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Purpose: To report the retrospectively-based, clinical diagnostic findings for the horizontal, distance, fusional facility (DFF) test in the non-TBI (traumatic brain inury), ABI (acquired brain injury) population., Methods: The DFF test (4 pd base-out/2 pd base-in) was assessed and compared retrospectively in the first author's optometric practice in three clinical populations: (1) post-mTBI, visually-symptomatic (n = 52), (2) post-ABI, non-mTBI, visually-symptomatic (n = 34), and (3) visually-normal, visually asymptomatic (n = 44)., Results: The DFF values in each group were significantly different from each other (p < 0.05). The mean non-TBI, ABI group value was significantly lower than found in the mTBI group, and both were significantly lower than the mean found in the normal cohort (p < 0.05). There was a significant reduction in DFF with increased age (p < 0.001). ROC values for the AUC ranged from excellent to acceptable (0.94-0.74)., Conclusion: The DFF test is a new and useful way to assess horizontal, distance, dynamic, fusional facility in those with presumed non-mTBI, ABI neurological conditions to assist in its diagnosis., Competing Interests: Conflicts of interest Dr. Barry Tannen has a financial interest in the Tannen Flipper Test., (Copyright © 2023 Spanish General Council of Optometry. Published by Elsevier España, S.L.U. All rights reserved.)

Purpose: To assess changes in the nearwork-induced transient myopia parameters of initial magnitude and its decay duration, as well as accuracy of the near accommodative steady-state response and clinically based accommodative facility, after 6 weeks of home-based accommodative training in asymptomatic myopes., Methods: Ten young adult, progressing myopes participated in the study. The experimental paradigm consisted of a baseline session and two follow-up sessions at the end of the third and sixth weeks of training. At the first session, baseline refractive state and selected accommodative functions were assessed. Measurements were repeated at the two follow-up sessions. Home-based vision training included accommodative flippers (+/-2 D) at near, Hart chart at distance (6 m) and near (40 cm), and prism flipper (6 pd) training at near (40 cm), for a total of 20 minutes a day performed 5 days a week for 6 weeks., Results: Several dynamic accommodative response functions improved significantly with training. Lens flipper rate increased significantly from 11 to 16 cpm in the OD (p = 0.04), 11 to 19 cpm in the OS (p = 0.03), and 8 to 11 cpm in the OU (p = 0.03). Hart chart rate increased significantly from 22 to 33 cpm in the OD (p = 0.01) and from 22 to 31 cpm in the OS (p = 0.02). There was a significant negative correlation between lens flipper rate and nearwork-induced transient myopia decay duration after training (p = 0.02) with binocular viewing., Conclusions: Training of the accommodative system in these progressing myopes resulted in improved dynamics in both laboratory and clinical measures. This is consistent with earlier reports in the literature of improvement in symptomatic myopic subjects.

Background: Unilateral spatial inattention (USI) (a.k.a. neglect, unilateral neglect, visual neglect) is a common occurrence after stroke. It can also occur subsequent to traumatic brain injury. Insult to the right inferior (posterior) parietal cortex is the structure that is virtually always involved, although other brain areas have been implicated. The major consequence of USI is that the patient is unaware of one side of the body, and/or one side of visual space. Current literature expresses this as USI in the individual's personal, peri-personal, and extra-personal spaces., Methods: We discuss the condition's natural history, occurrence and behavioral consequences., Conclusions: We propose a system for the optometric management of USI in extra-personal and peri-personal spaces.

Background: For nearly 75 years, optometric vision therapy has been an important mode of therapy for both children and adults who manifested a range of nonstrabismic accommodative and vergence disorders., Methods: In this article, the scientific basis for, and efficacy of, optometric vision therapy in such patients will be discussed. Using bio-engineering models of the oculomotor system as the conceptual framework, emphasis will be focused on studies that used objective recording techniques to directly assess therapeutically related changes in oculomotor responsivity., Results and Conclusions: The findings clearly support the validity of optometric vision therapy. Furthermore, the results are consistent with the tenets of general motor learning.

BACKGROUND: Visual dysfunctions are common in individuals following concussion/mild traumatic brain injury (C/mTBI). Many deficits have been uncovered in their oculomotor system, such as in the pupil and accommodation. OBJECTIVE: To describe the static and dynamic abnormalities in the pupillary and accommodative systems in those with C/mTBI. This includes both diagnostic and therapeutic aspects, with emphasis on objectively-based test findings, as well as their basic and clinical ramifications. METHODS: PubMed, Google Scholar, and Semantic Scholar databases were searched from 1980–2020, using key words of accommodation, pupil, vision therapy, vision rehabilitation, and objective testing, for peer-reviewed papers, as well as related textbooks in the area, in those with C/mTBI. RESULTS: For both systems, most static and dynamic response parameters were abnormal: they were typically reduced, slowed, delayed, and/or more variable. Most of the abnormal accommodative parameters could be significantly improved with vision therapy. CONCLUSIONS: For both systems, most response parameters were abnormal, which could explain their visual symptoms and related problems. For accommodation, the improvements following vision therapy suggest the presence of considerable visual system plasticity, even in older adults with chronic brain injury. [ABSTRACT FROM AUTHOR]

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Background: Traumatic brain injury (TBI) is a global, diffuse type of injury, which results in a constellation of visual dysfunctions. The extensive neural network of the oculomotor system makes it highly vulnerable following a TBI, hence the high prevalence of signs and symptoms related to accommodative and vergence dysfunctions. Methods: The present study evaluated the therapeutic effects on clinical (subjective) and laboratory (objective) measures, as well as their correlated improvements, following an equal dosage of six weeks of vergence and accommodation training in mild TBI (n=12). Results: With only three hours of training for each system, significant improvements in both static and dynamic parameters of both systems were found. Maximum amplitude of both systems increased markedly, along with faster dynamics demonstrating speedy responsivity, following training. Several key parameters between the two systems showed significant correlation (p<0.01), such as amplitudes (r = -0.87) and facilities (r = 0.88) of accommodation and vergence. Conclusions: Tire present findings demonstrate efficacy of oculomotor rehabilitation in 1 BI, with the improvements being suggestive of intact neuroplasticity in the compromised adult brain following mTBI. [ABSTRACT FROM AUTHOR]

The purpose of this experiment was to determine the effect of type and magnitude of retinal defocus on golf putting accuracy, and on the related eye, head, and putter movements. Eye, head, and putter movements were assessed objectively along with putting accuracy in 16 young adult, visually normal inexperienced golfers during a fixed 9-foot golf putt. Convex spherical (+0.50 D, +1.00 D, +1.50 D, +2.00 D, +10.00 D) and cylindrical (+1.00 D × 90, +2.00 D × 90) lenses were added binocularly to create various types and magnitudes of retinal defocus. Putting accuracy was significantly reduced only under the highest spherical blur lens condition (+10.00 D). No significant differences were found between any other lens conditions for eye, head or putter movements. Small amounts of spherical and astigmatic retinal defocus had a minimal impact on overall golf putting performance, except for putting accuracy under the highest blur condition. This is consistent with the findings of related studies. For a fixed putting distance, factors other than quality of the retinal image, such as blur adaptation and motor learning, appeared to be sufficient to maintain a high level of motor performance. [ABSTRACT FROM AUTHOR]

Purpose: This study sought to determine the effect of very brief, single and multiple pulses of light on spatial and temporal aspects of saccadic eye movements. Methods: Twelve visually normal, young adult subjects participated in the experiments. Horizontal eye position was monitored as subjects attempted to track target step displacements in the presence of either single or multiple brief flashes of light in the visual field. Results: Three primary findings were observed: (1) increased saccadic latency, (2) increased time for target acquisition and (3) increased initial saccadic error. Conclusion: The present findings suggest the influence of attentional processes and/or visual masking effects on saccadic eye movement control. [ABSTRACT FROM AUTHOR]

The depth of focus (DOF) was measured and compared objectively in free space and subjectively in Badal optical space in 10 young adults. The mean total objective DOF was ±0.59 ±0.10 D, with a range from ±0.46 D to ±0.75 D. The mean total subjective DOF was ±0.63 ±0.22 D, with a range from ±0.37 D to ±0.96 D. The objective and subjective DOF values were not significantly different. However, response variability was greater [∼2×] in the subjective test mode. Similarity between the objective and subjective results suggests that blur plays a dominant role in this process, which is in agreement with earlier experiments and model predictions under normal closed-loop viewing conditions. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the effect of the apparent depth of pictorial images on accommodation. Steady-state accommodation was assessed objectively while viewing eight pictorial stimuli containing varying degrees of monocular cues to depth. Sixteen young adult subjects were tested monocularly with accommodation either in the closed-loop or open-loop mode. Pictorial depth cues significantly influenced the mean level of accommodation under some of the open-loop conditions in which blur feedback was rendered ineffective. For nearly all stimuli and viewing modes, the mean accommodative responses were biased in the perceptually-appropriate direction, but they were larger in the open-loop condition. Apparent depth cues did not significantly affect accommodation under closed-loop viewing conditions, presumably because blur feedback markedly dampened any perceptually-driven influences. Consistent with current models of accommodation, and several earlier studies, perceptually-based accommodation had only a secondary effect on the overall accommodative response level under naturalistic viewing conditions, with blur dominating. [ABSTRACT FROM AUTHOR]

Although the effect of retinal defocus on the foveal blur detection threshold has been well investigated, knowledge regarding the foveal blur discrimination threshold is limited. In the present study, both thresholds were assessed psychophysically using the ascending method of limits at the fovea with accommodation paralyzed. The unidirectional blur detection threshold was 0.87 ± 0.18 D (±1 S.E.M.). The subsequent blur discrimination thresholds were relatively constant and significantly smaller than the blur detection threshold, with an average value of 0.48 ± 0.006 D (±1 S.E.M.). We speculate that the difference in magnitude between these two thresholds may be attributed to the defocus-related change in the ocularmodulation transfer function (MTF) and its interaction with contrast discrimination ability, as well as to the presence of a neuroperceptual blur buffering mechanism. [ABSTRACT FROM AUTHOR]

There has been no comprehensive study involving each of the primary dynamic components of accommodation in the same cohort as related to age and presbyopic onset; furthermore, the current findings are equivocal. Dynamic monocular components of accommodation (latency, time constant, peak velocity/amplitude relationship, and microfluctuations) were assessed objectively using an infrared optometer within the linear region of accommodation in 30 visually-normal human subjects aged 21–50 years. The time constant and the peak velocity/amplitude relationship did not change with age. However, latency progressively increased, and microfluctuation amplitude and frequency progressively decreased, with increasing age. The invariance in time constant suggests that the gross biomechanical aspects of the lens and related structures in the remaining linear region are relatively unaffected by age. In contrast, the decrease in microfluctuation activity with age suggests more subtle alterations in the biomechanical aspects of the lens to these very small perturbations, such as a response amplitude non-linearity. With respect to neurologic control, the progressive latency increase suggests a processing delay of the blur input, and this is consistent with age-related changes in reaction time measures. The lack of any age-related changes in the peak velocity/amplitude relationship implies normalcy of central and peripheral neuromotor control, as well as grossly normal first-order lens biomechanics, in this linear response region. The results are consistent with the Hess–Gullstrand theory of presbyopia. [Copyright &y& Elsevier]

A number of previous studies have examined the effects of age and the development of presbyopia on either the accommodative convergence to accommodation (AC/A) or convergent accommodation to convergence (CA/C) ratios. However, changes in the interaction of these oculomotor crosslinks with increasing age have received relatively little attention, especially over a wide age distribution. Accordingly, the present study examined both crosslink ratios in 42 subjects ranging from 22 to 65 years of age. A dual haploscope-optometer was used to measure accommodation and vergence. The response AC/A ratio showed a small but significant positive correlation with age in those subjects under 45 years of age, while no significant correlation was observed between the stimulus AC/A ratio and age for all subjects. The CA/C ratio exhibited a significant negative correlation with age for all subjects. Furthermore, a trend was observed for lower CA/C findings to be associated with higher response AC/A ratios. However, the two ratios were inversely but not reciprocally related, with the mean difference between the CA/C ratio and the reciprocal of the response AC/A ratio being significantly different from zero. These age-related changes in the output of the oculomotor crosslinks provide further evidence of the continual oculomotor adaptation that occurs concurrent with the loss of accommodative responsivity. [ABSTRACT FROM AUTHOR]

Part I of this review considered basic aspects of tonic accommodation (TA). i.e. the accommodative response observed under degraded stimulus conditions. Part II considers accommodative adaptation, i.e. the apparent change in TA following periods of sustained fixation, and clinical aspects of both baseline TA and accommodative adaptation. It is suggested that the apparent post-task shift in TA reflects the slow rate of decay of the stimulus-mediated adaptive accommodative response, while the actual level of tonic innervation to the ciliary muscle remains relatively constant. The clinical implications of both TA and accommodative adaptation are discussed with regard to night, space and instrument myopia and refractive error development, notably nearwork-induced myopia. It is concluded that the evidence for any association between this Form of myopia and either TA or accommodative adaptation is equivocal, and furthermore it seems likely that TA plays only a minor rule in influencing the closed-loop steady-sate accommodative response. [ABSTRACT FROM AUTHOR]

Many investigations have attempted to demonstrate a relationship between sustained near-vision and the aetiology of environmentally-induced myopia, but it remains unclear whether myopic development relates to the actions of either accommodation or vergence. The present study investigated the effect of varying the disparity-vergence demand during a near-vision task while maintaining the accommodative stimulus constant. We required 20 young subjects to perform a near task (viewing distance = 20 cm) for 20 min through base-in, zero power and base-out prisms. The magnitude of the prisms for each individual corresponded to one-third their near vergence range. Pre- and post-task measurements of refractive state were determined objectively using an infrared optometer, with post-task readings being recorded over the initial 50 s following task completion. The results indicated no significant difference between the transient far-point shift for the three disparity-vergence conditions. However, combining data across conditions, a significant, mean shift in the myopic direction of 0.14 D was observed during the 10-20s period immediately following task completion which dissipated within 20-50s post-task. These findings suggest that the transient post-task myopic shift was not related to the output of disparity-vergence. [ABSTRACT FROM AUTHOR]

The human accommodation system was investigated using a dynamic infra-red optometer to determine whether its feedback control process exhibited dual-mode behaviour. Ramp changes of target accommodative demand presented monocularly at various velocities (0.5-0.6 D s-1) with a fixed 2 D amplitude elicited two modes of behaviour. Smooth ramp movements were observed for low-velocity stimuli, whereas step responses predominated for high-velocity stimuli. At intermediate velocities, combined step-ramp responses were more prevalent. The characteristic of these step-ramp responses showed two important properties that suggest a pre-programming mechanism. The amplitude of the step portion of a step-ramp response approximated the value of the ramp stimulus at the time corresponding to the end of the step movement. Also, the initial step amplitude increased with increasing target ramp velocity. It appears that the amplitude of the preprogrammed accommodative movement was based on an estimate of the expected ramp target position at the end of the response. These findings are consistent with a recent unifying theory of oculomotor control in which the various oculomotor subsystems (versional and vergence eye movements and accommodation) each has fast and slow components. The fast component exhibits preprogramming, while the slow component shows continuous feedback control. [ABSTRACT FROM AUTHOR]

Monocular steady-state accommodation was measured to harmonically related complex grating patterns and their components to determine the contribution of the various spatial waveforms to accommodative accuracy. Accommodative accuracy was greater for those waveforms containing summed odd-harmonic spatial components than for those waveforms with specific spatial components either removed or isolated. The results suggest that the contrast gradient produced by the summed waveforms, rather than the presence of any particular subset of spatial frequency components per se, was a critical factor for accurate accommodation. [ABSTRACT FROM AUTHOR]

A successive two-alternative, forced-choice procedure incorporating a double-interleaved staircase was used to measure monocular contrast discrimination in strabismic and/or anisometropic amblyopes, strabismics without amblyopia, and normals. Standard contrast was 25%, with comparison contrasts starting at 10 and 40%. Spatial frequencies were 0.5, 2.0, and either 4.0 or 8.0 c deg-1. The amblyopic eye consistently required more contrast than the fellow dominant eye for the task. Results in each eye of the normals and strabismics without amblyopia were similar and normal. The findings clearly demonstrate impairment of contrast discrimination in amblyopic eyes, presumably due to early abnormal visual experience. Such impairment could contribute to the increased steady-state accommodative error found in amblyopic eyes. [ABSTRACT FROM AUTHOR]

Changes in tonic accommodation and tonic vergence were monitored before, during and immediately after a 45 min period of reading adult level text displayed on either a computer monitor or hard copy at 20 cm under binocular viewing conditions. Both tonic accommodation and tonic vergence gradually increased during the reading period, with changes in tonic accommodation occurring more rapidly. The average increases in tonic accommodation and tonic vergence following reading were 0.35 dioptres and 0.38 metre angles, respectively. Decay of both tonic components to the baseline in either light or total darkness occurred within the first 3 min. These results suggest that a moderate period of interrupted reading at a close distance can produce a transient increase in the tonic oculomotor levels. [ABSTRACT FROM AUTHOR]

This study sought to determine whether proximally-induced accommodation (PLA) is capable of sustaining an accommodative response over time. Accordingly. the steady-slate PIA response was measured during the course of a continuous 5 rain stimulus period for targets located at distances of 0.2 or 6 m. The vergence and accommodation loops were opened by subjects (n = 8) monocularly viewing the targets through a 0.5 mm pinhole while accommodation was assessed using an objective, open-field, infrared optometer. The mean PIA response did not change significantly during the fixation period. This finding suggests that PIA is indeed capable of maintaining a sustained response. This observation is consistent with the constancy of apparent target distance perception during extended fixation of a stationary' object of regard under these conditions. [ABSTRACT FROM AUTHOR]

Optometrists are being asked to provide vision care to increasing numbers of individuals with mild traumatic brain injury (mTBI). However, the complexity of both the vision-based, and non-vision-based symptoms and related problems, as well as the multiple levels of concurrent care provided by other health-related professionals, may make the task appear daunting. We propose a four-tiered, conceptual model of optometric care in these patients that should render the task more easily achievable. The four-tiered model includes the basic optometric examination, and analysis of ocular motor problems, non-ocular motor problems, and non-vision-based problems. [ABSTRACT FROM AUTHOR]

A number of studies have demonstrated that visual responsivity is optimum when viewing either horizontal or vertical stimuli but is significantly reduced when viewing an obliquely oriented object of regard. Accordingly this study examined the accommodative response in 10 subjects to targets oriented at 45, 90, 135 and 180 degrees to the horizontal. Stimuli were located at distances of 1, 3 or 5 D, and steady-state accommodation was measured subjectively from the right eye using a Hartinger coincidence optometer. The data indicate that, for high contrast, supra-threshold targets, variation in target orientation did not produce any significant change in accommodative response. These results suggest that neural sensitivity for monocular blur-driven accommodation is orientation independent. This finding would imply that accommodation and contrast detection are mediated by dissimilar processes. [ABSTRACT FROM AUTHOR]