Horizontal Strabismus Research Articles

Prevalence of manifest horizontal strabismus among basic school children in Khartoum City, Sudan

Aim: To determine the prevalence of horizontal strabismus, the relationship between the family's socioeconomic factors and their attitude towards the child's eye health, its types, and to determine the attitude and compliance of the patients and their parents towards it among basic school children in Khartoum city between July and December 2010. Materials and Methods: A cross-sectional survey was conducted in Khartoum city among basic school children by questionnaire and eye examination. Sampling was with systematic random sampling for schools, probability proportional to size for children number in each school and systematic random sampling for children after obtaining a written consent from the ministry of basic education and parents. Results: 768 children were interviewed using questionnaire with a response rate of 100%. The questionnaires were analyzed using SPSS version 19 giving prevalence of horizontal squint of 2.8%, significant association between the father's educational level, socioeconomic status and their attitude towards eyes' health. Esotropia is the predominant type with a 2.2% and a slightly acceptable compliance towards regular eye follow up. Conclusion: Most of families didn't show good compliance towards the eye health unless they had a problem but almost all of them had the desire to know more.

Outcomes of Asymmetric Primary Inferior Oblique Muscle Overaction Managed by Bilateral Myectomy and Tucking of Proximal Muscle End: A Cohort Study.

Background:We present the outcomes of bilateral myectomy and tucking of the proximal end of the muscle for the treatment of asymmetric primary inferior oblique (IO) overaction.Methods:This was a one-armed prospective cohort study. An ophthalmologist and orthoptist evaluated cases of primary IO muscle overaction presenting between January 2010 and December 2013. All eyes underwent bilateral myectomy and tucking of the proximal end of the IO muscle. Data were collected on ocular motility, the angle of deviation, postoperative complications, and status of hypertropia at 6 months postoperatively. The 95% confidence intervals (CI) were calculated. The statistical significance was indicated by P < 0.05.Results:The patient cohort was comprised of 51 patients with primary IO muscle overaction. Preoperatively, all eyes had +2 or greater overaction of the IO muscle except one patient with +1 and +3 overaction in the right and left eyes, respectively. At 6 months postoperatively, the reduction in the angle of deviation for distance and near was 32.6 prism diopters (PD) ([95% CI 30.3–34.9], P < 0.001) and 32.6 PD ([95% CI: 29.8–35.3], P < 0.001), respectively. There was no significant difference in the postoperative variation of the reduction in the angle of deviation based on gender, right or left eye, and type of horizontal strabismus. There were no cases of “A” or “V” patterns, clinically a significant IO underaction or “adherence syndrome” postoperatively.Conclusion:Bilateral myectomy and tucking of the proximal end of the muscle is likely an effective method of treating asymmetric primary IO muscle overaction.

Intraocular pressure decreases after muscle union surgery for highly myopic strabismus.

To analyze the relationship between changes in the intraocular pressure (IOP) and dislocation angle in highly myopic strabismus patients who had undergone muscle union surgery. Medical data were examined of eight eyes of seven consecutive patients with highly myopic strabismus, who had some limitation in abduction, received muscle union surgery and undergone pre- and postoperative IOP evaluation with a noncontact tonometer, and were retrospectively reviewed. In addition, 15 eyes of 15 patients with comitant horizontal strabismus who underwent unilateral recess-resect procedure as well as pre- and postoperative IOP evaluation were also included. The correlation between IOP changes after strabismus surgery and the dislocation angle of the globe was analyzed. The IOP was significantly reduced in the highly myopic strabismus group (-5.6 mmHg) but not in the fellow eye or in comitant horizontal strabismus patients. The decrease in IOP after surgery was significantly correlated with the preoperative dislocation angle of the globe (r = -0.725, p = 0.042). IOP is often higher in highly myopic strabismus patients than perceived, and it may indicate abnormal anatomy of the orbit rather than glaucoma. In that case, muscle union surgery can improve eye position and normalizes the IOP.

Outcome of horizontal strabismus surgery and parents' satisfaction.

A clinical audit of strabismus surgery in children in terms of functional and cosmetic outcomes helps improve the quality of services in pediatric ophthalmology. To evaluate the outcome of strabismus surgery and assess the satisfaction of the patients' parents with respect to the surgery outcome. A study of an interventional series of cases that included 60 strabismic subjects was carried out. The bilateral strabismus surgery under general anesthesia was performed on all subjects using the fornix approach. The parents' understanding about strabismus and the cosmetic outcome was assessed through a set of interview questionnaires. The main outcome measures were the amount of deviation, the parents' knowledge about strabismus and their satisfaction after the intervention. Of the 60 subjects, 32 (53.3%) were esotropic and 28 (46.7%) exotropic. The male to female ratio was 1:1. The mean age with standard deviation was 16.6±8.5 years,with a range of 3 to 35 years. The pre- operative mean esotropia with standard deviation was 48.2±14.8 pd, with a range of 22 to 114 pd). The pre-operative mean exotropia was 57.8±14.2 pd, with a range of 25 to 90 pd). In 93.47% of the subjects, the ocular deviation after surgery reduced significantly (p=less than 0.00). After the strabismus surgery, orthophoria was achieved in 15 (25%) subjects, and with excellent cosmetics. After surgery, gross binocular single vision was attained in 39.3% of the exotropes and in 17.9% of the esotropes. Only 30% of the parents were aware about the strabismus and the treatment modalities. Nearly 90% of the parents were satisfied with the cosmetic outcome. Horizontal and bilateral strabismus has good surgical outcome with improved cosmetic acceptance.

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.

Pattern strabismus and torsion needs special surgical attention.

Pattern strabismus is relatively common in strabismus practice. Although it is classically used to include A and V patterns, the term has been expanded to include additional vertically incomitant horizontal strabismus. This article reviews the clinical features, etiopathogenesis, and surgical options for the patients with pattern strabismus.

Inter-examiner variability and agreement of the alternate prism cover test (APCT) measurements of strabismus performed by 4 examiners

Purpose: To investigate the inter-examiner variability and agreement of the alternate prism cover test (APCT) measurements of strabismus at near and distance fixation performed by 4 examiners. Methods: Forty-one participants (median age 12 years, range 3–74) with horizontal strabismus completed APCT measurements at near (1/3 m) and distance (5 m) fixation. Each participant was assessed by 4 masked experienced orthoptists on the same visit. Bland-Altman plots and inter-examiner variability (1.96xSD of the difference) were used to determine a clinical value suggestive of real change. Results: The inter-examiner variability was ±10 prism diopters (PD) at near and ±9 PD at distance fixation. The mean difference between measurements per examiner pair for near fixation ranged between −3 and 1.5 PD, with inter-examiner variability ranging between ±6.9 and ±12.5 PD, and mean difference for distance fixation between −0.8 and 1.6 PD, with inter-examiner variability ranging between ±7.5 and ±11.7 PD. Larger variability was found between some examiner pairs than others. Magnitude of the deviation, test distance, and age had no significant influence on the variation in APCT measurement. Conclusion: A variation in APCT measurement between 4 examiners of less than 10 PD for both near and distance fixation is likely to be due to inter-examiner variability. Changes of 10 PD or more are suggestive of a real change and may be employed as a management threshold.

Unilateral and bilateral medial rectus recession in Graves’ Orbitopathy patients

Purpose: To evaluate the effect of uni- and bilateral medial rectus recession on squint angle and ductions in Graves’ Orbitopathy (GO) patients.Design: Retrospective case series.Materials and methods: Consecutive GO patients seen between January 2000 and March 2012 who were operated on one or both medial rectus muscles were selected for the study. Data regarding squint angle, abduction, and adduction were collected starting 3 months before surgery and 3 and 6–12 months after surgery.Results: 102 patients were eligible for inclusion. Of these, 24 patients were operated on one medial rectus and 78 on two medial rectus muscles. The dose-effect response was 1.0 [−0.6–3.8]°/mm in the unilateral and 1.4 [0.2–3.0]°/mm in the bilateral group (p = 0.000). In the bilateral group, the maximal abduction and adduction changed significantly (p = 0.000). However, the total duction range remained unchanged (unilateral: p = 0.525; bilateral: p = 0.137). The extent of the preoperative abduction did not influence the dose-effect response (r = −0.234; p = 0.040), nor did the muscle volume (unilateral p = 0.989; bilateral p = 0.397). Twenty-three patients (23%) needed additional horizontal squint surgery.Conclusion: In this large series of medial rectus recessions in patients with Graves’ disease we found significantly lower dose-effect response ratios as compared to other studies. The amount of abduction deficit does not influence outcome.

False amblyopia prediction in strabismic patients by fixation preference testing correlates with contralateral ocular dominance

Binocular fixation preference testing is commonly used to predict strabismic amblyopia in preverbal children. However, false positives can occur and can lead to unnecessary patching treatment. We explored potential causes for this phenomenon. In this prospective cohort study (2013-2014) of consecutive verbal strabismic patients without incomitance or decreased vision other than strabismic amblyopia, binocular fixation preference testing was graded from 1 (strong preference) to 4 (free alteration), with grade 1 or 2 considered predictive of amblyopia and the examiner masked to visual acuity. These results were compared to the presence/absence of true strabismic amblyopia. Ocular dominance and hand dominance were assessed, and previous patching history was documented. Of 114 enrolled subjects (mean age, 7.9 years; range, 3.4-22.4; 63 males), 98 (86%) had esotropia and 16 (14%) had exotropia (mean primary position horizontal strabismus, 27.9(Δ); range, 8(Δ)-70(Δ), with only one <10(Δ)). For the 39 false positives (34%), the fixating eye correlated with ipsilateral ocular dominance (79.5%; P < 0.0001 [χ(2)]) but not with hand dominance or recent patching history. Positive predictive value was poor (45.8%; 95% CI, 34.0%-58.0%), but negative predictive value was high (97.6%; 95% CI, 87.4%-99.6%). Subgroup analysis revealed no significant correlations with degree or type of strabismus. False positives during binocular fixation preference testing of strabismic patients are common and likely due to contralateral ocular dominance. The test is more useful for predicting the absence rather than the presence of strabismic amblyopia.

Magnetic resonance imaging (MRI) demonstrates adduction tethering by the optic nerve (ON) in esotropia (ET) and exotropia (XT)

The ON's role in limiting ocular duction is previously unappreciated. This study employed MRI to demonstrate that the ON constrains adduction in horizontal strabismus.

Effect of inferior oblique weakening surgery on horizontal deviations

It is common for inferior oblique overaction to be combined with horizontal strabismus, requiring surgical correction. Our aim was to assess the effect inferior oblique (IO) weakening surgery, performed as an initial procedure, on the horizontal deviation and to identify if there were cases where this effect meant further horizontal surgery was not required.

Surgery for monocular elevation deficit (MED)—outcomes in a series of 31 cases

Inspite of various available surgical options, the management of MED is a challenge, especially when associated with horizontal strabismus. We report surgical outcomes in 31 cases of MED.

Surgical outcome of strabismus surgery in patients with unilateral vision loss and horizontal strabismus.

To report on the surgical outcome of horizontal strabismus surgery in patients diagnosed as having unilateral vision loss. Medical records of all patients with unilateral vision loss who underwent surgical repair of horizontal strabismus between 2008 and 2013 at three medical centers were reviewed. Data collected included age at time of surgery, type of strabismus, preoperative and postoperative deviation, procedure performed, and length of follow-up. Surgical success was defined as final alignment of 10 prism diopters (PD) or less unless more than one surgery was required to realign the eyes. Twenty-one patients (9 children) were reviewed. Mean age at time of surgery was 28.3 years (range: 3 to 64 years) and mean follow-up was 20 months (range: 6 months to 5 years). Mean preoperative logMAR visual acuity in the deviating eyes (14 right eyes) was 1.4 ± 0.7 (range: 1.0 to 2.8) and mean deviation was 33 PD (range: 15 to 90 PD). All procedures were performed only on the deviating eye (13 recessions and 8 recession-resection procedures). Mean postoperative deviation was 6.4 PD (range: 0 to 25 PD) and 81% of patients had a manifest ocular deviation of 10 PD or less. Surgical success was comparable in children versus adults (P = .603), in patients with esotropia versus exotropia (P = 1.000), in patients with preoperative deviations larger than 30 PD compared to patients with smaller deviations (P = .521), and in patients in whom one muscle was operated on compared to all other patients (P = .617). Strabismus surgery in patients with unilateral vision loss is often successful in correcting ocular misalignment.

Application of dezoxine plus dexmedetomidine in strabismus surgery

To observe the effects of intra-operative combined dosing of dezoxine and dexmedetomidine on sedation, analgesia and the incidence of untoward events during and after surgery in teenagers undergoing horizontal concomitant strabismus surgery. For this prospective and randomized trial, approval was obtained from the Ethical Committee and informed consent from their parents. A total of 60 patients aged 10-16 years undergoing strabismus surgery at Second Affiliated Hospital from September to December 2013 were collected. The treatment group received an intravenous dose of dezoxine 0.1 mg×kg(-1) at 15 minutes before surgery. And another intravenous injection of dexmedetomidine was administered at 0.4 µg×kg(-1)×h(-1) until the end of the first ocular muscle correcting. The control group received the same volume of normal saline. Observational parameters including visual analogue scale (VAS), Ramsay scores, self-rating anxiety scale (SAS), heart rate (HR), blood pressure and the incidence of untoward events such as nausea and vomiting or arrhythmia were recorded. The VAS pain scores in the treatment group at T2-T5 decreased significantly versus the control group (P < 0.05) . The Ramsay scores in the treatment group at T2-T3 increased and significantly differences existed with the control group (P < 0.05). SAS scores showed significant differences between pre-operative and post-operative periods in the treatment group (P < 0.05). The treatment group has shorter operative duration with 5 cases of dragging pain in the treatment group versus 25 in the control group (P < 0.05). During dragging reflex, HR was lower in the control group at T2 and T3. There were significant differences with the control group (P < 0.05). A combination of dezoxine and dexmedetomidine provide multiple benefits for patients undergoing strabismus surgery. Compared with simple local anesthesia, it effectively attenuates pain and anxiety and provides mild sedation and better cooperation during strabismus surgery.

Clinical progression of untreated bilateral Brown syndrome

To present the natural history of bilateral Brown syndrome in patients without surgical intervention. The medical records of cases of bilateral Brown syndrome not treated surgically with long-term follow-up from 1987 to 2012 were retrospectively reviewed. A total of 9 cases were included. The majority of patients in this series had idiopathic Brown syndrome, were diagnosed in early childhood, and had minimal ophthalmic sequelae. Of the 9 patients, 8 were diagnosed with bilateral Brown syndrome at their first ophthalmologic assessment. The age range at first diagnosis was 3-6 years of age. The mean follow-up period was 7.9 years; the median, 5 years (range, 1-20 years). At the most recent follow-up visit, 6 patients remained orthophoric in primary position; 1 patient had a micro-esotropia; 1 had developed an exotropia of 30 D; and 1 had developed a right hyperphoria. All patients without concurrent horizontal strabismus developed normal stereopsis and visual acuity, with minimal or no compensatory head position or downshoot in adduction. Patients in this case series show minimal, if any, long-term visual impairment.

Impaired body balance control in adults with strabismus

Previous studies revealed that people with binocular vision disorders have poor postural stability. However, most of the research was performed only on children and under binocular viewing condition, that could negatively affect the results. The aim of the current study was to investigate the influence of extra-ocular proprioceptive signals on postural stability in young adults with binocular vision disorders. Moreover, additional mental task was introduced to detect any postural compensation which could possibly hide the real influence of afferent extra-ocular signals. 21 Subjects, aged 18-45 yrs, with horizontal strabismus, were qualified to binocular vision disorders (BVD) group. 41 subjects, aged 19-45 yrs, with no strabismus formed the normal binocular vision (NBV) group. Posturography data were collected in 2 separate parts: (1) quiet standing (Single-Task), and (2) performance of a mental task while standing (Dual-Task). Each part consisted of three 60-s viewing conditions, with: (1) dominant/fellow eye (DE), (2) non-dominant/strabismic eye (NDE), and with (3) both eyes closed (EC). Subjects were looking at X located at the distance of 150 cm. Generally, BVD group showed elevated body balance during quiet stance compared to NBV group. Interestingly, better stabilization in BVD group occurred under NDE viewing. Surprisingly, additional mental task improved the postural stability in BVD group almost to the level of NBV group. These findings emphasize the role of the eye-muscle signals in postural control and suggest that suitable vision therapy can be the appropriate way to improve body balance/motor functions in people with binocular vision disorders.

Factors related to strabismus decompensation after a period of prolonged postoperative stability

To identify factors associated with late decompensation of horizontal strabismus after a period of prolonged (>12 months) postoperative stability. Charts from all pediatric horizontal strabismus surgical cases from 1999 to 2009 were reviewed. Patients with a distance or near alignment of <10(Δ) at the first visit >12 months following surgery were included. The primary outcome was time from surgery to strabismus decompensation. Multiple variables were analyzed using the Cox proportional hazards model. A total of 185 cases were included. Mean age at surgery was 5.1 years and mean follow-up was 62.2 months. Late decompensation rate was 31%; of these, 54% underwent reoperation. Using two different models, a higher risk of decompensation was associated with both the presence of preoperative oblique dysfunction (P = 0.023/0.002) and larger distance/near deviations at the first >12 months postoperative visit (P = 0.033/0.012). Worsening of alignment >12 months after horizontal strabismus surgery occurs in almost one-third of patients. Preoperative oblique dysfunction is associated with long-term instability, possibly because it is a surrogate for sensory torsion and poor fusion. Additionally, larger distance and near deviations at >12 months after surgery were each associated with late decompensation. The rate of decompensation for patients with deviations of 0(Δ) to <4(Δ) was less than those with deviations of 4(Δ) to <8(Δ) and >8(Δ), suggesting that the biologic behavior of all deviations within the monofixation range (0(Δ) to 8(Δ)) is not uniform.

Surgery for Complete Vertical Rectus Paralysis Combined with Horizontal Strabismus

Aims. To report outcomes of the simultaneous surgical correction of vertical rectus paralysis combined with moderate-to-large angle horizontal strabismus. Methods. If a preoperative forced duction test was positive, antagonist muscle weakening surgery was performed, and then augmented partial rectus muscle transposition (APRMT) + partial horizontal rectus recession-resection was performed 2 months later. If a preoperative forced duction test was negative, APRMT + partial horizontal rectus recession-resection was performed. Antagonistic muscle weakening surgery and/or conventional recession-resection of the horizontal and/or vertical muscles of the contralateral eye was performed 2 months later, as needed. Results. Ten patients with a mean age of 22.3 ± 13.0 years were included and mean follow-up was 7.1 months. The mean vertical deviation that APRMT corrected was 21.4 ± 3.7 PD (prism diopter). The absolute deviation in horizontal significantly decreased from a preoperative value of 48.5 ± 27.4 PD to a value of 3.0 ± 2.3 PD 6 months postoperatively. The movement score decreased from a value of −5 ± 0 preoperatively to a value of −2.7 ± 0.8 at 6 months postoperatively. Conclusion. For patients with complete vertical rectus paralysis combined with a moderate- to-large angle of horizontal strabismus, combined APRMT and partial horizontal rectus recession-resection is safe and effective for correcting vertical and horizontal strabismus.

Resident and Fellow Participation in Strabismus Surgery

To investigate the effect of the level of training and number of assistants on operative time for uncomplicated, 2-muscle, horizontal strabismus surgery at an academic institution. Comparative case series. A total of 993 children and adults between the ages of 6 months and 75 years. Retrospective chart review of strabismus surgeries performed between July 1, 2008, and December 31, 2012, by any of 3 attending surgeons assisted by a resident in the postgraduate year 3 (PGY3), fellow in the postgraduate year 5 (PGY5), or both. Operative time (minutes) and associated operative cost (dollars). There were 373 cases with 1 assistant and 44 cases with 2 assistants. Of all cases with 1 assistant, there were 200 cases with a PGY3 assistant an average operative time of 62.5 minutes (standard deviation [SD], 15.1) and 173 cases with a PGY5 assistant an average operative time of 59.0 minutes (SD, 14.7); the difference of 3.5 minutes was statistically significant (P = 0.02). The average operative time for all cases with 2 assistants (both PGY3 and PGY5) was 10.6 minutes longer than all cases with 1 assistant (P = 0.0002). No statistically significant variation in operative times was demonstrated when comparing cases with a PGY3 (P = 0.29) and PGY5 (P = 0.44) assistant in their respective first and last halves of the academic year, but operative times within individual quarters of the academic year were significant for PGY3 (P = 0.03) but not for PGY5 (P = 0.24) assistant cases. Operative times were significantly different for individual PGY3 (P = 0.03) but not PGY5 (P = 0.22) assistant cases. Cost per PGY3 assistant per year for additional operative time is $3141.95. Operative time in strabismus surgery increased with PGY3 participation and further increased with both assistants over either assistant alone. Operative times earlier in the year did not vary from those later in the year for PGY3 or PGY5 assistants. The difference in quarterly and individual PGY3 but not PGY5 assistant operative times suggests that efficiency in strabismus surgery varies by assistants with less experience or interest.

Botulinum Toxin as a Postoperative Diplopia Test – It Can Also Reduce the Angle of Deviation Prior to Surgery

Purpose: To investigate how frequently botulinum toxin, when used as a postoperative diplopia test, reduces the angle of deviation prior to subsequent strabismus surgery.Methods: A retrospective study of 39 adult patients with constant concomitant horizontal strabismus who had undergone botulinum toxin injections to assess the risk of postoperative diplopia and then subsequently underwent strabismus surgery.Results: Fourteen out of 39 patients (36%) sustained a reduction of 15 prism diopters or more for near and/or distance when comparing the pre-injection angle of deviation with the preoperative angle of deviation.Conclusion: Approximately one-third of patients receiving botulinum toxin as a postoperative diplopia test maintained a significant reduction in the angle of their deviation prior to undergoing surgery.