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PloS One 2021Species vary widely in the conspicuousness of their eye morphology and this could influence gaze perception. Eyes with conspicuous morphology can enhance gaze perception...
Species vary widely in the conspicuousness of their eye morphology and this could influence gaze perception. Eyes with conspicuous morphology can enhance gaze perception while eyes with camouflaged morphology may hinder gaze perception. While evidence suggests that conspicuous eye morphology enhances gaze perception, little is known about how environmental conditions affect this interaction. Thus, we investigated whether environmental light conditions affect gaze perception. Human subjects (Homo sapiens) were instructed to find direct-gaze faces within arrays of averted-gaze faces or to find averted-gaze faces within arrays of directed-gaze faces. The faces were displayed under conditions simulating nighttime or daytime conditions. Furthermore, the faces had naturally-colored sclera (white) or modified sclera (same color as the iris). Participants were fastest and most accurate in detecting faces during the daytime and nighttime conditions when the sclera were naturally-colored. Participants were worst at detecting faces with modified sclera during the nighttime conditions. These results suggest that eyes with conspicuous morphology enhance gaze perception during both daytime and nighttime conditions.
Topics: Adult; Female; Fixation, Ocular; Humans; Male; Pigmentation; Sclera; Time Factors
PubMed: 33780503
DOI: 10.1371/journal.pone.0249137 -
Indian Journal of Ophthalmology Jul 2022Management of posterior scleral perforation is commonly done with cryotherapy/laser or scleral patch graft depending on the size of perforation. However, for large...
BACKGROUND
Management of posterior scleral perforation is commonly done with cryotherapy/laser or scleral patch graft depending on the size of perforation. However, for large perforations, the availability of donor sclera is always an issue. To overcome this problem, we tried using absorbable gelatin sponge to plug the perforation as an alternative.
PURPOSE
To evaluate the efficacy of gelatin foam as an alternative to scleral patch graft in cases with perforation of posterior sclera.
SYNOPSIS
Here we report the case of a 27-year-old male, who sustained penetrating injury to right eye with two metallic intraocular foreign bodies with visual acuity of hand movement close to face. Primary wound repair was done, followed by retrieval of the first piece of metallic foreign body that measured 11X3mm in size. The second foreign body visualized at posterior pole adjascent to the disc was removed using Machemar forceps and it measured 10X3 mmin size. Leakage of PFCL at the site confirmed a posterior scleral perforation. Cryotherapy was avoided due to its proximity to optic nerve head, and donor sclera was not readily available at that moment. We managed the case by plugging the defect with absorbable gelatin foam, followed by silicone oil injection into the vitreous cavity. Post operative outcome was good with restoration of anatomical integrity of the globe along with improvement in visual acuity upto 6/18.
HIGHLIGHTS
Gelatin foam being absorbable and inciting less reaction aids in sealing the perforation and maintenance of globe contour with the advantage being readily available, cost-effective and it can be left in situ without the need for additional surgery for its removal. This would be of use in situations where the donor sclera is not readily available, and thus can be a potential alternative. However, further studies with larger sample size need to be done to evaluate and compare its effectiveness over donor scleral grafts.
ONLINE VIDEO LINK
https://youtu.be/fkardnkMQQo.
Topics: Adult; Foreign Bodies; Gelatin; Humans; Male; Optic Disk; Sclera; Tissue Donors
PubMed: 35791255
DOI: 10.4103/ijo.IJO_1431_22 -
Journal of Vision Sep 2023Progression of myopia is usually accompanied by axial overgrowth of the eyeball, which affects scleral biomechanics (BM). To study scleral biomechanics, we propose the...
Progression of myopia is usually accompanied by axial overgrowth of the eyeball, which affects scleral biomechanics (BM). To study scleral biomechanics, we propose the use of air-puff deformation swept-source OCT imaging. Air-puff deformation imaging was performed at different sites of ex vivo porcine (n=5) and rabbit (n=3) eyes, (<24hr postmortem): Nasal/temporal equatorial and posterior sclera (NE, NP, TE, TP), superior (S) and inferior (I) sclera, and cornea (C). Intraocular pressure was kept at 15mmHg. Deformation data were used as input to inverse finite element model (FEM) algorithms to reconstruct BM properties. Experimental deformation amplitudes showed dependence on the animal model, with porcine scleras exhibiting greater inter-site variation (displacement of S, I was up to four times greater than that of N, T), while rabbit scleras exhibited at most 40% of displacement differences between all sites. Both models showed significant (p<.001) differences in the temporal deformation profile between sclera and (C), but similarities in all scleral locations, suggesting that the scleral temporal profile is independent of scleral thickness variations. The FEM estimated an elastic modulus of 1.84 ± 0.30 MPa (I) to 6.04 ± 2.11 MPa (TE) for the porcine sclera. The use of scleral air-puff imaging is promising for noninvasive investigation of structural changes in the sclera associated with myopia and for monitoring possible modulation of scleral stiffness with myopia treatment.
Topics: Animals; Rabbits; Swine; Tomography, Optical Coherence; Sclera; Algorithms; Biomechanical Phenomena; Myopia
PubMed: 37733540
DOI: 10.1167/jov.23.11.38 -
Investigative Ophthalmology & Visual... Aug 2014The structure and biomechanics of the sclera and cornea are central to several eye diseases such as glaucoma and myopia. However, their roles remain unclear, partly...
PURPOSE
The structure and biomechanics of the sclera and cornea are central to several eye diseases such as glaucoma and myopia. However, their roles remain unclear, partly because of limited noninvasive techniques to assess their fibrous microstructures globally, longitudinally, and quantitatively. We hypothesized that magic angle-enhanced magnetic resonance imaging (MRI) can reveal the structural details of the corneoscleral shell and their changes upon intraocular pressure (IOP) elevation.
METHODS
Seven ovine eyes were extracted and fixed at IOP = 50 mm Hg to mimic ocular hypertension, and another 11 eyes were unpressurized. The sclera and cornea were scanned at different angular orientations relative to the main magnetic field inside a 9.4-Tesla MRI scanner. Relative MRI signal intensities and intrinsic transverse relaxation times (T2 and T2*) were determined to quantify the magic angle effect on the corneoscleral shells. Three loaded and eight unloaded tendon samples were scanned as controls.
RESULTS
At magic angle, high-resolution MRI revealed distinct scleral and corneal lamellar fibers, and light/dark bands indicative of collagen fiber crimps in the sclera and tendon. Magic angle enhancement effect was the strongest in tendon and the least strong in cornea. Loaded sclera, cornea, and tendon possessed significantly higher T2 and T2* than unloaded tissues at magic angle.
CONCLUSIONS
Magic angle-enhanced MRI can detect ocular fibrous microstructures without contrast agents or coatings and can reveal their MR tissue property changes with IOP loading. This technique may open up new avenues for assessment of the biomechanical and biochemical properties of ocular tissues in aging and in diseases involving the corneoscleral shell.
Topics: Animals; Collagen; Cornea; Humans; Intraocular Pressure; Magnetic Resonance Imaging; Models, Animal; Models, Biological; Sclera; Sheep
PubMed: 25103267
DOI: 10.1167/iovs.14-14561 -
Biomedicine & Pharmacotherapy =... Dec 2018The aim of this study was to investigate the effects of pilocarpine-induced ciliary body constant contraction for a long time period on the elastic modulus and collagen...
The aim of this study was to investigate the effects of pilocarpine-induced ciliary body constant contraction for a long time period on the elastic modulus and collagen in corneal and scleral tissues in the early developmental stage. Twelve one-month-old New Zealand white rabbits were randomly monocularly treated with pilocarpine to cause ciliary body constant contraction. After 1- and 2-months, the sclera tissues and the eyeballs were obtained to assess the cornea and three regions of the sclera-anterior, equatorial and posterior. The corneal tissues and the three regions of the scleral tissues were cut into strips for elastic modulus measurement using an Instron 5544, the size distribution of collagen fibrils was examined using electron microscopy, the samples were homogenized, and the concentration of hydroxyproline was measured to determine the collagen content. For corneal tissues, long-term pilocarpine-induced ciliary body constant contraction did not affect the elastic modulus and collagen. For scleral tissues, long-term pilocarpine-induced ciliary body constant contraction affected the elastic modulus, diameter of collagen fibrils and collagen content in the equatorial and posterior sclera, however, the anterior sclera were unaffected. These results suggested that pilocarpine-induced ciliary body contraction could affect the scleral structure and lead to deformation of the sclera and eyeball, thereby affecting visual functions function in the process of ocular emmetropization.
Topics: Animals; Ciliary Body; Collagen; Cornea; Elastic Modulus; Hydroxyproline; Pilocarpine; Rabbits; Sclera
PubMed: 30372887
DOI: 10.1016/j.biopha.2018.10.032 -
Scientific Reports Nov 2022Homogeneously depigmented sclerae have long been proposed to be uniquely human-an adaptation to enable cooperative behaviour by facilitating interpersonal coordination...
Homogeneously depigmented sclerae have long been proposed to be uniquely human-an adaptation to enable cooperative behaviour by facilitating interpersonal coordination through gaze following. However, recent evidence has shown that deeply pigmented sclerae also afford gaze following if surrounding a bright iris. Furthermore, while current scleral depigmentation is clearly adaptive in modern humans, it is less clear how the evolutionarily intermediate stages of scleral pigmentation may have been adaptive. In sum, it is unclear why scleral depigmentation became the norm in humans, while not so in sister species like chimpanzees, or why some extant species display intermediate degrees of pigmentation (as our ancestors presumably did at some point). We created realistic facial images of 20 individually distinct hominins with diverse facial morphologies, each face in the (i) humanlike bright sclera and (ii) generalised apelike dark sclera version. Participants in two online studies rated the bright-sclera hominins as younger, healthier, more attractive and trustworthy, but less aggressive than the dark-sclera hominins. Our results support the idea that the appearance of more depigmented sclerae promoted perceived traits that fostered trust, increasing fitness for those individuals and resulting in depigmentation as a fixed trait in extant humans.
Topics: Animals; Humans; Sclera; Hominidae; Iris; Pan troglodytes; Pigmentation
PubMed: 36424405
DOI: 10.1038/s41598-022-24403-2 -
Cell and Tissue Research Aug 2013Considerable evidence indicates that the state of ocular connective tissues and their response in glaucomatous disease affect the degree of glaucoma damage. Both... (Review)
Review
Considerable evidence indicates that the state of ocular connective tissues and their response in glaucomatous disease affect the degree of glaucoma damage. Both experimental and clinical data suggest that improved diagnostic and prognostic information can be derived from the assessment of the mechanical responsiveness of the sclera and lamina cribrosa to intraocular pressure (IOP). Controlled mutagenesis of the sclera has produced a mouse strain that is relatively resistant to increased IOP. Alteration of the baseline scleral state can be accomplished through either increased cross-linking of fibrillar components or their reduction. The sclera is a dynamic structure, altering its structure and behavior in response to IOP change. The biochemical pathways that control these responses are fertile areas for new glaucoma treatments.
Topics: Animals; Connective Tissue; Disease Models, Animal; Glaucoma; Humans; Intraocular Pressure; Sclera; Stress, Physiological
PubMed: 23535950
DOI: 10.1007/s00441-013-1603-0 -
Eye (London, England) Sep 2022
Topics: Humans; Lens Implantation, Intraocular; Lenses, Intraocular; Sclera; Suture Techniques
PubMed: 35332290
DOI: 10.1038/s41433-022-02024-3 -
Current Eye Research Sep 2021Fibrillar collagen network and glycosaminoglycans (GAGs) are the primary components of extracellular matrix (ECM) of the sclera. The main goal of this study was to...
PURPOSE
Fibrillar collagen network and glycosaminoglycans (GAGs) are the primary components of extracellular matrix (ECM) of the sclera. The main goal of this study was to investigate the possible structural roles of GAGs in the scleral tensile properties as a function of preconditioning and displacement rate.
METHODS
Four-step uniaxial stress-relaxation tests were used for characterizing the viscoelastic tensile response of the posterior porcine sclera with and without enzymatic GAG removal. The scleral strips were divided into different groups based on the displacement rate and the presence or absence of a preconditioning step in the loading protocol. The groups were (1) displacement rate of 0.2 mm/min without preconditioning, (2) displacement rate of 1 mm/min without preconditioning, (3) displacement rate of 0.2 mm/min with preconditioning, and (4) displacement rate of 1 mm/min with preconditioning. The peak stress, equilibrium stress, and the equilibrium elastic modulus were calculated for all specimens and compared against each other.
RESULTS
Increasing the displacement rate from 0.2 mm/min to 1.0 mm/min was found to cause an insignificant change in the equilibrium stress and equilibrium elastic modulus of porcine scleral strips. Removal of GAGs resulted in an overall stiffer tensile behavior independent of the displacement rate in samples that were not preconditioned ( < .05). The behavior of preconditioned samples with and without GAG removal was not significantly different from each other.
CONCLUSIONS
The experimental measurements of the present study showed that GAGs play an important role in the mechanical properties of the posterior porcine sclera. Furthermore, using a preconditioning step in the uniaxial testing protocol resulted in not being able to identify any significant difference in the tensile behavior of GAG depleted and normal scleral strips.
Topics: Animals; Elasticity; Extracellular Matrix; Fibrillar Collagens; Glycosaminoglycans; Models, Animal; Sclera; Stress, Mechanical; Swine; Tensile Strength
PubMed: 34325593
DOI: 10.1080/02713683.2021.1874026 -
Asia-Pacific Journal of Ophthalmology... 2017The choroid is the most vascular tissue in the eye and it has been implicated in the pathophysiology of a variety of ocular diseases. A new era of research in the... (Review)
Review
The choroid is the most vascular tissue in the eye and it has been implicated in the pathophysiology of a variety of ocular diseases. A new era of research in the choroid began with the improved ability to visualize this layer and its inner and outer boundaries using spectral domain optical coherence tomography (OCT) with enhanced depth imaging and swept source OCT. The accuracy and precision of qualitative and quan-titative assessments of the choroidal layer support the potential use of OCT-derived choroidal parameters for diagnosis, monitoring of disease progression, planning surgical access, and evaluating treatment response. Although there is increasing interest in measuring choroidal thickness, there is currently no consensus nomenclature to classify choroidal layers and boundaries. Furthermore, the definition and description of the choroidal scleral interface is inconsistent in the literature, contributing to interstudy variation in choroidal thickness measurements. The purpose of this review is to provide an overview of the literature on the definition of choroidal layers and choroidal scleral boundary, review the discrepan-cies, and harmonize the terminology so that a consensus nomenclature can be proposed.
Topics: Choroid; Eye; Humans; Myopia; Posterior Eye Segment; Sclera; Terminology as Topic; Tomography, Optical Coherence
PubMed: 28161920
DOI: 10.22608/APO.201698