Normal Binocularity Research Articles

Traumatic superior oblique tendon rupture with ptosis: A case report

The traumatic rupture of the superior oblique tendon with ptosis is extremely rare, and the surgical treatment is very challenging. We reported a case of a 41-year-old man with superior oblique tendon rupture and ptosis due to an iron hook injury. The ocular movement disorders were not obvious except for mild superior oblique underaction but were accompanied by severe extorsion. The distal stump of the superior oblique tendon was shortened and anchored to the periosteum of the supra-nasal orbital margin near the trochlea. Post-operative follow-up revealed the surgical outcome was better than expected, which resulted in significant improvement in binocularity and cosmetic outcomes without complication in the present case. The exploration of the levator palpebral superioris (LPS) in the early post-traumatic stage might not be necessary in circumstances without eyelid laceration. Shortening and anchoring of the ruptured superior tendon could restore almost normal binocularity, decrease the extorsion, and avoid acquired Brown syndrome.

Neonatal Macular Hemorrhage in a Term Healthy Infant: 18-Year Follow-up.

Unobstructed binocular vision is required during the critical period of vision development to obtain optimal visual acuity in each eye and binocular stereopsis. In this article, we report 18-year follow-up of a full-term, otherwise healthy infant noted to have dense premacular hemorrhage occluding the visual axis in the left eye on retinal imaging performed 48 hours after birth. Serial examinations by the retina service were performed weekly for 10 weeks as the hemorrhage resolved spontaneously. Shortly thereafter, visual acuity revealed fixation was present, but the mother noted intermittent left eye esodeviation. At 90 days of life, the infant was seen by pediatric ophthalmology and started on 1 to 2 hours patching of the right eye daily for the esotropia, which was maintained through 24 months. At 18 years of age, the patient had orthophoria alignment, no spectacle correction, vision of 20/20 in the right eye and 20/25 in the left eye, and normal binocularity and stereopsis. Intermittent esodeviation on the left eye was observed when the patient was fatigued. Early identification of a visual axis occlusion led to prompt referral for the esotropia and initiation of patching therapy. This patient ultimately achieved a very favorable visual functional outcome that may not have been possible without early detection and management. This case report describes the longest-term published follow-up of a neonatal macular hemorrhage. [Ophthalmic Surg Lasers Imaging Retina 2024;55:354-357.].

Assessment of the effects of induced anisometropia on binocularity with glasses-free 3D technique.

To assess the effect of experimentally induced anisometropia on binocularity in normal adults with glasses-free three-dimensional (3D) technique. Totally 54 healthy medical students with normal binocularity in the cross-sectional study were enrolled. Anisometropia was induced by placing trail lenses over the right eye, in 0.5 D steps including lenses of -0.5, -1, -1.5, -2, -2.5 D (hyperopic anisometropia) and lenses of +0.5, +1, +1.5, +2, +2.5 D (myopic anisometropia). The glasses-free 3D technique was used to evaluated not only fine stereopsis, but also coarse stereopsis, dynamic stereopsis, foveal suppression, and peripheral suppression in these subjects. One-way analysis of variance was used to compare quantitative data such as fine stereopsis, coarse stereopsis. Pearson's Chi-square test was performed to compare categorical data such as dynamic stereopsis, foveal suppression and peripheral suppression. The subjects showed a statistically significant decline in fine stereopsis, coarse stereopsis, and dynamic stereopsis with increasing levels of anisometropia (P<0.001). Binocularity was affected when induced anisometropia was more than 1 D (P<0.05). Foveal suppression and peripheral suppression were evident and increased in proportion to anisometropia (P<0.001). The relatively low degrees of anisometropia may have a potentially significant effect on high-grade binocular interaction. The mechanisms underlying the defect of binocularity seem to involve not only foveal suppression, but also peripheral suppression.

Assessment of stereovision with digital testing in adults and children with normal and impaired binocularity

New digital approaches allow stereovision to be assessed with greater precision than current clinical stereo tests. Those current tests present a relatively narrow range of stimulus disparities in coarsely quantized steps. With dichoptic treatments for amblyopia emerging, more accurate assessment of especially coarse stereopsis becomes increasingly important for verifying their aim to improve 3D vision. We used digital testing in subjects of a large age range (4–59 years), with groups having both normal (n = 34) and impaired binocular vision due to unilateral amblyopia, with or without strabismus (n = 27). Random-dot stimuli were presented on a 3D monitor with shutter glasses. The test applies adaptive procedures to measure psychometric functions and provides thresholds with associated confidence intervals. Digital thresholds for controls (range 11–160 arcsec) and stereodeficient subjects (range 43–911 arcsec) were compared to the TNO, a standard clinical test which uses similar random-dot targets presented with anaglyph glasses. Agreement between digital and TNO thresholds varied with the level of stereopsis. Stereoacuity was measurable in several subjects who failed on the TNO. With the digital test we found good repeatability for both groups, with the indication of a small learning effect for subjects with coarse stereopsis. Thus, assessment of all target groups for new tests is important, and repeated testing before therapy may avoid confusing learning and treatment effects. Our digital approach supplies a large range of accurate stereo data in children and adults; together with its associated measure of variability, it will be useful in longitudinal treatment studies.

A Randomized Clinical Trial of Immediate Versus Delayed Glasses for Moderate Hyperopia in Children 3 to 5 Years of Age

To compare visual acuity (VA) and binocularity outcomes in moderately hyperopic children with normal VA and binocularity assigned to glasses versus observation. Prospective randomized clinical trial (RCT). One hundred nineteen 3- to 5-year-old children with hyperopia between+3.00D and+6.00D spherical equivalent were randomly assigned to glasses versus observation (with glasses prescribed if deteriorated for subnormal distance VA or near stereoacuity, or manifest strabismus). Follow-up occurred every 6months. At 3 years, the treatment strategy was classified as "failed" if any of the following were met, both with and without correction: subnormal distance VA or stereoacuity; manifest strabismus; or strabismus surgery during follow-up. Of 84 (71%) children who completed the primary outcome examination, failure occurred in five (12%; 95% confidence interval [CI]: 4%-26%) of 41 assigned to glasses and four (9%; 95% CI: 3%-22%) of 43 assigned to observation (difference= 3%; 95% CI: -12%-18%; P= .72). Deterioration prior to 3 years (requiring glasses per protocol) occurred in 29% (95% CI: 19%-43%) assigned to glasses and 27% (95% CI: 17%-42%) assigned to observation. In an RCT comparing glasses to observation for moderately hyperopic 3- to 5-year-old children with normal VA and binocularity, failure for VA or binocularity was not common. With insufficient enrollment and retention, our study was unable to determine whether immediate glasses prescription reduces failure rate, but low failure rates suggest that immediate glasses prescription for these children may not be needed to prevent failure for VA and/or binocularity.

Cortical Visual Connections via the Corpus Callosum are Asymmetrical in Human Infantile Esotropia

ABSTRACTPurpose: Besides chiasmal hemidecussation, interhemispheric connections are likely important in human binocularity. The corpus callosum (CC) is the major fiber bundle in the mammalian brain which mostly connects homologous cortical areas in the two hemispheres. Visual interhemispheric connections were found abnormal in strabismic cats. No studies have investigated these pathways in humans with infantile strabismus.Methods: Diffusion tensor imaging was used in four subjects with infantile esotropia (IE) and nine control subjects with normal binocularity, in order to study interhemispheric fibers in the CC connecting the right and left primary visual cortical areas.Results: The number of callosal fibers linking both visual cortical areas between the hemispheres was found to be higher in subjects with IE. Also in IE, the amount of visual callosal fibers found after analysis from the primary visual cortical areas on one side appeared significantly different from the amount starting from the contralateral primary visual areas. The distribution area on one side is wider.Conclusion: We show callosal visual fibers to be abnormal in human IE. Subjects with IE showed abnormal numbers of transcallosal fibers connecting the visual cortical areas on both sides which likely results from an abnormal elimination process during development. Pruning of these fibers in IE favors the side of the visual cortex ipsilateral to the dominant eye. This study underlines the likely role of the CC in the development of human binocularity.

Normal Topography and Binocularity of the Superior Colliculus in Strabismus.

In subjects with alternating strabismus, either eye can be used to saccade to visual targets. The brain must calculate the correct vector for each saccade, which will depend on the eye chosen to make it. The superior colliculus, a major midbrain center for saccade generation, was examined to determine whether the maps serving each eye were shifted to compensate for strabismus. Alternating exotropia was induced in two male macaques at age 1 month by sectioning the tendons of the medial recti. Once the animals grew to maturity, they were trained to fixate targets with either eye. Receptive fields were mapped in the superior colliculus using a sparse noise stimulus while the monkeys alternated fixation. For some neurons, sparse noise was presented dichoptically to probe for anomalous retinal correspondence. After recordings, microstimulation was applied to compare sensory and motor maps. The data showed that receptive fields were offset in position by the ocular deviation, but otherwise remained aligned. In one animal, the left eye's coordinates were rotated ∼20° clockwise with respect to those of the right eye. This was explained by a corresponding cyclorotation of the ocular fundi, which produced an A-pattern deviation. Microstimulation drove the eyes accurately to the site of receptive fields, as in normal animals. Single-cell recordings uncovered no evidence for anomalous retinal correspondence. Despite strabismus, neurons remained responsive to stimulation of either eye. Misalignment of the eyes early in life does not alter the organization of topographic maps or disrupt binocular convergence in the superior colliculus.SIGNIFICANCE STATEMENT Patients with strabismus are able to make rapid eye movements, known as saccades, toward visual targets almost as gracefully as subjects with normal binocular alignment. They can even exercise the option of using the right eye or the left eye. It is unknown how the brain measures the degree of ocular misalignment and uses it to compute the appropriate saccade for either eye. The obvious place to investigate is the superior colliculus, a midbrain oculomotor center responsible for the generation of saccades. Here, we report the first experiments in the superior colliculus of awake primates with strabismus using a combination of single-cell recordings and microstimulation to explore the organization of its topographic maps.

A Model Explaining Infantile Esotropia: Dissociated Strabismus as a Result of Sensory Interhemispheric Dissociation and Crossed Dominance in the Brainstem

Over 150 million years, modern reptiles, birds and mammals evolved. Predatory birds and mammals have eyes on the front of their heads. In these animals, binocular correspondence, voluntary eye movements, eye-hand coordination, partial decussation at the optic chiasm and cortical interhemispheric pathways could develop at the cost of a smaller visual field. The subsequent enlargement of the cerebral neocortex and the hemispheric pathways are of central importance in binocular vision, sensory fusion and infantile strabismus. To investigate visual interhemispheric fibers, tractography was used in subjects with infantile esotropia (IE), callosal agenesis and control subjects with normal binocularity. In human callosal agenesis, normal binocularity could be explained by a different interhemispheric connection. In subjects with infantile esotropia, the analyses starting from the primary visual area on one side appeared different from the analysis from the other side. The distribution areas are asymmetrical between sides. Binocularity and alignment not only rely on correspondence between crossed and uncrossed hemi-representations but, in addition the corpus callosum, the most important interhemispheric pathway in placental mammals, seems important in the development of human binocularity. When correspondence is possible between the hemi-representations of the crossed and the uncrossed pathway on both sides of the cortex, the uncrossed pathway finds its way via the corpus callosum toward the contralateral hemi-representation of the same eye. A vertical midline must come out of this process. Meanwhile, however, the other uncrossed pathway strives to find the vertical midline of the other eye. Likely, the corpus callosum is important during the tuning of the pathways involved in sensory fusion. The anterior commissure might be an alternative in callosal agenesis. A failure in the offset will result in strabismus and crossed dominance after V1. Consequently, the normal binocular development of the brainstem (i.e., the superior colliculus), will not take place and latent nystagmus, as well as dissociated divergence, may ensue.

Accommodation and Phoria in Children Wearing Multifocal Contact Lenses.

To determine the effect of multifocal contact lenses on accommodation and phoria in children. This was a prospective, non-dispensing, randomized, crossover, single-visit study. Myopic children with normal accommodation and binocularity and no history of myopia control treatment were enrolled and fitted with CooperVision Biofinity single vision (SV) and multifocal (MF, +2.50D center distance add) contact lenses. Accommodative responses (photorefraction) and phorias (modified Thorington) were measured at four distances (>3 m, 100 cm, 40 cm, 25 cm). Secondary measures included high- and low-contrast logMAR acuity, accommodative amplitude, and facility. Differences between contact lens designs were analyzed using repeated measures regression and paired t-tests. A total of 16 subjects, aged 10 to 15 years, completed the study. There was a small decrease in high (SV: -0.08, MF: +0.01) and low illumination (SV: -0.03, MF: +0.08) (both P < .01) visual acuity, and contrast sensitivity (SV: 2.0, MF: 1.9 log units, P = .015) with multifocals. Subjects were more exophoric at 40 cm (SV: -0.41, MF: -2.06 Δ) and 25 cm (SV: -0.83, MF: -4.30 Δ) (both P < .01). With multifocals, subjects had decreased accommodative responses at distance (SV: -0.04; MF: -0.37D, P = .02), 100 cm (SV: +0.37; MF: -0.35D, P < .01), 40 cm (SV: +1.82; MF: +0.62D, P < .01), and 25 cm (SV: +3.38; MF: +1.75D, P < .01). There were no significant differences in accommodative amplitude (P = .66) or facility (P = .54). Children wearing multifocal contact lenses exhibited reduced accommodative responses and more exophoria at increasingly higher accommodative demands than with single vision contact lenses. This suggests that children may be relaxing their accommodation and using the positive addition or increased depth of focus from added spherical aberration of the multifocals. Further studies are needed to evaluate other lens designs, different amounts of positive addition and aberrations, and long-term adaptation to lenses.

Interhemispheric Connections between the Primary Visual Cortical Areas via the Anterior Commissure in Human Callosal Agenesis.

Aim: In humans, images in the median plane of the head either fall on both nasal hemi-retinas or on both temporal hemi-retinas. Interhemispheric connections allow cortical cells to have receptive fields on opposite sides. The major interhemispheric connection, the corpus callosum, is implicated in central stereopsis and disparity detection in front of the fixation plane. Yet individuals with agenesis of the corpus callosum may show normal stereopsis and disparity vergence. We set out to study a possible interhemispheric connection between primary visual cortical areas via the anterior commissure to explain this inconsistency because of the major role of these cortical areas in elaborating 3D visual perception.Methods: MRI, DTI and tractography of the brain of a 53-year old man with complete callosal agenesis and normal binocular single vision was undertaken. Tractography seed points were placed in both the right and the left V1 and V2. Nine individuals with both an intact corpus callosum and normal binocularity served as controls.Results: Interhemispheric tracts through the anterior commissure linking both V1 and V2 visual cortical areas bilaterally were indeed shown in the subject with callosal agenesis. All other individuals showed interhemispheric visual connections through the corpus callosum only.Conclusion: Callosal agenesis may result in anomalous interhemispheric connections of the primary visual areas via the anterior commissure. It is proposed here that these connections form as alternative to the normal callosal pathway and may participate in binocularity.

Peripheral prism glasses: effects of moving and stationary backgrounds.

Unilateral peripheral prisms for homonymous hemianopia (HH) expand the visual field through peripheral binocular visual confusion, a stimulus for binocular rivalry that could lead to reduced predominance and partial suppression of the prism image, thereby limiting device functionality. Using natural-scene images and motion videos, we evaluated whether detection was reduced in binocular compared with monocular viewing. Detection rates of nine participants with HH or quadranopia and normal binocularity wearing peripheral prisms were determined for static checkerboard perimetry targets briefly presented in the prism expansion area and the seeing hemifield. Perimetry was conducted under monocular and binocular viewing with targets presented over videos of real-world driving scenes and still frame images derived from those videos. With unilateral prisms, detection rates in the prism expansion area were significantly lower in binocular than in monocular (prism eye) viewing on the motion background (medians, 13 and 58%, respectively, p = 0.008) but not the still frame background (medians, 63 and 68%, p = 0.123). When the stimulus for binocular rivalry was reduced by fitting prisms bilaterally in one HH and one normally sighted subject with simulated HH, prism-area detection rates on the motion background were not significantly different (p > 0.6) in binocular and monocular viewing. Conflicting binocular motion appears to be a stimulus for reduced predominance of the prism image in binocular viewing when using unilateral peripheral prisms. However, the effect was only found for relatively small targets. Further testing is needed to determine the extent to which this phenomenon might affect the functionality of unilateral peripheral prisms in more real-world situations.

유발된 광학적 흐림이 시력과 대비감도에 미치는 영향

목적: 인위적으로 유발된 광학적 흐림이 원거리 시력과 대비감도에 미치는 영향을 <TEX>$Optec^{(R)}$</TEX> 6500으로 측정하여 알아보았다. 방법: 평균연령 <TEX>$22.90{\pm}1.92$</TEX>세의 대학생 31명(남자 16명, 여자 15명)을 대상자로 선정하였다. 타각적, 자각적 굴절검사를 실시하여 완전교정값을 구하였고, 광학적 흐림은 S0.00 D~S+3.00 D(+0.50 D step)까지 시험렌즈를 시험테에 장입하여 검사하였다. 원거리 시력과 대비감도는 <TEX>$Optec^{(R)}$</TEX> 6500을 이용하여 측정하였고, 검사환경은 명소시 조건하에서 양안으로 측정하였다. 결과: 원거리 시력은 광학적 흐림의 양이 증가하면 감소되었고, 시력의 감소율(decrease rate)은 점점 작아졌다. 대비감도는 광학적 흐림의 양이 증가하면 모든 공간주파수의 대비감도가 감소되었고, 정점대비감도는 중간 공간주파수(6 cpd)에서 낮은 공간주파수(1.5 cpd)로 이동하는 현상을 보였다. 또한 시력은 최고시력에서 약 0.77까지 구간에서만 정상적인 대비감도의 정점인 6 cpd의 공간주파수에서 정점을 나타내었다. 결론: 적은 양의 굴절이상을 교정하지 않거나 부적절한 굴절교정상태이면, 적은 양이라 할지라도 대비감도가 저하되고 비정상적으로 정점대비감도가 이동하여 일상생활에 시각적 불편함을 야기할 수도 있으므로 항상 주기적인 시력검사와 신중한 안경처방값을 결정하여야 된다고 사료된다. Purpose: To study the effect of an artificially induced dioptric blur on acuity and contrast sensitivity using the <TEX>$Optec^{(R)}$</TEX> 6500. Methods: Healthy 31 subjects aged <TEX>$22.90{\pm}1.92$</TEX> (male 16, female 15) who were recruited from university students with 6/6 (20/20) or better corrected visual acuity and normal binocularity. They were measured objective and subjective refraction for full correction and dioptric blur using 0.00 ~ +3.00 D (+0.50 D steps) trial lenses and trial frame. They were measured binocularly visual acuity and contrast sensitivity with the <TEX>$Optec^{(R)}$</TEX> 6500 (Stereo Optical Co., Inc., Chicago, Illinois, USA) under day conditions (photopic condition, <TEX>$85cd/m^2$</TEX>). Results: The higher dioptric blur, the less distance visual acuity and decrease rate of visual acuity. The higher dioptric blur, the less contrast sensitivity at all frequencies, and the peak of contrast sensitivity was shifted from middle frequency (6 cpd) to low frequency (1.5 cpd). When the visual acuity was best visual acuity to 0.77, there was the peak point at 6 cpd which was normal contrast sensitivity peak point. Conclusions: If the low refractive error is uncorrected or the refractive error is inappropriate, the contrast sensitivity is decreased and the peak point of contrast sensitivity frequency is shifted abnormally though small uncorrected refractive error. So it will be considered that regular eye test and decision of refractive error correction is important.

A switch from inter‐ocular to inter‐hemispheric suppression following monocular deprivation in the rat visual cortex

Binocularity is a key property of primary visual cortex (V1) neurons that is widely used to study synaptic integration in the brain and plastic mechanisms following an altered visual experience. However, it is not clear how the inputs from the two eyes converge onto binocular neurons, and how their interaction is modified by an unbalanced visual drive. Here, using visual evoked potentials recorded in the juvenile rat V1, we report evidence for a suppressive mechanism by which contralateral eye activity inhibits responses from the ipsilateral eye. Accordingly, we found a lack of additivity of the responses evoked independently by the two eyes in the V1, and acute silencing of the contralateral eye resulted in the enhancement of ipsilateral eye responses in cortical neurons. We reverted the relative cortical strength of the two eyes by suturing the contralateral eye shut [monocular deprivation (MD)]. After 7days of MD, there was a loss of interocular suppression mediated by the contralateral, deprived eye, and weak inputs from the closed eye were functionally inhibited by interhemispheric callosal pathways. We conclude that interocular suppressive mechanisms play a crucial role in shaping normal binocularity in visual cortical neurons, and a switch from interocular to interhemispheric suppression represents a key step in the ocular dominance changes induced by MD. These data have important implications for a deeper understanding of the key mechanisms that underlie activity-dependent rearrangements of cortical circuits following alteration of sensory experience.

Horizontal Saccade Dynamics After Childhood Monocular Enucleation

We investigated the effects of monocularity on oculomotor control by examining the characteristics of the horizontal saccades of people with one eye, and comparing them to those of a group of age-matched controls who viewed the stimuli monocularly and binocularly. Participants were tested in a no-gap, no-overlap saccadic task using a video-based remote eye tracker. One group consisted of unilaterally eye enucleated participants (N = 15; mean age, 31.27 years), the other of age-matched people with normal binocular vision (N = 18; mean age, 30.17 years). The horizontal saccade dynamics of enucleated people are similar to those of people with normal binocularity when they view monocularly and, with the exception of latency, when they view binocularly. The data show that the monocular saccades of control and enucleated observers have longer latencies than the binocular saccades of the control group, the saccades of the enucleated observers are as accurate as those of the controls viewing monocularly or binocularly, smaller saccades are more accurate than the larger ones, and abducting saccades are faster than adducting saccades. Our data suggest that the true monocularity produced by early enucleation does not result in slower visual processing in the afferent (sensory) pathway, or in deficits in the efferent (motor) pathways of the saccadic system. Possible mechanisms to account for the effects of monocular vision on saccades are discussed.

Environmental Enrichment Rescues Binocular Matching of Orientation Preference in Mice that Have a Precocious Critical Period

Experience shapes neural circuits during critical periods in early life. The timing of critical periods is regulated by both genetics and the environment. Here we study the functional significance of such temporal regulations in the mouse primary visual cortex, where critical period plasticity drives binocular matching of orientation preference. We find that the binocular matching is permanently disrupted in mice that have a precocious critical period due to genetically enhanced inhibition. The disruption is specific to one type of neuron, the complex cells, which, as we reveal, normally match after the simple cells. Early environmental enrichment completely rescues the deficit by inducing histone acetylation and consequently advancing the matching process to coincide with the precocious plasticity. Our experiments thus demonstrate that the proper timing of the critical period is essential for establishing normal binocularity and the detrimental impact of its genetic misregulation can be ameliorated by environmental manipulations via epigenetic mechanisms.

Same-day Cataract Surgery Should Be the Standard of Care for Patients With Bilateral Visually Significant Cataract

Same-day, or immediately sequential, bilateral cataract surgery (ISBCS) is being practiced with increasing frequency worldwide. It provides many advantages including convenience for the patient and the patient's family. ISBCS repairs the visual system, not merely one eye, restoring normal binocularity as well as unilateral clarity, creates a much more relaxed surgical atmosphere in harried operating rooms, and saves money for society. It is often preferred by busy professionals. The purported risks of ISBCS have been unsupported by the literature, including bilateral retinal detachment, bilateral corneal decompensation, bilateral diabetic macular edema, bilateral severe cystoid macular edema, significant IOL power errors in the first eye that could be refined and thereby prevented in the second eye, and toxic anterior segment syndrome. The greatest fear of ISBCS has been possible simultaneous bilateral endophthalmitis, which did not occur in a series of nearly 100,000 ISBCS cases and has only occurred elsewhere when complete separation of the two eyes and strict sterile protocol were not followed. The International Society of Bilateral Cataract Surgeons (www.isbcs.org) has prepared the “iSBCS General Principles for Excellence in ISBCS,” which should be followed for safe ISBCS.

Peripheral Prism Glasses

Unilateral peripheral prisms for homonymous hemianopia (HH) place different images on corresponding peripheral retinal points, a rivalrous situation in which local suppression of the prism image could occur and thus limit device functionality. Detection with peripheral prisms has primarily been evaluated using conventional perimetry, where binocular rivalry is unlikely to occur. We quantified detection over more visually complex backgrounds and examined the effects of ocular dominance. Detection rates of eight participants with HH or quadranopia and normal binocularity wearing unilateral peripheral prism glasses were determined for static perimetry targets briefly presented in the prism expansion area (in the blind hemifield) and the seeing hemifield, under monocular and binocular viewing, over uniform gray and more complex patterned backgrounds. Participants with normal binocularity had mixed sensory ocular dominance, demonstrated no difference in detection rates when prisms were fitted on the side of the HH or the opposite side (p > 0.2), and had detection rates in the expansion area that were not different for monocular and binocular viewing over both backgrounds (p > 0.4). However, two participants with abnormal binocularity and strong ocular dominance demonstrated reduced detection in the expansion area when prisms were fitted in front of the non-dominant eye. We found little evidence of local suppression of the peripheral prism image for HH patients with normal binocularity. However, in cases of strong ocular dominance, consideration should be given to fitting prisms before the dominant eye. Although these results are promising, further testing in more realistic conditions including image motion is needed.

Reliability of the Developmental Eye Movement Test

This study evaluated the repeatability of the Developmental Eye Movement Test (DEM) with three consecutive administrations on two separate visits to 181 children between the ages of 6 years and 11 years 11 months. Children with visual acuity of ≥ 20/25, normal binocularity, and accommodation were administered three different versions of the DEM test. One to 4 weeks after the first administration of the DEM, the children were tested again using the same order for the three versions of the DEM. Measures of within- and between-session repeatability for the vertical-adjusted time, horizontal-adjusted time, ratio, and error scores were determined. The within-session repeatability for vertical- and horizontal-adjusted time were good to excellent but were poor to good for ratio, and poor to fair for errors. The between-session intraclass correlation coefficients were fair to good for both the vertical and horizontal scores but poor for the ratio and error scores. The repeatability of the pass-fail diagnostic classification within a single session for each subject on test and retest was compared. The percentage of patients who remained in the same classification ranged from 71 to 100% for both vertical and horizontal scores. Wider variability was seen with the ratio and error scores showing between 47 and 100% of the children remaining classified as pass or fail with repeated administrations of the DEM. Such findings would suggest that children in this age range may show improvements in all four test scores without any intervention. Although the DEM is widely used in optometric practice, the results of this study suggest that clinicians should be cautious about using the DEM test in isolation for reaching a diagnosis or monitoring the effectiveness of treatment for saccadic dysfunction.

Distance Stereotest Using a 3-Dimensional Monitor for Adult Subjects

To evaluate the validity and test-retest reliability of a contour-based 3-dimensional (3-D) monitor distance stereotest (distance 3-D stereotest) and to measure the maximum horizontal disparity that can be fused with disparity vergence for determining the largest measurable disparity of true stereopsis. Observational case series. Sixty-four normal adult subjects (age range, 23 to 39 years) were recruited. Contour-based circles (crossed disparity, 5000 to 20 seconds of arc; Microsoft Visual Studio C(++) 6.0; Microsoft, Inc, Seattle, Washington, USA) were generated on a 3-D monitor (46-inch stereoscopic display) using polarization glasses and were presented to subjects with normal binocularity at 3 m. While the position of the stimulus changed among 4 possible locations, the subjects were instructed to press the corresponding position of the stimulus on a keypad. The results with the new distance 3-D stereotest were compared with those from the distance Randot stereotest. The results of the distance 3-D stereotest and the distance Randot stereotests were identical in 64% and within 1 disparity level in 97% of normal adults. Scores obtained with the 2 tests showed a statistically significant correlation (r = 0.324, P = .009). The half-width of the 95% limit of agreement was 0.47 log seconds of arc (1.55 octaves) using the distance 3-D stereotest--similar to or better than that obtained with conventional distance stereotests. The maximum binocular disparity that can be fused with vergence was 1828 ± 794 seconds of arc (range, 4000 to 500). The distance 3-D stereotest showed good concordance with the distance Randot stereotest and relatively good test-retest reliability, supporting the validity of the distance 3-D stereotest. The normative data set obtained from the present study can serve as a useful reference for quantitative assessment of a wide range of binocular sensory abnormalities.

Duane’s retraction syndrome: its sensory features

To investigate binocularity in Duane's retraction syndrome (DRS) and to evaluate whether or not there is a relationship between the sensory and clinical features of the syndrome. Clinical and sensory findings of 29 patients with DRS were recorded. Binocularity was tested with the Bagolini glasses (BG), Worth four-dot (W4D), TNO and the stereo-fly plate of the Titmus test. Twenty-four (83%) patients showed fusion with the BG at near and 23 (79%) had fusion at distance. With the W4D, 23 (79%) patients had fusion at near and 19 (65%) had fusion at distance. Seven (24%) patients demonstrated normal stereoacuity, 15 (52%) had reduced stereoacuity and the remaining seven (24%) patients had no measurable stereoacuity. In patients without stereoacuity, amblyopia (p < 0.001), type 2 and 3 DRS (p = 0.031) and exotropia (p = 0.003) in primary position were more common than in those with reduced or with normal stereoacuity. Restriction of ocular ductions was also more severe in patients without stereoacuity than in those with reduced or normal stereoacuity (p = 0.019, p = 0.016). Patients with type 2 and 3 DRS were significantly more likely to have amblyopia (p = 0.037), large-angle heterotropia (p = 0.005) in primary position, upshoot or downshoot (p = 0.010) than those with type 1 DRS. Although approximately 75% of DRS patients had fusion and measurable stereoacuity, only 25% demonstrated normal binocularity. This report provides new data on the relationship of sensory features to most of the clinical findings of this syndrome. Sensory features, as well as most clinical features of the syndrome, are better in patients with type 1 DRS.