Ciliary Muscle Research Articles

Gender differences in canine anterior chamber dimensions: Potential implications for primary angle-closure glaucoma.

This study aimed to explore anatomical differences in the aqueous humor (AH) outflow pathway between male and female dogs using ultrasound biomicroscopy (UBM). Clinical data were collected from 30 eyes of 30 dogs (15 males: 10 right eyes, 5 left eyes; and 15 females: 7 right eyes, 8 left eyes) treated at the Veterinary Medical Teaching Hospital of Chungbuk National University, South Korea, between August 2018 and February 2024. The study conducted an in-depth UBM examination, specifically observing peripheral anterior chamber depth (ACD), geometric iridocorneal angle (ICA), and angle-opening distance (AOD) alongside measurements of ciliary cleft width (CCW), length (CCL), and area (CCA), and assessed the longitudinal fibers of ciliary muscle thickness (Lf-CMT) and the longitudinal and radial fibers of ciliary muscle thickness (LRf-CMT) for gender-based differences. The study identified a significant sex difference in peripheral ACD, with females displaying shallower depths compared to males, potentially clarifying the higher incidence of glaucoma in female dogs. No significant gender differences were found in ICA, AOD, CC parameters, or ciliary muscle parameters measurements. This research uncovered that peripheral ACD is significantly shallower in females than in males, potentially indicating a risk factor that could contribute to the development of primary angle-closure glaucoma.

The impact of physical exercise with additional visual tasks on UDVA and accommodation sensitivity in children: the mediating role of kinetic visual acuity

PurposeThis study investigates the impact of physical exercise supplemented with visual tasks on children’s uncorrected distance visual acuity (UDVA), kinetic visual acuity (KVA), and accommodative sensitivity, with an analysis of the mediating role of KVA.MethodsA total of 168 third-grade students from four natural classes in a primary school in Suzhou City were randomly assigned to either an experimental group (n = 86) or a control group (n = 82). The experimental group engaged in 30 cycles of ciliary muscle training tasks with visual targets presented for 3 s during physical exercises, while the control group participated in regular physical exercises. The intervention lasted 16 weeks, during which KVA, UDVA, and accommodative sensitivity of children were measured before and after the intervention using a kinetic visual acuity tester, a standard logarithmic visual acuity chart lightbox, and a lens flipper.ResultsPost-intervention, the experimental group showed significant improvements in KVA, UDVA, and accommodative sensitivity (p < 0.05). The control group did not show significant changes in KVA and UDVA (p > 0.05), but did exhibit a significant improvement in accommodative sensitivity (p < 0.05). Additionally, children in the experimental group demonstrated significantly higher levels of KVA, UDVA, and accommodative sensitivity compared to the control group after the intervention (p < 0.05). A moderate positive correlation was found between KVA and both UDVA and accommodative sensitivity. KVA partially mediated the effect of additional visual tasks during physical exercise on UDVA in children (left eye 95% CI: 0.011—0.180; right eye 95% CI: 0.023—0.167). Moreover, KVA partially mediated the effect of additional visual tasks during physical exercise on accommodative sensitivity (95% CI: 0.021—0.245).ConclusionIncorporating additional visual tasks into physical exercise effectively enhances KVA, UDVA, and accommodative sensitivity in children. There is a significant positive correlation between KVA and UDVA as well as between KVA and accommodative sensitivity. These visual tasks directly impact UDVA and accommodative sensitivity and indirectly influence them through the mediating effect of KVA.

Study of the establishment of a guinea pig model of ocular accommodative spasm by carbachol eye drops.

To explore a method for establishing a model of ocular accommodative spasm in guinea pigs by using different concentrations of carbachol eye drops and different frequency of administration. Eighteen healthy guinea pigs were selected to establish models for both eyes. Guinea pigs were randomly divided into two groups. Group A was modeled with carbachol eye drops at a concentration of 2ml:0.1mg, and group B was modeled with carbachol eye drops at a concentration of 4ml:0.1mg. The two groups were further randomly divided into three groups according to the random number table method. Three groups of guinea pigs were established: In the A1, B1 group, the drug was administered one time/day; in the A2, B2 group, the drug was administered two times/day; and in the A3, B3 group, the drug was administered three times/day. Before modeling, retinoscopy optometry was performed on the guinea pigs without mydriasis and mydriasis, and a refractive state was recorded. On subsequent days, modeling was performed again, and carbachol eye drops were administered using the same administration times. Retinoscopy was performed in a dark room without mydriasis on days 1, 3, 7, 14 and 21, and the data were recorded. After optimizing the modeling method, the ciliary muscle tissue of the model guinea pig and normal guinea pig were obtained for hematoxylin and eosin (H&E) staining of paraffin sections to compare the morphological differences under a light microscope. (1) There was no statistical significance in the interaction of time*0 d and time*drug frequency between group A and group B (P > 0.05). However, the main effect of different dose times varied between group A and group B (P < 0.05), and the modeling effect of three drops was better. (2) The overall modeling methods of groups A and B were not affected by the time factor, but three doses of carbachol eye drops achieved the best modeling effect on the 7th day, and the diopter of guinea pigs stabilized on the 14th and 21st days. (3) To further optimize the medication, the A and B groups were given three drops. On the 7th day, the refractive data of guinea pigs were compared between the groups, and the refractive status of the two groups of guinea pigs before modeling was compared within the groups. There was no statistical difference between the groups (P > 0.05), and there was a statistical difference within the groups (P < 0.05). (4) In the H&E staining of paraffin sections, the color of the ciliary muscle of the guinea pig with spasm of accommodation was darker than that of the normal guinea pig, and the myofilaments were more closely arranged. (1) Carbachol has the effect of contracting the ciliary muscle; (2) Three drops of 2ml:0.1mg or 4ml:0.1mg of carbachol eye drops can be selected for seven days for modeling.

Kinin B1- and B2-Receptor Subtypes Contract Isolated Bovine Ciliary Muscle: Their Role in Ocular Lens Function and Intraocular Pressure Reduction.

Background: Bradykinin is an endogenously produced nonapeptide with many physiological and pathological functions that are mediated by two pharmacologically defined receptor subtypes, B1- and B2-receptors. Current studies sought to characterize the functional bradykinin (BK) receptors present in freshly isolated bovine ciliary muscle (BCM) using an organ-bath tissue contraction system. Methods: Cumulative longitudinal isometric tension responses of BCM strips (4-5 mm) were recorded before and after the addition of test compounds to BCM strips hooked up to an isometric strain gauge transducer system. Results: BK and its analogs (7-11 concentrations) contracted BCM in a biphasic concentration-dependent manner. The first high affinity/potency phase accounted for 40-60% of the maximal contraction by each of BK (potency, EC50 = 0.9 ± 0.3 nM), Lys-BK (EC50 = 0.7 ± 0.1 nM), Met-Lys-BK (EC50 = 1 ± 0.1 nM), Hyp3-BK (EC50 = 1 ± 0.2 nM), RMP-7 (EC50 = 3.5 ± 0.5 nM), and Des-Arg9-BK (EC50 = 10 ± 0.4nM) (mean ± SEM, n = 3-8). The second lower activity phase of contraction potency values for these peptides ranged between 100 nM and 3 µM. In the presence of a selective B1-receptor antagonist (R715; 0.1-10 µM), the concentration-response curves to Des-Arg9-BK (B1-receptor agonist) were still observed, indicating activation of B2-receptors by this kinin. Likewise, when B2-receptors were completely blocked by using a B2-selective antagonist (WIN-64338; 1-10 µM), BK still induced BCM contraction, now by stimulating B1-receptors. Conclusions: This agonist/antagonist profile of BCM receptors indicated the presence of both B1- and B2-receptor subtypes, both being responsible for contracting this smooth muscle. The BCM kinin receptors may be involved in changing the shape of the ocular lens to influence accommodation, and since the ciliary muscle is attached to the trabecular meshwork through which aqueous humor drains, endogenously released kinins may regulate intraocular pressure.

Preparation and Stability Study of an Injectable Hydrogel for Artificial Intraocular Lenses.

Currently available intraocular lenses (IOLs) on the market often differ significantly in elastic modulus compared to the natural human lens, which impairs their ability to respond effectively to the tension of the ciliary muscles for focal adjustment after implantation. In this study, we synthesized a polyacrylamide-sodium acrylate hydrogel (PAH) through the cross-linking polymerization of acrylamide and sodium acrylate. This hydrogel possesses excellent biocompatibility and exhibits several favorable properties. Notably, the hydrogel demonstrates high transparency (94%) and a refractive index (1.41 ± 0.07) that closely matches that of the human lens (1.42). Additionally, it shows strong compressive strength (14.00 kPa), good extensibility (1400%), and an appropriate swelling ratio (50 ± 2.5%). Crucially, the tensile modulus of the hydrogel is 2.07 kPa, which closely aligns with the elastic modulus of the human lens (1.70-2.10 kPa), enabling continuous focal adjustment under the tension exerted by the ciliary muscles.

Lutein protects senescent ciliary muscle against oxidative stress through the Keap1/Nrf2/ARE pathway

BackgroundAging-induced decline in ciliary muscle function is an important factor in visual accommodative deficits in elderly adults. With this study, we provide an innovative investigation of the interaction between ciliary muscle aging and oxidative stress. MethodsTricolor guinea pigs were used for the experiments in vivo and primary guinea pig ciliary smooth muscle cells were used for the experiments in vitro. ResultsWe enriched for genes associated with muscle-aging-lutein relationship using bioinformatics, including Nuclear factor-erythroid 2-related factor-2 (Nrf2), Glutathione Peroxidase (GPx) gene family, Superoxide Dismutase (SOD) gene family, NAD(P)H: Quinone Oxidoreductase 1 (NQO1) and Heme Oxygenase-1 (HO-1). After gavage to aged guinea pigs, lutein reduced Reactive Oxygen Species (ROS) and P21 levels in senescent ciliary muscle; lutein decreased refractive error and restored accommodation of the eye. In addition, lutein increased GPx, SOD, and Catalase (CAT) levels in serum; lutein increased GPx and CAT levels in ciliary bodies. Lutein regulated the expression of proteins such as Nrf2, Kelch-like ECH-associated protein 1 (Keap1), and downstream proteins in senescent ciliary bodies. Similarly, guinea pig ciliary muscle cell senescence was associated with oxidative stress. In vitro, 100 μM lutein reversed the damage caused by 800 μM H2O2; it reduced Senescence-Associated β-galactosidase (SA-β-Gal) and ROS activites, cell apoptosis and cell migration. Also, lutein increased the expression of smooth muscle contractile proteins. Lutein also increased the expression of Nrf2, GPx2, NQO1 and HO-1, decreased the expression of Keap1. A reduction in Nrf2 activity led to a reduction in the ability of lutein to activate antioxidant enzymes in the cells, thus reducing its inhibitory effect on cell senescence. Conclusionlutein improved resistance to oxidative stress in senescent ciliary muscle in vivo and in vitro by regulating the Keap1/Nrf2/Antioxidant Response Element pathway. We have innovatively demonstrated the molecular pharmacological mechanism by which lutein reverse age-related ciliary muscle systolic and diastolic deficits.

Pilocarpine mediated excessive calcium accumulation leads to ciliary muscle cell senescence and apoptosis.

The ciliary muscle constitutes a crucial element in refractive regulation. Investigating the pathophysiological mechanisms within the ciliary muscle during excessive contraction holds significance in treating ciliary muscle dysfunction. A guinea pig model of excessive contraction of the ciliary muscle induced by drops pilocarpine was employed, alongside the primary ciliary muscle cells was employed in invitro experiments. The results of the ophthalmic examination showed that pilocarpine did not significantly change refraction and axial length during the experiment, but had adverse effects on the regulatory power of the ciliary muscle. The current data reveal notable alterations in the expression profiles of hypoxia inducible factor 1 (HIF-1α), ATP2A2, P53, α-SMA, Caspase-3, and BAX within the ciliary muscle of animals subjected to pilocarpine exposure, alongside corresponding changes observed in cultured cells treated with pilocarpine. Augmented levels of ROS were detected in both tissue specimens and cells, culminating in a significant increase in cell apoptosis in invivo and invitro experiments. Further examination revealed that pilocarpine induced an increase in intracellular Ca2+ levels and disrupted MMP, as evidenced by mitochondrial swelling and diminished cristae density compared to control conditions, concomitant with a noteworthy decline in antioxidant enzyme activity. However, subsequent blockade of Ca2+ channels in cells resulted in downregulation of HIF-1α, ATP2A2, P53, α-SMA, Caspase-3, and BAX expression, alongside ameliorated mitochondrial function and morphology. The inhibition of Ca2+ channels presents a viable approach to mitigate ciliary cells damage and sustain proper ciliary muscle function by curtailing the mitochondrial damage induced by excessive contractions.

Prevalence and associated factors of myopia among adolescents aged 12–15 in Shandong Province, China: a cross-sectional study

Myopia is a growing concern worldwide, especially among adolescents. This study aimed to investigate the prevalence and associated factors of myopia in adolescents aged 12–15 in Shandong Province, China. This cross-sectional study adhered to the Strengthening the Reporting of Observational Studies in Epidemiology guidelines and involved stratified random cluster sampling of 128,678 students from 186 middle schools across 17 cities in Shandong Province. Data collection was conducted from March to April 2024. We excluded students with organic eye diseases, abnormal binocular vision functions, or a history of eye injuries or surgeries. Myopia was assessed using the standard logarithmic visual acuity chart and autorefractor without inducing ciliary muscle paralysis. A comprehensive questionnaire survey was conducted to gather demographic characteristics and daily life behaviors. With the chi-squared test for univariable analysis and multivariable logistic regression for identifying significant factors. This study included 126,375 participants, with a gender distribution of 51.02% male and 48.98% female. The overall prevalence of myopia was 71.34%. Higher prevalence was observed in girls (72.26%) compared to boys (70.45%), and the prevalence increased with age, peaking at 73.12% in 15-year-olds. Urban residents had a higher prevalence (71.86%) than rural (70.39%). Factors such as increased frequency of eye usage while lying down or leaning forward, frequent use of eyes while walking or riding in a car, prolonged screen time, and extended homework duration were associated with higher odds of developing myopia. Conversely, higher frequency of outdoor exercise, maintaining proper posture during reading and writing, greater distance from eyes to screen, and longer sleep duration were associated with lower odds. Additionally, female gender, older age, urban residence, and parental history of myopia increased the risk. The high prevalence of myopia among adolescents in Shandong Province was influenced by a combination of demographic, behavioral, and environmental factors. The study highlighted the importance of lifestyle modifications, such as increasing outdoor activities and maintaining proper visual habits, limiting the duration of screen exposure and homework sessions, and extending sleep duration, to mitigate the risk of developing myopia. These findings underscored the need for targeted public health interventions and educational campaigns to address this significant public health issue.

Thermo-sensitive Poloxamer based antibacterial anti-inflammatory and photothermal conductive multifunctional hydrogel as injectable, in situ curable and adjustable intraocular lens

Cataract patients look forwards to fewer postoperative complications and higher vision quality after surgery. However, the current intraocular lens (IOL) implanted after cataract surgery neither can adjust focal length in response to ciliary muscle contraction as natural lens nor have the ability to prevent postoperative complications. Herein, a thermosensitve Poloxamer based hybrid hydrogel with antibacterial anti-inflammatory and photothermal functional elements doping was designed and used as injectable, in situ curable, and adjustable IOL (FHTAB IOL). The FHTAB IOL was composed of thermosensitve triblock-polymer F127DA and a small amount of HAMA, combined with BP NS, TA, and Ag NPs. FHTAB IOL can be injected into the empty lens capsule after cataract surgery via an injectable thermos-gel under NIR illumination and then be rapidly cured to form a full-size IOL under short-time blue light irradiation. The designed injectable FHTAB IOL possesses high transparency and transmittance, with a refractive index similar to the natural lens and adjustable properties. It was stabilized as a refractive medium without any leakage in the eye. In addition, the TA and Ag NPs loaded in the FHTAB IOL displayed significant antibacterial and anti-inflammatory effects in vitro and vivo. This study presents a potentially effective new strategy for the development of multifunctional adjustable IOLs.

Amplitude of Accommodation in Young Caucasian Adults in Greece

Objective: This study aims to determine the prevalence of accommodation insufficiency among young Caucasian adults in Greece. Methods: Accommodation amplitude was assessed using the minus to blur method (PRA). Results were compared against Donder's and Hofstetter's values. Participants were categorized into "normal," "borderline," and "insufficient" based on deviations from expected values. Results: Over 50% of participants exhibited accommodation insufficiency. Men had significantly lower rates of normal accommodation amplitude compared to women. Further research is required to explore the impact of refractive errors on accommodation issues. Conclusions: Accommodation insufficiency is a significant issue among young adults, necessitating further studies and the establishment of standardized measurement methods. Investigating the role of the ciliary muscle in accommodation is also recommended.

Current Issues Related to Biomechanics in Engineering

Motion capture was employed by Eadweard Muybridge and Etienne-Jules Marey. Industry standard for computing joint kinematics is motion capture. Kinematic analysis is a technique used in biomechanics and mechanical engineering to quantify stiff body motion. A joint moment can be computed in one of two ways: bottom-up or top-down. Joint moments measure muscle and joint tension indirectly. Researchers predicted joint moments using kinematic-based characteristics and machine learning outside of the biomechanics lab.Ankle osteoarthritis causes significant biomechanical issues in the foot and lower leg. Patients' 3D multi-segment kinematic foot models were studied. The technique used is Openpose, which recognises the human body from a single photograph.Falling fear is linked to decreased activity, despondency, and anxiety in the elderly. They adopt a hip approach to manage their GRFs and balance. The lateral ankle technique corrects minor foot placement problems by swiftly moving the pressure point. Angular momentum is affected by foot placement and ground reaction forces. Changing the body's centre of mass along a curved trajectory implies large changes in both ground reaction force impulses and ground reaction force.Lens stiffness and a ciliary muscle anterior/inward displacement produce presbyopia. By 55, the majority of folks have lost their ability to accommodate. Cataracts become common around this time, reaching over 70% by 75. The circumferential and meridional stiffnesses rose with anisotropy from pole to equator, but dropped with distance. The Holzapfel model accurately fits the data from inflation and uniaxial mechanical tests.Anatomical motions of the femur during knee flexion were examined. The data revealed morphological and physiological knee kinematic characteristics. The data led to several hypotheses about axial femoral condyle rotation. This review discusses lower limbs, foot positioning, lens capsule, femoral condyle, muscle activation, collagen fibre, knee joint, and walking speed. The purpose is to provide a general overview on the subject matter.

Ultrasound biomicroscopy analysis of ciliary muscle dynamics and its relation to intra-ocular pressure after phacoemulsification in dogs.

This study investigates the relationship between ciliary muscle dynamics, thickness, and the regulation of intraocular pressure (IOP), focusing on the progression of cataracts and changes post-phacoemulsification. It explores how these factors impact canine ocular health, particularly in the context of cataract development and subsequent surgical intervention. Data was collected using Ultrasound Biomicroscopy (UBM) from dogs at the Veterinary Medical Teaching Hospital of Chungbuk National University, Korea. The study involved 57 eyes from 35 dogs, categorized into five groups: 13 normal eyes, 14 with incipient cataracts, 12 with immature cataracts, 6 with mature cataracts, and 12 post-phacoemulsification. UBM measurements assessed various ciliary muscle parameters including ciliary body axial length (CBAXL), ciliary process-sclera angle (CPSA), longitudinal fibers of ciliary muscle thickness (Lf-CMT), and longitudinal and radial fibers of ciliary muscle thickness (LRf-CMT). Findings indicated a decrease in CBAXL and an increase in Lf-CMT as cataracts progressed in severity. Post-phacoemulsification, there was a notable increase in CBAXL and a decrease in CPSA, Lf-CMT, and LRf-CMT, compared to both cataractous and normal eyes. Regression analysis revealed a significant positive association between CBAXL and IOP, alongside a negative association between Lf-CMT and IOP. These findings suggest that variations in ciliary muscle dynamics and thickness, as influenced by cataract progression and phacoemulsification, have distinct impacts on intraocular pressure. The study proposes that phacoemulsification leads to ciliary muscle contraction, causing an inward and anterior movement of the ciliary muscle. This movement results in the narrowing of the ciliary cleft and constriction of the unconventional outflow pathway, potentially causing an increased risk of glaucoma post-surgery. Our research contributes to understanding the anatomical and physiological changes in the canine eye following cataract surgery and underscores the importance of monitoring IOP and ciliary muscle dynamics in these patients.

Ciliary muscles contraction leads to axial length extension--The possible initiating factor for myopia.

This study aimed to investigate the underlying factors driving the onset of myopia, specifically the role of the ciliary muscle's contraction in the elongation of the axial length of the eye. The retrospective study was conducted utilizing data from three ophthalmic centers in Shanghai and Beijing. Both Chinese and Caucasian children were involved. The axial length of the subjects' eyes was measured in both relaxed and contracted state of the ciliary muscle. A comprehensive mechanical model was also developed to observe the influence of ciliary muscle contraction on the axial length. This study included a sample of 198 right eyes of 198 myopic children. Of these, 97 were male and 101 were female, 126 were of Chinese ethnicity and 72 were Caucasian. The age of onset for myopia ranged from 5.9 to 16.9 years old. The axial length of the eye decreased 0.028 ± 0.007mm following dilation, indicating relaxation of the ciliary muscle (t paired student = 15.16, p = 6.72 x 10-35). In contrast, ciliary muscle contraction resulted in an increase in axial length. Considering proportionality, a significant 90.4% (179 eyes) exhibited a reduced axial length, while a minor 9.6% (19 eyes) demonstrated an increase post-mydriasis. Finite element modeling demonstrated that muscle contraction caused a tension force that transmits towards the posterior pole of the eye, causing it to extend posteriorly. The contraction of the ciliary muscle leads to an extension of the axial length. This could potentially be the initiating factor for myopia.

Model of zonular forces on the lens capsule during accommodation

How the human eye focuses for near; i.e. accommodates, is still being evaluated after more than 165 years. The mechanism of accommodation is essential for understanding the etiology and potential treatments for myopia, glaucoma and presbyopia. Presbyopia affects 100% of the population in the fifth decade of life. The lens is encased in a semi-elastic capsule with attached ligaments called zonules that mediate ciliary muscle forces to alter lens shape. The zonules are attached at the lens capsule equator. The fundamental issue is whether during accommodation all the zonules relax causing the central and peripheral lens surfaces to steepen, or the equatorial zonules are under increased tension while the anterior and posterior zonules relax causing the lens surface to peripherally flatten and centrally steepen while maintaining lens stability. Here we show with a balloon capsule zonular force model that increased equatorial zonular tension with relaxation of the anterior and posterior zonules replicates the topographical changes observed during in vivo rhesus and human accommodation of the lens capsule without lens stroma. The zonular forces required to simulate lens capsule configuration during in vivo accommodation are inconsistent with the general belief that all the zonules relax during accommodation.

Ciliary muscle and anterior segment characteristics in pre-presbyopic adults with Down syndrome.

Previous research has shown that accommodation deficits are common in individuals with Down syndrome (DS), but the origin and mechanisms behind these deficits are still unknown. The aim of this study was to investigate the characteristics of different ocular structures involved in accommodation, in particular the ciliary muscle (CM), in a population of individuals with DS to further understand this deficit and its mechanisms. Thirty-two volunteer participants of pre-presbyopic age with (n = 16) and without DS (n = 16) were recruited. Temporal and nasal images of the CM were acquired using anterior segment optical coherence tomography (AS-OCT) while participants fixated an eccentrically located target. Analysis of CM parameters was undertaken using validated semi-automated software. Axial length, anterior chamber depth, lens thickness and corneal curvature were obtained with the Topcon Aladdin Optical Biometer and Corneal Topographer. Non-cycloplegic refractive error and accommodative ability were obtained with an open-field autorefractor and dynamic retinoscopy, respectively. Independent t-tests were conducted to determine differences in CM and other anterior segment parameters between participants with and without DS. No significant differences were found in the CM parameters studied between participants with and without DS (p > 0.05). In contrast, significant differences were found in visual acuity (p < 0.001), accommodative response (p < 0.001) and corneal curvature (K1 p = 0.003 and K2 p < 0.001) between participants with and without DS. Despite having poorer accommodation, pre-presbyopic adults with DS do not have a different CM morphology to that found in typically developing adults. These findings suggest that the accommodative deficit found in this population is not due to a mechanical deficit of the CM.

Vitamin D and myopia: a review.

Myopia is a worldwide public health problem of vision disorder caused by multiple factors, which has posed a huge socioeconomic burden, raising concerns about sight-threatening ocular complications. Vitamin D, as a kind of fat-soluble vitamin, related to time-spent-outdoors, has been considered by extensive studies to have potential relationship with myopia. We reviewed studies published in a decade which estimated the association of blood vitamin D status with myopia and summarized the universality and individuality of all research articles. Several research articles suggested the known environmental risk factors of myopia, including age, gender, ethnicity, education level, parental and school conditions, time-spent-outdoors, and sunlight exposure, and recent epidemiological studies demonstrate that increased vitamin D levels, by virtue of the extended outdoor time, may be an important modifiable factor and a protective effect that delay the progression of myopia in children and adolescents rather than in adults. The genetic studies have been conducted to get access to the evidence of gene polymorphism for explaining the association of serum vitamin D status and myopia, but the precise genetic interpretation of vitamin D and myopia remains unclear so far; on the other hand, the possible mechanisms are various like copolymerization mechanism, calcium homeostasis and imbalance of ciliary muscle function regulation, but nearly all of the investigators are inclined to remain skeptical. This article reviews the age-related epidemiological proofs, existent genetics correlations, possible underlying biological mechanisms and further values for the protective association between vitamin D and myopia, providing the possibility of prevention or postponement for myopia.

Effect of Capsule Thickness and Material Properties on the Central Optical Power of Natural Human Lens

Background: A thin membrane capsule covers the eye lens and links the lens and the applied forces by the ciliary muscles. The capsule converts the tension of the concentrated zonules to distributed surface tractions over the cortex surface during the lens accommodation. The gradual changes of the capsule geometry and material properties with age and its important role in the design of intraocular lens implants were the motivation of extensive researches on describing the capsule biomechanical behavior. Aim: The present work aimed to study the lens accommodation response to different capsule thicknesses and material properties at different ages. Materials and Methods: A material and geometry parametric study was performed, drawing some guidelines on the choice of lens capsule thickness and biaxial/uniaxial material parameters and exploring the response sensitivity of the finite element model at different age groups Results: The 16-, 35- and 48-year-old lenses were considered for lens accommodation simulation. The sensitivity of lens accommodation was studied at each age group by considering constant thickness (cnst-t) and variable thickness (var-t) capsules and biaxial (Biax) and uniaxial (Uniax) material characteristics tests. The lens was stretched through zonules, and corresponding absolute changes in central optical power (COP) were measured. Conclusion: After the stretch, the lens anterior and posterior curvatures increased, producing a change in COP. The Biax models underestimated the ΔCOP compared to the Uniax models. The 16-year lens model was more sensitive to material properties than thickness variation, while thickness variation was more relevant to the ΔCOP of the 35-year lens model. The 48-year model had the least sensitivity to capsule thickness and material property variations.

Expression of the SARS-CoV-2 Receptor ACE2 and Protease TMPRSS2 in Ocular Hypertension Eyes of Nonhuman Primate and Human

Purpose Coronavirus disease 2019 is a disease caused by the novel severe acute respiratory syndrome coronavirus 2. The double-positive of angiotensin-converting enzyme 2 and transmembrane protease serine type 2 have a higher risk of being infected by severe acute respiratory syndrome coronavirus 2. The susceptibility of coronavirus disease 2019 in patients with chronic diseases, especially in different tissues of ocular hypertension eyes like glaucoma, is not yet known. Methods An ocular hypertension model was established by laser photocoagulation in rhesus monkeys. The expression of angiotensin-converting enzyme 2 and transmembrane protease serine type 2 in three ocular hypertension eyes and the three control eyes were analyzed using immunofluorescence. Results No difference was observed between ocular hypertension and control eyes in the expression of angiotensin-converting enzyme 2 and transmembrane protease serine type 2 in the conjunctival epithelium, corneal epithelium, and ciliary muscle. In ocular hypertension eyes and control eyes, angiotensin-converting enzyme 2 and transmembrane protease serine type 2 expression were both observed in the retina. Angiotensin-converting enzyme 2 staining of retinal ganglion cells was found to be significantly higher in ocular hypertension eyes than in control eyes. However, there was no difference in angiotensin-converting enzyme 2 and transmembrane protease serine type 2 expression in retinal vessels and choroidal vessels between ocular hypertension and control eyes. In our study, the expression and distribution of angiotensin-converting enzyme 2 and TMPREE2 in human retina were similar to that of non-human primates as expected. Conclusion Our study confirmed that angiotensin-converting enzyme 2 and transmembrane protease serine type 2 were expressed widely in rhesus monkey eyes. When compared with controls eyes, the expression of angiotensin-converting enzyme 2 was higher in the retinal ganglion cells in ocular hypertension eyes, suggesting that high ocular pressure may affect the patients’ ocular susceptibility to severe acute respiratory syndrome coronavirus 2 infection.

The size of the ciliary body in human enucleated chronic angle‐closure glaucoma

Aims/Purpose:: The size of the body of the ciliary stroma in relation to the morphology of the angle of the anterior chamber in human enucleated eyes.Methods: A histomorphometric analysis of enucleated human eyes using a light microscope.Results: 107 enucleated human eyes (mean axial length 25.1 ± 2.8 mm; range 21.0–36.0 mm) were included for analysis using light microscope. 68 of those eyes had an open anterior chamber angle and 39 had an endothelialized and closed angle. The body of the ciliary stroma measured was broadest with 541 ± 210 μm vs 59 ± 179 μm (p &lt; 0.001) and narrowest with 214 ± 107 μm vs 17 ± 55 μm (p &lt; 0.001) and the highest ciliary muscle height was 593 ± 557 μm vs 293 ± 111 μm (p &lt; 0.001). In the angle‐closure group these parameters were significantly smaller, than in the open‐angle group. The width of the broadest section of the stroma of the ciliary body increased with the presence of an open‐angle anterior chamber (beta:0.82; B:517; 95%CI:435599; p &lt; 0.001) and a longer axial length (beta:0.17; B:18.2; 95%CI:4.2,32.2; p = 0.01). The width of the narrowest section of the stroma of the ciliary body correlated with an open anterior chamber angle (beta:0.65; B:177; 95%CI:140213; p &lt; 0.001) and an increase in the height of the ciliary body muscle (beta:0.23; B:0.06; 95%CI:0.03,0.10; p = 0.001). The height of the ciliary body muscle increased with increasing maximal height of the stroma (beta:0.43; B:1.54; 95%CI:0.92,2.17; p &lt; 0.001).Conclusions: The size of the stroma of the ciliary body in eyes with an angle of the anterior chamber closed by endothelial cells is smaller than in open‐angle eyes. Due to the tightening of the anterior angle the access of aqueous humour to the trabecular meshwork and to the ciliary body stroma may cause a reduction of the uveoscleral or uveovortex outflow.

The Role of Pilocarpine Eye Drops in the Management of Presbyopia: A Systematic Review

Introduction: Presbyopia is characterized by progressive loss of accommodation resulting in loss of visual acuity and is known to affect quality of life. Mainstay treatment include reading spectacles, contact lenses, and a series of surgical techniques. Until recently, pharmacologic treatment have been available. In this paper, we aim to review the role of pilocarpine eye drops in managing presbyopia. Methods: A comprehensive literature search was performed using Medline, EMBASE, and grey literature databases for articles from inception until 06 June 2024. Search terms included “presbyopia”, “presbyopia correction/treatment”, “pilocarpine”, and “pharmacological presbyopia treatment”. All relevant articles examining the efficacy and side effects of pilocarpine formulations and written in the English language were included in the review. Results: The initial search yielded 587 publications, of which 19 met our inclusion criteria and were included in analysis. Pilocarpine, a parasympathomimetic drug, increases the power of accommodation by increasing the lens thickness via the muscarinic receptors on the iris and ciliary muscles. Clinical trials utilizing pilocarpine eye drops in the management of presbyopia have reported positive outcomes in terms of near visual acuity. Pilocarpine HCL ophthalmic 1.25% formulation; Vuity™ and 0.4% formulation, Qlosi™ are currently the only approved pharmacologic treatment options shown to be effective in managing presbyopia. Conclusion: Overall, pilocarpine eye drops appear to be an effective option in improving near visual acuity in presbyopia patients. Long term follow-up data on the use of pilocarpine-based eye drops is not available. With the increase in the number of users overtime, the long-term effects of its prolonged use may be determined. Further research is needed to optimize the concentrations and combinations of pilocarpine and other substances to maximize efficacy and minimize adverse effects.