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Cureus Aug 2021Pseudomyopia is an inappropriately excessive accommodation of the eye due to overstimulation or ciliary spasm, which leads to a marked approximation of the far point.... (Review)
Review
Pseudomyopia is an inappropriately excessive accommodation of the eye due to overstimulation or ciliary spasm, which leads to a marked approximation of the far point. Common symptoms of pseudomyopia include eye strain or fatigue, and it is classified as organic or functional. The latter is due to eye strain and functional increase in the ciliary tonus. Pseudomyopia can vary from being a transient condition or continue to progress to myopia. Head trauma is the most common cause followed by psychiatric illnesses, neurologic diseases, and drug-induced causes. There is an association between psychological stress-inducing events and pseudomyopia as it affects the autonomic nervous system. The human body counteracts anxiety by activating the parasympathetic nervous system, causing ciliary muscle contraction. Underlying psychiatric diseases in pseudomyopia patients have been reported in the past in multiple studies. Generalized anxiety disorder is the most common psychiatric illness associated with pseudomyopia with a positive correlation between anxiety-somatization scores and accommodation amount of the eye. It is strongly advised that a psychiatric consultation should be included in the multidisciplinary evaluation of every case. If patients have coexisting anxiety disorders, a multidisciplinary approach using psychiatric consultations, work environment changes, ocular exercises, and cycloplegic drugs can be used. This review aims to shed light on the association of psychiatric disorders such as anxiety with pseudomyopia.
PubMed: 34589322
DOI: 10.7759/cureus.17411 -
Progress in Retinal and Eye Research May 2021The Zonule of Zinn, or ciliary zonule, is the elaborate system of extracellular fibers that centers the lens in the eye. In humans, the fibers transmit forces that... (Review)
Review
The Zonule of Zinn, or ciliary zonule, is the elaborate system of extracellular fibers that centers the lens in the eye. In humans, the fibers transmit forces that flatten the lens during the process of disaccommodation, thereby bringing distant objects into focus. Zonular fibers are composed almost entirely of 10-12 nm-wide microfibrils, of which polymerized fibrillin is the most abundant component. The thickest fibers have a fascicular organization, where hundreds or thousands of microfibrils are gathered into micrometer-wide bundles. Many such bundles are aggregated to form a fiber. Dozens of proteins comprise the zonule. Most are derived from cells of the non-pigmented ciliary epithelium in the pars plana region, although some are probably contributed by the lens and perhaps other tissues of the anterior segment. Zonular fibers are viscoelastic cables but their component microfibrils are rather stiff structures. Thus, the elastic properties of the fibers likely stem from lateral interactions between microfibrils. Rupture of zonular fibers and subsequent lens dislocation (ectopia lentis) can result from blunt force trauma or be a sequela of other eye diseases, notably exfoliation syndrome. Ectopia lentis is also a feature of syndromic conditions caused typically by mutations in microfibril-associated genes. The resulting ocular phenotypes raise the possibility that the zonule regulates lens size and shape, globe size, and even corneal topology, in addition to its well-recognized role in accommodation.
Topics: Ciliary Body; Ectopia Lentis; Fibrillins; Humans; Lens, Crystalline; Microfibrils
PubMed: 32980533
DOI: 10.1016/j.preteyeres.2020.100902 -
Experimental Eye Research Apr 2022Emmetropization is affected by the temporal parameters of visual stimulation and the spectral composition of light, as well as by autonomic innervation. The goal of the...
Emmetropization is affected by the temporal parameters of visual stimulation and the spectral composition of light, as well as by autonomic innervation. The goal of the current experiments is to test the hypothesis that different types of visual stimulation interact with ocular innervation in the process of emmetropization. For that, selective lesions of the autonomic nervous system were performed in chickens: involving transection of parasympathetic input to the eye from either the ciliary ganglion, innervating accommodation and pupil responses (CGX; n = 32), or pterygopalatine ganglion, innervating choroidal blood vessels and cornea (PPGX; n = 26). After 1 week of recovery, chicks were exposed to sinusoidally modulated light (3 days, 2 Hz, 680 lux) that was either achromatic (black to white [RGB], or black to yellow [RG]), or chromatic (blue to yellow [B/Y] or red to green [R/G]). Exposure to light stimulation was followed by ocular biometry (Lenstar and a Hartinger refractometer). Surgical conditions revealed a small reduction in anterior chamber depth with CGX but no other significant changes in ocular biometry/refraction under standard light conditions. With RGB achromatic stimulation, CGX eyes produced an effect on ocular components, with a further reduction in anterior chamber depth and an increase in vitreous chamber depth, while RG stimulation showed no effect. No effect was detected in PPGX under both achromatic protocols. With chromatic stimulation, CGX with R/G modulation increased eye length, while PPGX with B/Y modulation decreased eye length. We conclude that the two different types of parasympathetic innervations have antagonistic effects on eye growth and the anterior eye when challenged with the appropriate stimulus, with possible implications for the role of choroidal blood flow in emmetropization.
Topics: Accommodation, Ocular; Animals; Chickens; Choroid; Emmetropia; Eye; Refraction, Ocular
PubMed: 35120871
DOI: 10.1016/j.exer.2022.108964 -
Journal of Refractive Surgery... Jun 2021
Topics: Accommodation, Ocular; Humans; Presbyopia
PubMed: 34170767
DOI: 10.3928/1081597X-20210408-01 -
Indian Journal of Ophthalmology Aug 2020Asthenopic and related symptoms are a major problem in school-going children. With the inception of computers and other gadgets for near work, the unseen problems... (Review)
Review
Asthenopic and related symptoms are a major problem in school-going children. With the inception of computers and other gadgets for near work, the unseen problems arising out of constant and continuous near work, are on the rise. Parents wander from pillar to post, seeking respite from their child's constant complaints from near work; but despite best spectacle correction and avoidance of excessive near work, the complaints continue. Studies have shown that the majority of these problems arise from defects in accommodation, even in a young child. Therefore, various aspects of accommodation deficiencies have to be studied clinically, detected, and treated to ameliorate the symptoms.
Topics: Accommodation, Ocular; Asthenopia; Child; Computers; Eyeglasses; Humans; Schools
PubMed: 32709767
DOI: 10.4103/ijo.IJO_1973_18 -
Seminars in Cell & Developmental Biology Oct 2020Raptors have always fascinated mankind, owls for their highly sensitive vision, and eagles for their high visual acuity. We summarize what is presently known about the... (Review)
Review
Raptors have always fascinated mankind, owls for their highly sensitive vision, and eagles for their high visual acuity. We summarize what is presently known about the eyes as well as the visual abilities of these birds, and point out knowledge gaps. We discuss visual fields, eye movements, accommodation, ocular media transmittance, spectral sensitivity, retinal anatomy and what is known about visual pathways. The specific adaptations of owls to dim-light vision include large corneal diameters compared to axial (and focal) length, a rod-dominated retina and low spatial and temporal resolution of vision. Adaptations of diurnal raptors to high acuity vision in bright light include rod- and double cone-free foveae, high cone and retinal ganglion cell densities and high temporal resolution. We point out that more studies, preferably using behavioural and non-invasive methods, are desirable.
Topics: Adaptation, Physiological; Animals; Raptors; Vision, Ocular
PubMed: 32654971
DOI: 10.1016/j.semcdb.2020.05.004 -
European Journal of Translational... Sep 2022The aim of this study was to identify the efficacy of drug agents for pharmacological Treatment of Presbyopia. Published research papers were reviewed using the relevant...
The aim of this study was to identify the efficacy of drug agents for pharmacological Treatment of Presbyopia. Published research papers were reviewed using the relevant terms in PubMed, Science direct, Google scholar, Medline, Google patent, Ovid, Cochrane Database of Systematic Reviews, Scopus. In the initial search, 2270 records were obtained. By removing duplicate articles and all articles that did not meet the inclusion criteria or were inappropriate due to indirect relevance to the subject, 44 studies were selected. It should be noted that all studies had inclusion criteria. There are a number of topical pharmacological agents available for treating presbyopia such as FOV Tears and PresbiDrop. They consist of parasympathetic agent and non-steroidal anti-inflammatory drugs (NSAIDs), to contract the ciliary and pupil muscle and restore the accommodation. Another example of topical pharmacological agent is EV06. It is a lens-softening eye drop which can affect the rigid lens in presbyopia. Currently there is no pharmacological agent available to treat presbyopia. Although there are limited number of peer-reviewed articles available, the outcome for future agents under investigation are promising.
PubMed: 36121117
DOI: 10.4081/ejtm.2022.10781 -
Biomedical Optics Express Dec 2022We evaluated the interaction of multifocal patterns with eye's accommodation. Seven patterns were mapped on the spatial light modulator and the deformable mirror of an...
We evaluated the interaction of multifocal patterns with eye's accommodation. Seven patterns were mapped on the spatial light modulator and the deformable mirror of an adaptive optics visual simulator, and projected onto the subjects' eyes, representing different contact lens designs: NoLens, Bifocal Center Distance (+2.50D), Bifocal Center Near (+2.50D) and Multifocal Center Near-MediumAdd (+1.75D) and Center Near HighAdd (+2.50D), positive and negative spherical aberration (±1µm). The change in spherical aberration and the accommodative response to accommodative demands were obtained from Hartmann-Shack measurements. Positive spherical aberration and Center Distance designs are consistent with a higher accommodative response (p=0.001 & p=0.003): steeper shift of SA towards negative values and lower accommodative lag.
PubMed: 36589586
DOI: 10.1364/BOE.473595