular rectus muscles with anterior segment optical coherence tomography (AS-OCT). The right eyes of 46 patients underwent AS-OCT. The horizontal and vertical extraocular rectus muscle insertion distances from the limbus were measured in a masked fashion by two pediatric ophthalmologists. Forty-two lateral rectus, 43 medial rectus, 35 inferior rectus, and 40 superior rectus muscles of the right eyes of 46 patients were included. Insertion to limbus measurements (mean ± SD) were as follows: lateral rectus = mean 6.8 ± 0.7 mm, range = 4.8 to 8.4 mm; medial rectus = mean 5.7 ± 0.8 mm, range = 4.3 to 7.8 mm; inferior rectus = mean 6.0 ± 0.6 mm, range = 4.8 to 7.0 mm; superior rectus = mean 6.8 ± 0.6 mm, range = 5.5 to 8.1 mm. The intraobserver and interobserver correlation coefficients for the insertion to limbus measurements of all four rectus muscles exceeded 0.75 (excellent correlation). The study showed that AS-OCT is capable of imaging all four of the rectus muscle insertions and measuring the insertion to limbus distance, and is the second AS-OCT study to image the superior and inferior rectus muscle insertions. The insertion to limbus measurements between examiners and on repeat measurements were consistent and reproducible. The ability to accurately image extraocular rectus muscle insertions may have future implications for the preoperative procedure planning in patients who have had previous surgery. [J Pediatr Ophthalmol Strabismus. 2016;53(3):141-145.].

Oculocardiac Reflex during Strabismus Surgery: Experience from a Tertiary Hospital

ABSTRACTPurpose: To evaluate the incidence of the oculocardiac reflex (OCR) and its associated risk factors during strabismus surgery at a tertiary referral center.Methods: Over a 2-year period, all strabismus surgery candidates were enrolled in the study. OCR was defined as heart rate reduction ≥15% after traction on extraocular muscle(s). The rate of OCR was determined and possible associations were explored. Variables included age, gender, type of strabismus, nature of surgery (weakening versus strengthening), specified extraocular muscle, times of surgery, and the sequence of operated muscles (eg, first, second, or third operated muscle). We avoided the use of atropine pre- and postoperatively.Results: Seventy-six patients with mean age of 15±12 years were enrolled; 51.3% of subjects were male. OCR occurred in 65 out of 76 (85.5%) patients and with 84 out of 173 (48.6%) operated muscles. OCR was more common in subjects less than 20 years of age; however, it showed a decreasing trend afterwards. OCR was more frequent during operation on cyclovertical muscles than horizontal recti (P=0.02). Moreover, during procedures on horizontal rectus muscles, OCR was more common if baseline heart rate was more than 61 (P=0.008). OCR was not correlated with gender, type of strabismus, nature of surgery, times of the surgery, or the sequence of operated extraocular muscles.Conclusions: The great majority of patients undergoing strabismus surgery, especially younger subjects, those undergoing operation on cyclovertical muscles, and subjects with higher baseline heart rate, experience OCR during strabismus surgery. During surgery on cyclovertical muscles, the amount of pull is usually more due to more difficult exposure.

A prospective evaluation of retroequatorial recession of horizontal rectus muscles and Hertle-Dell'Osso tenotomy procedure in patients with infantile nystagmus with no definite null position

To compare results of retroequatorial recession of horizontal rectus muscles and Hertle-Dell'Osso tenotomy procedure in patients with infantile nystagmus with null in primary position. In this prospective study, 10 subjects ≥5years of age with infantile nystagmus with null in primary position were randomly assigned to two groups: group 1 underwent a large retroequatorial recession of the four horizontal rectus muscles; group 2, simple tenotomy and resuturing (Hertle-Dell'Osso procedure) of the four muscles. Patients were evaluated using Snellen and logMAR visual acuity charts, contrast sensitivity testing, color vision testing, stereopsis testing (TNO), and electronystagmography (ENG) for nystagmus waveforms, frequency, amplitude, and intensity. Group 1 patients showed a trend toward 1-line improvement in their visual acuity for distance on the logMAR and ETDRS charts (P=0.32); there was no improvement in group 2 patients. Contrast sensitivity improved significantly in both groups (P=0.03), as did stereopsis (P=0.02 [group 1], P=0.04 [group 2]). The amplitude and intensity of nystagmus showed a tendancy to decrease in both the groups in all gazes, although the frequency showed no change in either group. Intergroup variability on all the parameters was not statistically significant. Both retroequatorial recession of horizontal recti and the Hertle-Dell'Osso procedure showed a trend toward reducing ENG amplitude and improved contrast sensitivity and stereopsis in infantile nystagmus with null in primary position.

Magnetic resonance imaging (MRI) in Duane retraction syndrome

Purpose: To study the magnetic resonance imaging (MRI) findings in Duane retraction syndrome (DRS). Materials and Methods: In this case–control study, 16 consecutive cases of Duane syndrome underwent MRI of the brain and orbit, after informed consent. MRI (fast imaging enhancing state acquisition) was done with special focus on pontomedullary junction to look for the status of abducens nerve and associated abnormalities along with quasi-coronal sections of orbit to estimate thickness and cross sectional area of horizontal extra-ocular muscles (EOMs). Thickness and cross-sectional area of EOMs were compared to the contralateral side and to age-matched controls. Results: Of 16 cases, 14 had DRS Type I, and 2 had DRS Type II. MRI revealed absent abducens nerve on the ipsilesional side in 12 out of 14 in DRS I, whereas two DRS II patients revealed intact abducens nerve on the affected side. Thickness and cross-sectional area of the horizontal recti was statistically comparable to the contralateral side and age-matched controls. Conclusions: All the DRS patients in study had structurally normal horizontal recti muscles, whereas 12 out of 14 of DRS-I patients had an absent abducens nerve on MRI.

Особенности биоэлектрических потенциалов наружных горизонтальных прямых мышц глаза при сходящемся и расходящемся содружественном неаккомодационном косоглазии

Особенности биоэлектрических потенциалов наружных горизонтальных прямых мышц глаза при сходящемся и расходящемся содружественном неаккомодационном косоглазии

Predictability of horizontal versus vertical muscle surgery outcomes in thyroid eye disease.

Surgical repair of vertical muscles in thyroid eye disease (TED) is believed to yield more unpredictable results than horizontal muscle surgery. The purpose of this study is to determine if the short-term outcomes for strabismus surgery in TED are equally predictable for horizontal and vertical muscle surgery. We retrospectively reviewed the charts of 27 consecutive patients who underwent strabismus surgery for TED from a single surgeon's practice. Eligibility for inclusion in the study included biochemically stable thyroid disease for at least a year and stable orthoptic measurements for at least 6months prior to surgery. Nine patients had surgery only on vertical rectus muscles, three only on horizontal, and fifteen on both vertical and horizontal rectus muscles. Mean follow-up was 2.4±5.2months. In primary gaze at 6m, a mean horizontal deviation of 16.6±22.3 PD, and a mean vertical deviation of 19.7±14.1 PD were measured pre-operatively. Post-operatively, this measured 2.3±8.4 PD horizontally and 2.1±7.8 PD vertically (p=0.933). There was no statistically significant difference between post-operative horizontal and vertical deviations in elevation, depression, adduction, and abduction. Nine patients required reoperation to attain satisfactory ocular alignment; seven of these cases involved repeat surgery on vertical muscles, while two cases required operation on both horizontal and vertical muscles. Results suggest that surgical outcomes of both horizontal and vertical muscle surgery are equally predictable in stable TED; however, reoperation rates were higher for vertical muscles compared to horizontal muscles.

Anterior segment optical coherence tomography of the horizontal and vertical extraocular muscles with measurement of the insertion to limbus distance

Purpose To assess the possibility of determining the insertion distance from the limbus of horizontal and vertical extraocular rectus muscles with anterior segment optical coherence tomography (AS-OCT). Methods The right eyes of 46 patients underwent AS-OCT. The horizontal and vertical extraocular rectus muscle insertion distances from the limbus were measured in a masked fashion by two pediatric ophthalmologists. Results Forty-two lateral rectus, 43 medial rectus, 35 inferior rectus, and 40 superior rectus muscles of the right eyes of 46 patients were included. Insertion to limbus measurements (mean ± SD) were as follows: lateral rectus = mean 6.8 ± 0.7 mm, range = 4.8 to 8.4 mm; medial rectus = mean 5.7 ± 0.8 mm, range = 4.3 to 7.8 mm; inferior rectus = mean 6.0 ± 0.6 mm, range = 4.8 to 7.0 mm; superior rectus = mean 6.8 ± 0.6 mm, range = 5.5 to 8.1 mm. The intraobserver and interobserver correlation coefficients for the insertion to limbus measurements of all four rectus muscles exceeded 0.75 (excellent correlation). Conclusions The study showed that AS-OCT is capable of imaging all four of the rectus muscle insertions and measuring the insertion to limbus distance, and is the second AS-OCT study to image the superior and inferior rectus muscle insertions. The insertion to limbus measurements between examiners and on repeat measurements were consistent and reproducible. The ability to accurately image extraocular rectus muscle insertions may have future implications for the preoperative procedure planning in patients who have had previous surgery. [J Pediatr Ophthalmol Strabismus. 2016;53(3):141-145.].

Effect of Horizontal Strabismus Surgery on the Refractive Status

Purpose: To evaluate the effects of horizontal strabismus surgery on the refractive and astigmatic status of eyes following horizontal muscle surgery using double-angle vector analysis.Materials and Methods: This was a retrospective analysis of 137 patients (250 eyes) conducted between February 1997 and October 2010 in patients who had unilateral or bilateral recession or monocular recession and/or underwent resection of horizontal muscles by a single surgeon. Refraction data were obtained at 1–2 weeks preoperative and at 4–6 weeks and 4–6 months postoperative. Surgically induced refractive changes were calculated using double-angle vector analysis.Results: The mean change in the spherical equivalent (SE) of the refraction was 0.23 ± 0.78 D for surgically induced refractive changes at 4–6 weeks postoperative (SIRC1; p < 0.0001) and 0.14 ± 0.85 D (p = 0.018) for surgically induced refractive changes at 4–6 months postoperative (SIRC2), indicating a small shift in the myopic direction with regression at 4–6 months. The mean amplitudes of the induced cylinders were 0.072 ± 1.22 D (p = 0.262) in SIRC1 and 0.20 ± 1.14 D (p = 0.012) in SIRC2, and the mean axis of the induced plus cylinder was 21.74° in SIRC1, indicating a small shift in the with-the-rule direction, but no statistically significant difference from zero (p = 0.331). The changes in the surgically induced refraction over time (SIRC d), ie, 0.05 ± 0.64 in SE (p = 0.255) and 0.09 ± 0.65 in the cylinder (p = 0.049), were stable. There was no significant correlation between the amounts of horizontal rectus muscle recession and/or resection and the cylinder power of individual induced astigmatism at 4–6 weeks after surgery (p = 0.266) and the myopic shift (p = 0.345). Moreover, there were no significant correlations between the ages of the patients and the spherical equivalent for SIRC1 (p = 0.858) and the induced cylinder for SIRC1 (p = 0.750).Conclusion: Horizontal rectus muscle surgery tended to induce a transient, statistically significant change in the spherical equivalent of refraction, with a myopic shift that was clinically not important. Our findings did not strongly support that the astigmatism induced changes. There was no correlation between the amount of recession and/or resection and the amount of induced refractive error.

Inferior oblique weakening surgery on ocular torsion in congenital superior oblique palsy.

To investigate changes in fundus excyclotorsion after inferior oblique myectomy or myotomy. The records of 21 patients undergoing strabismus surgery by a single surgeon between 2009 and 2012 were examined. Only patients who had undergone an inferior oblique myectomy or myotomy, with or without horizontal rectus muscle surgery, were evaluated. Digital fundus photographs were obtained, and the angle formed by a horizontal line passing through the optic disc center and a reference line connecting the foveola and optic disc center was measured. Associated clinical factors examined include age at the time of surgery, presence or absence of a head tilt, degree of preoperative vertical deviation, torsional angle, inferior oblique muscle overaction/superior oblique muscle underaction, and surgery laterality. Whether the procedure was performed alone or in combination with a horizontal rectus muscle surgery was also examined. Mean preoperative torsional angle was 12.0±6.4°, which decreased to 6.9±5.7° after surgery (P<0.001, paired t-test). Torsional angle also decreased from 15.1±7.0° to 6.2±4.3° in the myectomy group (P<0.001, paired t-test) but there were no significant changes in the myotomy group (P=0.093, Wilcoxon signed rank test). Multivariable linear regression analysis showed that preoperative torsional angle, degree of inferior oblique overaction, and age at surgery independently and significantly affected postoperative torsional angle. Mean torsional angle decreased after inferior oblique myectomy. Degree of preoperative torsional angle, inferior oblique overaction, and age at surgery influence postoperative torsional angle.

Enhanced-depth optical coherence tomography for imaging horizontal rectus muscles in Graves' orbitopathy.

Graves' orbitopathy (GO) is an extraocular eye disease with symptoms ranging from minor discomfort from dry eyes to strabismus and visual loss. One of the hallmarks of active GO is visible hyperemia at the insertion of the extraocular muscles. The aim of the present study was to evaluate the use of enhanced-depth imaging spectral domain anterior segment optical coherence tomography (EDI SD AS-OCT) for detecting pathological changes in horizontal recti muscles of patients with GO. Prospective cross sectional study of 27 eyes. Only women were included. EDI AS-OCT was used to measure the thickness of the tendons of the horizontal recti muscles in a predefined area in patients with GO and healthy controls. EDI AS-OCT was able to image the tendons of the horizontal recti muscles in both healthy controls and patients suffering from GO. The mean thickness of the medial rectus muscle (MR) tendon was 256.4 μm [±17.13 μm standard deviation (SD)] in the GO group and, therefore, significantly thicker (p = 0.046) than in the healthy group which had a mean thickness of 214.7 μm (±5.516 μm SD). There was no significant difference in the mean thickness of the tendon of the lateral recti muscles (LRs) between these groups. This is the first report showing that EDI AS-OCT is suitable to detect swelling at the insertion site of the MR muscle in GO. MR tendon thickness may be a useful parameter to monitor activity in these patients.

Long-Term Outcome and Recurrence of Abnormal Head Posture after Surgery in Patients with Nystagmus

Purpose: To evaluate the long-term outcome and recurrence of abnormal head posture after modified Kestenbaum surgery in patients with nystagmus. Methods: The medical records of 46 patients who underwent modified Kestenbaum procedure in horizontal recti muscles for nystagmus with abnormal head turn were retrospectively reviewed. We assessed the effect of surgery by comparing preoperative and postoperative clinical data such as visual acuity (log MAR) and degree of head turn. A reoperation or abnormal head turn of 10° or more at final visit were defined as recurrence. Patients were divided into 2 groups according to the presence of recurrence or reoperation. Clinical factors associated with recurrence or reoperation were compared between the 2 groups. Results: The mean visual acuity was 0.38 in the better eye and 0.42 in the worse eye before surgery, which improved to 0.15 and 0.21 after surgery (each p < 0.001), with a mean follow-up period of 124 months. The mean degree of head turn was 41.41° preoperatively and was changed to 2.61° postoperatively (p < 0.001). The recurrence rate was 23.9% and the reoperation rate was 10.9%. Mental retardation, amblyopia, preoperative visual acuity, degree of head turn, and presence of strabismus were not associated with recurrence or reoperation. The mean age at first surgery was significantly lower in the reoperation group (p = 0.009). The mean visual acuity in the better eye at postoperative 6 months and in better and worse eyes at postoperative 1 year was significantly worse in the reoperation group (p = 0.034, 0.012 and 0.009, respectively). Conclusions: The visual acuity and head turn was improved after modified Kestenbaum surgery in patients with nystagmus and abnormal head posture. The reoperation rates were associated with earlier age of first operation and worse postoperative visual acuity. However, further prospective studies are necessary to clarify these factors. J Korean Ophthalmol Soc 2015;56(2):263-269

Retrospective study of recession of four horizontal rectus muscle in periodic alternating nystagmus.

PurposePeriodic alternating nystagmus (PAN) is a spontaneous horizontal nystagmus observed in disorders of the central nervous system. Patients with congenital PAN complain of oscillating vision at high rates. Medication is the first-choice treatment for PAN; however, clinicians still seek better therapy. The aim of this study was to evaluate outcomes of recession of four horizontal rectus muscle (R-FHR) in patients with congenital PAN.Patients and methodsThis study reports a retrospective case series of ten patients (seven males and three females; mean age 24.4±10.9) with congenital PAN who underwent R-FHR between 2007 and 2012, which was performed by the same surgeon at the Hyogo College of Medicine. Patients were evaluated for complications, recession amount, deviation angle, eye movements including a nystagmus amplitude, and visual acuity during pre- and post-operative periods.ResultsPre-operatively, patients complained of oscillating vision, abnormal head posture, esotropia, and congenital superior oblique palsy. Post-operatively, changes from the previous observations of nystagmus amplitudes and abnormal head posture demonstrated a complete reversal in all patients. In addition, visual acuity determined with a Snellen chart improved in two patients. However, esotropia occurred in three patients who underwent additional strabismus surgery 2 days after R-FHR. R-FHR was particularly effective in eight patients who pre-operatively had periodic oscillating vision with a regular pattern of periodic nystagmus.ConclusionWe demonstrated that ten patients with congenital PAN had improved vision following R-FHR, indicating that R-FHR was an effective procedure, especially in patients suffering PAN with periodic oscillating vision.

Combining rectus muscle recessions with a central tenectomy to treat large-angle horizontal strabismus

To report the effectiveness of incorporating a central tenectomy on the recessed rectus muscles when treating large-angle horizontal deviations. Patients undergoing recession and central tenectomy from March 2010 to January 2013 were prospectively enrolled. The procedure entails making two longitudinal incisions, each 4 mm, on the muscle adjacent to sutures made during the recession procedure. With recession complete and muscle sutured to the sclera, the central flap (with approximately one-third of the insertion width) is excised. The following variables were analyzed: expected correction (according to surgical dose tables), achieved correction (preoperative deviation minus postoperative deviation), and tenectomy effect (achieved correction minus expected correction). A total of 16 horizontal rectus muscles of 16 eyes of 12 patients were included, 8 with exotropia and 4 with esotropia. No cases of significant limitation in duction in the field of the recessed muscle occurred. In all patients, the median achieved corrections at distance (55(Δ)) and at near (53.5(Δ)) were significantly higher than the median expected corrections (45(Δ) for both distance and near [P = 0.002]). The postoperative deviations at distance and near were lower in the unilateral surgery group (n = 8; statistically significant only for near deviation). The tenectomy effects in the esotropia group for both distance and near were more pronounced than those of the exotropia group (although not statistically significant). In our patients central tenectomy of the recessed rectus muscles increased the effect of recession procedures without limiting ductions. There were possible greater effects in esotropia patients and recession-resection procedures.

Unilateral strabismus surgery in patients with exotropia results in postoperative lateral incomitance

To determine whether unilateral strabismus surgery creates lateral incomitance in patients with exotropia. Patients >7 years of age with intermittent or constant exotropia who underwent unilateral horizontal rectus muscle surgery between December 2009 and January 2012 were prospectively evaluated. Prism and alternate cover testing was performed with distance fixation in primary position, right gaze, and left gaze after 1 hour of monocular occlusion. Measurements were obtained within 1 month prior to surgery, within 1 week after surgery, and >3 months after surgery. The surgical procedure varied according to the surgeon's discretion. The change in deviation induced by strabismus surgery in lateral gaze was expressed as a percentage of the change in deviation induced in primary position. A total of 12 patients met inclusion criteria. Of the 11 patients with postoperative examinations within 1 week after surgery, 10 (91%) had greater surgical effect with gaze toward the operated eye (P = 0.007). All 9 patients with >3 months' follow-up had greater surgical effect with gaze toward the operated eye (P = 0.003). On average, the surgical effect in gaze toward the operated eye was 120% of that achieved in primary position; in gaze away from the operated eye, 75% (P < 0.001). Three patients had diplopia in lateral gaze toward the operated eye that remained >6 months after surgery. Unilateral strabismus surgery induces lateral incomitance that may cause diplopia >6 months after surgery in patients with exotropia. This should be considered when planning strabismus surgery and counseling patients.