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Topic Review
NO-cGMP Signaling in Retinal Ganglion Cell in Glaucoma
Glaucoma is a progressive age-related disease of the visual system and the leading cause of irreversible blindness worldwide. Currently, intraocular pressure (IOP) is the only modifiable risk factor for the disease, but even as IOP is lowered, the pathology of the disease often progresses. Hence, effective clinical targets for the treatment of glaucoma remain elusive. Glaucoma shares comorbidities with a multitude of vascular diseases, and evidence in humans and animal models demonstrates an association between vascular dysfunction of the retina and glaucoma pathology. Integral to the survival of retinal ganglion cells (RGCs) is functional neurovascular coupling (NVC), providing RGCs with metabolic support in response to neuronal activity. NVC is mediated by cells of the neurovascular unit (NVU), which include vascular cells, glial cells, and neurons. Nitric oxide-cyclic guanosine monophosphate (NO-cGMP) signaling is a prime mediator of NVC between endothelial cells and neurons, but emerging evidence suggests that cGMP signaling is also important in the physiology of other cells of the NVU. NO-cGMP signaling has been implicated in glaucomatous neurodegeneration in humans and mice.
  • 1.2K
  • 21 Nov 2022
Topic Review
Posterior Capsule Opacification
Posterior capsule opacification (PCO) is the most common complication arising from the corrective surgery used to treat cataract patients. PCO arises when lens epithelial cells (LEC) residing in the capsular bag post-surgery undergo hyper-proliferation and transdifferentiation into myofibroblasts, migrating from the posterior capsule over the visual axis of the newly implanted intraocular lens (IOL). The developmental pathways underlying PCO are yet to be fully understood and the current literature is contradictory regarding the impact of the recognised risk factors of PCO. The aim of this review is firstly to collate the known biochemical pathways that lead to PCO development, providing an up-to-date chronological overview from surgery to established PCO formation. Secondly, the risk factors of PCO are evaluated, focussing on the impact of IOLs’ properties. Finally, the latest experimental model designs used in PCO research are discussed to demonstrate the ongoing development of clinical PCO models, the efficacy of newly developed IOL technology, and potential therapeutic interventions. This review will contribute to current PCO literature by presenting an updated overview of the known developmental pathways of PCO, an evaluation of the impact of the risk factors underlying its development, and the latest experimental models used to investigate PCO. Furthermore, the review should provide developmental routes for research into the investigation of potential therapeutic interventions and improvements in IOL design in the aid of preventing PCO for new and existing patients.
  • 1.2K
  • 11 Oct 2021
Topic Review
Pediatric Conjunctivitis
Conjunctivitis is a common pediatric problem and is broadly divided into infectious and non-infectious etiologies. Bacterial conjunctivitis makes up the majority of cases in children and often presents with purulent discharge and mattering of the eyelids. Treatment is supportive with an individual approach to antibiotic use in uncomplicated cases since it may shorten symptom duration, but is not without risks. Viral conjunctivitis is the other infectious cause and is primarily caused by adenovirus, with a burning, gritty feeling and watery discharge. Treatment is supportive. Allergic conjunctivitis is largely seasonal and presents with bilateral itching and watery discharge. Treatment can include topical lubricants, topical antihistamine agents, or systemic antihistamines. Other causes of conjunctivitis include foreign bodies and non-allergic environmental causes. 
  • 1.2K
  • 15 May 2023
Topic Review Video
Toxic External Exposure Leading to Ocular Surface Injury
The surface of the eye is directly exposed to the external environment, protected only by a thin tear film, and may therefore be damaged by contact with ambient particulate matter, liquids, aerosols, or vapors. In the workplace or home, the eye is subject to accidental or incidental exposure to cleaning products and pesticides. Organic matter may enter the eye and cause infection. Ocular surface damage can trigger a range of symptoms such as itch, discharge, hyperemia, photophobia, blurred vision, and foreign body sensation. Toxin exposure can be assessed clinically in multiple ways, including via measurement of tear production, slit-lamp examination, corneal staining, and conjunctival staining. At the cellular level, environmental toxins can cause oxidative damage, apoptosis of corneal and conjunctival cells, cell senescence, and impaired motility. Outcomes range from transient and reversible with complete healing to severe and sight-compromising structural changes.
  • 1.2K
  • 13 Apr 2023
Topic Review
Diabetic Macular Edema
Diabetic retinopathy (DR), with increasing incidence, is the major cause of vision loss and blindness worldwide in working-age adults. Diabetic macular edema (DME) remains the main cause of vision impairment in diabetic patients, with its pathogenesis still not completely elucidated. Vascular endothelial growth factor (VEGF) plays a pivotal role in the pathogenesis of DR and DME. 
  • 1.2K
  • 02 Nov 2022
Topic Review
Nitrosative Stress in Retinal Pathologies
Nitric oxide (NO) is a gas molecule with diverse physiological and cellular functions. In the eye, NO is used to maintain normal visual function as it is involved in photoreceptor light transduction. In addition, NO acts as a rapid vascular endothelial relaxant, is involved in the control of retinal blood flow under basal conditions and mediates the vasodilator responses of different substances such as acetylcholine, bradykinin, histamine, substance P or insulin. However, the retina is rich in polyunsaturated lipid membranes and is sensitive to the action of reactive oxygen and nitrogen species. Products generated from NO (i.e., dinitrogen trioxide (N2O3) and peroxynitrite) have great oxidative damaging effects. Oxygen and nitrogen species can react with biomolecules (lipids, proteins and DNA), potentially leading to cell death, and this is particularly important in the retina.
  • 1.2K
  • 22 Sep 2021
Topic Review
Choriocapillaris OCTA in AMD
The advent of optical coherence tomography angiography (OCTA) has facilitated remarkable advancements in our ability to image the blood vessels of the retina and choroid. This is particularly true of the choriocapillaris (CC), the blood vessel bed that feeds the outer retina. OCTA has more clearly defined the integral role of the CC in age-related macular degeneration (AMD), the leading cause of vision loss people over 50 years old. OCTA imaging shows that the choriocapillaris is impaired in intermediate and advanced non-neovascular AMD, and the severity of impairment may predict the advancement of disease. In advanced non-neovascular AMD, the choriocapillaris is severely impaired underneath the area of geographic atrophy, and the level of impairment surrounding geographic atrophy can predict the rate of atrophy enlargement. Macular neovascularization, harmful new blood vessels that grow in neovascular AMD, can be readily identified and classified using OCTA. It is still unclear however if neovascularization features with OCTA can predict the lesion’s level of activity. However, the choriocapillaris surrounding macular neovascularization is impaired while the more peripheral choriocapillaris is spared, implying that choriocapillaris disease may drive the growth of these new blood vessels. With continued innovation in OCTA image acquisition and analysis methods, new discoveries in AMD are set to follow.
  • 1.2K
  • 22 Sep 2021
Topic Review
Advanced DDS for Delivering Anti-VEGF Agents
The treatment of posterior segment eye diseases is challenging due to the complex anatomy of the eye, which limits the effective delivery of medications. Conventional treatments such as topical eye drops and intravitreal injections have poor bioavailability and short residence time, requiring frequent dosing. Biodegradable nano-based drug delivery systems (DDSs) offer a potential solution to these limitations, with longer residence time in ocular tissues and better penetration through ocular barriers. These DDSs use biodegradable polymers that are nanosized, reducing the risk of toxicity and adverse reactions.
  • 1.2K
  • 12 May 2023
Topic Review
Normal Tension Glaucoma
Glaucoma is a neurodegenerative disease of the eye, which involves degeneration of retinal ganglion cells (RGCs): the output neurons of the retina to the brain, which with their axons comprise the optic nerve. Glaucoma is usually associated with elevated intraocular pressure (IOP), but there is a subtype of glaucoma, termed normal tension glaucoma, that presents with normal IOP.
  • 1.2K
  • 12 Feb 2021
Topic Review
Small Leucine-Rich Proteoglycans in Retina
Small Leucine-Rich Proteoglycans (SLRPs) are key extracellular matrix proteins that play a role in many fundamental biological processes involved in the maintenance of retinal homeostasis. 
  • 1.2K
  • 26 Jul 2021
Topic Review
Tear Hyperosmolarity and Dry Eye Disease
Dry eye disease (DED) is a multifactorial disorder of the lacrimal system and ocular surface, characterized by a deficiency in the quality and/or quantity of the tear fluid. The multifactorial nature of DED encompasses a number of interconnected underlying pathologies, including loss of homeostasis, instability and hyperosmolarity of the tears, and the induction and propagation of detrimental inflammatory responses in the eyes, which finally results in the development of neurosensory dysfunction and visual disruption.
  • 1.2K
  • 12 Dec 2023
Topic Review
Suprachoroidal Delivery of Therapeutic Agents
Suprachoroidal drug delivery technology has advanced rapidly and emerged as a promising administration route for a variety of therapeutic candidates, targeting multiple ocular diseases, ranging from neovascular age-related macular degeneration to choroidal melanoma. This entry summarizes the latest preclinical and clinical progress in suprachoroidal delivery of therapeutic agents, focusing on small molecule suspensions.
  • 1.2K
  • 22 Sep 2021
Topic Review
Intelligent Sensor arrays for Early Detection of Diabetes
At present, it is unquestionable that machine learning (ML) modeling is one of the most promising and powerful tools for the development of diagnosis methods and technologies. It permits the fast cribbage and analysis of huge amounts of data from overwhelmingly complex biological matrices which, applied to diagnostics, can be translated into valuable support technologies that would ease rapid decision-making in early diagnosis and screening programs. It has been seen that one can find a great number of colorimetric and electrochemical sensing methods for the detection of biomarkers related to diabetes mellitus (DM) and diabetic rethinopathy (DR), including some recent efforts towards the development of sensor-array technologies exploiting or not ML models for the sensing of diverse biomarkers and for diagnose purposes (including DM). 
  • 1.2K
  • 14 Mar 2022
Topic Review
Fundus Autofluorescence Imaging
Non-invasive in vivo FAF imaging is based on the visualization of endogenous fluorophores in the ocular fundus. The first scanning laser ophthalmoscope was presented in 1980 by Webb et al. and continuously improved in the following years. FAF imaging using confocal scanning laser ophthalmoscopy (cSLO) was described in 1995. Since then, continuous and further developments have strengthened FAF imaging to become a safe and reproducible imaging method that is essential for the routine clinical examination of various chorioretinal diseases. Nowadays, different commercially available devices are used to record FAF. They may not be absolutely equivalent and comparable. Therefore, it is essential to understand the basic principles of FAF imaging techniques and to know the different imaging systems.
  • 1.2K
  • 28 Apr 2022
Topic Review
Sex Hormones and Ocular Dryness
Dry eye syndrome (DES) is strictly connected to systemic and topical sex hormones. Breast cancer treatment, the subsequent hormonal therapy, the subsequent hyperandrogenism and the early sudden menopause, may be responsible for ocular surface system failure and its clinical manifestation as dry eye disease. This local dryness is part of the breast cancer iatrogenic dryness, which affects overall mucosal tissue in the fragile population of those with breast cancer.
  • 1.2K
  • 18 Sep 2021
Topic Review
Nanocarrier-Based Ocular Therapeutic System
Many strategies were designed in terms of the therapeutic modality of ocular diseases. The advent of nanotechnology-based therapeutic systems has acquainted the novel facet toward the optimized nanosize particle, which enables minimizing irritation, addressing the poor bioavailability, and improving ocular biocompatibility of therapeutics. 
  • 1.2K
  • 10 Mar 2022
Topic Review
Aqueous Prostaglandin Eye Drop Formulations
Glaucoma is one of the leading causes of irreversible blindness worldwide. It is characterized by progressive optic neuropathy in association with damage to the optic nerve head and, subsequently, visual loss if it is left untreated. Among the drug classes used for the long-term treatment of open-angle glaucoma, prostaglandin analogues (PGAs) are the first-line treatment and are available as marketed eye drop formulations for intraocular pressure (IOP) reduction by increasing the trabecular and uveoscleral outflow. PGAs have low aqueous solubility and are very unstable (i.e., hydrolysis) in aqueous solutions, which may hamper their ocular bioavailability and decrease their chemical stability. Additionally, treatment with PGA in conventional eye drops is associated with adverse effects, such as conjunctival hyperemia and trichiasis. It has been a very challenging for formulation scientists to develop stable aqueous eye drop formulations that increase the PGAs’ solubility and enhance their therapeutic efficacy while simultaneously lowering their ocular side effects.
  • 1.1K
  • 28 Oct 2022
Topic Review
Molecular and Clinical Aspects of Anti-VEGF Drugs
Vascular endothelial growth factor (VEGF) is a major angiogenic molecule that induces choroid neovascularization (CNV). VEGF has five ligand member in human: VEGFA, VEGFB, VEGFC, VEGFD, and placenta growth factor, and there are three receptors: VEGFR1, VEGFR2 and VEGFR3. VEGFs play an important role in vascular development and choroid maintenance in the normal eye. The basolateral secretion of VEGF from the retinal pigment epithelium (RPE) continues throughout life and mediates RPE survival. However, the increase in VEGF secretion from RPE and the loss of RPE polarity are causes of the pathologic CNV condition. Since the off- label bevacizumab started to be used to treat CNV, neovascular age-related macular degeneration (nAMD), there are several anti-VEGF agents approved: pegaptanib, ranibizumab, aflibercept, conbercept, brolucizumab, faricimab.
  • 1.1K
  • 04 Sep 2023
Topic Review
Natural Antioxidant Activities of Plants in Preventing Cataractogenesis
A cataract is a condition where the eye’s lens clouds and can lead to progressive loss of vision. The formation of cataracts is linked to both the production of reactive oxygen species (ROS) and the reduction of endogenous antioxidants. Numerous studies have demonstrated that plants contain numerous antioxidant compounds that can be used as cataract preventatives or inhibitors. 
  • 1.1K
  • 02 Aug 2022
Topic Review
SARS-CoV-2 Affect Eyes
The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection has become a worldwide threat resulting in a pandemic in 2020. SARS-CoV-2 infection manifests itself as coronavirus disease 2019 (COVID-19) that is evidenced in a vast number of either specific or nonspecific symptoms. Except for typical (but nonspecific) symptoms such as fever, dry cough, or muscle weakness, the infected patients might also present atypical symptoms including neurological, dermatological, or ophthalmic manifestations.
  • 1.1K
  • 20 Jun 2022
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