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Objective To study the long-term efficacy and the complications of several transposition techniques for the treatment of Duane syndrome. These included, full vertical rectus transposition, partial vertical rectus transposition, transposition without muscle disinsertion, and superior rectus transposition. Material and methods A retrospective study of the patients diagnosed with Duane syndrome, and who underwent any of the different transposition techniques associated or not to the medial rectus recession with a follow-up longer than 12 months. A good result was considered a final deviation ≤10 prism dioptres (pd) in primary position, anomalous head posture Results Seven cases were included (6 women, 6 unilateral), and a mean age of 37.71 years. Pre-operative central gaze esotropia of 28 ± 11.68 pd decreased to 6 ± 4.62 pd at the final visit (p = .009). The anomalous head posture decreased in 6 patients, and the abduction improved one degree from −3.14 to −2.14 (mean). An induced vertical deviation ≤8 pd was observed in 4 cases. None experienced diplopia at the final visit. The percentage of reoperations was 71.42%. Only 28.57% had a favourable outcome with a single surgery, which increased to 71.42% with further surgeries at the final follow-up. Mean evolution time was 52 ± 31.65 months. Conclusion Vertical rectus transpositions in DS with moderate or severe clinical signs have only been effective in a small percentage of the cases. Most of them required further surgeries to resolve the complications or the under-corrections.

Background/Objective: To evaluate the success of combining ipsilateral inferior and superior oblique muscle surgery in young children with congenital unilateral superior oblique under action who present in infancy with a large socially noticeable head-tilt. Methods: A consecutive retrospective case series of young children was analysed. The success of surgery in eliminating the head-tilt was evaluated by pre- and postoperative ocular motility assessment focusing on the vertical misalignment in primary position and downgaze, the magnitude of the head-tilt in degrees and the status of the superior oblique tendon. Results: Five children had a mean age at first surgery of 41 (range 25–63) months, a mean primary position vertical deviation of 26 (25–30) prism dioptres, a head-tilt of 30 (20–35) degrees and a mean post-operative follow up of 24 (8–43) months. While there was a uniform surgical plan, nonetheless each operation required individualisation based on a spectrum of per-operative superior oblique tendon findings. The head tilt was eliminated in 40% and reduced in the remainder, to a mean of 7 (0–18) degrees and with a mean post-operative primary position vertical misalignment of 3 (range 0–10) and of 10 (range 0–40) prism dioptres in downgaze. Conclusion: Combined, ipsilateral oblique muscle surgery reduced the severe head tilt and primary position alignment to a psychosocially and functionally acceptable level. For the majority, the outcome was stable or associated with further decremental improvement. A persistent downgaze vertical tropia occurred in children with macroscopically abnormal superior oblique tendons but these cases were not identifiable clinically pre-operatively.

Objective To evaluate outcomes of surgery for vertical strabismus in thyroid eye disease (TED) employing a set of surgical principles aimed at avoiding reversal of downgaze deviation while restoring binocular single vision (BSV). Methods A retrospective review of consecutive patients undergoing vertical strabismus surgery for TED using a set of surgical principles between 2008 and 2017. Principle outcome measure was the presence of BSV in primary position and downgaze 3 months postoperatively and at latest follow-up. Results Thirty five patients (29% male) with a mean age of 58 years (range 31-83 years) were included. Median follow-up was 16 months. At presentation, 17 (49%) used monocular occlusion to avoid diplopia; the remainder used a prism and/or abnormal head posture. In 12 (34%), combined horizontal and vertical muscle surgery was required. Median (inter-quartile range) preoperative vertical deviations in primary position and downgaze respectively were 20 prism dioptres (Δ) (15, 30) and 18Δ (8, 22), which improved to 1Δ (0, 3) and 1Δ (0, 3) after the first operation. BSV in primary position and downgaze, without prism, after a single surgery was achieved in 29 (83%). Second surgery was required in 5 (14%) and one patient who had reactivation of her TED required a third surgery. At final follow-up (median 16 months), 32 (91%) were diplopia free without prisms; 3 (9%) used a small prism correction (range 2-12Δ); no patients were left with intractable diplopia. Conclusions Our management principles are characterised by prioritising downgaze alignment to avoid downgaze diplopia reversal, whilst limiting adjustable sutures and employing standard surgical dosing. They give favourable outcomes in TED associated vertical strabismus.

Background/AimsTo compare the long-term surgical outcomes between unilateral lateral rectus recession-medial rectus resection (RR) and lateral rectus recession-medial rectus plication (RP) in children with intermittent exotropia.MethodsChildren who underwent RR or RP for intermittent exotropia between January 2008 and July 2016, with a minimum follow-up period of 2 years were retrospectively reviewed. Postoperative angle of deviations and clinical factors including sex, age, refractive errors, preoperative angle of deviation, types of exotropia and stereopsis were investigated. Based on the angle of deviation at year 2, surgical outcomes were classified into two groups as follows: success (esodeviation ≤5 prism dioptres (PD) to exodeviation ≤10 PD) and failure (overcorrection (esodeviation >5 PD) and undercorrection or recurrence (exodeviation >10 PD)).ResultsOf the 186 patients, 114 underwent RR and 72 underwent RP. The angle of exodeviation steadily increased over time in both groups after surgery. The durations of exodrift were longer in the RP group than in the RR group. The surgical success at postoperative year 2 was 55.3% in the RR group and 27.8% in the RP group (pConclusionsIn children with intermittent exotropia, RR group presented better surgical outcomes than RP group. The amount of initial overcorrection was important to achieve favourable outcomes in children with intermittent exotropia.

Aim: To compare the effect of induced vertical diplopia (small and large separation) on reading speed and accuracy.\ud Method: The Radner Reading Chart (RRC) was used to measure reading speed (correct words per minute (wpm)) and accuracy (percentage). Accuracy was measured using two different methods: ‘accuracy-omission’ where only the omission of a word reduced the score, and ‘accuracy-addition and omission’ where any error reduced the score. Three viewing conditions were created using Fresnel prisms on plano glasses: a control condition without diplopia (6 prism dioptres (Δ) base up (BU) over each eye), small separation vertical diplopia (3Δ BU right eye and 3Δ base down (BD) left eye) and large separation vertical diplopia (6Δ BU right eye and 6Δ BD left eye). Viewing conditions were counterbalanced to minimise order effects.\ud Results: Twenty-four participants were included with a mean age of 20.1 years. The mean reading speed in the control condition was 156.90 wpm. Both diplopic conditions significantly reduced the reading speed compared to the control condition, small separation diplopia to 62.75 wpm (p < 0.001) and large separation diplopia to 105.71 wpm (p < 0.001). The mean reading speed with small separation diplopia was significantly slower than the mean reading speed with large separation diplopia (p < 0.01). Median accuracy scores in the control and the large separation diplopia conditions were 100% using both methods of measuring accuracy. The small separation diplopia condition significantly reduced accuracy to 92.86% (accuracy-omission method) and to 57.50% (accuracy-addition and omission method) compared to the control condition (p < 0.01) and the large separation diplopia condition (p < 0.05).\ud Conclusion: When vertical diplopia was induced using Fresnel prisms, diplopia of smaller separation resulted in the greatest reduction in reading speed and accuracy, compared to without diplopia and large separation diplopia.

PURPOSE: To compare botulinum neurotoxin (BNT) injections to surgery as first-line therapy in large-angle essential infantile esotropia (IE). PATIENTS AND METHODS: Children between the ages 6 months and 6 years with IE of ≥40 prism dioptres (PD) were randomised to either a maximum of three BNT injections or surgical intervention of bimedial rectus muscle recession for angles ≤60 PD and augmented with BNT injection in angles >60 PD. Time taken for each procedure was documented. Orthophoria or misalignment of ≤10 PD was regarded as a complete response (CR). Follow-up visits were done at 3, 6, 12 and 24 weeks. RESULTS: Mean (SD) age and baseline angle of esotropia were 26.9 (14.5) months and 61.9 PD (12.8), respectively, for the overall cohort. The proportion of children who achieved CR was significantly higher in the surgery arm compared to the BNT injection arm (OR = 4.01, 95% CI 1.74–9.22) but the time taken was six times longer (p 24 months achieved CR. In children with esotropia ≤60 PD, CR was achieved in 50% while those with esotropia >60 PD CR was achieved in 25%. CONCLUSION: Surgery remains the gold standard for treatment of esotropia but BNT injection is a safe and effective alternative in children ≤24 m and with smaller angles of esotropia ≤60 PD in resource-limited centres.

Background To determine whether a sense of deviation remains in adults with successful motor alignment who fulfil diplopia criteria after surgery and to examine the factors associated with this judgement. Methods This was a retrospective study. Adult patients defined as having a successful outcome based on more than 1 year of post-operative follow-up visits were included in the study. The sense of deviation was determined at the last visit. Pre- and post-operative deviation and characteristics including age, gender, education level, occupation, diagnosis, size of deviation, extraocular movement (EOM), binocular function, and health-related quality of life (HRQOL) were recorded. Results In total, 22 (24%) of the 91 adults with successful surgical outcomes reported a sense of deviation. No significant differences were noted between subjects with and without a sense of deviation regarding patient demographics, pre- and post-operative deviation, changes in deviation, sensory fusion or EOM. Subjects with a sense of deviation had an increased prevalence of and larger post-operative vertical deviation, poorer stereo function, and lower HRQOL scores than those with no sense of deviation. The presence of post-operative vertical deviation was associated with a sense of deviation. Conclusions Approximately one-fourth (24%) of adults defined as having successful surgical outcomes who still had a sense of deviation exhibited worse stereo function, higher vertical deviation size and lower HRQOL scores. The presence of 3 to 5 prism dioptres(pd) of vertical deviation would be the main factor associated with a sense of deviation post-operatively.

ObjectiveTo compare the cost implications of botulinum neurotoxin (BNT) injection to surgery in infantile esotropia (IE) in a public/government funded hospital.Methods and analysisA simple costing comparison was undertaken for a randomised clinical trial in IE. Patients were randomised to receive either BNT or standard surgery. The participants in the BNT arm were further subdivided into subgroups based on their age in months and degree of esotropia in prism dioptres (PD) at presentation: G1 ≤60 PD/24 months, G2 ≤24 months/>60 PD, G3 >24 months/≤60 PD, G4 >24 months/>60 PD. The costs were calculated for each arm from primary treatment to eventual satisfactory outcome defined as orthophoria or microtropia (≤10 PD). A bottom-up costing analysis was done for single and multiple procedures for each arm. Comprehensive variable costs as well as fixed costs were calculated at each point of intervention and expressed in local currency ZAR (US$1=ZAR15.00). Costing was analysed for surgery and BNT subgroups (based on clinical success)ResultsThere were 101 patients enrolled in the trial. 54 in the BNT arm and 47 in the surgery arm. Cost for single surgery and single BNT was ZAR 7743.04 and 1713.14, respectively. A favourable clinical outcome was achieved in 72% of surgery arm and 37% of BNT arm. The mean cost for eventual favourable outcome in BNT arm was ZAR9158.08 and in surgery arm ZAR9124.27 (p=0.26). Mean cost in G1 was ZAR6328.45, in G2 ZAR7197.45, in G3 ZAR11891.93 and G4 ZAR12882.44 (p=0.018).ConclusionBNT has a cost–benefit in IE and is a viable option in the primary treatment of IE in resource constrained regions. Clinical outcomes and economic benefit in smaller angle of esotropia and younger patients are comparable to surgery.

The information about superior rectus (SR) recession in cases with SR contracture coexisting with superior oblique palsy (SOP) is very limited in previous literature. The aim of this study is to evaluate the effect of SR recession, as a combined procedure with inferior oblique (IO) disinsertion, in long-standing SOP with secondary SR contracture.The medical records of the 145 patients operated for SOP were retrospectively reviewed and 15 patients who underwent SR recession met the inclusion criteria. The mean follow-up was 50.4 months.The preoperative angle of deviation was within the range of 16-35 prism dioptres (PD) with a mean of 23.0 ± 5.03 PD. In all of the cases, SR recession was performed in combination with IO disinsertion. Adult patients (12) underwent adjustable SR recession. Postoperative overcorrection developed in 3 cases (20%), and in 12 patients, the postoperative vertical deviation was within the range of 0-5 PD with a mean of 1.41 ± 1.88 PD. The overcorrected three patients underwent botulinum toxin A (BTXA) injection into the ipsilateral inferior rectus muscle. The deviation is well controlled by BTXA injection in two patients, whereas the other one was considered as masked bilateral SOP and underwent IO disinsertion in the other eye.Our results suggested that SR recession in combination with IO disinsertion is an effective procedure to control large vertical deviations in SOP with SR contracture in the majority of cases. However, the risk of overcorrection should be considered despite adjustable SR weakening and BTXA injection seems efficient to rescue overcorrections in long term.

To evaluate the role of achieving immediate target angles on the success of strabismus surgery.We performed a retrospective cohort study of all patients over 12 years old undergoing strabismus surgery with either adjustable or non-adjustable sutures. Target angle for patients with esotropia and vertical deviation was within 4 prism dioptres (PD) of orthotropia and for patients with exotropia between orthotropia and 8 PD of esotropia. Success was defined as alignment within 10 PD for horizontal rectus surgery and within 5 PD of orthotropia for vertical rectus surgery, without diplopia or reoperations. The main outcome measure was surgical success rate.Three hundred and fifty-three patients were included in the study with mean follow-up of 13.9 (4-132) months. Patients achieving the target angle immediately postoperatively had higher success rate than patients who did not (83.6% vs 63.7%, p0.0001, OR 2.9, 95% CI 1.8 to 4.9). When target angle was achieved, adjustable and non-adjustable sutures had similar success (84.8% and 80.9%, respectively, p=0.46, OR 1.3, CI 0.58 to 2.9). However, patients undergoing adjustable surgery were more likely to obtain the target angle (75.5% vs 54%, p0.0001, OR 2.7, CI 1.7 to 4.2). Success for exotropia surgery was significantly higher when the immediate target angle was achieved (86.4% vs 58.7%, p0.0001, OR 4.47, CI 2.3 to 8.6). For esotropia and vertical deviations, a similar beneficial effect was not shown (p=0.31, OR 1.6, CI 0.65 to 4.0 and p=0.33, respectively). On multiple logistic regressions, sex, amblyopia, binocularity and reoperations were not significant factors in surgical success.Our results suggest that achieving the immediate target angle is the most significant factor in the success of strabismus surgery for exotropia. Adjustable suture surgery results in higher proportion of patients achieving this target angle.

Few reports have discussed long-term outcomes of muscle transposition procedures. In this study, cases with abducens palsy treated with a muscle transposition procedure were followed for 12, 25, or 26 years. The preoperative alignments were esotropia of 65 degrees, 47 prism dioptres (PD), and 24 PD, respectively. Orthophoria was postoperatively achieved in all cases. The postoperative alignment in one case deteriorated at 8 years postoperatively, although orthophoria were maintained in the other two cases. These findings indicate that it is possible that esotropia can recur even though orthophoria was maintained for several years postoperatively in some cases that underwent a muscle transposition procedure.

Strabismus from third nerve palsy (3NP) is difficult to treat. Our goal was to explore factors associated with successful surgical outcomes in 3NP. Institutional records of all adult patients (>18 years) from 1988 to 2012 with 3NP who underwent strabismus surgery or botulinum toxin injections were retrospectively reviewed. Success was defined as absence of diplopia, vertical deviation ≤2 prism dioptres (PD), and horizontal deviation ≤10 PD. Fifty-six patients from four surgeons were included. Thirty (54%) were female; mean age was 48 (range: 20–80). Forty-four (79%) had unilateral 3NP; 9 (16%) had other ocular motor nerve palsies. 3NP were complete in 24 (43%). Underlying aetiology was idiopathic/microvascular in 5 (9%), traumatic in 13 (23%), neoplastic in 12 (21%), aneurysmal in 10 (18%), and other central nervous system related in 16 (29%). Trauma was associated more frequently with aberrant regeneration than other aetiologies: 9/13 (69%) versus 4/43 (9%) (p 1 surgery. Surgical success was achieved in 28/56 (50%). Success rate was unaffected by aetiology, degree of palsy, pupillary involvement, presence of aberrant regeneration, or number of other cranial nerves involved. However, adjustable sutures were used in 27 patients (48%), and there was a trend toward higher success rates when adjustable versus nonadjustable sutures were used (63% versus 38%; p = 0.06). Unlike with sixth nerve palsies, the aetiology and degree of 3NP does not appear to affect the success rates or number of procedures performed. Strabismus surgeries for 3NP with adjustable sutures may be associated with better outcomes.

Aim To evaluate safety profile and surgical outcomes of a novel modification of loop myopexy with silicone band for myopic strabismus fixus (MSF). Design Retrospective interventional case series. Methods A retrospective chart review of patients who underwent silicone band loop myopexy between January 2008 and December 2012 for MSF at a tertiary eye care centre was undertaken. A minimum of 2 months of follow-up after surgery was required for inclusion. Patients who underwent conventional suture loop myopexy and cases with incomplete details pertaining to the preoperative alignment and movement restriction were excluded. The main outcome measures were improvement in alignment postoperatively, improvement in extra-ocular motility postoperatively, and intraoperative and postoperative complications. Results 26 eyes of 15 patients (male (9):female (6)=1.5:1) underwent silicone band loop myopexy at a mean age of 27.8±16.4 years (range 7–72 years). Mean follow-up was 7.9±8.4 months (range 2–28 months, and median 4 months). 11 patients underwent bilateral loop myopexy whereas four patients underwent unilateral loop myopexy. 16 eyes underwent additional medial rectus (MR) recession. At the last follow-up, mean abduction limitation improved to −1.5±1.3 from −2.9±1.2, p=0.0000; mean elevation limitation improved to −1.2±0.9 from −2.8±1.1, p=0.0000; mean esotropia improved to 16.9±17.4 prism dioptres (PD) from 79.3±32.3PD, p=0.0000; and success (deviation ≤20PD) was achieved in 73% (95% CI 48 to 89%). Mean hypotropia at presentation was 8.9±10.1PD (range 0–25PD), which improved to 0.6±1.3PD (range 0–4PD), p=0.007. Conclusions Modified scleral fixated silicone band loop myopexy with or without MR recession is a safe and effective procedure in the management of MSF and improves alignment significantly.

To evaluate the outcomes following surgery on patients with bilateral Duane's Retraction Syndrome (DRS) associated with exotropia or exophoria.Eleven consecutive patients with exotropic DRS were identified in a 10-year period. The case notes were reviewed, and data was analysed to evaluate the results following surgery. The preoperative and postoperative outcomes were evaluated for the angle of deviation in primary position, abnormal head posture, stereovision for near-fixation and horizontal ocular ductions.All patients had a significant improvement in their angle of deviation in primary position, and 82% had a residual angle within 10 prism dioptres of orthotropia/phoria (p0.001). For those patients with abnormal head posture, 86% resolved or improved. The postoperative cumulative horizontal ocular ductions measured less in nine patients by an average of 1.5 units. Pre-existing near-stereovision improved in 83% of the patients by an average of 40″ arc.Surgery for bilateral exotropic DRS resulted in an improvement in the primary position angle and abnormal head posture. Patients demonstrated reduced cumulative horizontal ocular ductions restrictions and enhanced near-stereovision. This case series on exotropic bilateral DRS provides further evidence into successful postoperative surgical and functional outcomes.

Purpose To describe surgical outcomes in intermittent exotropia (X(T)), and to relate these to preoperative and surgical characteristics. Methods 87 children (aged Results 35% of patients had excellent, 28% had fair and 37% had poor primary outcome. Preoperative and surgical characteristics did not influence primary outcome. Satisfactory control was achieved in 65% of patients, while X(T) remained/recurred in 20%. Persistent over-correction occurred in 15% of children. There was no relationship between over-correction and preoperative characteristics or surgical dose/type. Median angle improved by 12 prism dioptres (PD) at near and 19 PD at distance (p Conclusions Whilst excellent motor/sensory outcome was achieved in one-third and satisfactory control in two-thirds of patients, the 37% poor outcome and 15% persistent over-correction rate is of concern. Surgical dose was similar in those under- and over-corrected, suggesting that over-corrections cannot be avoided merely by getting the dosage right: a randomised controlled trial (RCT) would shed light on this issue. Initial over-correction did not improve the chance of a good outcome, supporting the growing literature on this topic and further highlighting the need for randomised controlled trials of X(T) surgery.

Objective: The study’s aims were to evaluate the success of bimedial rectus recession as a primary surgical procedure for patients with congenital esotropia; describe the demographic data of the study group; and compare surgical success with patient age at the time of surgery. Method: A retrospective review of 52 patients with congenital esotropia ≥ 50∆ (prism dioptres) was conducted. All patients underwent bimedial rectus recession and were followed-up postoperatively for a minimum of 6 months. Results: The study period was from January 1992 to September 2003. Fifty-two patients were included in the study group. The pre-operative angle of deviation ranged from 50∆–85∆. Patient ages ranged from 15 months to 22 years, with a mean of 5.3 years and a median of 4 years. The gender distribution was 42% male ( n = 20) and 58% female ( n = 28). Surgery was successful (within 10∆ of orthophoria) in 77% ( n = 40), a partial success (10∆–20∆ from orthophoria) in 17% ( n = 9) and a failure (> 20∆ from orthophoria) in 6% ( n = 3). No statistically significant relationship was found between surgical success and patient age at the time of surgery. Conclusion: The study confirmed that bilateral medial rectus recession, performed as a primary procedure for patients with large-angle (> 50∆) congenital esotropia, has a high success rate. This finding corresponds with the outcomes of similar international studies.

Purpose. To evaluate the surgical outcomes of unilateral or bilateral medial rectus (MR) muscle resection for recurrent exotropia after bilateral lateral rectus (BLR) muscle recession based on a novel surgical formula.Methods. Forty-one consecutive patients with unilateral or bilateral MR muscle resection for recurrent exotropia after BLR muscle recession were included in this retrospective study. All surgeries were performed according to the formula: 1.0 mm MR muscle resection for every 5 prism dioptres (PD) of exotropia, with an addition of 0.5 mm to each MR muscle operated on.Results. The mean recurrent exotropia distant deviation was 28 PD ± 11.2 (range 14 to 55 PD). Overall at postoperative 1 month, 36 (88%) achieved successful outcomes, 4 (10%) had undercorrection, and 1 (2%) had overcorrection. At postoperative 6 months, 29 (71%) achieved successful outcomes, 12 (29%) had undercorrection, and none had overcorrection. Subgroup analysis showed no statistically significant difference in success rates between unilateral and bilateral MR groups.Conclusion. Unilateral or bilateral MR muscle resection using our surgical formula is a safe and effective method for calculating the amount of MR resection in moderate to large angle recurrent exotropia, with a low overcorrection rate.

To identify the best treatment option for intermittent exotropia.A retrospective analysis of the progress of 150 treated intermittent exotropia patients was performed. Treatment forms considered are: (i) surgery combined with orthoptic/occlusion therapy; (ii) surgery; (iii) orthoptic/occlusion therapy; and (iv) observation. Pearson's chi(2)-analysis of association of therapy form with success was performed. Reduction of exodeviation in prism dioptres between groups and subgroups were compared at 6 months, 1, 2 and 5 years follow up and the "within group" variations were compared. Exodeviation reduction in prism dioptres per millimetre of horizontal rectus surgery performed in the "surgery with orthoptic/occlusion therapy" and "surgery only" groups were compared.Chi(2)-analysis revealed a significantly highest (P0.001) association with success in the "surgery with orthoptic/occlusion therapy" group at follow up. ANOVA analysis revealed that surgery with orthoptic/occlusion therapy resulted significantly (P0.001) in the highest reduction of exodeviation as compared with the other three treatment modalities at each follow up. Reduction of exodeviation in prism dioptres per millimetre of horizontal rectus surgery performed was significantly higher (P0.05) in the surgery with orthoptic/occlusion therapy group as compared with surgery only at all follow ups. Chi(2)-test revealed no significant association of success with the magnitude of initial exodeviation (P0.05).Surgery with preoperative orthoptic/occlusion therapy had the highest success rates. Surgery with orthoptic/occlusion therapy was more effective in reducing exodeviation (prism dioptres per millimetre of horizontal rectus surgery), compared with surgery only.

A retrospective review of the Toxin Clinic database was carried out over an 18-year period. We identified 68 patients with esotropia of 20 prism dioptres and under who were treated with Botulinum toxin. There were 47 females and 21 males, with a mean age of 34 years (range 11-78 years). Thirty-two (47%) patients had residual esotropia, 20 (29%) had primary esotropia, 11 (16%) had consecutive esotropia, 4 (6%) had secondary esotropia and 1 (1.5%) had a decompensating esophoria. The mean pre-toxin angle was 16 prism dioptres (range 6-20). A total of 434 injections were given, with an average of 6 per patient (range 1-36). Forty-five (66%) patients underwent continued toxin treatment with an interval of 3 to 31 months. Thirteen (19%) patients achieved long-term benefit from only one injection. Seven were unable to demonstrate binocular vision pre-injection but demonstrated it post-injection. Following an initial injection, nine (13%) patients proceeded to surgery. Botulinum toxin was a successful treatment for these patients and was well tolerated, with no side effects. It appears to have a definite role in the treatment of small-angle esotropia.

A 12-year-old boy was evaluated in our emergency services for complaints of diplopia and mild generalised headache since past 4 days. The patient was a known case of frequently relapsing idiopathic nephrotic syndrome and was currently in remission since 5 days. He was normal and oriented on general physical and systemic examination. Urine microscopy had revealed only traces of protein on repeated evaluation, and serum albumin was 2.2 g/dL on presentation. Visual acuity was 6/6 in both eyes, and the pupillary reflexes were brisk. The ocular motility examination revealed an esotropia of 20 prism dioptres (figure 1A) along with limitation of the abduction movements in both eyes (figure 1B,C). However, right eye showed a …

To compare prospectively the surgical outcomes of different surgery procedures for convergence insufficiency (CI)-type intermittent exotropia (IXT) in children.Forty-five children with CI-type IXT were included in this prospective surgical study with 6 months follow-up. According to the different surgical procedures, all children were randomly divided into three groups: the unilateral medial rectus resection (UMR) group (15 cases), the bilateral medial rectus resections (BMR) group (14 cases) and the improved unilateral recession-resection (RR) group (16 cases). In the UMR and BMR groups, the medial rectus resection(s) were based on the distance exodeviation. In the RR group, UMR was based on the near exodeviation while lateral rectus recession was based on the distance exodeviation. A successful surgical alignment was defined as the distant deviation in the primary gaze to be between ≤ 10 prism dioptres (PD) of exophoria/tropia and ≤ 5 PD of esophoria/tropia. The success rate, the preoperative and postoperative deviations at distance and near and near-distance differences among groups were compared.At the last follow-up of 6 months, the success rate in the RR (87.5%) group was significantly higher than those in the UMR (13.3%) and BMR (42.9%) groups (p=0.000 and 0.008); the mean exodeviations at distance and near in the RR group were significantly different from those in the UMR and BMR groups (p=0.000 and 0.001); there were no significant differences in the mean near-distance differences between the RR group and the other two groups (p0.05).The improved RR procedure in which medial rectus resection based on the near deviation with lateral rectus recession based on the distant deviation has a better alignment than the UMR and BMR surgeries for the treatment of children with CI-type IXT. All the UMR, BMR and improved RR surgery can reduce near-distance differences in children with CI-type IXT.

Background We aimed to determine the impact of the preoperative prism adaptation test (PAT) on surgical outcomes in patients with primary exotropia. Methods Thirty-eight consecutive patients with primary exotropia were enrolled. Pre-operative PAT was performed in 18 randomly selected patients (Group 1). Surgery was based on the angle of deviation at distance measured after PAT. The remaining 20 patients in whom PAT was not performed comprised Group 2. Surgery was based on the angle of deviation at distance in these patients. Surgical success was defined as ocular alignment within eight prism dioptres (PD) of orthophoria. Results Satisfactory motor alignment (± 8 PD) was achieved in 16 Group 1 patients (88.9 per cent) and 16 Group 2 patients (80 per cent) one year after surgery (p = 0.6; chi-square test). There were no statistically significant differences in demographic parameters, pre-operative and post-operative angle of deviation between the two groups (p > 0.05; Mann-Whitney U and chi-square tests). Nine patients in Group 1 (50 per cent) and two patients in Group 2 (10 per cent) had increased binocular vision one year post-operatively. A statistically significant difference was determined in terms of change in binocular single vision between the two groups (p = 0.01; chi-square test). Conclusion Although the prism adaptation test did not lead to a significant increment in motor success, it may be helpful in achieving a more favourable functional surgical outcome in patients with primary exotropia.

To compare surgical outcomes between preterm and full-term patients with infantile-onset esotropia.This study included 56 preterm and 162 full-term patients with infantile-onset esotropia who underwent strabismus surgery. The extent of surgery was reduced by 0.5 mm per muscle in preterm patients who were born at30 weeks of gestation. Surgical outcomes over time, including surgical success, overcorrection rate, undercorrection rate and surgical dose-response were compared between preterm and full-term patients.The Cox proportional hazards regression model and competing risk analysis showed no statistically significant differences in the rate of surgical success or undercorrection over time between preterm and full-term patients. However, the final overcorrection rate was greater in preterm children than in full-term children (p=0.019). The average surgical dose-response was 3.99 prism dioptres (PD)/mm in full-term children and 4.40 PD/mm in preterm children.The results of this study showed a favourable outcome using a mildly reduced amount of surgery in preterm patients with infantile-onset esotropia. Surgical dose-response was significantly greater in preterm patients than in full-term patients.

The effect of conventional CR39 and Fresnel prisms on high and low contrast letter acuity was studied. Visual acuity of the fully corrected better eyes of 15 subjects was measured with the high (90%) and low (10%) contrast logMAR letter charts, while they wore prisms of varying power. The results showed that when the power of the conventional CR39 prism and the Fresnel prism reached 10 prism dioptres and 5 prism dioptres, respectively, significant reduction (1 tail t-test, p < 0.05) of the high and low contrast acuity occurred. The Fresnel prism caused a significantly greater acuity reduction than the conventional CR39 prism for powers ranging from 5 to 30 prism dioptres for both contrasts. The rate of acuity reduction with increasing prism power was greater with the low contrast targets than with the high contrast targets for both prisms. In addition, the rate of acuity reduction with increasing prism power was greater with the Fresnel prism than with the conventional CR39 prism for both contrasts. The conventional CR39 prism reduced acuity by a ratio of about 0.8-0.9 of that of the Fresnel prism for powers ranging from 5 to 20 prism dioptres and by about 0.7 for 30 prism dioptres. These ratios applied for both high and low contrast acuity, and therefore were independent of the level of contrast used.

Background: A retrospective study was undertaken to examine the hypothesis that esophoria is associated with higher amounts of myopia. Methods: One hundred and forty-four subjects were selected from the files of optometry clinics at the Department of Optometry, National University of Malaysia, from the years 1995 to 1998 inclusive. These subjects were matched in terms of age group, sex, race and near phoria group. Near phorias were determined by Maddox wing technique and were classified into three groups: more than six prism dioptres exophoria, zero to six prism dioptres exophoria and any esophorias. Results: One way analysis of variance revealed that there were significant differences in mean myopias between the three phoria groups (ANOVA, F(2,141) = 5.34, p < 0.01). Further analysis with the Student-Newman-Keuls test showed that the amount of myopia is significantly higher in the esophoric group than in the other two groups. Conclusions: The results support the hypothesis that near esophoria is associated with high myopia. This study suggests that near phoria might be an important factor in myopia development.

BACKGROUND: Near tasks have been associated with binocular stress to induce myopia. The aim of this study was to investigate the effects of accommodation on reading-induced near heterophoria. METHODS: We measured the near heterophoria of 22 young adults before and after 30 minutes of reading. The reading task comprised a column of local English newsletter studied monocularly at 33 cm. One of three addition lenses (that is, 0.00 D, +1.50 D and +3.00 D) was randomly incorporated into the optical prescription. The difference in near heterophoria between the pre- and post-reading task was recorded. The experiment was completed on separate days for the other lens powers. RESULTS: Reading for 30 minutes with a plano lens addition (control) increased the near heterophoria by 3.81 +/- 0.95 prism dioptres (SEM) toward exo-deviation (p < 0.002). Addition of a +3.00 D lens significantly decreased the reading-induced exophoric shift to 1.36 +/- 0.55 prism dioptres (SEM). Similarly, a +1.50 D lens reduced the exophoric shift to 3.14 +/- 0.85 prism dioptres (SEM) but the difference was not statistically significant when compared with the control. CONCLUSIONS: The results showed that close work might cause eye strain via the extraocular muscles. Incorporation of plus lens into the optical correction caused a power-dependent reduction in the stress, that is, smaller exophoric shift. Whether binocular stress contributes to myopia and its response to addition lens therapy deserve further investigation.

Anteropositioning of inferior oblique is of late becoming popular but it inadvertently also entails a compulsory recession which may be undesirable at times. We have evaluated the effect of a 'pure' anteropositioning procedure (11 eyes), with Elliot & Nankin's anteropositioning (10 eyes) and Parks' recession (17 eyes). The mean change of vertical deviation in elevation in adduction (surso adduction) was 15.09 +/- 8.3 prism dioptres (p.d.) in pure anteropositioning; 23.50 +/- 5.6 p.d. in E & N's anteropositioning and 14.82 +/- 5.9 p.d. in Parks' recession, showing this procedure to be as effective as a conventional recession procedure. However, while the latter two methods produced an intorsion, 'pure' anteropositioning produced no significant change in torsion. It is a much simpler procedure to weaken the elevation without affecting the torsion.

Background: The purposes of this study are to determine the viewing distance with minimum heterophoria and its relationship with refractive error and the resting position of accommodation. Methods: The heterophoria and the accommodation responses of 36 optometry students (25 emmetropes and 11 myopes) were tested. Heterophoria was measured with the Free-Space Heterophoria Card at five different viewing distances (25 cm, 33 cm, 50 cm, 100 cm and 300 cm). The dioptric viewing distance with minimum heterophoria for each individual was estimated from the graph, where heterophoria in prism dioptres was plotted against viewing distance in centimetres. The Canon R-1 autore-fractor was used to determine the accommodation response at six different viewing distances (25 cm, 33 cm, 50 cm, 100 cm, 300 cm and 600 cm). The resting position of accommodation for each individual was estimated from the graph where the accommodative stimulus in dioptres was plotted against the accommodative response in dioptres. Results: The dioptric viewing distance with minimum heterophoria ranges from 0.003 D to 0.65 D in emmetropes and ranges from 0.03 D to 2.36 D in myopes. There is no difference in the dioptric viewing distance with minimum heterophoria between myopes and emmetropes. Our results show a possible but not significant correlation between the dioptric viewing distance with minimum heterophoria and the resting position of accommodation. Conclusions: The viewing distance with minimum heterophoria is not affected by refractive error (stable early-onset myopia) and is poorly correlated with the resting position of accommodation.

BACKGROUND: Clinicians frequently assess the accommodative convergence to accommodation (AC/A) ratio using near phoria measurements and accommodative stimuli. The purpose of this study was to evaluate the repeatability of AC/A ratio measurements and to compare the response AC/A ratio to stimulus AC/A ratios determined two different ways. METHODS: Heterophorias and accommodative responses to different stimuli were measured simultaneously on eight subjects at two visits. A Canon Auto Ref R-1 autorefractor was used to measure accommodative response, while vergence posture was measured using the modified Thorington heterophoria technique. These results were used to calculate response-slope, stimulus-slope and stimulus-gradient AC/A ratios and the means of these ratios for each session were compared. Correlations between the response AC/A ratios and the stimulus AC/A ratios were calculated. RESULTS: The mean response AC/A ratios for the two sessions were 3.8 prism dioptres per dioptre for each session. The correlation between the slope-determined ratios was 0.56, and between the response-slope and the stimulus-gradient AC/A ratios the correlation was -0.03. The regression equation for the slope-determined AC/A ratios was calculated. CONCLUSIONS: Means for the two sessions were not significantly different for any of the AC/A ratios. The response-slope and stimulus-slope AC/A ratios had a moderately significant correlation and a predictive regression equation was determined. The stimulus-gradient AC/A ratios were not correlated with the response-slope AC/A ratios.

Background To compare outcomes following contralateral lateral rectus (LR) recession and recess–resect (RR) procedures for recurrent exotropia of 20–25 prism dioptres (PD) after unilateral RR. Methods 39 subjects were included in this retrospective study. All underwent, as a primary surgery for intermittent exotropia, unilateral RR on the non-dominant eye. They were assigned to the subsequent contralateral LR recession (LR, n=19) or RR (n=20) group for recurrent exotropia of 20–25 PD. Surgical success was defined as alignment between 5 PD esodeviation and 10 PD exodeviation. Results The mean follow-up duration after the reoperation was 32.3±26.4 months in the LR group and 30.5±26.8 in the RR group (p=0.945). The mean deviation angles at postoperative 1 day were −0.7 PD (overcorrection) in the LR group and −4.3 PD in the RR group (p=0.047). The deviation angles at 3 and 6 months postoperatively were not significant (p=0.771, p=0.923). The final successful outcome was achieved in 63.2% of patients in the LR group and in 65% of patients in the RR group (p=0.905). Conclusions Contralateral LR recession was found to be a safe and effective procedure for the treatment of recurrent exotropia of 20–25 PD after unilateral RR for intermittent exotropia. With LR recession, the intentional overcorrection in the immediate postoperative period could be avoided.

To validate a table of amounts of three horizontal muscle surgery in patients with large-angle infantile esotropia (≥60 prism dioptres, PD). A prospective interventional case series reporting the postoperative alignment of 51 patients (27 male, 24 female) over a 15-year period was conducted. Surgery amounts were according to a published table developed on a previous patient cohort (n=49), using bilateral medial rectus recession with graded unilateral lateral rectus resection. Kaplan–Meier life-table survival curves were formulated for success to orthotropia (±10 PD) after one and subsequent horizontal muscle surgeries for up to 8 years follow-up. The median preoperative deviation was 65 PD (range 60–80 PD) and median age at surgery was 11.8 months (range 5.1 months–3.6 years). Surgical success to orthotropia (±10 PD) after one surgery was 100% at 2 months, 95.7% at 6 months, 91.3% at 12 months, 77.8% at 4 years, and 73.6% at 8 years. Postoperative failure requiring further horizontal surgery occurred in 17.6% (residual esotropia 4, consecutive exotropia 5). Our second cohort has reproduced the success rate of the previous cohort (77.8% vs 77.1% at 4 years). If the published table of surgical amounts is used, three horizontal muscle surgery in large-angle infantile esotropia (≥60 PD) appears to have a good long-term success rate, and does not lead to the high rates of either residual esotropia or consecutive exotropia reported by others in the literature.

We determined the vergence position of rest (horizontal component) in two sessions, 1 to 6 weeks apart. Each session contained 8 trials. Twenty observers with normal eyes looked through Risley prisms that allowed a continuous modulation of their strength. We asked the observers to look at a fully fusionable picture, and to adjust the prisms such that viewing appeared most relaxing. The viewing distances were 400 cm and 50 cm.The standard deviation among the 8 trials of each session, averaged over the two sessions, the viewing distances of 400 cm and 50 cm, and the 20 observers, was + or -1.4 prism dioptres (cm/m). From the first session to the second, many observers changed the preferred prism significantly. At a viewing distance of 400 cm, 10 of 20 observers changed their preferred prism by more than 1.0 prism diopter, up to 3.3 prism diopters. At a viewing distance of 50 cm, 11 of 20 observers changed their preferred prism by more than 1.0 prism diopter, up to 5.1 prism diopters.The prismatic strength estimated as being most relaxing can be very variable. Before considering a prescription, the practitioner should determine whether the preferred prismatic strength remains reasonably stable. To ascertain this consistency, more than one session seems to be necessary.

To assess the efficacy of prismatic correction of residual esotropiaor=20 prism dioptres (PD) after full hypermetropic correction in patients with partially accommodative esotropia.Medical records of 64 patients who received prismatic correction for residual esotropia/=20 PD were reviewed. Outcomes were considered successful if patients maintained orthotropia or esophoria for at least 1 year and did not require surgery. Factors including age, sex, visual acuity, refractive errors, amount of deviation, sensory status, and the presence of amblyopia were analysed and compared between the success and failure groups.Prismatic correction was successful in 28 of 64 patients (44%). The success group showed better results both with Worth 4-dot test (P=0.001 at distance and P=0.046 at near) and Randot stereo test (P=0.003 for dots and P=0.000 for animals). Success rate increased to 58% without amblyopia, 72 and 93% with normal fusional response at near and at distance with Worth 4 dot test respectively, and 92% with stereoacuity of 800 s of arc or better. In all patients in success group, fusion and stereoacuity improved or maintained during follow-up.Prismatic correction was successful in 44% of the patients with residual esotropiaor=20 PD and the success group showed an improved or stable sensory status with time. With a baseline fusion on Worth 4-dot test or stereopsis of 800 s of arc or better, prismatic correction could be considered as the first-line treatment.

This report describes a patient who was suffering from incomitant vertical diplopia due to Graves' ophthalmopathy. Previous optical treatment was a diffusing lens for the left eye resulting in monocular vision only. We proceeded to measure the amount of diplopia and prescribed a vertical Fresnel prism to be placed on the left spectacle lens to alleviate his diplopia and resolve his mobility problems. The amount of prism was further reduced by five prism dioptres after extraocular muscle surgery.

An expert system is described for the differential diagnosis of vertical deviation strabismus (squint) from measurements taken in the standard prism cover test. The deviations are represented as optical powers in prism dioptres using the graphic representation of strabismus (after Jampolsky). The expert is implemented in MatLab® (Mathworks Ltd., Cambridge, UK) both as a stand-alone program on a PC and as a web application available over the Internet (see http://www.strabnet.com). In trial and clinical datasets a diagnostic accuracy of 100% was achieved.

The core function of optometrists is the prescribing of refractive corrections, yet a literature review revealed a lack of evidence-based research on criteria for determining when a refractive correction is required. The reported criteria used by practising optometrists were investigated using a questionnaire to survey prescribing habits for borderline hypermetropia, presbyopia, astigmatism, and horizontal and vertical heterophoria. Thirty-eight questionnaires were returned and the results analysed. We calculated the 'cut off' point above which the anomaly would be corrected over 50% of the time that it was encountered. There was a large variation for each category, but it was clear that the presence or absence of symptoms was an important factor for most optometrists when deciding whether to correct a small error. It was found that for symptomatic patients, most optometrists would correct an anomaly if it reached: +1.00 D of hypermetropia, a reading addition of +0.75 D for presbyopia, -0.75 DC of astigmatism, 1.5 prism dioptres (Delta) of horizontal aligning prism, and 1 Delta of vertical dissociated heterophoria. For asymptomatic patients, optometrists would not correct any of the hypermetropic anomalies or heterophorias that were specified in our questionnaire. However most would correct a presbyopic error of +1.50 D or above, or an astigmatic error of -1.50 DC or above, even in the absence of symptoms. These results were compared with previously published guidelines.

Background: Previous studies have found that crossed disparities give better stereoacuity than uncrossed. When near phoria is considered, exophores had a better crossed stereoacuity and esophores had a better uncrossed stereoacuity. The current study investigated the effect of heterophoria on distant crossed and uncrossed stereoacuity. Methods: Seventy-two subjects were recruited and their distant heterophoria measured. Heterophoria within two prism dioptres was considered as orthophoric. Esophoric group had esophoria greater than two prism dioptres. Exophoric group had exophoria greater than two prism dioptres. There were 40 orthophores, 23 exophores and nine esophores. Their stereoacuity was measured with a three-rod apparatus at 6 m. Results: The mean crossed stereoacuity was 4.8″ and uncrossed stereoacuity was 7.2″ (t=−3.03, p

Background: Adjustable suture used for years to improve the outcome of strabismus surgery. We surveyed outcome of our patients with strabismus who underwent adjustable suture. Materials and Methods: This retrospective study was performed at Ophthalmology Centre of Feiz Hospital in Isfahan on 95 participants that candidate for adjustable suture strabismus surgery. Patients were divided into three age groups: Under 10 years, 10-19 years, and 20 years and over. Outcome of adjustable suture surgery consequence of residual postoperative deviation was divided into four groups: Excellent, good, acceptable, and unacceptable. Results: Out of 95 patients studied, 51 (53.7%) were males and 44 (46.3%) were females. The mean of deviation angles were 53.8 ± 17.9 PD (Prism dioptres) in alt XT, 44.5 ± 12 PD in alt ET and 52 ± 13.5 PD in const ET, 47.1 ± 13.1PD in cons XT, respectively. There was no significant difference between the groups ( P = 0.051). Results of surgery were in 38 patients (40%) excellent, in 31 patients (32.6%) good, in 19 patients (20%) acceptable, and in 7 patients (7.4%) unacceptable. Seven (7.4%) patients required reoperation. Conclusions: In the present study, the frequency of re-operation was much lower than other similar studies (7.4% vs. 30-50%). This suggests that the adjustable technique that used in our study can be associated with lower reoperation than other adjustable techniques used in the other similar studies.

AIM To compare the efficacy of reoperation and botulinum toxin injection in treating infantile esotropes early after unsatisfactory surgical alignment. METHODS 55 strabismic children who had been unsuccessfully operated for infantile esotropia were randomised to reoperation (28 patients) or botulinum toxin injection (27 patients). The motor outcomes (percentage of successful motor outcome and percentage change in deviation) were compared at 6 months, 1 year, and 3 years after retreatment, and the sensory outcomes (percentage with fusion ability and stereo perception) at the 3 year follow up visit. RESULTS The motor and sensory outcomes and the stability of motor results were similar in patients reoperated and treated with botulinum injection. At the 3 year visit 67.8% and 59.2% of children were, respectively, within 8 prism dioptres of orthotropia (p=0.72). The frequency of fusion ability was, respectively, 60.7% and 51.8% (p=0.71), and the frequency of stereo perception (⩽400 seconds of arc, Randot circles), 57.1% and 48.1% (p=0.70). The botulinum injection was more likely to be effective when carried out in the 6 months following initial surgery. CONCLUSIONS Botulinum injection is a rapid and less invasive alternative to reoperation in children who have been unsuccessfully treated with surgery to correct infantile esotropia.

Photorefractive keratectomy (PRK) was performed on a 19-year-old man with hyperopic astigmatism end refractive accommodative esotropia, The patient was orthophoric while wearing spectacles, but had an esotropia of 30 prism dioptres at near and distance vision without spectacles, The best corrected visual acuity of the right eye was 20/50 and of the left eye was 20/20, The excessive accommodative convergence of the patient was eliminated by correcting the hyperopic refractive error by performing PRK, and the patient became orthophoric after the treatment.

Sixteen patients with large angle infantile esotropia with deviations of 80-90 prism dioptres were operated at the age of about 2 years. All patients underwent 8 mm bilateral medial rectus recessions. At the last follow up examination, 6 to 48 months postoperatively (average 16.3 months), successful horizontal alignment was achieved in 12 patients (75%). Four patients (25%) were undercorrected. Clinically significant limitation of adduction or convergence was not observed postoperatively in any of the patients. Consecutive exotropia was not encountered in this series but a longer follow up is probably needed in order to assess its delayed appearance. These results suggest that 8 mm recession of the medial recti is an effective procedure for the correction of large angle infantile esotropia of 80-90 prism dioptres and can be considered as an acceptable alternative to operations on three or four muscles.

The measurement of the deviation of strabismus is usually performed by the prism cover test (PCT) and the synoptophore. The corneal reflex test (CRT) (Hirschberg test) has been used as an objective method of determining the angle of deviation. Recent papers (Brodie 1987, Carter & Roth 1978) have re-evaluated the CRT and proposed significantly different ratios (21–22 prism dioptres per millimetre). In strabismus clinics the CRT is frequently used with the patient wearing glasses. However, the corneal reflex test through glasses poses some problems. The reflections from glasses disturb the corneal reflexes. Glasses themselves have prismatic effects. Only one paper has mentioned the CRT through glasses.

Ninety-seven patients with congenital esotropia with deviations of 50 prism dioptres or greater underwent large (6 and 7 mm) bimedial rectus recessions. The overall success rate with one operation was 83.5%. Judgment of final alignment was made at the last follow-up examination, six to 61 months (average 23.4 months) postoperatively. Large bimedial rectus recessions for congenital esotropia are an effective surgical treatment which does not significantly alter adduction.

The monocular and binocular depth thresholds of strabismic subjects have been measured with a modified Howard-Dolman apparatus. Seven out of the 14 strabismic subjects tested were found to have binocular thresholds significantly higher than their monocular ones. These strabismic subjects all had small angles of deviation less than 8 prism dioptres and high acuities in both eyes.

Sixteen patients with moderate angle esotropia of 30 to 35 prism dioptres were treated with a unilateral medial rectus muscle recession of 6 or 6.5 mm. Thirteen of sixteen patients (80%) were straight postoperatively or had 12 prism dioptres or less of esotropia. Three of the 16 had greater than 12 prism dioptres of esotropia, and none were exotropic. This procedure should be considered as an alternative approach in the treatment of moderate angle esotropia.

The author presents a continued study of 82 cases of pseudoparalysis of the bilateral rectus muscles in early-onset convergent strabismus following early surgery. Up to 10 years after surgery motor results show that 72% of cases remain within +/- 10 prism dioptres after a single surgical procedure. Sensorial findings corroborate the results of other authors' studies in that binocular association is only achieved in those patients where surgery was carried out at a very young age, not older than 1 year. Surgical procedures consisting of bimedial rectus recession with retroequatorial myopexy are described and the development of alphabetical syndromes and dissociated vertical divergence discussed. The evolution of refraction in these cases is also shown.

The modified O'Connor cinch operation is a useful, but little used, adjustable resection operation. For increased understanding of its shortening and adjustment characteristics, a standard cinch was performed in animals and patients with strabismus. Animal studies showed that, as each strand of the cinch was removed, a small, relatively equal release of the cinch effect occurred. Measurement of the shortening obtained in patients with strabismus showed a consistent resection effect of about 4 mm. Review of 17 cases in which the cinch was used as part of the surgical treatment showed the technique to be adjustable by reducing the overcorrection in 6 cases. Ten to 20 prism dioptres of reduction in the deviation was obtained with adjustment of the cinch on the first postoperative day. All 17 cases had satisfactory adjustment. The largest residual deviation was 12 prism dioptres.

The success rate of large (6 and 7 mm) bimedial rectus recessions in 45 congenital esotropes with deviations of 50 prism dioptres or greater was found to be 91%. Judgment of final alignment was made six weeks postoperatively, with an average follow-up of 13 months. Large bimedial rectus recessions are an effective surgical treatment for congenital esotropia. This procedure does not significantly alter adduction, and leaves other muscles available should further surgery be necessary. These findings show that initial surgery on three or more muscles is unnecessary in congenital esotropia.

The ability to extract depth from disparity may be hindered under fusional stress, as alignment of the eyes may be more difficult to maintain consistently. Therefore we aim to determine the effect of fusional demand on stereoacuity in individuals with no known binocular vision impairments. A novel static and dynamic binocular depth detection task, capable of assessing many discrete levels of stereoacuity, was presented on digital displays attached to each tube of the Synoptophore. Stereoacuity was measured with any latent deviation fully corrected and compared to that measured at the ‘recovery’ angle. This recovery angle is where single vision is restored after decompensation to diplopia, during vergence range assessment. Seventy-two subjects (50 Female, 22 Male; mean (SD) age 22 (6) years) were assessed. The amount of fusional demand was between 1 and 26 prism dioptres (PD), with a mean (SD) of 8(6)PD. Under zero fusion demand the mean (SD) static and dynamic depth detection thresholds were 322(53)” and 69(23)”. Under fusional stress these were 224(40)” and 77(21)”. There was no significant difference between thresholds in stressed and zero demand fusion (p = 0.08). Dynamic depth detection thresholds were significantly lower than static (P