Role of dopaminergic receptors in glaucomatous disease modulation

Effects and potential mechanisms of exercise and physical activity on eye health and ocular diseases

In the field of eye health, the profound impact of exercise and physical activity on various ocular diseases has become a focal point of attention. This review summarizes and elucidates the positive effects of exercise and physical activities on common ocular diseases, including dry eye disease (DED), cataracts, myopia, glaucoma, diabetic retinopathy (DR), and age-related macular degeneration (AMD). It also catalogues and offers exercise recommendations based on the varying impacts that different types and intensities of physical activities may have on specific eye conditions. Beyond correlations, this review also compiles potential mechanisms through which exercise and physical activity beneficially affect eye health. From mitigating ocular oxidative stress and inflammatory responses, reducing intraocular pressure, enhancing mitochondrial function, to promoting ocular blood circulation and the release of protective factors, the complex biological effects triggered by exercise and physical activities reveal their substantial potential in preventing and even assisting in the treatment of ocular diseases. This review aims not only to foster awareness and appreciation for how exercise and physical activity can improve eye health but also to serve as a catalyst for further exploration into the specific mechanisms and key targets through which exercise impacts ocular health. Such inquiries are crucial for advancing innovative strategies for the treatment of eye diseases, thereby holding significant implications for the development of new therapeutic approaches.

Reduced Thickness of the Retina in de novo Parkinson's Disease Shows A Distinct Pattern, Different from Glaucoma

Background

Parkinson's disease (PD) patients experience visual symptoms and retinal degeneration. Studies using optical coherence tomography (OCT) have shown reduced thickness of the retina in PD, also a key characteristic of glaucoma.

Objective

To identify the presence and pattern of retinal changes in de novo, treatment-naive PD patients compared to healthy controls (HC) and early primary open angle glaucoma (POAG) patients.

Methods

Macular OCT data (10×10 mm) were collected from HC, PD, and early POAG patients, at the University Medical Center Groningen. Bayesian informative hypotheses statistical analyses were carried out comparing HC, PD-, and POAG patients, within each retinal cell layer.

Results

In total 100 HC, 121 PD, and 78 POAG patients were included. We showed significant reduced thickness of the inner plexiform layer and retinal pigment epithelium in PD compared to HC. POAG patients presented with a significantly thinner retinal nerve fiber layer, ganglion cell layer, inner plexiform layer, outer plexiform layer, and outer photoreceptor and subretinal virtual space compared to PD. Only the outer segment layer and retinal pigment epithelium were significantly thinner in PD compared to POAG.

Conclusions

De novo PD patients show reduced thickness of the retina compared to HC, especially of the inner plexiform layer, which differs significantly from POAG, showing a more extensive and widespread pattern of reduced thickness across layers. OCT is a useful tool to detect retinal changes in de novo PD, but its specificity versus other neurodegenerative disorders has to be established.

α-Synuclein modulates fibronectin expression in the trabecular meshwork independent of TGFβ2

α-Synuclein (α-Syn) is implicated in Parkinson's disease (PD), a neuromotor disorder with prominent visual symptoms. The underlying cause of motor dysfunction has been studied extensively, and is attributed to the death of dopaminergic neurons mediated in part by intracellular aggregation of α-Syn. The cause of visual symptoms, however, is less clear. Neuroretinal degeneration due to the presence of aggregated α-Syn has been reported, but the evidence is controversial. Other symptoms including those arising from primary open angle glaucoma (POAG) are believed to be the side-effects of medications prescribed for PD. Here, we explored the alternative hypothesis that dysfunction of α-Syn in the anterior eye alters the interaction between the actin cytoskeleton of trabecular meshwork (TM) cells with the extracellular matrix (ECM), impairing their ability to respond to physiological changes in intraocular pressure (IOP). A similar dysfunction in neurons is responsible for impaired neuritogenesis, a characteristic feature of PD. Using cadaveric human and bovine TM tissue and primary human TM cells as models, we report two main observations: 1) α-Syn is expressed in human and bovine TM cells, and significant amounts of monomeric and oligomeric α-Syn are present in the AH, and 2) primary human TM cells and human and bovine TM tissue endocytose extracellular recombinant monomeric and oligomeric α-Syn via the prion protein (PrP^C), and upregulate fibronectin (FN) and α-smooth muscle actin (α-SMA), fibrogenic proteins implicated in POAG. Transforming growth factor β2 (TGFβ2), a fibrogenic cytokine implicated in ∼50% cases of POAG, is also increased, and so is RhoA-associated coiled-coil-containing protein kinase 1 (ROCK-1). However, silencing of α-Syn in primary human TM cells reduces FN, α-SMA, and ROCK-1 in the absence or presence of over-expressed active TGFβ2, suggesting modulation of FN and ROCK-1 independent of, or upstream of TGFβ2. These observations suggest that extracellular α-Syn modulates ECM proteins in the TM independently or via PrP^C by activating the RhoA-ROCK pathway. These observations reveal a novel function of α-Syn in the anterior eye, and offer new therapeutic options.

Gamma-Synuclein Dysfunction Causes Autoantibody Formation in Glaucoma Patients and Dysregulation of Intraocular Pressure in Mice

Dysregulation of intraocular pressure (IOP) is one of the main risk factors for glaucoma. γ-synuclein is a member of the synuclein family of widely expressed synaptic proteins within the central nervous system that are implicated in certain types of neurodegeneration. γ-synuclein expression and localization changes in the retina and optic nerve of patients with glaucoma. However, the mechanisms by which γ-synuclein could contribute to glaucoma are poorly understood. We assessed the presence of autoantibodies to γ-synuclein in the blood serum of patients with primary open-angle glaucoma (POAG) by immunoblotting. A positive reaction was detected for five out of 25 patients (20%) with POAG. Autoantibodies to γ-synuclein were not detected in a group of patients without glaucoma. We studied the dynamics of IOP in response to IOP regulators in knockout mice (γ-KO) to understand a possible link between γ-synuclein dysfunction and glaucoma-related pathophysiological changes. The most prominent decrease of IOP in γ-KO mice was observed after the instillation of 1% phenylephrine and 10% dopamine. The total protein concentration in tear fluid of γ-KO mice was approximately two times higher than that of wild-type mice, and the activity of neurodegeneration-linked protein α2-macroglobulin was reduced. Therefore, γ-synuclein dysfunction contributes to pathological processes in glaucoma, including dysregulation of IOP.

Evaluation of neural innervation in the human conventional outflow pathway distal to Schlemm's canal

The distal outflow pathway of the human eye consists of the outer wall of Schlemm's canal, collector channels, and the deep-scleral, mid-scleral and episcleral vessels. It is the last region of transit for aqueous humor before returning to the venous system. While the trabecular meshwork, scleral spur, and inner wall of Schlemm's canal have been extensively analyzed to define their contributions to aqueous outflow, the role of the distal outflow pathway is not completely understood. Collector channels, emanating from Schlemm's canal were previously thought to be passive conduits for aqueous humor. However, recent studies have shown many collector channels contain flap-like appendages which move with changes in pressure. These findings, along with studies demonstrating innervation of episcleral vessels, have led to questions regarding whether other structures in the distal outflow pathway are under neural regulation and how this may influence aqueous humor outflow. This study evaluates the innervation of the outer wall of Schlemm's canal and collector channels, along with the deep-scleral, mid-scleral and episcleral vasculature with microcomputed tomography and 3-dimensional reconstruction, correlative light microscopy, immunohistochemistry, and transmission electron microscopy. Peripheral, autonomic, and sensory nerve fibers were found to be present adjacent to Schlemm's canal outer wall endothelium, collector channel endothelium, and in the different regions of the distal outflow vasculature. Nerves were more commonly identified in regions that contained collector channels when compared to regions without collector channels. These findings regarding the neural anatomy suggest an active neural regulation of aqueous humor outflow throughout the proximal and distal regions of the conventional outflow pathway.

Retinal Diseases and Parkinson Disease: A Population-Based Study

Introduction

Patients with Parkinson disease (PD) tend to have ophthalmic symptoms. Retinal diseases are associated with central nervous system diseases, especially neurodegenerative diseases. Here, we investigated the association of retinal diseases with PD, especially the temporal relationship before and after PD diagnosis.

Methods

Data were obtained from the National Health Insurance Research Database of Taiwan. In total, 21,845 patients with newly diagnosed PD were matched with four controls each on the basis of propensity score. This study was bidirectional. A case–control study evaluated the adjusted odds ratio (aOR) of retinal disease before PD diagnosis by using conditional logistic regression. Furthermore, a cohort study evaluated the adjusted subdistribution hazard ratio (aSHR) for new-onset retinal and optic nerve diseases after PD diagnosis by using competing risk analysis. The association between PD with optic nerve diseases and glaucoma (another common ophthalmic diseases with the consequence of retinal dysfunction) were also analyzed as reference.

Results

In the case–control study, PD was found to be significantly comorbid with recent and remote retinal disease [recent: ≤ 5 years, aOR: 1.12, 95% confidence interval (CI): 1.03–1.23; remote: > 5 years, aOR: 1.18, 95% CI: 1.04–1.34]. No similar association was identified between optic nerve disease or glaucoma with PD. In the cohort study, patients with PD were found to have a low risk of retinal disease in short-term (≤ 5 years, aSHR: 0.81, 95% CI: 0.71–0.93) and long-term (> 5 years, aSHR: 0.82, 95% CI: 0.72–0.93) follow-up.

Conclusion

The study findings demonstrated that patients with prediagnostic PD were at greater risk of retinal disease than non-PD participants, but the risk reversed afterward. Thus, retinal disease may be a premotor manifestation of PD, and there may be some possible effect of dopamine supplements on retina.

The effect of daily life activities on intraocular pressure related variations in open-angle glaucoma

The recent advent of continuous intraocular pressure (IOP) telemetry has led to an increased awareness of the importance of IOP fluctuations, and theories have emerged that IOP variations could play as much a role in glaucoma progression as the mean level of IOP. The aim of the present study was to evaluate the direct effect of common daily activities on IOP-related profiles. Primary open-angle glaucoma and glaucoma suspect patients were prospectively enrolled from specialist clinics at the University of California San Diego (UCSD), USA. Patients were fitted with a SENSIMED Triggerfish (TF) contact lens sensor (CLS) and were instructed to return to their usual daily activities for 24 h. They were asked to record each specific activity or event in a diary. The protocol was repeated twice. The following events were recorded: "walking/cycling", "resistance training", "yoga/meditation", and "emotional stress". CLS measurements recorded 60-to-30 min prior to each event were used as a baseline reference, and all IOP-related fluctuations for 120 min after the start of each event were reported in relation to this reference. Forty relevant events from 22 CLS recordings in 14 patients were retrieved from the diaries. Walking/cycling (n = 10) caused a small but statistically significant elevation of the IOP-related profile during the activity (p = 0.018). Resistance training (n = 11) caused a persistent elevation of the IOP-related profile from the onset of the activity (p = 0.005) through 120 min after the activity was stopped (p = 0.007). Yoga/meditation (n = 4) caused a sustained drop in the IOP-related profiles through to 120 min, although this was not statistically significant (p > 0.380). Emotional stress (n = 13) was associated with a gradual elevation of the IOP-related profile from the start of the stressful stimulus. Both early and late variations were statistically significant (p = 0.038 and p = 0.021, respectively). The present study suggests that emotional stress and resistance training may be associated with persistent IOP-related profile elevation.

Computational Analysis of Clinical and Molecular Markers and New Theranostic Possibilities in Primary Open-Angle Glaucoma

Primary open-angle glaucoma (POAG) is a paramount cause of irreversible visual disability worldwide. We focus on identifying clinical and molecular facts that may help elucidating the pathogenic mechanisms of the disease. By using ophthalmological approaches (biomicroscopy, ocular fundus, optical coherence tomography, and perimetry) and experimental tests (enzyme-linked immunosorbent assay (ELISA), high performance liquid chromatography (HPLC), and Western blot/immunoblotting) directed to evaluate the oxidative stress, inflammation, apoptosis, and neurodegeneration processes, we gather information to build a network of data to perform a computational bioinformatics analysis. Our results showed strong interaction of the above players and its downstream effectors in POAG pathogenesis. In conclusion, specific risk factors were identified, and molecules involved in multiple pathways were found in relation to anterior and posterior eye segment glaucoma changes, pointing to new theranostic challenges for better managing POAG progression.

High myopic patients with and without foveoschisis: morphological and functional characteristics

PURPOSE

Myopic foveoschisis (MF) is characterized by the splitting of the retinal layers in the fovea of patients with high myopia (HM). MF may progress into foveal detachment or macular hole formation with consequent loss of central vision. The aim of this study is to investigate morphological and functional changes of the macular region in myopic subjects with and without foveoschisis.

DESIGN

Observational, cross-sectional, comparative study.

METHODS

Forty-eight patients with HM and 24 healthy controls were evaluated by spectral domain-optical coherence tomography (SD-OCT), multifocal electroretinography (mfERG) and microperimetry (MP-1) tests to assess macular thickness, functionality and sensitivity values, respectively. The results of the diagnostic examinations were compared between three groups: HM patients with MF (N = 24), HM patients without MF (N = 24) and control group (CG) (N = 24). All statistical analyses were performed with STATA 14.0 (Collage Station, Texas, USA). One-way analysis of variance (ANOVA) followed by Tukey's post hoc test was used to analyze differences between groups unless specified; p values < 0.05 were considered as statistically significant. Gender distribution was compared by the Chi square test.

RESULTS

The statistical analysis with one-way ANOVA followed by Tukey's post hoc test showed a significant increase in macular thickness in HM patients with MF when compared to both HM patients without MF and CG. Morphological changes were associated with functional impairment as demonstrated by the significant decrease in amplitude of the P1 wave and MP-1 sensitivity (p < 0.05), according to the anatomical landmarks.

CONCLUSIONS

This study showed that the morphological changes observed in the central retina of HM patients with MF are associated with functional alterations. High-tech diagnostic tests such as SD-OCT, mfERG and MP-1 could be useful for management in complications of MF.

Expression of Melatonin and Dopamine D3 Receptor Heteromers in Eye Ciliary Body Epithelial Cells and Negative Correlation with Ocular Hypertension

BACKGROUND

Experiments in the late nineties showed an inverse relationship in the eye levels of melatonin and dopamine, thereby constituting an example of eye parameters that are prone to circadian variations. The underlying mechanisms are not known but these relevant molecules act via specific cell surface dopamine and melatonin receptors. This study investigated whether these receptors formed heteromers whose function impact on eye physiology. We performed biophysical assays to identify interactions in heterologous systems. Particular heteromer functionality was detected using Gi coupling, MAPK activation, and label-free assays. The expression of the heteroreceptor complexes was assessed using proximity ligation assays in cells producing the aqueous humor and human eye samples. Dopamine D₃ receptors (D₃Rs) were identified in eye ciliary body epithelial cells. We discovered heteromers formed by D₃R and either MT₁ (MT₁R) or MT₂ (MT₂R) melatonin receptors. Heteromerization led to the blockade of D₃R-Gi coupling and regulation of signaling to the MAPK pathway. Heteromer expression was negatively correlated with intraocular hypertension.

CONCLUSIONS

Heteromers likely mediate melatonin and dopamine actions in structures regulating intraocular pressure. Significant expression of D₃R-MT₁R and D₃R-MT₁R was associated with normotensive conditions, whereas expression diminished in a cell model of hypertension. A clear trend of expression reduction was observed in samples from glaucoma cases. The trend was marked but no statistical analysis was possible as the number of available eyes was 2.

Intracameral lidocaine as supplement to classic topical anesthesia for relieving ocular pain in cataract surgery

AIM

To evaluate safety, efficacy, and patient adherence of intracameral lidocaine as supplement of classic topical anesthetic drops in cataract surgery.

METHODS

A prospective and controlled trial including a large cohort of 1650 individuals suffering with bilateral cataract not complicated, in program by phacoemulsification surgery, were randomly assigned to 2 different groups for the type of anesthesia received, 0.4% oxybuprocaine hydrochloride (INN) drops, and INN drops associated to intracameral 1% lidocaine hydrochloride monohydrate. At the end of surgery, tables were assigned to each patient indicating the degree of pain (0-3) felt during the operation.

RESULTS

Thirty-two percent of patients in group 1 declared to have not felt any pain against the 77% of patients in group 2. Fifty-nine percent of patients in group 1 complained about only a slight discomfort against 20% of group 2 patients. Only a small percentage of patients in group 1 (5%) admitted severe pain, while no patient in group 2 admitted severe pain. Four patients of group 2 reported an episode of transient amaurosis, lasting several hours after surgery.

CONCLUSION

Intracameral administration of lidocaine is a simple and secure method able to increase the analgesia during the cataract surgery, eliminating the discomfort and increasing also the cooperation of the patients during the steps of manipulation.

Biochemical and Functional Changes in the Eye As a Manifestation of Systemic Degeneration of the Nervous System in Parkinsonism

Parkinson's disease (PD) is a systemic neurodegenerative condition caused by the death of dopaminergic neurons of the nigrostriatal system of the brain. This disease is diagnosed after most neurons have already been lost, which explains the low efficiency of treatment. Hope for increasing treatment efficiency rests in the development of new strategies for early diagnosis of PD based on a search for peripheral markers that appear as early changes in non-motor functions. Since impairment of the visual function is one of the manifestations of PD, the purpose of our work was to identify biochemical and physiological changes in a mouse's eye and eyelid in models of preclinical (presymptomatic) and clinical (symptomatic) stages of PD. We found that the norepinephrine, dopamine, and serotonin levels in the mouse eye reduced not only in the model of the early clinical stage, but also in the model of preclinical stage, an indication that pathological changes in the monoaminergic systems of the brain had affected the eye even before the motor disorders emerged. Moreover, in both models of PD, mice had increased intraocular pressure, indicating the development of both metabolic and functional impairments, which can be used as diagnostic markers. Unlike in the eye, the serotonin level in the eyelid was increased in mice at both parkinsonism stages and in presymptomatic mice to a much higher extent than in symptomatic ones. Given that serotonin is involved in the regulation of lacrimal glands of the eyelid, an increase in its level in parkinsonian mice should alter the composition of tear fluid, which could serve as a diagnostic marker of early stage of PD. Thus, the changes in the metabolism of monoamines in the eye and eyelid observed in mice at the early stage of parkinsonism are accompanied by changes in the function of these structures and, therefore, can be used as diagnostic markers of the early stage of PD.

Neuroprotective strategies for retinal disease

Diseases that affect the eye, including photoreceptor degeneration, diabetic retinopathy, and glaucoma, affect 11.8 million people in the US, resulting in vision loss and blindness. Loss of sight affects patient quality of life and puts an economic burden both on individuals and the greater healthcare system. Despite the urgent need for treatments, few effective options currently exist in the clinic. Here, we review research on promising neuroprotective strategies that promote neuronal survival with the potential to protect against vision loss and retinal cell death. Due to the large number of neuroprotective strategies, we restricted our review to approaches that we had direct experience with in the laboratory. We focus on drugs that target survival pathways, including bile acids like UDCA and TUDCA, steroid hormones like progesterone, therapies that target retinal dopamine, and neurotrophic factors. In addition, we review rehabilitative methods that increase endogenous repair mechanisms, including exercise and electrical stimulation therapies. For each approach, we provide background on the neuroprotective strategy, including history of use in other diseases; describe potential mechanisms of action; review the body of research performed in the retina thus far, both in animals and in humans; and discuss considerations when translating each treatment to the clinic and to the retina, including which therapies show the most promise for each retinal disease. Despite the high incidence of retinal diseases and the complexity of mechanisms involved, several promising neuroprotective treatments provide hope to prevent blindness. We discuss attractive candidates here with the goal of furthering retinal research in critical areas to rapidly translate neuroprotective strategies into the clinic.

How Does Usage of Serotonin Noradrenaline Reuptake Inhibitors Affect Intraocular Pressure in Depression Patients?

PURPOSE

To evaluate anterior segment parameters and intraocular pressure (IOP) modifications in patients using serotonin noradrenaline reuptake inhibitors (SNRIs) due to major depressive disorder.

METHODS

This cross-sectional study included 170 eyes of 85 subjects. All subjects were divided into three groups: group 1 included 44 healthy control subjects, group 2 included 22 patients receiving antidepressants for 1 week to 6 months, and group 3 included 19 patients receiving antidepressants for >6 months. All subjects underwent a detailed ophthalmologic examination, including gonioscopy. Anterior segments of all subjects were evaluated with the Scheimpflug system and pupil diameter (PD), central corneal thickness, anterior chamber depth (ACD), anterior chamber volume, and anterior chamber angle (ACA) measurements were enrolled.

RESULTS

The median IOP was significantly lower in patients using antidepressants [16.0 (11.0-21.0) mmHg] than the control group [17.5 (12.0-21.0) mmHg] (P = 0.041). The PD was significantly larger in patients using antidepressants [3.56 (2.29-5.60) mm] than the control group [2.95 (2.00-4.40) mm] (P = 0.000). In the study group, PD was also significantly larger in patients using SNRIs for ≥6 months [3.67 (2.38-5.08) mm] than <6 months [3.31 (2.29-5.60) mm] (P = 0.000). The median ACD was significantly lower in patients using antidepressants for ≥6 months [3.21 (2.52-4.06) mm] than the control group [3.44 (2.63-4.29) mm] (P = 0.000). ACAs were measured between 25° and 55° by Scheimpflug imaging.

CONCLUSIONS

Treatment of SNRIs causes mydriasis and decrease in width of ACD. These changes may not increase IOP as long as the patient has an open angle. SNRIs lead to decrease in IOP particularly in long-term usage.

[Ophthalmic disorders as a manifestation of Parkinson's disease]

Parkinson's disease is a severe neurodegenerative disease accompanied with the degeneration of dopaminergic neurons in the central and peripheral nervous system. The diagnosis of Parkinson's disease can still be made only on the stage of irreversible and nearly total degeneration of the nigrostriatum dopaminergic system and exhaustion of brain compensatory mechanisms that explains the low efficacy of therapy. Ophthalmic pathology is one of the nonmotor symptoms of Parkinson's disease. This can be explained firstly by the fact that eye is a 'peripheral part of brain' and secondly by the involvement of dopaminergic neurons (dopamine-producing cells) that are subject to the selective degeneration during Parkinson's disease in the regulation of visual function in the eye and brain. Dopaminergic neurons and dopamine receptors are present in all structures of the eye. Parkinson's disease cause abnormalities not only in the retina but in the whole optic tract and can be considered as peripheral manifestations of the disease that precede the well-known motor dysfunctions. This review describes ophthalmological symptoms of Parkinson's disease, possible pathophysiological mechanisms of their development, optical disorders in experimental models of Parkinson's disease and also the perspectives of experimental and clinical studies of visual disorders for the development of preclinical diagnosis of Parkinson's disease.

Activation-Induced Conformational Changes of Dopamine D3 Receptor Promote the Formation of the Internal Water Channel

The atomic-level dopamine activation mechanism for transmitting extracellular ligand binding events through transmembrane helices to the cytoplasmic G protein remains unclear. In the present study, the complete dopamine D3 receptor (D3R), with a homology-modeled N-terminus, was constructed to dock different ligands to simulate conformational alterations in the receptor’s active and inactive forms during microsecond-timescale molecular dynamic simulations. In agonist-bound systems, the D3R N-terminus formed a “lid-like” structure and lay flat on the binding site opening, whereas in antagonist and inverse agonist-bound systems, the N-terminus exposed the binding cavity. Receptor activation was characterized using the different molecular switch residue distances, and G protein-binding site volumes. A continuous water pathway was observed only in the dopamine-G_αi-bound system. In the inactive D3Rs, water entry was hindered by the hydrophobic layers. Finally, a complete activation mechanism of D3R was proposed. Upon agonist binding, the “lid-like” conformation of the N-terminus induces a series of molecular switches to increase the volume of the D3R cytoplasmic binding part for G protein association. Meanwhile, water enters the transmembrane region inducing molecular switches to assist in opening the hydrophobic layers to form a continuous water channel, which is crucial for maintaining a fully active conformation for signal transduction.

Myopia induced by flickering light in guinea pig eyes is associated with increased rather than decreased dopamine release

PURPOSE

It is well known that the dopaminergic signaling pathway plays a pivotal role in the control of axial elongation. Much research has shown that retinal dopamine (DA) is decreased in experimental myopia, but the exact alteration in DA quantity underlying the myopia model induced by flickering light (FL) has not yet been fully elucidated. Therefore, in this study, we first attempted to prove the feasibility of the myopia model induced by FL and then to determine whether and how DA and its receptors changed in myopia induced by FL.

METHODS

Forty-five 2-week-old guinea pigs were randomly divided into three groups, as follows: the control group, form-deprivation myopia (FDM) group, and FL-induced myopia (FLM) group. Animals in the control and FDM groups were raised under normal illumination, and the right eyes of the FDM group were covered with semitransparent hemispherical plastic shells serving as eye diffusers. Guinea pigs in the FLM group were raised under illumination with a duty cycle of 50% at a flash rate of 0.5 Hz. The refraction, axial length (AL), and corneal radius of curvature (CRC) were measured using streak retinoscopy, A-scan ultrasonography, and keratometry, respectively, before and after 2, 4, 6, and 8 weeks of treatment. The contents of DA, 3,4-dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) in the retina, vitreous body, and RPE were measured at the end of the 8-week experiment using high-performance liquid chromatography (HPLC). The numbers of retinal D1 DA receptor (D1DR) and D2 DA receptor (D2DR) were evaluated via immunohistofluorescence and western blot assay.

RESULTS

The refraction of the FLM group became more myopic throughout the experimental period, which was mainly indicated by decreased refraction and a longer AL compared with the control group (p<0.05). The contents of DA, DOPAC, and HVA in the retina, vitreous body, and RPE of the FLM group were significantly increased, but decreased in the FDM group, compared with those of the control group (both p<0.05). Like form-deprived eyes, the expressions of retinal D1DR and D2DR in FL eyes were significantly upregulated compared with controls (p<0.05).

CONCLUSIONS

Myopia can be induced by 0.5-Hz FL in guinea pigs at puberty. Contrary to FDM, dopaminergic neuron activity and DA release were significantly elevated in FLM. Like in FDM, the expressions of D1DR and D2DR were upregulated in FLM. Thus, the results of our study may further demonstrate that the DA system is associated with the development of myopia.

Age-related changes in the kinetics of human lenses: prevention of the cataract

The crystalline lens is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina and, by changing shape, it adjusts focal distance (accommodation). The three classes of structural proteins found in the lens are α, β, and γ crystallins. These proteins make up more than 90% of the total dry mass of the eye lens. Other components which can be found are sugars, lipids, water, several antioxidants and low weight molecules. When ageing changes occur in the lens, it causes a gradual reduction in transparency, presbyopia and an increase in the scattering and aberration of light waves as well as a degradation of the optical quality of the eye. The main changes that occur with aging are: 1) reduced diffusion of water from the outside to the inside of the lens and from its cortical to its nuclear zone; 2) crystalline change due to the accumulation of high molecular weight aggregates and insoluble proteins; 3) production of advanced glycation end products (AGEs), lipid accumulation, reduction of reduced glutathione content and destruction of ascorbic acid. Even if effective strategies in preventing cataract onset are not already known, good results have been reached in some cases with oral administration of antioxidant substances such as caffeine, pyruvic acid, epigallocatechin gallate (EGCG), α-lipoic acid and ascorbic acid. Furthermore, methionine sulfoxide reductase A (MSRA) over expression could protect lens cells both in presence and in absence of oxidative stress-induced damage. Nevertheless, promising results have been obtained by reducing ultraviolet-induced oxidative damage.

Omega-3 fatty acid supplementation improves dry eye symptoms in patients with glaucoma: results of a prospective multicenter study

PURPOSE

The purpose of this study is to assess the effectiveness and tolerability of a dietary supplement with a combination of omega-3 fatty acids and antioxidants on dry eye symptoms caused by chronic instillation of antihypertensive eye drops in patients with glaucoma.

PATIENTS AND METHODS

A total of 1,255 patients with glaucoma and dry eye symptoms related to antiglaucoma topical medication participated in an open-label, uncontrolled, prospective, and multicenter study and were instructed to take three capsules a day of the nutraceutical formulation (Brudypio(®) 1.5 g) for 12 weeks. Dry eye symptoms (graded as 0-3 [none to severe, respectively]), conjunctival hyperemia, tear breakup time, Schirmer I test, Oxford grading scheme, and intraocular pressure were assessed.

RESULTS

After 12 weeks of administration of the dietary supplement, all dry eye symptoms improved significantly (P<0.001) (mean 1.3 vs 0.6 for scratching, 1.4 vs 0.7 for stinging sensation, 1.6 vs 0.7 for grittiness, 1.0 vs 0.4 for tired eyes, 1.1 vs 0.5 for grating sensation, and 0.8 vs 0.3 for blurry vision). The Schirmer test scores and the tear breakup time also increased significantly. There was an increase in the percentage of patients grading 0-I in the Oxford scale and a decrease in those grading IV-V. Compliance was recorded in 62.5% of patients. In compliant patients, the mean differences at 12 weeks vs baseline of dry eye symptoms were statistically significant as compared to noncompliant patients.

CONCLUSION

Dietary supplementation with Brudypio(®) may be a clinically valuable additional option for the treatment of dry eye syndrome in patients with glaucoma using antiglaucoma eye drops. These results require confirmation with an appropriately designed randomized controlled study.

Association Between Glaucoma and the Risk of Dementia

We investigated the association of primary open-angle glaucoma (POAG) and primary angle-closure glaucoma (PACG) with the risk of dementia by evaluating their clinical and epidemiological similarities by using a nationally representative sample in Taiwan. Data were collected from the National Health Insurance Research Database of Taiwan. In total, 6509 patients with glaucoma (3304 with POAG and 3205 with PACG) were enrolled, and a comparison cohort of 26,036 individuals without glaucoma was established after matching for age and sex. The cumulative incidence curve of overall dementia for each cohort was evaluated. The risk of dementia was analyzed using univariate and multivariate Cox proportional hazard models after adjustment for demographic characteristics and comorbidities. The patients with glaucoma exhibited a significantly higher risk of dementia than the individuals without glaucoma did (hazard ratio [HR] = 1.13, 95% confidence interval [CI] = 1.01-1.27). The patients with POAG exhibited a 1.21-fold increased risk of dementia compared with the individuals without glaucoma (HR = 1.21, 95% CI = 1.02-1.43). However, the patients with PACG were not significantly associated with an increased risk of dementia compared with the individuals without glaucoma (HR = 1.09, 95% CI = 0.95-1.26). Patients with POAG aged ≥65 years were significantly associated with an increased risk of dementia compared with the individuals without glaucoma (HR = 1.28, 95% CI = 1.07-1.54). Females with POAG exhibited a 1.34-fold increased risk of dementia compared with females without glaucoma (95% CI = 1.06-1.69). This study demonstrated that patients with POAG but not those with PACG were associated with an increased risk of dementia compared with the general population.

Nd: Yag laser iridotomy in Shaffer-Etienne grade 1 and 2: angle widening in our case studies

AIM

To obtain widening of a potentially occludable angle, in according to Kanski's indications, through preventive Nd:Yag laser iridotomy. The observational study was performed by using gonioscopy for the selection and follow-up of 1165 treated eyes and exploiting Shaffer-Etienne gonioscopic classification as a quality/quantity test of the angle recession.

METHODS

Between September 2000 and July 2012, 586 patients were selected at the Outpatients' Ophthalmological Clinic of the Policlinico Umberto I of Rome in order to undergo Nd: Yag laser iridotomy. A Goldmann type contact lens, Q-switched mode, 2-3 defocus, and 7-9 mJ intensity with 2-3 impulse discharges were used for surgery.

RESULTS

From as early as the first week, a whole 360° angle widening were evident in the patients, thus showing the success of Nd:Yag laser iridotomy in solving relative pupil block. The angle remained narrow by 270° in 14 eyes only, despite repetitions of further treatment with laser iridotomy in a different part of the iris, twice in 10 eyes and three times in 4 eyes.

CONCLUSION

Nd:Yag laser iridotomy revealed itself as being a safe and effective treatment in widening those critical Shaffer-Etienne grade 1 and 2 potentially occludable angles.

The Correlation of Retinal Nerve Fiber Layer Thickness With Blood Pressure in a Chinese Hypertensive Population

To investigate the association between retinal nerve fiber layer (RNFL) thickness and blood pressure (BP) in subjects with systemic hypertension. Subjects with systemic hypertension on anti-hypertensive medications were screened by fundus photography and referred for glaucoma work-up if there was enlarged vertical cup-to-disc (VCDR) ratio ≥0.6, VCDR asymmetry ≥0.2, or optic disc hemorrhage. Workup included a complete ophthalmological examination, Humphrey visual field test, and RNFL thickness measurement by optical coherence tomography. The intraocular pressure (IOP) and RNFL thicknesses (global and quadrant) were averaged from both eyes and the means were correlated with: the systolic BP (SBP), diastolic BP (DBP), and mean arterial pressure (MAP) using Pearson correlation. Among 4000 screened hypertensive subjects, 133 were referred for glaucoma workup and 110 completed the workup. Of the 4000 screened subjects, 1.3% had glaucoma (0.9% had normal tension glaucoma [NTG], 0.2% had primary open angle glaucoma, and 0.2% had primary angle closure glaucoma), whereas 0.3% were NTG suspects. The SBP was negatively correlated with the mean superior RNFL thickness (P = 0.01). The DBP was negatively correlated with the mean global (P = 0.03), superior (P = 0.02), and nasal (P = 0.003) RNFL thickness. The MAP was negatively correlated with the mean global (P = 0.01), superior (P = 0.002), and nasal (P = 0.004) RNFL thickness while positively correlated with the mean IOP (P = 0.02). In medically treated hypertensive subjects, glaucoma was present in 1.3%, with NTG being most prevalent. MAP control may help with IOP lowering and RNFL preservation, although future prospective studies will be needed.

Role of the dopaminergic system in the development of myopia in children and adolescents

This review summarizes the experimental evidence that supports the role of dopamine in the regulation of ocular axial growth. The most important functions attributed to dopamine are light adaptation and regulation of the retinal circadian rhythm. An increase of the retinal levels of dopamine activates D1 and D2 dopaminergic receptors present throughout the retina, generating a signal that inhibits axial growth once the eye has reached emmetropization. Researchers induced form-deprivation myopia in animal models in order to assess the different changes of ocular axial growth. Other studies have shown that phenylethylamine is an endogenous precursor-neurotransmitter capable of modulating the activity of dopamine. Considering the role of the dopaminergic system in the development of myopia (in children and adolescents) and the fact that phenylethylamine improves the consequences of a dopamine deficit, it would be interesting to study the effect of phenylethylamine on the regulation of axial growth, which represents the genesis of myopia.

Effect of dorzolamide/timolol combination on the visual field in glaucoma

PURPOSE

To evaluate the effect of treatment for 3 years with a dorzolamide/timolol (1%/0.5%) fixed combination (DTFC) on visual field progression in patients with open-angle glaucoma.

PARTICIPANTS

A total of 14 consecutive patients were enrolled who had been previously treated with monotherapy or any combination of a beta blocker, carbonic anhydrase inhibitor, and/or prostaglandin analog for primary open-angle glaucoma (POAG; n=4) or normal-tension glaucoma (NTG; n=10).

METHODS

Patients were switched to DTFC from their prior glaucoma therapy. The IOP was measured at intervals of 4-6 weeks, and the visual fields were examined at least twice a year for 3 years. The annual change of mean deviation (MD slope) was used to quantify visual field loss.

RESULTS

The mean MD value was -5.9±5.0 dB at baseline; it was -5.6±4.8 dB at 12 months, -5.9±5.0 dB at 24 months, and -5.6±5.1 dB at 36 months after switching. The mean MD slope was -0.2±0.8 dB/year before switching and 0.3±1.3 dB/year from baseline to 1 year, -0.3±1.1 dB/year from 1-2 years, and 0.3±0.9 dB/year from 2-3 years after switching. The mean MD slope from baseline to 36 months was correlated with the IOP reduction rate at 36 months after switching. Visual field progression was associated with the IOP reduction rate at 12 months after switching.

CONCLUSION

Switching to DTFC from prior glaucoma therapy improved the MD slope for at least 3 years. Reduction of the IOP after switching to DTFC was effective for delaying visual field progression. Although our study was not nonrandomized and was small in scale, the findings suggest that DTFC might have a beneficial effect on the visual fields in patients with open-angle glaucoma.

Hypobaric hypoxia: effects on intraocular pressure and corneal thickness

Objective. The purpose of this study focused on understanding the mechanisms underlying ocular hydrodynamics and the changes which occur in the eyes of subjects exposed to hypobaric hypoxia (HH) to permit the achievement of more detailed knowledge in glaucomatous disease. Methods. Twenty male subjects, aged 32 ± 5 years, attending the Italian Air Force, were enrolled for this study. The research derived from hypobaric chamber, using helmet and mask supplied to jet pilotes connected to oxygen cylinder and equipped with a preset automatic mixer. Results. The baseline values of intraocular pressure (IOP), recorded at T1, showed a mean of 16 ± 2.23 mmHg, while climbing up to 18,000 feet the mean value was 13.7 ± 4.17 mmHg, recorded at T2. The last assessment was performed returning to sea level (T4) where the mean IOP value was 12.8 ± 2.57 mmHg, with a significant change (P < 0.05) compared to T1. Pachymetry values related to corneal thickness in conditions of hypobarism revealed a statistically significant increase (P < 0.05). Conclusions. The data collected in this research seem to confirm the increasing outflow of aqueous humor (AH) in the trabecular meshwork (TM) under conditions of HH.