Suppression of PI3K signaling is linked to autophagy activation and the spatiotemporal induction of the lens organelle free zone.

The terminal steps of lens cell differentiation require elimination of all organelles to create a central Organelle Free Zone (OFZ) that is required for lens function of focusing images on the retina. Previous studies show that the spatiotemporal elimination of these organelles during development is autophagy-dependent. We now show that the inhibition of PI3K signaling in lens organ culture results in the premature induction of autophagy within 24 h, including a significant increase in LAMP1+ lysosomes, and the removal of lens organelles from the center of the lens. Specific inhibition of just the PI3K/Akt signaling axis was directly linked to the elimination of mitochondria and ER, while pan-PI3K inhibitors that block all PI3K downstream signaling removed all organelles, including nuclei. Therefore, blocking the PI3K/Akt pathway was alone insufficient to remove nuclei. RNAseq analysis revealed increased mRNA levels of the endogenous inhibitor of PI3K activation, PIK3IP1, in differentiating lens fiber cells preceding the induction of OFZ formation. Co-immunoprecipitation confirmed that PIK3IP1 associates with multiple PI3K p110 isoforms just prior to formation of the OFZ, providing a likely endogenous mechanism for blocking all PI3K signaling and activating the autophagy pathway required to form the OFZ during lens development.

Effects of pulsed electric fields on exciton propagation efficiency along Müller cell intermediate filaments. Possible separation mechanism of high- and low-contrast images by the eye-brain system.

In the current study, we tested a possible mechanism of low- and high-contrast image component discrimination by the vertebrate eye-brain system. Apparently the eye-brain system has to discriminate between the low-contrast image component formed by light scattered within the retina, due to interaction of photons with cells and their parts, and the high-contrast image component transmitted by excitons via the quantum mechanism. Presently, effects of pulsed electric fields applied to Müller cell (MC) intermediate filaments (IFs) on the efficiency of exciton propagation were explored. The effects of both pulse duration and amplitude were recorded. These experimental results show that the eye-brain system may be using signal modulation to discriminate between high- and low-contrast image components, improving our understanding of high-contrast vision in vertebrates.

OCULAR SURFACE TEMPERATURE DIFFERENCES IN RETINAL VASCULAR DISEASES.

PURPOSE: To define the effect of age-related macular degeneration (AMD) and diabetic retinopathy (DR) on the ocular thermographic profile. METHODS: This retrospective cross-sectional study included subjects diagnosed with DR or AMD between January and April 2019. Individuals without ocular disease served as controls. A thermal imaging camera was used for ocular surface temperature (OST) acquisition. The mean temperatures of the medial cantus, lateral cantus, and cornea were calculated. RESULTS: Thermographic images were obtained from 133 subjects (260 eyes, 97 DR and 163 AMD) and 48 controls (55 eyes). Ocular surface temperature was higher among patients with AMD and lowest among patients with DR (P < 0.001). A subgroup analysis revealed that eyes with diabetic macular edema had significantly higher OSTs than DR eyes without diabetic macular edema. Moreover, the OST in eyes with diabetic macular edema was similar to the measurements of the AMD group. There were no differences in OSTs between neovascular and nonneovascular AMD eyes. CONCLUSION: Although AMD and DR are considered posterior segment conditions, their effect on OST implies that the entire globe is involved. Although both conditions result from similar multifactorial pathophysiologic changes, the differences in OST between DR and AMD might be due to dissimilarity in the balance of pathologic processes involved in each condition. Further research is required to better understand the pathophysiology of these diseases and their effect on OST as well as to determine the effect of vasculature, circulation, and tissue metabolism on ocular temperature.

The acts of opening and closing the eyes are of importance for congenital blindness: Evidence from resting-state fMRI.

Volitional eye closure is observed only in conscious and awake humans, and is rare in animals. It is believed that eye closure can focus one's attention inward and facilitate activities such as meditation and mental imagery. Congenital blind individuals are also required to close their eyes for these activities. Resting-state functional magnetic resonance imaging (RS-fMRI) studies have found robust differences between the eyes-closed (EC) and eyes-open (EO) conditions in some brain regions in the sighted. This study analyzed data from 21 congenital blind individuals and 21 sighted controls by using amplitude of low-frequency fluctuation (ALFF) of RS-fMRI. The blind group and the sighted group shared similar pattern of differences between the EC and EO condition: ALFF was higher in the EC condition than the EO condition in the bilateral primary sensorimotor cortex, bilateral supplementary motor area, and inferior occipital cortex, while ALFF was lower in the EC condition than the EO condition in the medial prefrontal cortex, highlighting the "nature" effect on the difference between the EC and EO conditions. The results of other matrices such as fractional ALFF (fALFF) and regional homogeneity (ReHo) showed similar patterns to that of ALFF. Moreover, no significant difference was observed between the EC-EO pattern of the two subgroups of congenital blind (i.e., with and without light perception), suggesting that the EC-EO difference is irrespective of residual light perception which reinforced the "nature" effect. We also found between-group differences, i.e., more probably "nurture effect", in the posterior insula and fusiform. Our results suggest that the acts of closing and opening the eyes are of importance for the congenital blind, and that these actions and their differences might be inherent in the nature of humans.

Smoothened overexpression causes trochlear motoneurons to reroute and innervate ipsilateral eyes.

The trochlear projection is unique among the cranial nerves in that it exits the midbrain dorsally to innervate the contralateral superior oblique muscle in all vertebrates. Trochlear as well as oculomotor motoneurons uniquely depend upon Phox2a and Wnt1, both of which are downstream of Lmx1b, though why trochlear motoneurons display such unusual projections is not fully known. We used Pax2-cre to drive expression of ectopically activated Smoothened (SmoM2) dorsally in the midbrain and anterior hindbrain. We documented the expansion of oculomotor and trochlear motoneurons using Phox2a as a specific marker at E9.5. We show that the initial expansion follows a demise of these neurons by E14.5. Furthermore, SmoM2 expression leads to a ventral exit and ipsilateral projection of trochlear motoneurons. We compare that data with Unc5c mutants that shows a variable ipsilateral number of trochlear fibers that exit dorsal. Our data suggest that Shh signaling is involved in trochlear motoneuron projections and that the deflected trochlear projections after SmoM2 expression is likely due to the dorsal expression of Gli1, which impedes the normal dorsal trajectory of these neurons.

Ocular Fluid Mechanics and Drug Delivery: A Review of Mathematical and Computational Models.

The human eye is a complex biomechanical structure with a range of biomechanical processes involved in various physiological as well as pathological conditions. Fluid flow inside different domains of the eye is one of the most significant biomechanical processes that tend to perform a wide variety of functions and when combined with other biophysical processes play a crucial role in ocular drug delivery. However, it is quite difficult to comprehend the effect of these processes on drug transport and associated treatment experimentally because of ethical constraints and economic feasibility. Computational modeling on the other hand is an excellent means to understand the associated complexity between these aforementioned processes and drug delivery. A wide range of computational models specific to different types of fluids present in different domains of the eye as well as varying drug delivery modes has been established to understand the fluid flow behavior and drug transport phenomenon in an insilico manner. These computational models have been used as a non-invasive tool to aid ophthalmologists in identifying the challenges associated with a particular drug delivery mode while treating particular eye diseases and to advance the understanding of the biomechanical behavior of the eye. In this regard, the author attempts to summarize the existing computational and mathematical approaches proposed in the last two decades for understanding the fluid mechanics and drug transport associated with different domains of the eye, together with their application to modify the existing treatment processes.

Altered neuronal activity in the visual processing region of eye-fluke-infected fish.

Fish, like most vertebrates, are dependent on vision to varying degrees for a variety of behaviours such as predator avoidance and foraging. Disruption of this key sensory system therefore should have some impact on the ability of fish to execute these tasks. Eye-flukes, such as Tylodelphys darbyi, often infect fish where they are known to inflict varying degrees of visual impairment. In New Zealand, T. darbyi infects the eyes of Gobiomorphus cotidianus, a freshwater fish, where it resides in the vitreous chamber between the lens and retina. Here, we investigate whether the presence of the parasite in the eye has an impact on neuronal information transfer using the c-Fos gene as a proxy for neuron activation. We hypothesized that the parasite would reduce visual information entering the eye and therefore result in lower c-Fos expression. Interestingly, however, c-Fos expression increased with T. darbyi intensity when fish were exposed to flashes of light. Our results suggest a mechanism for parasite-induced visual disruption when no obvious pathology is caused by infection. The more T. darbyi present the more visual stimuli the fish is presented with, and as such may experience difficulties in distinguishing various features of its external environment.

Carotid endarterectomy restores decreased vision due to chronic ocular ischemia.

BACKGROUND: The therapeutic effect of carotid endarterectomy (CEA) on visual disturbance caused by chronic ocular ischemia due to carotid artery stenosis has not been validated. This prospective observational study aims to investigate whether CEA is associated with an increase in ocular blood flow (OBF) and postoperative visual improvement. METHODS: In total, 41 patients with carotid artery stenosis treated by CEA between March 2015 and September 2018 were enrolled in this study. OBF was evaluated by laser speckle flowgraphy, which can measure the mean blur ratio (MBR) which is well correlated to the absolute retinal blood flow. Visual acuity was assessed before and after CEA by subjective improvement and objective visual assessment using CSV-1000, an instrument used to test contrast sensitivity. RESULTS: OBF increased after CEA on the operated side (mean MBR 33.5 vs 38.2, p < 0.001) but not on the non-operated side (mean MBR 37.8 vs 37.5, p = 0.50). After CEA, 23 patients (56.1%) reported subjective visual improvement on the operated side. The mean CSV-1000 score among the patients with increased OBF after CEA (5.44 vs 5.88, p = 0.04) but not among those without increased OBF (5.48 vs 5.95, p = 0.09). The mean CSV-1000 scores increased significantly after CEA in 18 patients with decreased vision and decreased OBF (4.51 vs 5.37, p < 0.001), but not in the 23 patients without those (6.19 vs 6.31, p = 0.6). CONCLUSION: CEA may successfully reverse visual dysfunction caused by chronic ocular ischemia due to carotid artery stenosis by increasing OBF.

Regulation of Limbal Epithelial Stem Cells: Importance of the Niche.

Limbal epithelial stem/progenitor cells (LSCs) reside in a niche that contains finely tuned balances of various signaling pathways including Wnt, Notch, BMP, Shh, YAP, and TGFß. The activation or inhibition of these pathways is frequently dependent on the interactions of LSCs with various niche cell types and extracellular substrates. In addition to receiving molecular signals from growth factors, cytokines, and other soluble molecules, LSCs also respond to their surrounding physical structure via mechanotransduction, interaction with the ECM, and interactions with other cell types. Damage to LSCs or their niche leads to limbal stem cell deficiency (LSCD). The field of LSCD treatment would greatly benefit from an understanding of the molecular regulation of LSCs in vitro and in vivo. This review synthesizes current literature around the niche factors and signaling pathways that influence LSC function. Future development of LSCD therapies should consider all these niche factors to achieve improved long-term restoration of the LSC population.

Evaluation of ocular symptoms in COVID-19 subjects in inpatient and outpatient settings.

PURPOSE: Evaluation of subtle ocular involvement and clinically significant conjunctivitis symptoms in a group of patients with COVID-19 in outpatient and inpatient settings. METHOD: Overall, 1083 patients infected with SARS-CoV-2 were recruited as subjects. Patients were divided into inpatients (group 1, n = 371) and outpatients (group 2, n = 712). Demographical and general medical data included age, sex, and comorbidities. Patients whose diagnosis was confirmed by reverse-transcriptase polymerase chain reaction (RT-PCR) were called by phone, and their chronic ocular disease, previous ocular surgery, ocular medication, contact lens wear and ocular irritation symptoms were queried during the active disease period. RESULTS: The mean age of the patients was 44.2 ± 16.5 (19-97) years; 635 (58.6%) were male, and 448 (41.4%) were female. Comorbidity, chronic ocular disease, ophthalmic medication and previous ocular surgery rates were significantly higher in group 1 (p < 0.05), while contact lens wear was not significantly different between groups. The main complaints received from patients were sore eye or burning sensation, foreign body sensation, itching and red eye and were significantly higher in group 1. Clinically significant conjunctivitis symptoms, such as red eye, ocular discharge and eyelid edema, were observed in 28 patients (2.6%), with 14 (3.8%) patients in group 1 and 14 (2%) patients in group 2. CONCLUSION: Clinically significant conjunctivitis symptoms were detected in 28 subjects in the inpatient and outpatient groups. As systemic findings of COVID-19 intensify.

Pathogenic variants in NUBPL result in failure to assemble the matrix arm of complex I and cause a complex leukoencephalopathy with thalamic involvement.

Disorders of the white matter are genetically very heterogeneous including several genes involved in mitochondrial bioenergetics. Diagnosis of the underlying cause is aided by pattern recognition on neuroimaging and by next-generation sequencing. Recently, genetic changes in the complex I assembly factor NUBPL have been characterized by a consistent recognizable pattern of leukoencephalopathy affecting deep white matter including the corpus callosum and cerebellum. Here, we report twin boys with biallelic variants in NUBPL, an unreported c.351 G > A; p.(Met117Ile) and a previously reported pathological variant c. 693 + 1 G > A. Brain magnetic resonance imaging showed abnormal T2 hyperintense signal involving the periventricular white matter, external capsule, corpus callosum, and, prominently, the bilateral thalami. The neuroimaging pattern evolved over 18 months with marked diffuse white matter signal abnormality, volume loss, and new areas of signal abnormality in the cerebellar folia and vermis. Magnetic resonance spectroscopy showed elevated lactate. Functional studies in cultured fibroblasts confirmed pathogenicity of the genetic variants. Complex I activity of the respiratory chain was deficient spectrophotometrically and on blue native gel with in-gel activity staining. There was absent assembly and loss of proteins of the matrix arm of complex I when traced with an antibody to NDUFS2, and incomplete assembly of the membrane arm when traced with an NDUFB6 antibody. There was decreased NUBPL protein on Western blot in patient fibroblasts compared to controls. Compromised NUBPL activity impairs assembly of the matrix arm of complex I and produces a severe, rapidly-progressive leukoencephalopathy with thalamic involvement on MRI, further expanding the neuroimaging phenotype.

Ophthalmic and orbital considerations in the evaluation of skull base malignancies.

INTRODUCTION: The orbital contents, afferent and efferent visual pathways, and the cranial nerves involved in eye movement, corneal sensation and eyelid closure traverse the skull base, a region bounded by the intracranial cavity, the paranasal sinuses, and the deep spaces of the face and head. As such, tumors from above or below have potential to affect some aspect of the visual system. METHODS: We discuss here the clinical ophthalmologic and orbital considerations in the evaluation of patients with these tumors, as well as the ophthalmic sequelae of treatment with radiation or surgery (or both). And for the surgeon, we discuss the ophthalmic and orbital considerations in surgical planning, the role of the orbital surgeon in skull base surgery, and briefly discuss transorbital approaches to the skull base. RESULTS AND CONCLUSION: Ophthalmic and orbital dysfunction may be the main source of disability in patients with skull base malignancy; it is thus incumbent on those who manage patients with tumors of this region to be aware of the ophthalmic, neuro-ophthalmic and orbital manifestations, so as to best tailor therapy and monitor treatment outcomes.

Relating wavefront error to visual acuity in pre- and post-LASIK eyes: a comparison of methods.

Contrast threshold and visual Strehl ratio methods are used to predict visual acuity from wavefront error for a sample population of pre- and post-LASIK patients. Relative error (in logMAR) between predicted and measured visual acuity values are computed for each method and compared using paired t-tests. Differences in aberration data between pre- and post-LASIK eyes are then evaluated. The visual acuity prediction using visual Strehl proved to be more accurate for pre-LASIK patients than contrast threshold. However, both methods are comparable for post-LASIK patients.

Eyeing the Extracellular Matrix in Vascular Development and Microvascular Diseases and Bridging the Divide between Vascular Mechanics and Function.

The extracellular matrix (ECM) is critical in all aspects of vascular development and health: supporting cell anchorage, providing structure, organization and mechanical stability, and serving as a sink for growth factors and sustained survival signals. Abnormal changes in ECM protein expression, organization, and/or properties, and the ensuing changes in vascular compliance affect vasodilator responses, microvascular pressure transmission, and collateral perfusion. The changes in microvascular compliance are independent factors initiating, driving, and/or exacerbating a plethora of microvascular diseases of the eye including diabetic retinopathy (DR) and vitreoretinopathy, retinopathy of prematurity (ROP), wet age-related macular degeneration (AMD), and neovascular glaucoma. Congruently, one of the major challenges with most vascular regenerative therapies utilizing localized growth factor, endothelial progenitor, or genetically engineered cell delivery, is the regeneration of blood vessels with physiological compliance properties. Interestingly, vascular cells sense physical forces, including the stiffness of their ECM, through mechanosensitive integrins, their associated proteins and the actomyosin cytoskeleton, which generates biochemical signals that culminate in a rapid expression of matricellular proteins such as cellular communication network 1 (CCN1) and CCN2 (aka connective tissue growth factor or CTGF). Loss or gain of function of these proteins alters genetic programs of cell growth, ECM biosynthesis, and intercellular signaling, that culminate in changes in cell behavior, polarization, and barrier function. In particular, the function of the matricellular protein CCN2/CTGF is critical during retinal vessel development and regeneration wherein new blood vessels form and invest a preformed avascular neural retina following putative gradients of matrix stiffness. These observations underscore the need for further in-depth characterization of the ECM-derived cues that dictate structural and functional properties of the microvasculature, along with the development of new therapeutic strategies addressing the ECM-dependent regulation of pathophysiological stiffening of blood vessels in ischemic retinopathies.

Human eye conditions: insights from the fly eye.

The fruit fly Drosophila melanogaster has served as an excellent model to study and understand the genetics of many human diseases from cancer to neurodegeneration. Studying the regulation of growth, determination and differentiation of the compound eyes of this fly, in particular, have provided key insights into a wide range of diseases. Here we review the regulation of the development of fly eyes in light of shared aspects with human eye development. We also show how understanding conserved regulatory pathways in eye development together with the application of tools for genetic screening and functional analyses makes Drosophila a powerful model to diagnose and characterize the genetics underlying many human eye conditions, such as aniridia and retinitis pigmentosa. This further emphasizes the importance and vast potential of basic research to underpin applied research including identifying and treating the genetic basis of human diseases.

An update on the genetics of ocular coloboma.

Ocular coloboma is an uncommon, but often severe, sight-threatening condition that can be identified from birth. This congenital anomaly is thought to be caused by maldevelopment of optic fissure closure during early eye morphogenesis. It has been causally linked to both inherited (genetic) and environmental influences. In particular, as a consequence of work to identify genetic causes of coloboma, new molecular pathways that control optic fissure closure have now been identified. Many more regulatory mechanisms still await better understanding to inform on the development of potential therapies for patients with this malformation. This review provides an update of known coloboma genes, the pathways they influence and how best to manage the condition. In the age of precision medicine, determining the underlying genetic cause in any given patient is of high importance.

Prospects and modalities for the treatment of genetic ocular anomalies.

Over the last three decades, genetic studies have made great strides toward the identification of genes and genetic mechanisms underlying congenital disorders of the eye. However, despite the vast knowledge available this has not translated into treatments to prevent or repair the damage in the clinical setting. Recently, new research in technologies, such as tissue regeneration, next generation designer drugs, and genome editing, have become available for some genetic disorders that might be applicable to congenital ocular diseases in the near future. Here, we provide an overview of the emerging therapeutic modalities and the future prospects they hold for debilitating ocular defects.

Mouse models for microphthalmia, anophthalmia and cataracts.

Mouse mutants are a long-lasting, valuable tool to identify genes underlying eye diseases, because the absence of eyes, very small eyes and severely affected, cataractous eyes are easily to detect without major technical equipment. In mice, actually 145 genes or loci are known for anophthalmia, 269 for microphthalmia, and 180 for cataracts. Approximately, 25% of the loci are not yet characterized; however, some of the ancient lines are extinct and not available for future research. The phenotypes of the mutants represent a continuous spectrum either in anophthalmia and microphthalmia, or in microphthalmia and cataracts. On the other side, mouse models are still missing for some genes, which have been identified in human families to be causative for anophthalmia, microphthalmia, or cataracts. Finally, the mouse offers the possibility to genetically test the roles of modifiers and the role of SNPs; these aspects open new avenues for ophthalmogenetics in the mouse.

Genetics of congenital eye malformations: insights from chick experimental embryology.

Embryological manipulations in chick embryos have been pivotal in our understanding of many aspects of vertebrate eye formation. This research was particularly important in uncovering the role of tissue interactions as drivers of eye morphogenesis and to dissect the function of critical genes. Here, we have highlighted a few of these past experiments to endorse their value in searching for hitherto unknown causes of rare congenital eye anomalies, such as microphthalmia, anophthalmia and coloboma. We have also highlighted a number of similarities between the chicken and human eye, which might be exploited to address other eye pathologies, including degenerative ocular diseases.