Eye Alignment Research Articles

Refractive error and ocular alignment in school-aged children from low-income areas of São Paulo, Brazil

BackgroundUncorrected refractive errors and amblyopia are reported as the two main causes of childhood visual impairment and blindness worldwide. Our purpose was to evaluate refractive status, ocular alignment and effective refractive error coverage (eREC) of school-aged children from low-income areas of Sao Paulo city, Brazil.MethodsData from the “Ver na Escola” Project were used for the current study. Children enrolled in the selected schools had an ophthalmic exam including eye alignment assessed by cover test, automatized and subjective dynamic and static refraction. The associations of demographic variables with occurrence and magnitude of refractive errors and eREC were investigated by multiple logistic regressions and multilevel mixed effect models.ResultsA total of 17,973 children (51.12% females) with mean ± sd age 8.24 ± 3.54 years old examined from July 2018 to July 2019, were included in the study. Most of the participants (73%) showed orthoposition of the visual axis for both distance and near. Heterophoria was found in about 25% of participants (N = 4,498), with 71.7% of them (N= 3,222) classified as exophoria. Less than 2% (N = 232) showed strabismus, most of them (N = 160) esotropia. Overall, 1,370 (7.70%) of participants had myopia and 577 (3.24%) had hyperopia. Age was found to be significantly associated with increasing static subjective refraction spherical equivalent (Coefficient: -0.18; 95% Confidence Interval (CI): -0.21 to -0.16; p < 0.001). Female sex (Odds Ratio (OR) = 1.13; 95%CI: 1.01–1.27; p = 0.027) and older age (OR = 1.17; 95%CI: 1.16–1.19; p < 0,001) were significantly associated with myopia diagnosis. Older age decreased the odds of hyperopia (OR = 0.95; 95%CI: 0.93–0.98; p < 0.001). The overall effective refractive coverage was 51.76% and was significantly associated with age group, ranging from 32.25% in children aged 3 to 7 years to 61.35% in children aged 8 to 12 years.ConclusionsMost children have shown eye alignment for both distance and near assessments and no refractive error. Myopia was observed in 7.70% of the population and it was associated with older age and female sex. Hyperopia was observed in 3.24% and was associated with younger age. The overall eREC was 51.76%, significantly associated with age.

Outcome of extraocular muscle transpositions in various types of strabismus

Background: Transposition surgery of extraocular muscles helps in paralytic strabismus by altering the direction of force in relation to the center of rotation of the eye. Hence, the study was done to report the outcome of muscle transpositions. Materials and Methods: This was a prospective interventional study of 20 patients conducted at our tertiary ophthalmic institute over a period of 2 years and included ten patients with “V” pattern and four patients with “A” pattern strabismus, two patients with monocular elevation deficiency (MED), two patients with third nerve palsy, and one patient each with Duane’s retraction syndrome (DRS) and Crouzon’s syndrome. Fourteen patients underwent correction of horizontal strabismus with vertical transposition of horizontal recti, four patients underwent upward transposition of lateral rectus (LR) muscle, one patient underwent modified Knapp’s procedure, and one patient had “Y” split of LR muscle with transposition. Results: Ten patients with “V” pattern strabismus and four patients with “A” pattern strabismus had satisfactory collapse of pattern postoperatively with &lt;10 prism diopters (PD) and 15 PD of mean residual horizontal strabismus, respectively. Both patients with MED had good improvement in primary position alignment. Upshoot in DRS patient was corrected. Two out of six patients who had preoperative limitation of duction had improvement postoperatively. Conclusion: Extraocular muscle transposition resulted in alignment of eyes, collapse of alphabet pattern, and improvement in ocular motility in these patients. Proper patient selection and planning of the suitable type of transposition surgery helps in achieving the desired outcome.

Binocular Visual Deficits at Low to High Spatial Frequency in Intermittent Exotropia After Surgery.

To investigate binocular visual deficits at low to high spatial frequencies in patients with intermittent exotropia (IXT) after surgical correction, using the binocular orientation combination task. Thirteen patients whose IXT has been aligned surgically (17 ± 4.8 years old; 7 females) and 13 normal individuals (21.8 ± 2.5 years old; 6 females) were recruited. All participants had normal or corrected-to-normal visual acuity. The IXT patients had undergone surgery at least one month prior to the study and achieved successful eye alignment post-surgery. We measured participants' balance points (BPs), defined as the interocular contrast ratio (nondominant eye/dominant eye) when both eyes contributed equally to binocular combination, using the binocular orientation combination task at three spatial frequencies (0.5, 4.0, and 8.0 cycles/degree). The absolute values of log10(BP) (i.e., |logBP|) and the area under of the |logBP| versus spatial frequency curve were used to quantify the extent of binocular imbalance. Surgery aligned the eye position of patients with IXT, with a postoperative exodeviation of -4.92 ± 4.29 prism diopters at distance. Participants' |logBP| values showed significant differences between groups, F(1,24) = 9.175, P = 0.006, and across spatial frequencies, F(2,48) = 7.127, P = 0.002. However, the interaction between group and spatial frequency was not significant, F(2,48) = 0.379, P = 0.687. Patients whose IXT has been alighted surgically experience binocular imbalance across a wide range of spatial frequencies, with greater binocular imbalance occurring at high spatial frequencies than low spatial frequencies.

Constructional Emergence in A1–C1: A Bird’s Eye Perspective and Alignment

This study aims to take a usage–based constructionist approach to observing the emergence of constructions in L2 speakers of English from a bird’s eye perspective and aligns some of them with CEFR levels. To do this, five equally balanced subparts from the EFCAMDAT corpus were compiled and analyzed using TAASSC and SPSS. The findings present strong evidence for and confirm previous studies that speakers at lower proficiency levels use fixed or prototypical expressions and do not deviate as much from conventional ways of combining constructions, i.e., collexemes. As proficiency increases, their constructicon gets lexicogrammatically richer and less prototypical, as such prototypical examples serves as training wheels for further expansion. While there seems to be evidence for low–frequency constructions to follow a developmental path through CEFR levels, high–frequency constructions do not seem to follow this path. In the end, the study presents a set of constructions aligned for each CEFR level, which appears to be in line with the characteristics of CEFR levels described at englishprofile.org.

Can viewing a 3D movie improve visual function in children with a history of amblyopia and neurotypical children?: A pilot study.

The aim of this pilot study was to determine whether viewing an immersive 3D movie with large disparities in a cinema resulted in improved visual acuity (VA), stereoscopic depth perception (ST), and improved eye alignment in residual amblyopic children and children without amblyopia. A total of 24 children aged between 5 and 12 years with a history of anisometropic and/or strabismic amblyopia, that had been previously treated and who currently have residual amblyopia (N = 14), and in children with typical development without amblyopia (N = 10) viewed the movie in 3D Sing 2 in a cinema for 110 minutes. Visual acuity, stereoacuity and ocular deviation were assessed before viewing the movie, and three months later. Stereoacuity and ocular deviation were also measured immediately after viewing the movie. We observed an improvement in visual acuity in the non-dominant (amblyopic) eye 3 months after viewing the movie in the amblyopic group (P<0.001). Stereopsis improved immediately after viewing the movie (P = 0.02), and after 3 months by ≈ 40% (P = 0.01). Moreover, improvements in stereopsis were also observed in children without amblyopia (P = 0.04). No significant changes in ocular deviation were observed in either group. These pilot results suggest that brief exposure to large disparities by viewing a 3D movie in a cinema can help to improve stereopsis and visual acuity in children aged 5‒12 years with previously treated amblyopia, and provide a rationale for a randomized clinical trial.

Botulinum toxin type A in treating early-stage patients with small-angle acute acquired comitant esotropia.

To investigate botulinum toxin A (BTXA) efficacy on small-angle (≤25Δ) acute acquired concomitant esotropia (AACE) in early-stage patients. The electronic medical record data of AACE patients during March 2019 and June 2023 were collected in this retrospective and hospital-based cohort study. A total of 72 small-angle AACE patients received BTXA extraocular muscle injection. Patients were grouped by onset-to-treatment time (Group A: ≤6mo, Group B: >6mo). Deviation of esotropia, eye alignment and stereopsis were analyzed at the period of pre/post-injection (1wk, 1, 3, and 6mo). Orthophoria rate at 6mo (horizontal deviation <10Δ and binocular single vision) were considered as outcome index. There were no significant baseline differences (P>0.05) between two groups except onset-to-treatment time (2mo vs 11mo, P<0.001). Higher orthophoria rates were in Group A at last follow-up (94.74% vs 73.53%, P=0.013). Post-BTXA deviations of two groups at 1mo showed no difference (P>0.05); while in 3 and 6mo Group A was significantly smaller than group B (all P<0.001). No statistically significant differences were observed among all post-BTXA deviations of near and distance in Group A. In Group B, deviation at 3mo (near: 2Δ vs 0, P<0.001; distance: 4Δ vs 0, P<0.001) and 6mo (near: 6Δ vs 0, P<0.001; distance: 6Δ vs 0, P<0.001) was significant increased compared to deviation at 1wk after treatment. Group A showed better stereopsis recovery in last follow-up compared to Group B (80″ vs 200″, P=0.002). Both groups obtained improved stereopsis after treatment (Group A: 80″ vs 300″, P<0.001; Group B: 200″ vs 300″, P=0.037). BTXA is effective for AACE with small deviation (≤25Δ) in early stage. Delayed treatment (>6mo) may reduce BTXA efficacy. Early BTXA intervention benefits long-term eye alignment and stereopsis recovery.

Pattern electroretinography response in amblyopic adults

IntroductionAmblyopia is generally a unilateral disorder, defined by at least a difference of two lines of visual acuity between both eyes with the best-corrected visual acuity, a decrease in contrast sensitivity, and a decrease in stereopsis. Pattern electroretinogram (PERG) is a noninvasive technique that provides a retinal biopotential and is a highly sensitive indicator of changes in the macular area. Our aim was to evaluate if there are differences in the retinal response of an amblyopic eye compared with a normal eye (NE).MethodsWe evaluated twenty-four adult volunteers, twelve amblyopes (mean 43.42 ± 12.72 years old), and twelve subjects with NE (mean 35.58 ± 12.85 years old). None of the subjects in the two groups had comorbidities. A complete optometric examination was performed including parameters such as visual acuity (VA) by far and near with ETDRS chart, eye alignment with cover test, and evaluation of retinal cells response with PERG.ResultsThe refractive error found in the NE group of subjects had a mean of − 0.95 ± 1.65D, while the amblyopic group showed a mean of − 2.03 ± 4.29D. The VA in amblyopic eyes had a mean of 0.38 ± 0.20 logMAR. Analyzing PERG data, we observed significant differences in the P50-N95 amplitudes of the amblyopic group compared with the NE group (p < 0.0001–amblyopic eye vs. NE; p = 0.039–fellow eye vs. NE).DiscussionThese findings suggest that amblyopic patients may also present other impairments beyond the visual cortex. PERGs seem to be an important complementary examination in the diagnosis of other impairments in amblyopia.

Strabismus Surgery for Traumatic Ocular Misalignment: Twelve Cases in Five Years

Introduction : Trauma can cause an ocular misalignment due to damage of extraocular muscles, nerves and orbital tissue around the eye. Direct trauma causing extraocular muscle rupture needs immediate surgery, meanwhile indirect trauma resulting in traumatic sixth nerve palsy or other reversible ocular misalignment without orbital floor fracture can be observed for six months. This study describe the characteristic of patients undergo single-step strabismus surgery for traumatic ocular misalignment, mechanism of injury, eye alignment, amount of ocular deviation before and after strabismus surgery.&#x0D; Case Illustration : This was a case series based on medical record of patients underwent strabismus surgery secondary to head or eye injury from 2017 until 2022.&#x0D; Discussion : Twelve individuals with post-traumatic strabismus correction participated in this study. All subjects were male age ranging from 18-51 years. Direct trauma was observed in 6 (50%) patients causing medial rectus muscle rupture in 4 patients and inferior rectus muscle rupture in 2 patients. Indirect trauma was observed in 6 (50%) patients caused by sixth nerve palsy on 4 patients The misalignment was exotropia, esotropia, and hypertropia with amount of 5, 4, and 3 respectively. The deviation was between 30-90 prism dioptre (PD) and 7 (58%) patients had deviation less than 65 PD. Strabismus surgery performed was muscle transposition with or without recession of the antagonist muscle.&#x0D; Conclusion : Single step surgery for traumatic ocular misalignment can provide good result in cases of deviation less than 65 PD

Morphometric Analysis of the Eye by Magnetic Resonance Imaging in MGST2-Gene-Deficient Mice.

Strabismus, a neuro-ophthalmological condition characterized by misalignment of the eyes, is a common ophthalmic disorder affecting both children and adults. In our previous study, we identified the microsomal glutathione S-transferase 2 (MGST2) gene as one of the potential candidates for comitant strabismus susceptibility in a Japanese population. The MGST2 gene belongs to the membrane-associated protein involved in the generation of pro-inflammatory mediators, and it is also found in the protection against oxidative stress by decreasing the reactivity of oxidized lipids. To look for the roles of the MGST2 gene in the development, eye alignment, and overall morphology of the eye as the possible background of strabismus, MGST2 gene knockout (KO) mice were generated by CRISPR/Cas9-mediated gene editing with guide RNAs targeting the MGST2 exon 2. The ocular morphology of the KO mice was analyzed through high-resolution images obtained by a magnetic resonance imaging (MRI) machine for small animals. The morphometric analyses showed that the height, width, and volume of the eyeballs in MGST2 KO homozygous mice were significantly greater than those of wild-type mice, indicating that the eyes of MGST2 KO homozygous mice were significantly enlarged. There were no significant differences in the axis length and axis angle. These morphological changes may potentially contribute to the development of a subgroup of strabismus.

Correlation of Strabismus Surgical Outcomes Graded by Goal-Determined Metric With Patient Satisfaction Survey

PurposeWhile strabismus surgery outcomes can be objectively measured, patient perception of results may differ. We present surgical outcomes graded by a prospective, “goal-determined metric” and compare these outcomes to results of a patient satisfaction survey. DesignValidity analysis comparing a clinical “goal-determined metric” to patient satisfaction MethodsGoal-determined metric outcomes (2018-2021) for two surgeons treating esotropia or exotropia for diplopia control or reconstructive goals were collected. Inclusion required complete post-operative examination 2-6 months after surgery and a satisfaction survey. ResultsRecord review identified 275 patients; 228 (median age 41 years (IQR 13-59)) met inclusion criteria. For the entire cohort, 87% were graded as “excellent” outcomes, and 78% of patients were overall “very satisfied”. Agreement between patients’ and surgeons’ grading was 75-79% for all reconstructive surgery and for treatment of diplopia from esotropia. Agreement was lower, though not statistically different, for treatment of diplopia from exotropia (64%; 95% CI 43-80%) (P=0.184). Pre-operative risk factors, concurrent vertical or oblique surgery, and sex did not affect outcomes or satisfaction. Performance of activities requiring distance viewing improved more than performance of activities at near after esotropia-diplopia surgery (odds ratio 3.0 (95% CI: 1.5-6.4, P=0.004)). For reconstructive cases achieving “much better” eye alignment, 62% and 72% (previously esotropic and exotropic) reported enhanced self-confidence. ConclusionsOutcomes graded by goal-determined metric correlated well with many aspects of patient satisfaction. Patient-perceived improvement in appearance was important regardless of goal. Greater improvement in performance of activities requiring distance rather than near viewing characterized treatment of diplopia from esotropia.

How Do Most Young Moderate Hyperopes Avoid Strabismus?

Uncorrected hyperopic children must overcome an apparent conflict between accommodation and vergence demands to focus and align their retinal images. This study tested hypotheses about simultaneous accommodation and vergence performance of young hyperopes to gain insight into ocular motor strategies used to maintain eye alignment. Simultaneous eccentric photorefraction and Purkinje image tracking were used to assess accommodative and vergence responses of 26 adult emmetropes (AE) and 94 children (0-13 years) viewing cartoons. Children were habitually uncorrected (CU) (spherical equivalent refractive error [SE] -0.5 to +4 D), corrected and aligned (CCA), or corrected with a history of refractive esotropia (CCS). Accommodative and vergence accuracy, dissociated heterophoria, and vergence/accommodation ratios in the absence of retinal disparity cues were measured for 33- and 80-cm viewing distances. In binocular viewing, median accommodative lags for 33 cm were 1.0 D (AE), 1.33 D (CU), 1.25 D (CCA), and 1.0 D (CCS). Median exophorias at 80 and 33 cm were 1.2 and 4.5 pd (AE), 0.8 and 2.5 pd (CU), and 0 and 1.2 pd (CCA), respectively. Without disparity cues, most response vergence/accommodation ratios were between 1 and 2 meter angle/D (∼5-10 pd/D) (69% of AE, 44% of CU, 60% of CCA, and 50% of CCS). Despite apparent conflict in motor coupling, uncorrected hyperopes were typically exophoric and achieved adultlike accuracy of both vergence and accommodation simultaneously, indicating ability to compensate for conflicting demands rather than bias to accurate vergence while tolerating inaccurate accommodation. Large lags and esophoria are therefore atypical. This analysis provides normative guidelines for clinicians and a deeper mechanistic understanding of how hyperopes avoid strabismus.

Objective assessment of eye alignment and disparity-driven vergence in Parkinson's disease.

Self-reported diplopia is described in up to one-third of Parkinson's disease (PD) patients. The purpose of our study was to expand our understanding of the mechanistic underpinnings of diplopia in PD. We hypothesize that the time-based control of eye alignment and increased eye deviation under binocular viewing will be related to the fusion-initiating and fusion-maintaining component deficits of disparity-driven vergence in PD. We used high-resolution video-oculography to measure eye alignment under binocular and monocular viewing and disparity-driven vergence in 33 PD and 10 age-matched healthy participants. We computed eye deviation and time-based control of eye alignment, occurrence of conjugate saccadic eye movements, latency and gain of vergence (fusion initiation), and variance of eye position at the end of dynamic vergence (fusion maintenance). We categorized PD subjects into three groups, considering their time-based control of eye alignment as compared to healthy controls in binocular viewing. Group 1 = 45% had good control and spent >80% of the time when the eyes were well-aligned, Group 2 = 26% had intermediate control and spent <80% but greater >5% of the time when the eyes were well-aligned, and Group 3 = 29% had very poor control with increased eye deviation majority of the times (<5% of the time when the eyes were well-aligned). All three groups exhibited greater eye deviation under monocular viewing than controls. PD subjects exhibited fusion-initiating and fusion-maintaining vergence deficits (prolonged latencies, reduced vergence gain, increased variance of fusion-maintaining component) with a greater probability of saccadic movements than controls. Group 2 and Group 3 subjects were more likely to exhibit failure to initiate vergence (>20%) than Group 1 (13%) and controls (0%) trials. No significant difference was found in the Unified Parkinson's Disease Rating Scale (UPDRS-a tool to measure the severity of PD) values between the three PD groups (Group 1 = 33.69 ± 14.22, Group 2 = 38.43 ± 22.61, and Group 3 = 23.44 ± 1, p > 0.05). The majority of PD subjects within our cohort had binocular dysfunction with increased eye deviation under monocular viewing and disparity-driven vergence deficits. PD subjects with intermediate or poor control of eye deviation under binocular viewing had greater fusion-initiating and fusion-maintaining vergence deficits. The study highlights the importance of assessing binocular dysfunction in PD subjects independent of the severity of motor symptoms.

Retinal Microvascular Density and Perfusion during an Insulin-Induced Hypoglycemia Episode: A Warning Call.

To evaluate retinal vascular perfusion and density by optical coherence tomography angiography (OCTA) before, during, and after hypoglycemia in individuals with diabetes mellitus with or without diabetic retinopathy (DR). A focused clinical history was performed, followed by an ophthalmological examination to document retinopathy status. OCTA was performed at baseline, at hypoglycemia, and at glucose normalization. Eye tracking and eye alignment devices on the platform were used to obtain a macular thickness cube (512 × 128) and vascular perfusion and density protocols of 3 × 3 mm. Retinal vascular reactivity was analyzed with superficial plexus vascular perfusion and density protocols on OCTA. Fifty-two participants encompassing 97 eyes fulfilled the eligibility criteria. Their mean age was 42.9 ± 15.1 years (range, 22 to 65), and 20 (38.2%) were men. We found a statistically significant difference in vascular perfusion and density when comparing all groups at baseline. The controls had higher vascular perfusion and density values than the cases. Vascular perfusion and density were significantly reduced in all groups during the hypoglycemia episode, except for vascular density in DR cases. Acute hypoglycemia significantly alters the retinal vascularity in DM patients with and without DR, suggesting that repeated episodes of acute hypoglycemia could exacerbate retinopathy in the long term.

A Novel Technique Using Paretic Superior Rectus as a Globe Suspender for Monocular Elevation Deficiency.

Surgical innovations in strabismus provide opportunities to improve visual function, eye alignment, and cosmesis in rare pediatric ophthalmological conditions. Monocular elevation deficiency is a rare and multifactorial disease in which the affected eye is equally limited in terms of elevation during adduction and abduction. We aimed to present a novel procedure for the treatment of acquired monocular elevation deficiency using the paretic superior rectus muscle as a globe suspender to resolve hypotropia. We report the case of an eight-year-old girl with left eyelid ptosis and hypotropia two months after draining a left orbital abscess. Left inferior rectus muscle recession was performed at five years, with residual left hypotropia. Ophthalmological examination revealed a best-corrected visual acuity of 20/20 OD and 20/100 OS. Severe left eyelid ptosis and poor levator function were also observed. Extraocular motility showed left hypotropia of 40 prism diopters with the left superior rectus muscle under action (-4) in the adduction and abduction positions. A force duction test negative for restrictions on the inferior rectus muscle was performed intraoperatively. To reduce the risks of the Knapp procedure, the left superior rectus muscle was split into medial and temporal halves. Double-armed sutures were secured in half, and the halves were detached from the sclera. The medial and temporal halves were reattached anteriorly to the medial and lateral rectus insertions, respectively. Eight weeks after surgery, the patient had nine prism diopters of hypotropia in the primary gaze. Ten weeks after surgery, there was no change in visual acuity. In the cover test, the patient exhibited residual left hypotropia of nine prism diopters with a restriction (-4) of elevation in adduction and abduction. The parents were pleased with the satisfactory cosmetic outcomes, and postoperative clinical photographs of the patient showed improved hypotropia and persistent minimal elevation of the left eye during adduction and abduction. Superior rectus muscle splitting and vertical transposition to the medial and lateral rectus could be safer and simpler alternatives to the Knapp procedure and may offer a lower risk of anterior segment ischemia. Further studies are required to confirm these findings.

Comparison between bupivacaine injection and mini-tenotomy in the management of horizontal small angle strabismus in children

ABSTRACT Purpose To compare the outcome of bupivacaine (BUP) injection vs mini-tenotomy of extra-ocular muscles in treating small angle horizontal strabismus in children. Methods A prospective comparative study that included a total of 40 patients. Twenty patients received 3 ml of 0.75% Bupivacaine (BUP) injection in both medial recti in case of exotropia and in both lateral recti in case of esotropia. MRI orbit was performed before and 30–60 days’ post injection of bupivacaine to estimate changes in muscle size. Mini-tenotomy was done in the other 20 patients, performed on both lateral recti in case of exotropia and on both medial recti in case of esotropia. Results Mean change of alignment at the end of 6 months in exotropic patients in bupivacaine group was 5.50 ± 4.10 PD and in esotropia patients 4.00 ± 3.38 PD with an average increase in muscle thickness of 0.12 mm ± 0.08 and 0.13 mm ± 0.09 in exotropia and esotropia, respectively. There was an average increase in volume 23 mm3 ± 17.3 and 17.00 mm3 ± 9.50 in exotropia and esotropia, respectively, as measured with MRI. The mean change of alignment in mini-tenotomy was 5.33 ± 4.12 PD, 5.75 ± 4.95 PD in exotropia and esotropia, respectively. Conclusion Bupivacaine and mini-tenotomy are safe and effective alternative treatment, that improved eye alignment in 65% of patients with small angle horizontal deviation.

Robotic Optical Coherence Tomography of Human Subjects with Posture-Invariant Head and Eye Alignment in Six Degrees of Freedom.

Ophthalmic optical coherence tomography (OCT) has achieved remarkable clinical success but remains sequestered in ophthalmology specialty offices. Recently introduced robotic OCT systems seek to expand patient access but fall short of their full potential due to significant imaging workspace and motion planning restrictions. Here, we present a next-generation robotic OCT system capable of imaging in any head orientation or posture that is mechanically reachable. This system overcomes prior restrictions by eliminating fixed-base tracking components, extending robot reach, and planning alignment in six degrees of freedom. With this robotic system, we show repeatable subject imaging independent of posture (standing, seated, reclined, and supine) under widely varying head orientations for multiple human subjects. For each subject, we obtained a consistent view of the retina, including the fovea, retinal vasculature, and edge of the optic nerve head. We believe this robotic approach can extend OCT as an eye disease screening, diagnosis, and monitoring tool to previously unreached patient populations.

Vergence and accommodation responses in the control of intermittent exotropia.

Individuals with different types of intermittent exotropia (IXT) may use neurally coupled accommodation and vergence responses differently from those without exotropia to achieve eye alignment. This study examined the relationship between simultaneously recorded accommodation and vergence responses in children and young adults with a range of types of IXT while aligned and deviated. Responses of 29 participants with IXT (4-31 years) and 24 age-matched controls were recorded using simultaneous eye-tracking and eccentric photorefraction while they watched a movie in binocular or monocular viewing at varying viewing distances. Gradient response AC/A ratios and fusional vergence ranges were also assessed. Eight participants had divergence or pseudo-divergence excess type IXT, 5 had convergence insufficiency and 16 had basic IXT. Control and IXT participants accommodated similarly both in monocular and binocular-aligned conditions to visual targets at 80 and 33 cm. When deviated in binocular viewing, most participants with IXT exhibited changes in accommodation <0.5D relative to alignment. Gradient response AC/A ratios were similar for control [0.56 MA/D (IQR: 0.51 MA/D)] and IXT participants [0.42 MA/D (0.54 MA/D); p = 0.60]. IXT participants showed larger vergence to accommodation ratios with changes from distance to near fixation [1.19 MA/D (1.45 MA/D)] than control participants [0.78 MA/D (0.60 MA/D); p= 0.02], especially among IXT participants with divergence or pseudo-divergence excess. Participants with IXT exhibited typical fusional divergence ranges beyond their dissociated position [8.86 Δ (7.10 Δ)] and typical fusional convergence ranges from alignment [18 Δ (15.75 Δ)]. This study suggests that control of IXT is typically neither driven by accommodative convergence alone nor associated with over-accommodation secondary to fusional convergence efforts. These simultaneous measurements confirmed that proximal vergence contributed significantly to IXT control, particularly for divergence or pseudo-divergence excess type IXT. For IXT participants in this study, achieving eye alignment did not conflict with having clear vision.

Stereopsis following delayed strabismus surgery in early-onset strabismus.

Improved stereoacuity following delayed strabismus surgery is associated with long-term alignment of eyes and reduced severity of amblyopia. The objective of this study is to evaluate stereopsis following delayed strabismus surgery in early-onset strabismus. It is a hospital-based prospective, nonrandomized, interventional case study. Thirty patients with early-onset strabismus (before 3 years of age), presenting after 6 years of age were included. History taking and full orthoptic workup was done. Stereopsis was tested with Titmus Fly Chart test. The patients were treated surgically to correct strabismus and were followed up for 3 months. Quantitative parameters were compared between preoperative and postoperative follow-up at 3 months using McNemar test, Chi-square test, and independent t-test. Of the 21 patients who had gross stereopsis preoperatively, nine of them (42.86%) attained fine stereopsis at 3 months postoperatively (P = 0.003, McNemar test). Ten (33.33%) of 30 patients had amblyopia and three out of 30 patients (10%) had preoperative "nil" stereopsis. Of the patients who showed improvement (16 of 30 patients - 53.33%), most of the improvement was observed in (a) exodeviations (56.25%, n = 9), (b) earlier age of presentation-before 10 years of age (47.36%, n = 9). The benefits of surgical correction of early-onset strabismus include improvement in stereopsis. Therefore, even in an early-onset squint with a delayed presentation rehabilitation of stereopsis should be the goal of treatment.

Clinical efficacy of botulinum toxin type A on acute acquired comitant esotropia.

To investigate the effects of micro-injection of botulinum toxin A (BTXA) on acute acquired comitant esotropia (AACE). A total of 33 AACE patients who underwent BTXA micro-injection at Renmin Hospital of Wuhan University from September 1st, 2019 to July 1st, 2021 were retrospective analyzed. Esotropia, eye alignment, stereopsis, and complications were examined at baseline (except complications), 1wk, 1, 3, and 6mo after injection. The average angle of deviation before injection was (+20.24±6.80)Δ at near and (+24.76±6.43)Δ at distance, while (+5.15±5.85)Δ at near and (+7.30±6.17)Δ at distance 6mo after treatment (P<0.05). Six months after injection, the stereopsis of patients had improved. The number of patients having no stereopsis (>800 seconds of arc) decreased from 11 to 3. The number of patients having peripheral stereopsis (300-800 seconds of arc), macular stereopsis (70-200 seconds of arc) and central concave stereopsis (≤60 seconds of arc) increased from 10 to 11, 10 to 12, and 2 to 7, respectively. At the follow-ups at 1wk, 1, 3, and 6mo after injection, success rates were 96.97%, 96.97%, 93.94% and 87.88%, respectively. One week after injection, two patients (6.07%) showed subconjunctival hemorrhage; three patients (9.09%) showed limited eye movement and one patient (3.03%) showed mild vertical strabismus. All the symptoms disappeared by the final follow-up. Micro-injection of BTXA can reduce diplopia and improve binocular vision function of AACE patients. Furthermore, the operation is relatively safe with few complications, making it an ideal treatment modality for AACE.

Spatial–temporal contrast sensitivity of the eye alignment reflex

The binocular alignment of the eyes involves both voluntary and reflexive mechanisms, but little is known about the visual input and neurological pathway of the reflex component. Our studies examined the role of spatiotemporal frequency and contrast in the control of reflex eye alignment, and compared the contrast sensitivity of the alignment reflex with psychophysical contrast sensitivity. We measured the contrast sensitivity of vertical disparity-driven vergence eye movements in response to bandwidth filtered static or 6 Hz counterphase flickering noise and measured psychophysical detection sensitivity for the same stimuli. Contrast thresholds for producing a detectable vertical alignment change (measured with nonius lines) were determined using a staircase method for 7 spatial frequencies [0.25–16 cycles per degree] and 3 vertical disparities [5, 10, and 30 arcmin] in 7 adults with normal or corrected to normal vision. The main findings of this study are, (1) the vertical alignment reflex had overall relatively high contrast sensitivity, comparable to but somewhat less than visual detection thresholds, (2) the most effective stimulus spatial frequency scaled in inverse proportion to the disparity being stimulated, and (3) unlike psychophysical contrast sensitivity, the eye alignment reflex contrast sensitivity was not improved by flickering low spatial frequencies.