'Fixation disparity'

Fixation disparity is a small vergence error that does not disrupt fusion. Fixation disparity measures correlate with binocular symptoms. This paper covers methodological differences between clinical fixation disparity measurement devices, findings when objective and subjective fixation disparities are compared, and the potential impact of binocular capture on fixation disparity measurements.Fixation disparity is a small vergence error that occurs in non-strabismic individuals and does not disrupt fusion. This paper reviews clinical fixation disparity variables and their clinical diagnostic value...

BACKGROUND: To perform motor tasks, athletes must gather a considerable amount of visual information quickly. Evidence shows that visual skills vary between athletes and non-athletes, and impact athletic performance. However, there is no scientific evidence suggesting that there are any differences between the visual skills of federated and non-federated athletes. As such, the objective of this paper was to compare how visual skills influence the sports performance of federated and non-federated athletes, respectively...

PURPOSE: To evaluate the benefits on the eyes of taking breaks based on the 20-20-20 rule. METHODS: Bespoke computer software using the laptop webcam to assess user breaks, eye gaze and blinking, and emitting personalized reminders of breaks based on the 20-20-20 rule, was downloaded onto the laptops of 29 symptomatic computer users. Digital eye strain (DES), binocular vision and dry eye were assessed before and after two weeks of using the reminders and one week after the discontinuation of the strategy...

PURPOSE: To determine the fixation disparity and refractive error of first-year optometry students to ascertain any relationship between them and also identify any association between fixation disparity and visual symptoms at near. METHOD: It was an analytical cross-sectional study involving 85 participants aged 17 to 27 years (18.60 ± 1.37), 41% of whom were males. Subjective refraction was done at 3 m and fixation disparity was measured with and without spectacle correction using the Wesson Fixation Disparity Card...

SIGNIFICANCE: Binocular summation is a sensitive metric of binocular integration. As such, characterization of the mechanisms underlying binocular summation is a key step in translating and applying this knowledge to abnormal binocular systems afflicted with strabismus and amblyopia. PURPOSE: Computational models of binocular summation have advocated the operation of mechanisms sensitive to the interocular phase disparity of first-order carrier gratings. This study investigated if such generalization depended on carrier spatial frequency and orientation...

Many goal-directed, as well as spontaneous everyday activities (e.g., planning, mind-wandering), rely on an internal focus of attention. This fMRI-eye-tracking coregistration study investigated brain mechanisms and eye behavior related to internally versus externally directed cognition. Building on an established paradigm, we manipulated internal attention demands within tasks utilizing conditional stimulus masking. Internally directed cognition involved bilateral activation of the lingual gyrus and inferior parietal lobe areas as well as wide-spread deactivation of visual networks...

BACKGROUND: Sports vision is a specialisation of optometry whose objective is to improve and preserve visual function to increase sports performance. The main objective of the present study was to compare the visual expertise of non-athletes to skeet shooting athletes. METHODS: Participants underwent an optometric assessment in which all those with severe deviations from normal vision, after compensating for visual abnormalities, were eliminated. After that, the following six visuospatial components were measured: hand-eye coordination, peripheral awareness, fixation disparity, saccadic eye movements, speed of recognition and visual memory...

SIGNIFICANCE: Fixation disparity tests with various characteristics of fusional stimulus are very important for assessment of decompensated heterophoria. The results suggest that there was no reasonable agreement between the fixation disparity curve's parameters of the modified near Mallett unit and the Sheedy disparometer. PURPOSE: The purpose of this study was to determine the agreement of the fixation disparity curve parameters between the modified near Mallett unit and the Sheedy disparometer in patients with decompensated near heterophoria...

Eye behavior is increasingly used as an indicator of internal versus external focus of attention both in research and application. However, available findings are partly inconsistent, which might be attributed to the different nature of the employed types of internal and external cognition tasks. The present study, therefore, investigated how consistently different eye parameters respond to internal versus external attentional focus across three task modalities: numerical, verbal, and visuo-spatial. Three eye parameters robustly differentiated between internal and external attentional focus across all tasks...

In reading, binocular eye movements are required for optimal visual processing and thus, in case of asthenopia or reading problems, standard orthoptic and optometric routines check individual binocular vision by a variety of tests. The present study therefore examines the predictive value of such standard measures of heterophoria, accommodative and vergence facility, AC/A-ratio, NPC and symptoms for binocular coordination parameters during read-ing. Binocular eye movements were recorded (EyeLink II) for 65 volunteers during a typical reading task and linear regression analyses related all parameters of binocular coordination to all above-mentioned optometric measures: while saccade disconjugacy was weakly pre-dicted by vergence facility (15% explained variance), vergence facility, AC/A and symp-toms scores predicted vergence drift (31%)...

Clinical relevance : Several parameters are likely to affect the magnitude of fixation disparity (FD) and FD curve characteristics. Presence of a central fusion lock may have an important effect on clinical testing of FD and interpretation of its results. Background : The aim of this study was to evaluate FD curve parameters using the modified near Mallett unit (with a central fusion lock) and the Sheedy disparometer (without a central fusion lock) in symptomatic and asymptomatic subjects. Methods : This cross-sectional study was conducted in 147 patients with a mean age of 22...

The aim of this study was to investigate perceptual eye position (PEP) and to evaluate the effect of dichoptic visual perceptual training in postoperative intermittent exotropia [X(T)]. We enrolled 30 non-strabismus children (control group) and 54 postoperative X(T) children [divided into training group (33 patients) and non-training group (21 patients)]. All subjects received measurements of PEP, and the postoperative X(T) children were measured both in the third postoperative day and the third postoperative month...

INTRODUCTION: Symptoms experienced when using digital devices are known as digital eyestrain (DES) or computer vision syndrome. They can be categorised as either external (associated with dry eye) or internal (related to refractive, accommodative or binocular vision anomalies). In a large cohort of adults with DES, we investigate the prevalence of binocular and accommodative anomalies, contrasting different diagnostic approaches, to evaluate potential mechanisms for the benefit from +0...

Background/Aim: An increasing number of pre-presbyopic patients are undergoing uniocular cataract extraction. We aim to compare the binocular status of subjects with uniocular cataracts, implanted either with a multifocal or a monofocal intraocular lens (IOL). Materials and Methods: Subjects were recruited from outpatient ophthalmology clinics and randomized to an IOL type. Corrected and uncorrected LogMAR distance visual acuity (VA) and near and intermediate VA using the Radner reading test were completed...

As the eyes continuously move in 3D space, they rarely converge at the exact depth of the plane even when fixating a 2D image or computer screen. Rather, the lines of gaze measured by eye movement recordings show some misalignment so-called fixation disparity. Fixation disparity occurs in front of or behind the plane and the eyes may also be lagged vertically. For those reasons, vision research requires mathematical tools to calculate where exactly the lines of gaze cross the stimulus plane. Seminal research on vergence eye movements targeting stimuli lying on isovergence curves has been content with simple computation of the difference between the two eye rotations angles...

Purpose : To evaluate binocular coordination using video-oculography (VOG) during smartphone reading in patients with esophoria (EP) compared with control subjects. Patients and methods : Ten young and adult patients with EP (25.3 ± 7.3 years) and seven orthophoric or small-angle exophoric control subjects (25.7 ± 4.8 years) were examined. Eye movements were recorded during smartphone reading at 20, 30, and 50 cm using VOG. Differences in the horizontal fixation disparity at each distance between and within the groups were analyzed...

Purpose : To describe the design and methodology of the Convergence Insufficiency Neuro-mechanism in Adult Population Study (CINAPS), the first randomized clinical trial (RCT) studying young adults with symptomatic convergence insufficiency (CI) using a combination of traditional clinical tests, objective eye movement recordings, and functional brain activities as outcome measures. Methods : In this double-masked RCT, binocularly normal controls (BNC) (N = 50) and CI patients (N = 50) are randomized into office-based vergence/accommodative therapy (OBVAT) or office-based placebo therapy (OBPT)...

Purpose : Smartphone use is now ubiquitous and is associated with a range of ocular and visual symptoms. However, little is known about the etiology of the symptoms which accompany smartphone use and the relative contribution of accommodation/vergence versus that of the ocular surface and of blinking. This study examined the effects of 60 min reading on a smartphone on ocular symptoms, binocular vision, tear function, blinking and working distance. Methods : Twelve young adults (18-23 years; 9F:3M) with normal vision and without dry eye, or major accommodative/binocular vision disorders, completed this pilot study...

BACKGROUND: Various instruments have been developed to measure aligning prism, the prism that eliminates a fixation disparity (associated heterophoria). This includes the established Mallett near vision unit and recently developed Thomson Vision Toolbox on the iPad. With no previous research investigating the agreement between these instruments, practitioners may question if they can be used interchangeably. METHODS: 80 participants underwent near vision testing with the Mallett unit and iPad fixation disparity test...

BACKGROUND: Parkinson's disease patients are classically described by having motor disorder symptoms. Freezing of gait is one of these motor symptoms that presents in some of these patients. Even though freezing of gait is classically considered as motor dysfunction, it is now widely accepted that deficits in other sensory systems, for example visual system, may lead or contribute to freezing of gait. The purpose of this study is to characterise some of the binocular vision functions in freezing of gait patients, non-freezing of gait Parkinson's disease patients and age-matched healthy controls...