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Vision Research Nov 2020Recent work has transformed our ideas about the neural mechanisms, behavioral consequences and effective therapies for amblyopia. Since the 1700's, the clinical... (Review)
Review
Recent work has transformed our ideas about the neural mechanisms, behavioral consequences and effective therapies for amblyopia. Since the 1700's, the clinical treatment for amblyopia has consisted of patching or penalizing the strong eye, to force the "lazy" amblyopic eye, to work. This treatment has generally been limited to infants and young children during a sensitive period of development. Over the last 20 years we have learned much about the nature and neural mechanisms underlying the loss of spatial and binocular vision in amblyopia, and that a degree of neural plasticity persists well beyond the sensitive period. Importantly, the last decade has seen a resurgence of research into new approaches to the treatment of amblyopia both in children and adults, which emphasize that monocular therapies may not be the most effective for the fundamentally binocular disorder that is amblyopia. These approaches include perceptual learning, video game play and binocular methods aimed at reducing inhibition of the amblyopic eye by the strong fellow eye, and enhancing binocular fusion and stereopsis. This review focuses on the what we've learned over the past 20 years or so, and will highlight both the successes of these new treatment approaches in labs around the world, and their failures in clinical trials. Reconciling these results raises important new questions that may help to focus future directions.
Topics: Adult; Amblyopia; Child; Child, Preschool; Depth Perception; Humans; Infant; Video Games; Vision, Binocular; Visual Acuity
PubMed: 32866759
DOI: 10.1016/j.visres.2020.07.014 -
Investigative Ophthalmology & Visual... Apr 2021The role of accommodation in myopia development and progression has been debated for decades. More recently, the understanding of the mechanisms involved in... (Review)
Review
The role of accommodation in myopia development and progression has been debated for decades. More recently, the understanding of the mechanisms involved in accommodation and the consequent alterations in ocular parameters has expanded. This International Myopia Institute white paper reviews the variations in ocular parameters that occur with accommodation and the mechanisms involved in accommodation and myopia development and progression. Convergence is synergistically linked with accommodation and the impact of this on myopia has also been critiqued. Specific topics reviewed included accommodation and myopia, role of spatial frequency, and contrast of the task of objects in the near environment, color cues to accommodation, lag of accommodation, accommodative-convergence ratio, and near phoria status. Aspects of retinal blur from the lag of accommodation, the impact of spatial frequency at near and a short working distance may all be implicated in myopia development and progression. The response of the ciliary body and its links with changes in the choroid remain to be explored. Further research is critical to understanding the factors underlying accommodative and binocular mechanisms for myopia development and its progression and to guide recommendations for targeted interventions to slow myopia progression.
Topics: Accommodation, Ocular; Convergence, Ocular; Disease Progression; Humans; Myopia; Refraction, Ocular; Vision, Binocular
PubMed: 33909034
DOI: 10.1167/iovs.62.5.4 -
Clinical & Experimental Optometry Sep 2019Smartphone and tablet use in Australia and worldwide is reaching saturation levels and associated visual and ocular discomfort such as headaches, eyestrain, dry eyes and... (Review)
Review
Smartphone and tablet use in Australia and worldwide is reaching saturation levels and associated visual and ocular discomfort such as headaches, eyestrain, dry eyes and sore eyes are widespread. This review synthesises the available literature and considers these symptoms in the context of a binocular vision and/or ocular surface aetiology. Eye discomfort with smartphones and tablets is discussed alongside similar symptoms reported with desktop computer use. Handheld devices differ from computers in viewing position and distance, screen size and luminance, and patterns of use. Accommodation is altered with handheld device use, with increased lag and decreased amplitude. Smartphone and tablet use results in reduced fusional convergence and possibly a receded near point of convergence. This is similar to what happens with computer use. Findings related to blink rate with smartphone and tablet use are contradictory, perhaps due to the influence of task difficulty, and there is limited evidence related to blink amplitude. Reduced blink rate and amplitude are consistently reported with computer use. Use of handheld digital devices, like computers, may adversely impact tear stability. There is insufficient evidence to support the impact of handheld devices on tear volume, although this is reduced with computer use. The available literature does not conclusively link eye and visual discomfort symptoms reported with handheld digital devices, with changes in binocular vision, blinking or ocular surface. However, there is a gap in our understanding of symptoms which occur with smartphone and tablet use in the context of how these devices are used. In addition, studies are required in high users such as teenagers, and in patients with dry eye or accommodative/binocular vision anomalies, all of whom may have a higher risk of symptoms. A better understanding of symptom aetiology can guide clinical advice to minimise adverse impacts on visual and ocular surface health and discomfort.
Topics: Asthenopia; Computers; Computers, Handheld; Dry Eye Syndromes; Humans; Smartphone; Vision Disorders; Vision, Binocular
PubMed: 30663136
DOI: 10.1111/cxo.12851 -
Journal of Optometry 2022Convergence insufficiency (CI) is a common binocular vision (BV) disorder characterized by difficulty in maintaining motor fusion at near, which affects approximately... (Review)
Review
Convergence insufficiency (CI) is a common binocular vision (BV) disorder characterized by difficulty in maintaining motor fusion at near, which affects approximately 7.5 percent of the population. Diagnostic criteria for the disorder are inconsistent, ranging from one to many clinical signs. Methodology for clinical tests is inconsistent in measurement technique, visual targets, required repetitions, and normative values. This manuscript demonstrates the inconsistencies amongst published studies, and highlights the importance of consistent clinical diagnostic signs, measurement techniques, visual targets, and cut-off criteria. For each clinical sign, the recommended methodology for the procedure is described. Several studies do not take age into account when diagnosing CI in their cohorts. As such, the review emphasizes changes in diagnostic signs with age. This manuscript highlights the need for consistent and clear procedures and diagnostic criteria amongst clinicians and provides the basis for future studies in terms of diagnostic testing required for CI of varying age groups.
Topics: Accommodation, Ocular; Convergence, Ocular; Humans; Ocular Motility Disorders; Vision Disorders; Vision, Binocular
PubMed: 34963569
DOI: 10.1016/j.optom.2021.11.002 -
Indian Journal of Ophthalmology May 2023Amblyopia is a monocular or binocular reduction in visual acuity that results from prolonged visual deprivation in the early years of life. It is second only to... (Review)
Review
Amblyopia is a monocular or binocular reduction in visual acuity that results from prolonged visual deprivation in the early years of life. It is second only to refractive error as a cause of poor vision in children. The gold standard treatment of amblyopia includes patching and, less commonly, atropine penalization and filters. These therapies are aimed at improvements in the visual acuity of the amblyopic eye alone. They have compliance and psychosocial issues and gains are accrued after prolonged periods. Experimental studies have demonstrated the presence of binocular cortical communication even in amblyopes and neural plasticity in late childhood as well as adulthood. On this basis, binocular vision therapy aimed at the stimulation of both eyes rather than forced use of the amblyopic eye was developed. Such therapies involve visual tasks designed in such a way that they can be completed only by binocular viewing. These tasks vary from simple game play using red-green glasses, to engaging 3D games and movie viewing. Preliminary data suggest that binocular vision therapy has led to lasting improvements in visual acuity and can be a useful adjunct, if not replacement, to the conventional treatment of amblyopia. In this article, we aim to describe the various binocular vision therapies and review the available literature on the same.
Topics: Child; Humans; Adult; Amblyopia; Vision, Binocular; Visual Acuity; Eye; Vision, Low
PubMed: 37203032
DOI: 10.4103/IJO.IJO_3098_22 -
Contact Lens & Anterior Eye : the... Apr 2023To evaluate the benefits on the eyes of taking breaks based on the 20-20-20 rule.
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. Binocular measurements included visual acuity, accommodative posture, stereopsis, fixation disparity, ocular alignment, accommodative facility, positive/negative vergences and near point of convergence. Symptoms were evaluated using the computer vision syndrome questionnaire, ocular surface disease index (OSDI), and symptom assessment in dry eye questionnaire (SANDE) versions one and two. Dry eye signs were assessed by measuring tear meniscus height, conjunctival redness, blink rate and incomplete blinking, lipid layer thickness, non-invasive keratograph break-up time, corneal and conjunctival staining and lid wiper epitheliopathy.
RESULTS
A decrease in the duration of computer work and the duration of breaks, along with an increase in the number of breaks taken per day was observed as a result of the 20-20-20 rule reminders (p ≤ 0.015). No changes on any binocular parameter were observed after the management period (p ≥ 0.051), except for an increase in accommodative facility (p = 0.010). Dry eye symptoms and DES decreased with the rule reminders (p ≤ 0.045), although this improvement was not maintained one week after discontinuation (p > 0.05). No changes on any ocular surface and tear film parameter were observed with the rule reminders (p ≥ 0.089).
CONCLUSIONS
The 20-20-20 rule is an effective strategy for reducing DES and dry eye symptoms, although 2 weeks was not enough to considerably improve binocular vision or dry eye signs.
Topics: Humans; Vision, Binocular; Dry Eye Syndromes; Tears; Cornea; Conjunctiva
PubMed: 35963776
DOI: 10.1016/j.clae.2022.101744 -
Journal of Optometry 2021
Topics: Depth Perception; Humans; Vision, Binocular
PubMed: 34176573
DOI: 10.1016/j.optom.2021.06.001 -
Vision Research Mar 2021The horopter is defined by the criterion with which it is measured; these include the apparent frontoparallel plane, the region of binocular single vision, and identical...
The horopter is defined by the criterion with which it is measured; these include the apparent frontoparallel plane, the region of binocular single vision, and identical visual direction. Another criterion is one that "the positions of the points are such that none provides a stimulus for fusional movement of the eyes". Measuring the horopter using this criterion is the aim of the current paper. Based on previous research investigating corresponding points, we predicted the vergence horopter should trace an arc similar to the empirical horizontal horopter. We further predicted based on the characteristics of vergence eye movements in the periphery, that the range of horizontal disparities that do not elicit a vergence movement would increase with eccentricity. In experiment 1 we conducted the first measurements of the vergence horopter along the horizontal plane of regard and sagittal planes. We found that the vergence horopter consists of a stable range of disparities that do not increase with eccentricity. In experiment 2, we measured Panum's fusional range for the same eccentricities and elevations to determine the placement of the vergence horopter within the fusional ranges. In the horizontal plane, the vergence horopter sits centrally within Panum's fusional range. In the vertical plane, the data are suggestive that the vergence horopter is less slanted than the corresponding fusional range.
Topics: Convergence, Ocular; Eye Movements; Humans; Vision, Binocular
PubMed: 33373864
DOI: 10.1016/j.visres.2020.12.003 -
Vision Research Nov 2022Stereopsis provides us with a vivid impression of the depth and distance of objects in our 3- dimensional world. Stereopsis is important for a number of everyday visual... (Review)
Review
Stereopsis provides us with a vivid impression of the depth and distance of objects in our 3- dimensional world. Stereopsis is important for a number of everyday visual tasks, including (but not limited to) reaching and grasping, fine visuo-motor control, and navigating in our world. This review briefly discusses the neural substrate for normal binocular vision and stereopsis and its development in primates; outlines some of the issues and limitations of stereopsis tests and examines some of the factors that limit the typical development of stereopsis and the causes and consequences of stereo-deficiency and stereo-blindness. Finally, we review several approaches to improving or recovering stereopsis in both neurotypical individuals and those with stereo-deficiency and stereo-blindness and outline some emerging strategies for improving stereopsis.
Topics: Animals; Blindness; Depth Perception; Learning; Vision, Binocular
PubMed: 35841717
DOI: 10.1016/j.visres.2022.108082 -
Vision Research May 2022Binocular luster is a visual phenomenon that can be elicited by dichoptic stimuli showing an interocular difference in color or luminance contrast. For instance, when... (Review)
Review
Binocular luster is a visual phenomenon that can be elicited by dichoptic stimuli showing an interocular difference in color or luminance contrast. For instance, when the two eyes are presented with simple center-surround stimuli in which the center patch in one eye is brighter and in the other eye darker than the common surround, the center patch in the fused percept assumes a lustrous appearance reminiscent of metal or graphite. Soon after the discovery of this phenomenon in the mid-19th century, it was intensively studied and several explanations were proposed. After this initial phase, however, research interest waned significantly. Stimulated by new insights into related phenomena and the underlying physiological mechanisms, the last 20 years have seen an increase in research activity in this field, which has considerably expanded our understanding of binocular luster. In this paper, we provide a detailed review of research on binocular luster over the past 170 years. We present and discuss the existing findings in a number of separate sections, dealing with 1) the phenomenology of binocular luster, 2) different theories that have been proposed, 3) several factors influencing the lustrous impression, 4) the relationship between binocular luster and binocular rivalry, 5) the current understanding of its neural basis, and 6) potential applications based on binocular luster.
Topics: Humans; Vision Disparity; Vision, Binocular; Vision, Ocular
PubMed: 35182893
DOI: 10.1016/j.visres.2022.108008