Alternate Prism Cover Test Research Articles

Strabismus Measurements Using the Alternating and Simultaneous Prism Cover Tests

Purpose: Tocomparetheangleofdeviationbyperformingsimultaneousprismcover test (SPCT) and alternate prism cover test (APCT) at near (33cm) and far (6m). Study Design: Cross-sectional observational. Place and Duration of Study: Al-Ibrahim Eye Hospital, Karachi from July 2021 to December 2021. Methods: This study enrolled 32 participants diagnosed with constant esotropia, aged between 5 and 25 years, comprising 14 males and 18 females. Comprehensive ocular examinations for strabismus were performed, including simultaneous prism cover tests at both distance and near fixation, conducted with and without corrective glasses. Subsequently, an alternate prism cover test was administered at each fixation point, again both with and without glasses. Binocular single vision was evaluated using the Worth Four Dot test and the 10Δ test. Statistical analysis was conducted using SPSS version 20.0. Results: At distance fixation, the mean deviation angle measured by the simultaneous and alternate prism cover tests exhibited a significant difference of 9.78Δ (p=<.001). Similarly, at near fixation, the mean deviation angle between the simultaneous and alternate prism cover tests showed a significant difference of 10Δ (p=<.001). Conclusion: This study demonstrates a notable and statistically significant variance in the measured angle of deviation when employing different testing methodologies (SPCT and APCT).

An Alternative in Managing Duane Retraction Syndrome Type I Using Modified Nishida Procedure: A Case Report

Introduction : Various surgical approaches have been proposed to address the challenge in managing abduction deficit in Duane Retraction Syndrome (DRS) Type I, with no clear guidelines to achieve optimal result. This report aims to describe the outcome of combining medial rectus (MR) recession and modified Nishida procedure to improve abduction in DRS Type I.
 Case Illustration : Twenty six year-old female came with inability to abduct her left eye (LE) since early childhood and an abnormal left head turn. No complaints of double vision nor visual impairment. There was -5 abduction on LE with a noticeable narrowing of vertical palpebral fissure during adduction. Prism alternate prism cover test shared a 30 PD esotropia with normal anterior and posterior segment. Patient was assessed with DRS Type I of LE and managed with 5mm MR recession combined with modified Nishida procedure (vertical rectus transposition without tenotomy and muscle splitting). On postoperative day 1 and last follow-up (1 year), the alignment was ortophoric, abduction improvement of -2, and diminished anomalous head posture.
 Discussion : Although studies have only reported successful cases of modified Nishida procedure in CN VI palsy, it can be assumed that the procedure can also be implemented to treat lateral rectus muscle innervation abnormality such as in DRS type I. Surgical intervention may not normalize abduction deficit. However, the procedure successfully corrects ocular alignment, eliminates anomalous head posture, and able to improve abduction with no complications.
 Conclusion : Modified Nishida procedure can be implemented as an alternative in managing DRS type I with relatively satisfactory result.

Comparison of head tilt test between sagging eye syndrome and acquired unilateral trochlear nerve palsy

PurposeTo investigate the distinction between sagging eye syndrome (SES group) and acquired unilateral trochlear nerve palsy (Trochlear group) in the Bielschowsky head tilt test (BHTT).MethodsFifteen patients in the SES group (mean age 74.6 ± 5.2 years) and 14 patients in the Trochlear group (55.2 ± 15.9 years) visited the Department of Ophthalmology, Hyogo Medical University Hospital between November 2016 and October 2022 for treatment of their diplopia. Eye position was measured with the alternate prism cover test, and values for fixation of the dominant eye, or unaffected eye, were used. Cyclodeviation was measured with the synoptophore and the Glaucoma Module Premium Edition of the SPECTRALIS optical coherence tomography. In the BHTT, eye position was measured in three head postures: primary position (PP), head tilt to the side with hypertropia (Hyper), and head tilt to the side with hypotropia (Hypo). The differences in vertical deviation between PP and Hyper (Hyper − PP), PP and Hypo (PP − Hypo) and Hyper − Hypo were measured and compared.ResultsVertical deviation in primary position was 7.3 ± 4.5 PD in the SES group and significantly larger (17.1 ± 8.4 PD) in the Trochlear group (p = 0.002). The vertical deviation in Hyper was significantly larger in the Trochlear group with 7.7 ± 4.7 PD and 22.1 ± 9.4 PD, respectively (p < 0.001), whereas the that in Hypo was not significantly different between the two groups with 6.5 ± 3.4 PD and 8.4 ± 6.6 PD, respectively (p = 0.725). The SES group showed no significant difference according to the 3 head postures (p = 0.311), while the Trochlear group showed a significantly different with smaller mean values in vertical deviation in Hypo (p < 0.001). The difference in the vertical deviation for the 3 head postures was the largest in Hyper − Hypo (1.7 ± 2.1 PD and 13.6 ± 7.1 PD, respectively), and the accuracy of SES was at the cutoff value of 6 PD, and it was considered not to be SES if the value was 6PD or higher. The accuracy of SES determination was 100% sensitivity and 100% specificity, and the area under the curve was 1.0.ConclusionThe difference in Hyper − Hypo in the BHTT may be the most useful index in differentiating SES from acquired unilateral trochlear nerve palsy; if the difference was more than 6 PD, the probability of SES was very low.

Comparative Analysis of Strabismus Measurement Using a Video Oculagraphy System and Alternate Prism Cover Test.

The aim of the study was to compare distance vision measurements obtained with video oculography (VOG) and an alternate prism cover test (APCT). Single-center, retrospective, and cross-sectional. Eighty-seven subjects with strabismus were included. All patients underwent an optometric examination. The measurement of strabismus in distance vision was performed with the best optical correction using the APCT and the VOG GazeLab. Subjects were divided according to the type of strabismus; 41 were esotropic and 46 were exotropic. The general comparison of APCT and VOG showed a mean difference of 0.60±2.74 prism diopters (Δ), not observing statistical differences between both methods ( P =0.059) and presenting a correlation of 0.976 ( P <0.001). Using APCT, the mean amount of esotropia for the group was 18.31±11.64 Δ and that of exotropia was 19.62±8.80 Δ. Compared with the VOG, the mean value of esotropia for the group was 18.65±11.65 Δ and that of exotropia was 19.48±8.62 Δ. The means are statistically different for the esotropia group ( P =0.005) but not for the exotropia group ( P =0.318). There was a high direct correlation between the methods of measurement for both the esotropic ( R =0.980; P <0.001) and exotropic patients ( R =0.975; P <0.001). Bland-Altman analysis shows a mean difference of 1.37±2.76 Δ for the esotropia patients and 0.31±2.66 Δ for the exotropic patients, respectively. This study demonstrated comparable results in measuring strabismus between VOG and APTC for esotropia and exotropia, with an excellent correlation between both methods and good agreement, especially in subjects with exotropia.

Long-Term Surgical Outcomes of Bilateral Symmetrical Superior Oblique Nasal Tenotomy in Patients of Large A-Pattern Exotropia.

To report the long-term outcomes of bilateral symmetrical superior oblique (SO) nasal tenotomy in patients with large A-pattern exotropia (≥25 prism diopter [PD]). This retrospective study was conducted on 15 patients (aged: 4-28 years) of large A-pattern exotropia. An A-pattern was defined as >10 PD difference between up and down gaze at 6 m by use of the alternate prism cover test. Objective ocular torsion was assessed by fundus photography and subjective torsion by double Maddox rod test. All patients underwent horizontal muscle surgery according to the primary position horizontal deviation and bilateral symmetrical SO nasal tenotomy for A-pattern. Surgical success was defined as postoperative A-pattern of ≤10 PD, the absence of vertical and torsional diplopia, and the absence of V-pattern. The minimum follow-up period was 24 months. A total of 15 patients of large A-pattern exotropia (7 males and 8 females) with a mean age of 17.09 ± 7.9 years were included in the study. All patients had bilateral SO overaction of grade +3 or +4 with a mean preoperative A-pattern of 30.3 ± 3.9 PD. At 24 months of follow-up, esotropia in down gaze (V-pattern) was present in four patients with a mean of 11.25 ± 2.5 PD, (range, 10-15 PD). The rest of the 11 patients maintained successful alignment with a mean A-pattern of 3.18 ± 1.17 PD, (range, 2-5 PD). There was significant A-pattern collapse with a mean of 31 ± 9.1 PD after 2 years of follow-up, which was significantly associated with preoperative A-pattern (Pearson correlation, r = 0.7; t[15] = 4.0; P = 0.002). The mean of pre- and postoperative objective ocular torsion was found to be -0.5 ± 4° and -4.8 ± 3.8° with a mean extorsion effect of 4.67 ± 3.85°. There was a statistically significant difference between pre- and postoperative ocular torsion (°) (t [30] = 5.42; P < 0.001), the change in ocular torsion was significantly associated with preoperative torsion (Pearson correlation, r = 0.5; t [30] = 7.2; P < 0.001). None of the patients had subjective torsion on the double Maddox rod test pre- and postoperatively. Bilateral symmetrical SO nasal tenotomy is effective in cases with large A-pattern (>25 PD). The reduction of A-pattern and postoperative change in fundus torsion have a positive correlation with preoperative A-pattern and preoperative torsion, respectively.

Spasm of Near Reflex in a Patient with Autism Spectrum Disorder: A Case Report

Spasm of near reflex (SNR) involves intermittent spasm of one or more of the three near reflex components. Psychiatric disorders are one cause of SNR. We describe a patient with SNR diagnosed with autism spectrum disorder (ASD). A 36-year-old male with esotropia since childhood was referred due to headache and dizziness. The alternate prism cover test showed 30 prism diopters at both near and distant fixation. Four months after his first visit, he was diagnosed with ASD. Twenty-nine months after his first visit, he underwent strabismus surgery to treat concomitant esotropia. Postoperatively, the angle of strabismus improved but remained variable. Because the angle of strabismus varied, we suspected SNR; the diagnosis was performed after evaluating the patient’s microfluctuations in accommodation with Speedy-K. However, it was difficult to distinguish convergence spasm from concomitant esotropia in this patient because he has had a history of esotropia since childhood. In a patient with concomitant esotropia, if the symptoms are not exclusively due to strabismus, SNR should be suspected. Although the relationship between SNR and the pathology of ASD is unknown, it is possible that patients with ASD are more likely to develop SNR.

Feasibility study of an automated Strabismus screening Test using Augmented Reality and Eye-tracking (STARE)

BackgroundNew digital technologies (augmented reality headsets, eye-tracking) may potentially allow for automated assessments of ocular misalignment. Here, we evaluate the feasibility of a novel, open-source strabismus test (“STARE”) as an automated screening tool.MethodsWork progressed in 2 phases. In phase 1 (“development”), we used Fresnel prisms to elicit horizontal misalignments of known magnitude (1–40 prism dioptres) in orthotropic controls. In phase 2 (“validation”), we applied the system to adults with an established diagnosis of strabismus, and quantified the ability of the test to distinguish between those with horizontal misalignment and those without. Agreement between the alternate prism cover test measurements and STARE measurements was computed using Bland–Altman plots and product-moment correlation coefficients.ResultsSeven orthotropic controls and nineteen patients with strabismus were recruited (mean age 58.7 ± 22.4 years). STARE was able to identify the presence of horizontal strabismus with an area under the curve of 1.00 (100% sensitivity and 100% specificity). The mean difference (bias) {95% CI} was 2.1 {−1.8, 9.9} prism dioptres, and the 95% coefficient of repeatability {95% CI} was ±27.9 {14.8, 50.8} prism dioptres. The Pearson correlation between APCT and STARE was r24 = 0.62, P < 0.001.ConclusionsSTARE shows promise as a simple, automated tool for performing a screening assessment of strabismus. It is a rapid (60 s) test that can be performed using a consumer augmented reality headset with integrated eye-tracking, and might conceivably be used remotely by non-specialists in future as a means of highlighting individuals needing face-to-face specialist care.

Phased strabismus surgery under topical anesthesia.

To evaluate the feasibility and outcomes of phased strabismus surgery under topical anesthesia, with intraoperative comparison of ocular alignment in supine and seated positions. This retrospective clinical investigation analyzed the data of patients who underwent phased strabismus surgery with fixed sutures under topical anesthesia. The technique consisted of 2 phases, spaced out with an intraoperative alternate prism cover test (performed in supine and seated positions): (1) surgery on one or two muscles, as defined by a preoperative surgical plan; (2) if judged necessary, a further one-muscle surgery. Surgical success was defined as a residual angle of horizontal and vertical deviation ≤±8Δand ≤5Δ, respectively, and the presence of single binocular vision in primary position in patients with preoperative diplopia. Follow-up visits were scheduled 1 day, 1 month, and 6 months after surgery. The review identified 38 patients (age range: 10-80 years). Surgery was well tolerated by all patients. Twelve (32%) required a second phase. No statistically significant differences were found for intraoperative angles of deviation in supine and seated positions. Surgical success was reached, respectively, in 88% and 87% of cases with horizontal and vertical deviation 6 months after surgery. No patients were reoperated during the follow-up period. Phased strabismus surgery is a feasible technique for various types of strabismus in adults and children. Secondly, intraoperative evaluation of ocular alignment can be performed either with the patient seated or supine, with the same accuracy in terms of surgical success.

Partially Accommodative Esotropia Manifesting as Cyclic Esotropia: A Case Study

Purpose: Cyclic esotropia is a rare disease with alternating cycles of recurrent esotropia that has been reported after strabismus surgery, head trauma, and psychological stress. We report a patient who presented with accommodative esotropia that deteriorated to cyclic esotropia and was managed successfully.Case Summary: A 2-year-old girl with no previous ophthalmological or neurological illnesses presented with esotropia. The alternate prism cover test showed 16 prism diopters (PD) of esotropia during distance and near fixation, and cycloplegic refraction showed +2.00 diopters (D) right eye and +1.50 D left eye. Under the impression of accommodative esotropia, she was prescribed glasses to fully correct her cycloplegic refraction. Nine months later, her esotropia was 14 PD with hyperopic correction. Her parents also complained that she had ‘non-squinting’ and ‘squinting’ days. The history and clinical findings suggested cyclic esotropia and she was asked to start a daily diary documenting the presence or absence of her squint. This revealed that the esotropia alternated on a 24-hour cycle. With a diagnosis of cyclic esotropia, she underwent right medial rectus recession. Postoperatively, her angle of esodeviation improved to orthotropia (near and distance) and stereoacuity was restored; this was maintained at the 1-year follow-up.Conclusions: A daily diary documenting the presence or absence of squint in patients who complain of alternating esotropia, even after hyperopic correction, is important. Cyclic esotropia often responds well to surgical management.

Diagnostic performance of the spot vision photoscreener for the detection of exodeviation in preschool-aged children.

To evaluate the diagnostic performance of the Welch Allyn Spot Vision photoscreener in preschool children for detecting exotropia, the most prevalent type of strabismus among Asian children. Children aged 3-6 years were screened using the Spot Vision photoscreener and then underwent a complete ophthalmologic examination on the same day. A child with exodeviation ≥8 Δ in the primary position using the cover-uncover test and the alternate prism cover test was confirmed to have exotropia. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the photoscreener in detecting exotropia were calculated. Subgroup analyses were performed according to the angle of deviation (≥25 Δ vs. <25 Δ) and fusional control (good/fair vs. poor). Two hundred and ten children were included in this study. Among 80 exotropia-confirmed children, 23 needed referrals for exodeviation (screening-positive) and 57 were proven to be screening-negatives with the photoscreener. The overall sensitivity, specificity, PPV and NPV of the photoscreener for detecting exotropia were 28.8%, 95.4%, 79.3% and 68.5%, respectively. The positive and negative likelihood ratios were 6.26 and 0.75, respectively. Compared with the 57 children with false-negatives (71.3%), those with true-positive results with the photoscreener had significantly larger angles of exodeviation (p=0.02) and a higher proportion of poor fusional control (p=0.004). The photoscreener had low sensitivity even in detecting exotropia ≥25 Δ or those with poor fusional control (35.2% and 43.6%, respectively). Approximately 65% (42 out of 64) of the children with a significant exodeviation which needed strabismus surgery were not identified by the Spot Vision Photoscreener. The Spot Vision photoscreener has low sensitivity for detecting exodeviation. It should not be used alone for assessing exotropia in preschool-aged children.

Effect of patch testing on strabismus angular deviation in children

Diagnostic monocular occlusion (MO), or patch testing, prior to alternate prism cover test (APCT) is thought to determine the maximal angle of deviation prior to strabismus surgery. However, the exact degree to which MO increases angular deviation is understudied.

Surgical Outcomes of Nonadjustable Modified Harada-Ito Surgery.

PurposeThis study aimed to investigate the surgical outcomes of nonadjustable Harada-Ito surgery under general anesthesia.MethodsTwenty-two patients who underwent nonadjustable modified Harada-Ito surgery under general anesthesia were reviewed retrospectively. Among them, 21 out of the 22 patients who were followed up for 6 months after surgery were included in this study. Subjective cyclotorsion (double Maddox rod test) and objective cyclotorsions (fundus photography) were measured. Success of the surgery was defined as follows: success (the patients do not acknowledge diplopia at any direction), partial (the patients feel diplopia at a specific direction, but they do not feel discomfort in routine life), and fail (the patients feel diplopia in primary gaze, hence requiring a thorough investigation).ResultsThe mean age of the patients (18 male and 3 female) was 56.5 years (range, 40–77 years). Based on the alternate prism cover test, the patients had 4.2 ± 3.0 prism diopters of vertical deviation. The corrected amounts of cyclotorsion based on the double Maddox rod test and fundus photography were 14.8° ± 7.5° and 9.8° ± 7.9°, respectively, and were significantly different between the two methods (p = 0.006). After the surgery, 20 out of the 21 patients (95.2%) completely recovered from diplopia in the primary gaze. However, among the 20 patients, seven complained of diplopia in the secondary gaze (down gaze, four patients; head tilt gaze, three patients). The success group had a smaller preoperative subjective excyclotorsion than the partial and fail groups (12.6° ± 2.5° and 21.0° ± 8.9°, respectively; p = 0.046).ConclusionsNonadjustable modified Harada-Ito surgery under general anesthesia has favorable success rate, and preoperative subjective excyclotorsion can be a prognostic factor in patients with bilateral superior oblique palsy.

Efficacies of preoperative prism adaptation test and monocular occlusion for detecting the maximum angle of deviation in intermittent exotropia

BackgroundThe efficacies of prism adaptation test (PAT) and monocular occlusion (MO) and their optimal test durations to detect the maximum angles of deviation at near and distance in eyes with intermittent exotropia (IXT) were assessed and compared.MethodsWe retrospectively reviewed the medical records of 72 patients with IXT. All the patients had undergone the initial strabismus surgery between April 2015 and October 2018 and had been preoperatively tested by both PAT and MO performed on different days for 30 and 60 min. Near and distance deviations after 30 and 60 min of PAT and MO were compared to their baseline measurements obtained immediately after prism wear and before occlusion by alternate prism cover test. The near/distance measurements and required test duration to reveal the maximum deviation angle were also compared between PAT and MO.ResultsCompared with the baseline, the near deviation by PAT significantly increased after 30 (P < 0.05) and 60 (P < 0.01) minutes but not the distance deviation. However, the increase after 30 min was not significant. By MO, neither near nor distance deviation showed a significant difference from the baseline after 30 and 60 min. PAT showed a significantly larger near deviation than MO at 30 and 60 min, but a larger distance deviation by PAT was only observed at 30 min.ConclusionsIn patients with basic and convergence insufficiency types of IXT, a 30-minute PAT appears to be more effective than MO in revealing the maximum angle of deviation before strabismus surgery.

Evaluation of Efficacy and Lateral Gaze Incomitance in Symmetrical and Asymmetrical Surgery for Concomitant Esotropia and Exotropia.

PurposeEvaluation of asymmetrical and symmetrical horizontal strabismus surgery as regards efficacy and postoperative lateral gaze incomitance.Patients and MethodsThis prospective comparative interventional case series study included 40 patients of age more than 3 years with alternating horizontal strabismus. Patients were divided according to the type of horizontal deviation into esotropia and exotropia groups, which were further subdivided into asymmetrical and symmetrical subgroups in each type. The surgery was defined as symmetrical procedure if the surgery was done on the same muscle in the two eyes and it was defined as asymmetric in recess-resect procedures in one eye, and three horizontal muscles surgery. Preoperative and postoperative measurements were done in primary position, right, and left gaze using alternate prism cover test and hand-held orthopedic goniometer.ResultsAt the end of follow-up period, a statistically insignificant difference (P value = 0.8057) was present in the success rate between the asymmetrical and symmetrical subgroups of esotropia (90 and 86.67%, respectively) and it was 100% in both exotropia subgroups. Lateral gaze incomitance results were different between esotropia and exotropia subgroups. In esotropia, a statistically significant difference was reported at 1 month (0.009), which became insignificant at 6 months (0.077) and 12 months (0.077) between asymmetrical and symmetrical subgroups. In exotropia subgroups, there was a statistically insignificant difference in lateral gaze incomitance at 1, 6, and 12 months (P = 1).ConclusionAsymmetrical procedure had the same efficacy and success rate of symmetrical procedure for the correction of concomitant horizontal deviations in primary gaze without persistent postoperative lateral gaze incomitance, especially in exotropia.Clinical Trial RegistrationNCT04199286.

Automated alternate cover test for 'HINTS' assessment: a validation study.

ObjectiveThe alternate cover test (ACT) in patients with acute vestibular syndrome is part of the ‘HINTS’ battery test. Although quantitative, the ACT is highly dependent on the examiner’s experience and could theoretically vary greatly between examiners. In this study, we sought to validate an automated video-oculography (VOG) system based on eye tracking and dedicated glasses.MethodsWe artificially induced a vertical strabismus to simulate a skew deviation on ten healthy subjects, aged from 26 to 66, using different press-on Fresnel prisms on one eye while recording eye position with VOG of the contralateral eye. We then compared the system’s performance to that of a blinded trained orthoptist using conventional, semi-quantitative method of skew measurement known as the alternate prism cover test (APCT) as a gold standard.ResultsWe found a significant correlation between the reference APCT and the Skew VOG (Pearson’s R2 = 0.606, p < 0.05). There was a good agreement between the two tests (intraclass correlation coefficient 0.852, 95 CI 0.728–0.917, p < 0.001). The overall accuracy of the VOG was estimated at 80.53% with an error rate of 19.46%. There was no significant difference in VOG skew estimations compared with the gold standard except for very small skews.ConclusionsVOG offers an objective and quantitative skew measurement and proved to be accurate in measuring vertical eye misalignment compared to the ACT with prisms. Precision was moderate, which mandates a sufficient number of tests per subject.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00405-021-06998-w.

Evaluation of a Hirschberg Test-Based Application for Measuring Ocular Alignment and Detecting Strabismus

ABSTRACT Purpose: Photographic Hirschberg test applications are practical options for screening in areas where a specialist is not available. A semi-automated Hirschberg test-based application was developed and evaluated on its ability to detect and measure strabismus at distance and near fixation. Methods: This is a prospective cross-sectional inter-rater agreement study conducted at a tertiary hospital. Study A evaluated the ability of the application to determine the presence or absence of strabismus in subjects of unknown strabismus status (n = 28). Study B evaluated the ability of the application to measure the deviation of strabismic subjects (n = 8). All subjects underwent alternate prism cover test (APCT) at distance and near fixation. Facial photographs at distance and near fixation were taken. Each photograph underwent automated face and eye detection, manual limbus and corneal reflex identification, and strabismus detection and measurement. Results: The application obtained a matching rate of 95.14% for the face and eyes. The application yielded a sensitivity of 92.86% for horizontal strabismus at distance and near fixation, however, with low specificity values (7.692%, 14.81%, and 8%). The Bland–Altman plots derived from Study B showed bias values of application measurements between 3.625Δ and 6.125Δ with wide intervals of the limits of agreement. Repeatability of the measurements yielded bias values of −0.625Δ and 2.5Δ for horizontal and vertical strabismus at distance and 4.375Δ and 1.25Δ at near fixation, respectively. Conclusion: This semi-automated Hirschberg test-based application can effectively determine the face and eye location and shows potential as a screening tool for horizontal strabismus.

Study of reliability and validity of VOG Perea® and GazeLab® and calculation of the variability of their measurements

Abstract Objective To determine the reliability and validity of VOG Perea® (VP) and GazeLab® (GL), their correlation and concordance with cover test (CT), and define the margins of variability of the measurement of angle deviation in primary position. Methods Forty-four orthotropic patients were included. Alternating prism CT, an examination with VP, and GL were performed. Intraclass correlation coefficient (ICC) was calculated to determine the reliability, and mean comparison was used to study validity. Correlation coefficient (R) between CT and each video-oculographer was calculated. Bland-Altman diagrams were used to determine concordance. All measurements were expressed in prismatic dioptres (PD). Results The mean horizontal deviation was −0.571 PD with CT; 0.22 PD with VP and 0.4 PD with GL. ICC was 0.246 [95% CI (−0.402–0.595)] in GL and 0.984 [95% CI (0.970–0.992)] in VP. Mean comparison between CT and GL was −0.9286 [CI 95% (−1.822 −0.0355)] (P = .042) and −0.8423 [95% CI (−1.7190–0.03450)] (P = .0593) for CT-VP. Correlation coefficient for VP was R = 0.5704 [95% CI (0.319–0.747)] (P = .0001) and R = 0.4539 [95% CI (0.174–0.666)] (P = .0025) for GL. Margins of variability for a single horizontal measurement in primary position with VP were ±5.22 PD and ±2 DP for GL. Conclusion Both VP and GL are reliable and valid devices. Margins of variability for a horizontal measurement are 5.22 PD in VP and ±2 PD in GL.

Outcome of surgery for near angle in patient with incomitant distance/near esotropia and without manifest deviation at distance.

To investigate how a subset of patients with partially accommodative esotropia, with a manifest deviation <10 Prism Diopters (PD) at distance and an angle of strabismus at near wider than 10 PD, could respond to a surgical approach based on the misalignment at near. Six patients examined from 2015 to 2019 met criteria for inclusion: partially accommodative esotropia, patients compliant to full correction for at least 6 months, angle of esotropia for near larger at least 10 PD, angle of misalignment obtained with the alternate prism cover test and simultaneous prism cover test at distance <10 PD. All patients underwent bilateral medial recti recession. They were examined at 3 weeks and at 6 months. No significant difference in the angle of esotropia at distance was found at any follow-up (Baseline: 7.17 ± 1.33 PD vs 3 weeks: 7.0 ± 1.01 PD vs 6 months: 7.33 ± 1.03 PD, p = 0.65, and p = 0.36, respectively). No case of consecutive exotropia was described. Considering the angle at near, there was a significant reduction at 3 weeks (Baseline: 41.7 ± 6.83 PD vs 3 weeks: 9.33 ± 1.63 PD, p = 0.027), that remained stable at the final follow-up (9.0 ± 1.1 PD, p = 0.32). All patients were suppressors and had nil stereopsis pre-operatively, all of them developed fusion and a different degree of stereopsis [276 ± 284 arcseconds (Range 80-800)]. A surgical approach based on the angle of strabismus for near could obtain satisfactory ocular alignment without consecutive exotropia in children with partially accommodative esotropia wearing full refractive correction, with a manifest deviation for distance <10 PD and a higher misalignment for near, at least for 6 months after surgery.

ON THE ROLE OF MICRO ANISOMETROPIA (THE “BUTTERFLY” EFFECT) IN THE OCCURRENCE OF ESOTROPIA IN CHILDREN

Purpose: This report presents 3 cases of esotropia in children and an attempt is made to explain the cause of the development of esotropia in these children.Methods: A comprehensive ophthalmic examination was carried out in the following order: photorefraction using the Plusoptix A09 photoscreener without cycloplegia; orthoptic examination with the alternate prism cover test; anterior segment assessment using a slit lamp; fundus examination and cycloplegic retinoscopy; and, for autorefractometry measurements, Sure-Sight.Results: Threecases of esotropia in children are presented. In all cases, a slight microanisometropia was observed along the cylindrical component ofthe squinting eye.Conclusion:Our three examples show how a slight degree of ametropia can cause a deviation of the eyeball. Therefore, case-by-case analysis can be more informative than large statistical studies. Thus, it is appropriate to evaluate eachcase from these new perspectives. The timely elimination of a small degree of anisometropia in the astigmatic or spherical components can lead to the restoration of the symmetrical position of the eyes

Estudio de la fiabilidad y la validez de los videooculógrafos VOG Perea® y GazeLab® y cálculo de los márgenes de variabilidad

ObjectiveTo determine the reliability and validity of VOG Perea® (VP) and GazeLab® (GL), their correlation and concordance with cover test (CT), and define the margins of variability of the measurement of angle deviation in primary position. MethodsForty-four orthotropic patients were included. Alternating prism CT, an examination with VP, and GL were performed. Intraclass correlation coefficient (ICC) was calculated to determine the reliability, and mean comparison was used to study validity. Correlation coefficient (R) between CT and each video-oculographer was calculated. Bland-Altman diagrams were used to determine concordance. All measurements were expressed in prismatic dioptres (PD). ResultsThe mean horizontal deviation was −0.571 PD with CT; 0.22 PD with VP and 0.4 PD with GL. ICC was 0.246 (95% CI: [−0.402]-0.595) in GL and 0.984 [95% CI: 0.970-0.992)] in VP. Mean comparison between CT and GL was −0.9286 (CI 95%: [−1.822]-[0.0355], P=.042) and −0.8423 (95% CI: [−1.7190]-0.03450, P=.0593) for CT-VP. Correlation coefficient for VP was R=0.5704 (95% CI: 0.319-0.747, P=.0001) and R=0.4539 (95% CI: 0.174-0.666, P=.0025) for GL. Margins of variability for a single horizontal measurement in primary position with VP were±5.22 PD and±2 DP for GL. ConclusionBoth VP and GL are reliable and valid devices. Margins of variability for a horizontal measurement are ±5.22 PD in VP and±2 PD in GL.