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Purpose. This study aims to analyze sensory fusion recovery using method of LCD glasses with alternating occlusion of visual fields and compare its efficacy with orthoptic treatment using synoptophore. Material and methods. Eighty-six patients with prior esotropia, post-operative absence of bifoveal fusion and residual angle of deviation

To evaluate whether the results of the health-related quality of life (HRQOL) is associated with the various clinical aspects of intermittent exotropia in children. The HRQOL of children and their parents was evaluated prospectively using the Intermittent Exotropia Questionnaire (IXTQ). The deviation angle, stereo function, sensory fusion, and strabismus control were measured. Two hundred and sixty six children with intermittent exotropia (aged 5–17 years) were included in the study. Child HRQOL was significantly correlated with clinical severity; lower IXTQ scores were associated with a larger deviation (p

We describe a new unified model to explain both binocular fusion and depth perception, over a broad range of depths. At each location, the model consists of an array of paired spatial frequency filters, with different relative horizontal shifts (position disparity) and interocular phase disparities of 0, 90, ±180, or −90 degrees. The paired filters with different spatial profiles (non-zero phase disparity) compute interocular misalignment and provide phase-disparity energy (binocular fusion energy) to drive selection of the appropriate filters along the position disparity space until the misalignment is eliminated; sensory fusion is achieved locally. The paired filters with identical spatial profiles (0 phase disparity) compute the position-disparity energy. After sensory fusion, the combination of position and possible residual phase disparity energies is calculated for binocular depth perception. Binocular fusion occurs at multiple scales following a coarse-to-fine process. At a given location, the apparent depth is the weighted sum of fusion shifts combined with residual phase disparity in all spatial-frequency channels, and the weights depend on stimulus spatial frequency and stimulus contrast. To test the theory, we measured disparity minimum and maximum thresholds (Dmin and Dmax) at three spatial frequencies and with different intraocular contrast levels. The stimuli were Random-Gabor-Patch (RGP) stereograms consisting of Gabor patches with random positions and phases, but with a fixed spatial frequency. The two eyes viewed identical arrays of patches except that one eye’s array could be shifted horizontally and could differ in contrast. Our experiments and modeling reveal two contrast normalization mechanisms: (1) Energy Normalization (EN): Binocular energy is normalized with monocular energy after the site of binocular combination. This predicts constant Dmin thresholds when varying stimulus contrast in the two eyes; (2) DSKL model Interocular interactions: Monocular contrasts are normalized before the binocular combination site through interocular contrast gain-control and gain-enhancement mechanisms. This predicts contrast dependent Dmax thresholds. We tested a range of models and found that a model consisting of a second-order pathway with DSKL interocular interactions and a first-order pathway with EN at each spatial-frequency band can account for both the Dmin and Dmax data very well. Simulations show that the model makes reasonable predictions of suprathreshold depth perception.

AimsBagolini striated lenses are a useful test of binocular vision, but the variations in the striations (frequency and thickness) can impact on the perceived image. Also, responses can be difficult to interpret in young children. Therefore, the aims of this project were to evaluate the impact of striation frequency and the addition of coloured filters on subjective responses.MethodsThree sets of striated lenses were made (small, medium and large striations), each produced in two forms (both lenses clear, or with a red and blue lens). Also, Bagolini glasses (Optiker Ryser) were used, with and without the addition of red and blue filters. Subjects were asked to report what they perceived, with subsequent questions regarding the number and length of lines.ResultsForty-two adult subjects were tested, with uniocular VA ranging from -0.18 to 1.10 logMAR (mean 0.08 ± 0.25). The number of lines seen when varying the line thickness did not vary between coloured and clear lenses (post-hoc analysis following ANOVA, p > 0.1 in all comparisons). Adding red/blue filters to the original Bagolini glasses did not alter the rates of subjects perceiving a cross (Chi-square, p = 0.8). However, the laser-cut lenses produced a significantly shorter light streak than the original lenses (One-way ANOVA, p < 0.001), but the colour of the filters made no difference to the length of streak perceived (Tukey's Test, p = 0.20).ConclusionsThe addition of coloured filters did not impact on the responses given to the original or laser-cut lenses, suggesting this modification may aid responses in children. However, further evaluation is required with finer striations and thinner lenses to improve the visibility of the lines.

Objective: No method exists to measure aniseikonia tolerance in stereoacuity. The brain can compensate for 2%–3% aniseikonia (i.e. 2–3 dioptres of anisometropia) without impairing stereoacuity; however, a substantial proportion of anisometropic patients experience problems caused by disruptions of sensory fusion due to surgically induced aniseikonia. We hypothesized that individual differences in tolerance to aniseikonia exist and sought to develop a method to measure aniseikonia tolerance. Methods: A total of 21 eye-healthy phakic individuals older than 50 years of age and 11 patients awaiting clear lens extraction were included. Patients were tested with best corrected near and distance visual acuity, cover/uncover test, eye dominance test, stereoacuity threshold (TNO test), slit lamp examination and ocular coherence tomography. The stereoacuity threshold was determined with aniseikonia induced by different size lenses ranging from 1% to 9% magnification of both eyes in increments of 1%. The aniseikonia tolerance range (ATR) was defined as the percentage aniseikonia in which the stereoacuity threshold was maintained. Results: We examined 32 patients with a median age of 65 (95% CI: 62–66 years), CDVA better than 6/7.5 (0.1 logMAR), and median near visual acuity better than 6/6 (0.0 logMAR). The median stereoacuity threshold was 60 arcsec (maximum 30, minimum 120). We observed large inter-individual differences in ATR: 6/31 (19%) participants had an ATR of ≤1%, 1/31 (3%) had an ATR of 1-5%, 7/31 (22%) had an ATR of 5-10%, and 17/31 (54%) had an ATR of >10%. Conclusion: We present a reliable method for measuring the amount of aniseikonia that a person can tolerate without impairing stereopsis. We report large inter-individual differences in tolerance of aniseikonia.

PURPOSE: To evaluate fine motor ability in children treated for unilateral congenital or infantile cataract. METHODS: Twenty-three children 3–13 yearsof agewho were treated for unilateral congenital or infantile cataract and 38 age-similar control children were enrolled. Children completed five fine motor skills tasks (unimanual dexterity, bimanual dexterity, drawing trail, aiming, catching) from the Movement Assessment Battery for Children-2. Raw scores were converted into standardized scores, with higher scores indicating better performance. RESULTS: Compared with controls, children treated for unilateral cataract scored lower on drawing trail (P = 0.009), aiming (P = 0.009), and catching (P < 0.001) but not on unimanual (P = 0.77) or bimanual dexterity (P = 0.31). Poorer affected eye visual acuity was moderately related to poorer performance for unimanual dexterity (r = −0.47; P = 0.025), bimanual dexterity (r = −0.50; P = 0.014), and catching (r = −0.41; P = 0.051). Those with a poor visual outcome (>0.6 logMAR) had worse performance than those with a good visual outcome (≤0.6 logMAR) for all tasks (all P values, 0.008–0.09) except aiming. Cataract type (congenital, 9; infantile, 14) and sensory fusion by Worth 4-Dot testing at 33 cm (pass, 10; fail, 13) had no effect on fine motor performance (all P values, 0.12–0.98). CONCLUSIONS: In our study cohort, fine motor deficits were found in children treated for congenital or infantile unilateral cataract.

The aims of this study were to analyze the relationship between the performance on fine motor skills tasks and peripheral and bifoveal sensory fusion, phasic and tonic motor fusion, the level of visual acuity (VA) in the poorer seeing eye, and the interocular VA difference.Subjects aged 12 to 28 years with a range of levels of binocular vision and VA performed three tasks: Purdue pegboard (number of pegs placed in 30 s), bead threading task (with two sizes of bead to increase the difficulty, time taken to thread a fixed number of beads), and a water pouring task (accuracy and time to pour a fixed quantity into five glass cylinders). Ophthalmic measures included peripheral (Worth 4 dot) and bifoveal (4 prism diopter) sensory fusion, phasic (prism bar) and tonic (Risley rotary prism) motor fusion ranges, and monocular VA.One hundred twenty-one subjects with a mean age of 18.8 years were tested; 18.2% had a manifest strabismus. Performance on fine motor skills tasks was significantly better in subjects with sensory and motor fusion compared with those without for most tasks, with significant differences between those with and without all measures of fusion on the pegboard and bead task. Both the acuity in the poorer seeing eye (highest r value of all motor tasks = 0.43) and the interocular acuity difference were statistically significantly related to performance on the motor skill tasks.Both sensory and motor fusion and good VA in both eyes are of benefit in the performance of fine motor skills tasks, with the presence of some binocular vision being beneficial compared with no fusion on certain sensorimotor tasks. This evidence supports the need to maximize fusion and VA outcomes.

The most common functional benefits from strabismus surgery in the adult patient are restoration of binocular vision and elimination of diplopia and/or a compensatory head posture. Adult patients with chronic strabismus have been thought to have the potential to achieve only a cosmetic result from surgery. On the contrary, several studies have shown that unexpected sensory fusion is possible after excellent postoperative motor alignment in these patients. Other functional benefits of strabismus surgery in the adult patient include the expansion of binocular visual fields in patients with esotropia and the psychosocial and economic benefits from restoration of ocular alignment. This paper will explore the impact of untreated strabismus in the adult patient and what changes occur in the patient's quality of life once strabismus has been successfully treated.

Background: There is controversy regarding whether or not visually mature individuals can permanently lose stereoacuity and under what conditions stereoacuity can be regained. Some have proposed a critical duration of misalignment in adults beyond which recovery of fine stereoacuity is not possible, despite successful surgical alignment. Methods: Twenty-one adult patients (median age 59 years) with large-angle acquired strabismus and who were successfully surgically aligned after 7 to 501 months of misalignment were studied. Subjects had no evidence of motor or sensory fusion since the onset of strabismus, on preoperative exam, or by history. Stereoacuity was measured using 1 or more of the Frisby, Preschool Randot and Titmus tests, at 8 weeks and at 12 months. Data from tests with monocular clues were not used. Results: At total of 67% of patients with chronic acquired strabismus and no preoperative fusion regained measurable stereoacuity and 44% regained fine stereoacuity of at least 60 seconds of arc. Of 10 patients with no or subnormal stereoacuity 8 weeks postoperatively, 6 (60%) showed improvement at the 12-month visit. Misalignment for up to 4 years did not preclude the development of postoperative stereoacuity. Conclusions: Although a minority of adult strabismus patients may permanently lose stereoacuity despite successful alignment for acquired strabismus, the majority do show recovery. Such recovery of stereoacuity may take several months to occur. In our adult series, duration of misalignment did not predict failure to recover stereoacuity. (J AAPOS 2002;6:233-7)

O'Shea and Crassini (1982, Perception & Psychophysics32 195–196) demonstrated that fusion persists for vertical lines with an orientation disparity of 8°, but diplopia is experienced in simultaneously presented horizontal lines with the same disparity. They concluded that the neural fusion process fuses larger horizontal disparities than vertical disparities. Kertesz criticised their demonstration because it did not quantify the possible motor component associated with fusing their counter-rotated images. Krekling and Blika argued that the demonstrated anisotropy is due to a disparity bias in the visual system, owing to the temporalward tilt of corresponding vertical meridians. We addressed these criticisms with a novel stimulus and presentation protocol, that rendered compensatory cyclovergence eye movements unlikely and explored a wide range of orientation disparities. We confirmed O'Shea and Crassini's vertical/horizontal anisotropy in orientation fusion limits. In addition, our measurements of vertical lines showed that the distributions of fused responses as a function of orientation disparity in the upper and lower visual fields were shifted relative to each other. Therefore, the distributions of fusible orientation disparities are wider for vertical lines than horizontal lines and are relatively shifted as predicted if the fusional range is centred around the vertical horopter.

Anisometropia is reported to increase with age; however, the relationship between the development of anisometropia and binocular vision has not been determined. The purpose of this study was to determine the relationship between anisometropia and binocular vision after esotropia (ET) surgery. The medical records of 51 consecutive patients with ET who had undergone ET surgery were studied. Patients with amblyopia or anisometropia ≥2 diopters (D) before surgery were excluded. The average age of the patients at the time of surgery was 4.5 ± 3.7 years, and the average postoperative period was 5.0 ± 2.2 years. The refractive errors (spherical equivalent) in both eyes were measured preoperatively and postoperatively. Binocular visual function was evaluated with a modified Worth-4 dot test. At the final visit, average anisometropia was 0.98 ± 1.30 D, which was significantly greater than the preoperative value of 0.36 ± 0.46 D (P < 0.001). Anisometropia ≥2 D was observed in ten patients (23%) postoperatively. One patient was able to fuse a target of ≥2° (10%) in the anisometropia ≥2 D group, significantly fewer than the 13 patients (32%) in the anisometropia

The size of sensory fusional and refusional areas of seven observers were measured for three fixation distances and eight retinal eccentricities. Results show that sensory fusion is affected by fixation distance and retinal eccentricity.

To analyze the effectiveness of the checkerboard pattern stimulator (CPS) in facilitating stereopsis in patients with acquired esotropia. Fourteen patients were treated with checkerboard pattern stimulation following surgical correction of the ocular alignment. In order to determine the cause of the difference in the effectiveness of CPS on exotropes and esotropes, a separate study was carried out on 15 subjects: 5 orthophores, 5 exophores, and 5 esophores. Eight of the 14 patients achieved stereopsis; the remaining 6 cases did not show marked improvement in stereoacuity. The CPS was more effective on exotropes, as reported previously, than on esotropes (P = 0.047, χ2 test). By recording the ocular positions of the 15 subjects in the separate study, we found a tendency toward exodeviation in the orthophoric and exophoric subjects but not in esophoric subjects. Our results suggest that CPS develops sensory fusion by providing an identical pattern simultaneously to the foveas of both eyes and has no effect on convergence training and motor fusion.

The nature of sensory interactions during human fusional response was investigated using band-limited, 10th-derivative-of-Gaussian patterns. Experiments were performed to investigate the effects of spatial separation, disparity magnitude, and stimulus spatial frequency on horizontal sensory fusional amplitudes (SFA). When the disparities in the inducing and probe regions were in the same direction the SFA for the probe increased; when the disparities were in opposite directions the SFA was reduced. Increases and decreases in the SFA for the probe caused by the inducing stimulus were designated enhancement and inhibition respectively. Both enhancement and inhibition increased with increasing inducing disparity. They were evident over a range of spatial frequencies from 0.75 to 3.0 c/deg and among retinal regions separated by as much as 1.5 deg arc. The SFA for the probe was not inhibited when the peak spatial frequency of the inducing stimulus was 2 octaves higher than that of the probe. The observed changes in SFA were found to be due to shifts in location rather than changes in the extent of the fusional range for the probe.

Besides loss of convergence and accommodation, head injuries can cause fusion deficiency. Part function of sensory fusion is tolerance to sphaerical and meridional aniseikonia. We will present a patient, whose aniseikonia tolerance decreased after a brain concussion.

Simultaneous objective (based on binocular eye movement recording) and subjective (nonius line displacement) measurements of horizontal and vertical fusional response were carried out in order to examine the nature of sensory fusional compensation. It was found that the presence of sensory compensation in one retinal region affects the sensory representations of neighboring regions. Unlike motor compensation, however, sensory compensation affects fusible and nonfusible contours differently. The implication of these results is examined for the reliability of subjective determinants of binocular status.

Prism Adaptation is a successful means by which to facilitate the effective planning of strabismus surgery. When applied in certain types of ocular misalignment, it is thought to significantly impr...

Detection and diplopia thresholds for vertical disparities are found to decrease when the presentation time of the stimulus with disparity is increased between 20 msec and 2 sec. This result supports the following notions previously put forward in literature: (a) the human visual system embodies detection processes which reveal vertical disparities; there is no sensory fusion mechanism in this system that gradually conceals vertical disparities: (b) the detection of vertical disparity in tachistoscopically presented stimuli is not based upon the initial appearance of the stimulus with disparity.

IT SEEMS that Worth1considered fusion essentially as a mental process and made no distinction between the motor part of the fusion (the fusional movements) and the mental process of uniting two uniocular impressions into one single impression. This distinction was clearly indicated by Roelofs,2who also pointed out that binocular vision and fusion are different words to designate the same thing. Binocular vision is fusion, and this fusion should be differentiated into motor fusion (fusional movements) and sensory fusion, or the process of uniting the two retinal images into a unitary perception. The same distinction between motor and sensory fusion was recently stressed by Burian.3The work of Chavasse4has largely contributed to the present concept of binocular vision and fusion as reflexes, or, rather, as conditioned reflexes. This concept has been elaborated most completely along ontogenetic lines by Zeeman.5 When we apply this

Horizontal binocular disparity is the fundamental stimulus for both fusional vergence and stereopsis, but whether common disparity-sensitive mechanisms are involved in both responses is unknown. To determine whether the sensitivities of motor and sensory fusion are interdependent, we studied vergence eye movements and depth discrimination, using stimuli with haplopic binocular disparities, in subjects with normal stereopsis and in subjects with mild to severe stereoanomalies. Our results showed that the subjects' disparity discrimination functions varied from nearly perfect discrimination to chance performance for all of the experimental stimuli. Their sensory functions did not necessarily predict the shape of their motor fusion functions, but in most cases were correlated with the subject's fixation disparities. The results support the conclusion that the stereoanomalies and vergence anomalies that previously have been described for coarse binocular disparities also extend to the small, haplopic binocular disparities. The independence of the response properties of sensory and motor fusion suggests that neural pathways for sensory and motor fusion separate after the initial disparity-selective mechanisms in primary visual cortex.

Fusional cyclovergence was demonstrated for the first time, using ab objective photographic method. It was discovered that the results of subjective and objective measurements of cyclovergence agreed exactly. The largest fusional cyclovergence observed was 8 degrees. The cyclovergence partly cancels out the cyclodisparity presented. The greater part of the cyclodisparity usually remains. The maximum aplitude of the sensory cyclofusion is of the order of 8 degrees. The cyclovergence response is greatest when large fusion images with numerous horizontal contours are presented. The motor mechanism of cyclofusion presupposes the existence of recently demonstrated cyclodisparity detectors. The amplitude of sensory fusion is determined by the vertical diameter of the peripheral Panum areas.

Normal retinal correspondence is not stable. The arguments for the plasticity of correspondence in normal binocular vision have been given into previous papers (Nelson, 1975, 1977). In this paper, both laboratory research and the clinical strabismus literature are reviewed to show similarities between normal and abnormal binocular vision. In particular, it is argued that sensory fusion (Panum's areas) and anomalous retinal correspondence (AC) obey similar principles, and so a sensory fusional model of AC may be developed. Recent advances in the neurophysiology of binocular vision are reviewed, but current laboratory knowledge cannot account for many phenomena known clinically unless certain postulates are made. Two hypothesized intracortical interactions among binocular disparity detectors, termed disparity domain inhibition and spatial domain facilitation, play key roles in extending the neurophysiology of binocular vision to an account of both normally - and clinically - observed plasticities of correspondence. The fusional model of retinal correspondence developed here from postulated domain interactions contrasts with the older concept of fixed corresponding points, an approach which has failed to provide a unified foundation for the treatment of normal and abnormal binocular vision.

The outcome that is called vision is a product of a great many factors both broad and pervasive throughout the organism and peculiarly dependent upon specific tissues. No ordinary treatment can even touch on all of these factors. Some of them are possibly yet unknown, and a few of them, although known, have not yet been given much attention. It is this borderline of the known and the unknown and the littledealt-with to which I am going to give some consideration in what I have to say. I shall discuss briefly four items: (1) the alternation of response theory; (2) brightness enhancement; (3) some factors underlying sensory fusion from intermittent stimulation; and (4) the nature of the distribution of photic radiation on the retina. Naturally, the four items are not mutually independent and certain of their interrelations will be brought out. The first and third items have to do with