This document provides an overview of toxic responses in the ocular and visual system. It discusses various sites in the eye that can be affected by toxicants including the cornea, lens, retina, optic nerve, and central visual system. Evaluation methods for ocular toxicity and visual function are also outlined, such as the Draize test and various ophthalmologic and electrophysiological techniques. The mechanisms of several toxicants that can damage different ocular tissues are then reviewed.
Every component of the eye is vulnerable to damage from ROI, particularly retina. There are several reasons for the vulnerability of the retina, including high concentrations of polyunsaturated fatty acid (PUFA), constant exposure to visible light, high consumption of oxygen, an abundance of photosensitisers in the neurosensory retina and the RPE, the process of phagocytosis by the RPE which is known to generate hydrogen peroxide.
This document discusses ocular pharmacokinetics and drug delivery to the eye. It describes the major routes of administration for the anterior and posterior segments, including topical, subconjunctival, intracameral, transscleral, and intravitreal. Factors that influence absorption, distribution, metabolism and elimination of drugs in the eye are also examined, such as precorneal clearance mechanisms, corneal barriers, transporters, and disease state. The document concludes that ocular pharmacokinetics is complex due to unique ocular barriers and target sites for therapy in the anterior vs posterior segments.
This document discusses the ocular side effects of various systemic drugs. It begins by explaining how drug molecules can reach ocular tissues through blood circulation. It then discusses three major drug accumulation sites - the cornea, lens, and vitreous. Specific drugs like chloroquine, amiodarone, and chlorpromazine are mentioned as examples of drugs that can cause corneal side effects like keratopathy. Steroids, chlorpromazine, and allopurinol are provided as examples of drugs that may cause lens side effects like cataracts. Finally, various drugs like antimalarials, phenothiazines, tamoxifen, and interferon-alpha are discussed in relation to potential retinal side effects they
This document discusses drugs that can cause ocular toxicity and their side effects. It covers various classes of drugs including anti-infectives, anti-parasites, anti-inflammatories, cardiovascular drugs, nervous system drugs, anti-convulsants, anti-depressants, anti-parkinsonism drugs, benzodiazepines, hypnotics, anti-psychotics, and hormones. For each drug class, specific drugs are mentioned along with their potential ocular side effects such as optic neuritis, blurred vision, diplopia, mydriasis, papilledema, and retinal damage among others. The document provides an extensive overview of how different systemic medications can impact ocular health and cause toxicity
This document discusses dermal toxicity and its effects on the skin. It begins by defining dermal toxicity as the ability of substances to poison through skin contact. It then describes the three main layers of skin - the epidermis, dermis and hypodermis - and their functions. Various manifestations of dermal toxicity are outlined, including contact dermatitis, ulcers, pigment disturbances and skin cancer. Specific toxic chemicals that can cause these effects are also mentioned.
This document discusses dermal toxicology and cutaneous toxicity. It covers the anatomy of the skin, factors that affect absorption of toxicants through the skin like hydration and damage. It also outlines various conditions that can manifest from dermal exposure like contact dermatitis, ulcers, urticaria, toxic epidermal necrolysis, acneiform dermatoses, pigment disturbances, and skin cancer. Treatment options are provided for some of these conditions. Additionally, some toxicants present in foods that can cause dermal diseases are listed.
This document discusses hematotoxicity and local toxicity. It describes how hematotoxicity affects red blood cell mediated oxygen transport and the production of blood cells, potentially leading to hypoxia, tissue damage, and impaired immune function. Common occupational exposures that can cause hematotoxicity include benzene, aniline, nitrobenzene, hydrogen sulfide, and carbon monoxide. Local toxicity includes contact dermatitis from irritants or allergens, photosensitivity reactions, contact urticaria, and various drug-induced skin conditions. Some photoirritants have been associated with UV-induced skin carcinogenesis, and the p53 protein plays an important role in tumor suppression in skin cancer development.
General toxicology testing refers to a series of toxicity tests required by international regulators to prove safety in experimental animals prior to human testing. It includes acute, sub-acute, and chronic toxicity tests conducted according to OECD guidelines in rodents and non-rodents. Preclinical studies include phytochemistry, formulation development, pharmacology/pharmacokinetic profiling, safety toxicology studies, and efficacy studies. Toxicology studies are guided by regulatory requirements like OECD/ICH guidelines and Good Laboratory Practices to ensure quality. Acute, sub-acute, and chronic toxicity tests provide information on toxicity effects from single or repeated substance exposure over different time periods and help determine safe doses for clinical trials.
Every component of the eye is vulnerable to damage from ROI, particularly retina. There are several reasons for the vulnerability of the retina, including high concentrations of polyunsaturated fatty acid (PUFA), constant exposure to visible light, high consumption of oxygen, an abundance of photosensitisers in the neurosensory retina and the RPE, the process of phagocytosis by the RPE which is known to generate hydrogen peroxide.
This document discusses ocular pharmacokinetics and drug delivery to the eye. It describes the major routes of administration for the anterior and posterior segments, including topical, subconjunctival, intracameral, transscleral, and intravitreal. Factors that influence absorption, distribution, metabolism and elimination of drugs in the eye are also examined, such as precorneal clearance mechanisms, corneal barriers, transporters, and disease state. The document concludes that ocular pharmacokinetics is complex due to unique ocular barriers and target sites for therapy in the anterior vs posterior segments.
This document discusses the ocular side effects of various systemic drugs. It begins by explaining how drug molecules can reach ocular tissues through blood circulation. It then discusses three major drug accumulation sites - the cornea, lens, and vitreous. Specific drugs like chloroquine, amiodarone, and chlorpromazine are mentioned as examples of drugs that can cause corneal side effects like keratopathy. Steroids, chlorpromazine, and allopurinol are provided as examples of drugs that may cause lens side effects like cataracts. Finally, various drugs like antimalarials, phenothiazines, tamoxifen, and interferon-alpha are discussed in relation to potential retinal side effects they
This document discusses drugs that can cause ocular toxicity and their side effects. It covers various classes of drugs including anti-infectives, anti-parasites, anti-inflammatories, cardiovascular drugs, nervous system drugs, anti-convulsants, anti-depressants, anti-parkinsonism drugs, benzodiazepines, hypnotics, anti-psychotics, and hormones. For each drug class, specific drugs are mentioned along with their potential ocular side effects such as optic neuritis, blurred vision, diplopia, mydriasis, papilledema, and retinal damage among others. The document provides an extensive overview of how different systemic medications can impact ocular health and cause toxicity
This document discusses dermal toxicity and its effects on the skin. It begins by defining dermal toxicity as the ability of substances to poison through skin contact. It then describes the three main layers of skin - the epidermis, dermis and hypodermis - and their functions. Various manifestations of dermal toxicity are outlined, including contact dermatitis, ulcers, pigment disturbances and skin cancer. Specific toxic chemicals that can cause these effects are also mentioned.
This document discusses dermal toxicology and cutaneous toxicity. It covers the anatomy of the skin, factors that affect absorption of toxicants through the skin like hydration and damage. It also outlines various conditions that can manifest from dermal exposure like contact dermatitis, ulcers, urticaria, toxic epidermal necrolysis, acneiform dermatoses, pigment disturbances, and skin cancer. Treatment options are provided for some of these conditions. Additionally, some toxicants present in foods that can cause dermal diseases are listed.
This document discusses hematotoxicity and local toxicity. It describes how hematotoxicity affects red blood cell mediated oxygen transport and the production of blood cells, potentially leading to hypoxia, tissue damage, and impaired immune function. Common occupational exposures that can cause hematotoxicity include benzene, aniline, nitrobenzene, hydrogen sulfide, and carbon monoxide. Local toxicity includes contact dermatitis from irritants or allergens, photosensitivity reactions, contact urticaria, and various drug-induced skin conditions. Some photoirritants have been associated with UV-induced skin carcinogenesis, and the p53 protein plays an important role in tumor suppression in skin cancer development.
General toxicology testing refers to a series of toxicity tests required by international regulators to prove safety in experimental animals prior to human testing. It includes acute, sub-acute, and chronic toxicity tests conducted according to OECD guidelines in rodents and non-rodents. Preclinical studies include phytochemistry, formulation development, pharmacology/pharmacokinetic profiling, safety toxicology studies, and efficacy studies. Toxicology studies are guided by regulatory requirements like OECD/ICH guidelines and Good Laboratory Practices to ensure quality. Acute, sub-acute, and chronic toxicity tests provide information on toxicity effects from single or repeated substance exposure over different time periods and help determine safe doses for clinical trials.
This document summarizes skin toxicology. It discusses the structure and functions of the skin, percutaneous absorption, and various skin diseases and conditions including occupational skin diseases, contact dermatitis, phototoxicity, granulomatous disease, acne, pigmentary disturbances, urticaria, toxic epidermal necrolysis, and skin cancer. It provides details on the causes, mechanisms, and characteristics of these diseases and conditions.
Immunosuppressive agents in ophthalmologyTina Chandar
This document discusses various immunosuppressive agents used in ophthalmology, including their mechanisms of action, clinical indications, dosages, and potential adverse effects. It covers alkylating agents like cyclophosphamide and chlorambucil, antimetabolites like azathioprine and methotrexate, the antibiotic cyclosporin A, and newer agents like tacrolimus, daclizumab, and infliximab. Monitoring of blood counts is important when using these drugs due to risks of bone marrow suppression, infections, and other toxicities. Careful dosage adjustment and patient follow up is needed with immunosuppressive therapy for ocular conditions.
The document discusses multidrug use in the elderly. It notes that the elderly population is growing and consuming more prescription drugs. Age-related changes to pharmacokinetics and pharmacodynamics can increase risks of adverse drug events from polypharmacy. Drugs are metabolized and cleared more slowly from the body due to reduced liver and kidney function. The elderly also experience increased drug sensitivity. Careful monitoring is needed to balance treatment benefits and risks.
Chemical injuries to the eye can range from minor irritation to complete vision loss. They typically occur from contact with chemicals during domestic, agricultural, or laboratory accidents, deliberate attacks, or self-harm. Alkali burns, usually from strong bases like lime or ammonia, are the most severe and can lead to acute ischemic necrosis of the conjunctiva and cornea. Acid burns are less severe, as acids coagulate proteins on contact to limit penetration. Treatment involves thorough irrigation, removal of contaminated tissue, preventing complications like symblepharon, and addressing issues such as glaucoma, poor healing, or opacity with additional procedures. The severity is graded based on the extent of limbal and corneal damage.
This document discusses various topics in ophthalmic pathology and pharmacology. It covers:
1. The definitions and main branches of pharmacology, including pharmacokinetics and pharmacodynamics.
2. Different routes of drug delivery to the eye, including topical, local injections, and systemic administration.
3. Classes of anti-inflammatory drugs used to treat ocular inflammation, such as glucocorticoids, NSAIDs, mast cell stabilizers, and antihistamines.
4. Specific drugs used for various ocular conditions and their adverse effects.
5. Processes of wound healing, tissue fixation and processing, orientation and dissection of eye specimens, and staining for
This document provides an overview of ocular therapeutics, including principles of pharmacodynamics, pharmacokinetics, and factors influencing drug penetration into ocular tissues. It discusses various routes of ocular drug administration including topical eye drops, ointments, periocular injections, and systemic administration. Specific drug classes are covered in depth, such as corticosteroids, NSAIDs, mast cell stabilizers, and immunosuppressants. Recent advances in drug delivery and newer therapeutic agents are also mentioned.
This document discusses the ocular side effects of common systemic drugs. It begins by noting that many drugs can reach the eye through circulation and accumulate in the cornea, lens, and vitreous, prolonging their effects and increasing toxicity risks. Several classes of drugs are then described in more detail, including their ocular side effects. These include photosensitizers, cardiac glycosides, tetracyclines, corticosteroids, aminoquinolines, phenothiazines, antiseizure agents, and anti-coagulants. The document concludes by emphasizing the importance of recognizing potential ocular side effects from systemic medications to enable prompt management and prevent vision complications.
The document discusses guidelines for toxicity testing from the Organisation for Economic Co-operation and Development (OECD). It provides an overview of OECD guidelines for acute oral toxicity testing, including the fixed dose procedure (Guideline 420), acute toxic class method (Guideline 423), and up-and-down procedure (Guideline 425). It also discusses guidelines for acute dermal toxicity testing (Guideline 402) and repeated dose toxicity studies lasting 28 days (Guideline 407) or 90 days (Guideline 408). The purpose of the OECD guidelines is to enhance the validity and international acceptance of toxicity test data.
Regulatory guidelines for conducting toxicity studiesHimikaRathi
This document outlines regulatory guidelines for conducting toxicity studies, focusing on OECD guidelines. It provides an introduction to OECD guidelines and lists numerous guidelines for health effects testing. It defines key terms related to toxicity studies. It describes the objectives and procedures for various types of toxicity studies, including acute toxicity studies conducted over 14 days, subacute studies of 14-28 days, subchronic studies up to 90 days, and chronic studies of 6 months or more. Test guidelines covered include fixed dose, acute toxic class, and up-and-down methods. The document aims to help standardize toxicity testing internationally.
Vision screening is a cost-effective method to identify people with visual impairments or eye conditions that require further evaluation. Screenings can be performed using various techniques like eye exams, mobile clinics, photoscreening, and visual acuity tests. The goal is to detect issues like refractive errors, strabismus, and amblyopia and refer individuals for comprehensive eye exams. Proper vision screening helps ensure early detection and treatment of vision problems.
This document summarizes different types of anti-glaucoma drugs. It discusses the classification of these drugs based on their mechanism of action, which includes reducing aqueous production, increasing aqueous outflow, or both. The main classes covered are beta blockers, prostaglandin analogues, parasympathomimetics, sympathomimetics, carbonic anhydrase inhibitors, and hyperosmotics. Specific drugs are provided within each class along with their indications, mechanisms, dosages, and potential side effects. Combination drug therapies are also mentioned. Treatment protocols are outlined for primary open angle glaucoma and acute primary angle-closure glaucoma.
Toxicokinetics describes how chemicals enter and pass through the body, including absorption, distribution to tissues, biotransformation by the body, and excretion from the body. Key factors that influence toxicity include how well a substance is absorbed, whether it is transformed into more or less toxic metabolites, and how quickly it is removed from the body. Toxicokinetics examines these processes for chemicals at high, toxic doses and is thus important for understanding health risks from chemical exposures.
The document discusses optical aberrations in the eye, including monochromatic and chromatic aberrations. It describes how aberrations can be measured using wavefront analysis techniques like the Shack-Hartman test. Common aberrations discussed include defocus, astigmatism, coma, and spherical aberration. The document explains how these aberrations affect image quality and discusses techniques to measure and correct for aberrations.
This document defines exposure to toxicants and the factors that influence toxicity. It discusses the major routes of exposure including ingestion, inhalation, and dermal absorption. The effectiveness of different routes depends on how directly the chemical enters the bloodstream, with intravenous being most effective. Occupational exposures typically involve inhalation or dermal contact, while accidental poisonings often involve ingestion. Duration and frequency of exposure are also important, and are classified as acute, subacute, chronic, or sub-chronic depending on the length of exposure.
The document discusses various concepts related to pharmacology including dose-response relationships, drug potency and efficacy, therapeutic index, and factors that can influence drug response. It describes the graded and quantal types of dose-response curves and defines potency as the amount of drug required to produce a desired response. Therapeutic index is defined as the ratio of lethal to effective doses. The document also discusses how drug responses can be increased or decreased through summation, synergism, potentiation, and antagonism. Multiple factors are described that can affect drug response including route of administration, presence of other drugs, accumulation, and patient-related factors.
This document discusses various antifibrotic agents used in ophthalmology, including 5-fluorouracil, mitomycin C, and amniotic membrane. 5-fluorouracil inhibits DNA synthesis to reduce fibroblast proliferation and is used after glaucoma surgery and for ocular surface tumors. Mitomycin C inhibits cell proliferation and is applied during pterygium removal and glaucoma surgery to prevent scarring. Amniotic membrane promotes wound healing and inhibits scarring. It is used for ocular surface reconstruction after injuries or surgery.
The document discusses the principles of analytic toxicology. It describes how analytic toxicology involves the detection, identification, and measurement of foreign compounds in biological specimens using tools from analytical chemistry. It has several applications, including in general toxicology, clinical toxicology, therapeutic drug monitoring, and forensic toxicology. In forensic toxicology, analytic toxicology is used to identify toxins in autopsy specimens to determine cause of death or injury and provide evidence for the courts.
This is a slideshow presentation about common antimetabolites usage in ophthalmology. It included the summary of mode of actions, indication, contraindication, preparation, pharmacokinetic and pharmacodynamic of each drugs.
This document provides an overview of auditory and visual evoked potentials. It discusses brainstem auditory evoked potentials (BAEPs) and visual evoked potentials (VEPs). For VEPs, it describes the visual pathway and how VEPs are recorded and analyzed. Common VEP waveforms like P100 are discussed along with factors that influence VEPs. For BAEPs, it outlines the auditory pathway and describes the waves recorded, including waves I-V. It discusses how BAEPs are measured and clinical applications for both VEPs and BAEPs in evaluating diseases that impact the visual and auditory pathways.
Ophthalmology literally means "the science of eyes”. The branch of Ophthalmology and Visual Sciences is related with helping patients improve and maintain their vision. Ophthalmology is the study of medicine that deals with the diseases and surgeries of the eye. An ophthalmologist is a specialist in visual medical and surgical eye problems.These kind of treatments can be treated in Multispeciality hospitals
This document summarizes skin toxicology. It discusses the structure and functions of the skin, percutaneous absorption, and various skin diseases and conditions including occupational skin diseases, contact dermatitis, phototoxicity, granulomatous disease, acne, pigmentary disturbances, urticaria, toxic epidermal necrolysis, and skin cancer. It provides details on the causes, mechanisms, and characteristics of these diseases and conditions.
Immunosuppressive agents in ophthalmologyTina Chandar
This document discusses various immunosuppressive agents used in ophthalmology, including their mechanisms of action, clinical indications, dosages, and potential adverse effects. It covers alkylating agents like cyclophosphamide and chlorambucil, antimetabolites like azathioprine and methotrexate, the antibiotic cyclosporin A, and newer agents like tacrolimus, daclizumab, and infliximab. Monitoring of blood counts is important when using these drugs due to risks of bone marrow suppression, infections, and other toxicities. Careful dosage adjustment and patient follow up is needed with immunosuppressive therapy for ocular conditions.
The document discusses multidrug use in the elderly. It notes that the elderly population is growing and consuming more prescription drugs. Age-related changes to pharmacokinetics and pharmacodynamics can increase risks of adverse drug events from polypharmacy. Drugs are metabolized and cleared more slowly from the body due to reduced liver and kidney function. The elderly also experience increased drug sensitivity. Careful monitoring is needed to balance treatment benefits and risks.
Chemical injuries to the eye can range from minor irritation to complete vision loss. They typically occur from contact with chemicals during domestic, agricultural, or laboratory accidents, deliberate attacks, or self-harm. Alkali burns, usually from strong bases like lime or ammonia, are the most severe and can lead to acute ischemic necrosis of the conjunctiva and cornea. Acid burns are less severe, as acids coagulate proteins on contact to limit penetration. Treatment involves thorough irrigation, removal of contaminated tissue, preventing complications like symblepharon, and addressing issues such as glaucoma, poor healing, or opacity with additional procedures. The severity is graded based on the extent of limbal and corneal damage.
This document discusses various topics in ophthalmic pathology and pharmacology. It covers:
1. The definitions and main branches of pharmacology, including pharmacokinetics and pharmacodynamics.
2. Different routes of drug delivery to the eye, including topical, local injections, and systemic administration.
3. Classes of anti-inflammatory drugs used to treat ocular inflammation, such as glucocorticoids, NSAIDs, mast cell stabilizers, and antihistamines.
4. Specific drugs used for various ocular conditions and their adverse effects.
5. Processes of wound healing, tissue fixation and processing, orientation and dissection of eye specimens, and staining for
This document provides an overview of ocular therapeutics, including principles of pharmacodynamics, pharmacokinetics, and factors influencing drug penetration into ocular tissues. It discusses various routes of ocular drug administration including topical eye drops, ointments, periocular injections, and systemic administration. Specific drug classes are covered in depth, such as corticosteroids, NSAIDs, mast cell stabilizers, and immunosuppressants. Recent advances in drug delivery and newer therapeutic agents are also mentioned.
This document discusses the ocular side effects of common systemic drugs. It begins by noting that many drugs can reach the eye through circulation and accumulate in the cornea, lens, and vitreous, prolonging their effects and increasing toxicity risks. Several classes of drugs are then described in more detail, including their ocular side effects. These include photosensitizers, cardiac glycosides, tetracyclines, corticosteroids, aminoquinolines, phenothiazines, antiseizure agents, and anti-coagulants. The document concludes by emphasizing the importance of recognizing potential ocular side effects from systemic medications to enable prompt management and prevent vision complications.
The document discusses guidelines for toxicity testing from the Organisation for Economic Co-operation and Development (OECD). It provides an overview of OECD guidelines for acute oral toxicity testing, including the fixed dose procedure (Guideline 420), acute toxic class method (Guideline 423), and up-and-down procedure (Guideline 425). It also discusses guidelines for acute dermal toxicity testing (Guideline 402) and repeated dose toxicity studies lasting 28 days (Guideline 407) or 90 days (Guideline 408). The purpose of the OECD guidelines is to enhance the validity and international acceptance of toxicity test data.
Regulatory guidelines for conducting toxicity studiesHimikaRathi
This document outlines regulatory guidelines for conducting toxicity studies, focusing on OECD guidelines. It provides an introduction to OECD guidelines and lists numerous guidelines for health effects testing. It defines key terms related to toxicity studies. It describes the objectives and procedures for various types of toxicity studies, including acute toxicity studies conducted over 14 days, subacute studies of 14-28 days, subchronic studies up to 90 days, and chronic studies of 6 months or more. Test guidelines covered include fixed dose, acute toxic class, and up-and-down methods. The document aims to help standardize toxicity testing internationally.
Vision screening is a cost-effective method to identify people with visual impairments or eye conditions that require further evaluation. Screenings can be performed using various techniques like eye exams, mobile clinics, photoscreening, and visual acuity tests. The goal is to detect issues like refractive errors, strabismus, and amblyopia and refer individuals for comprehensive eye exams. Proper vision screening helps ensure early detection and treatment of vision problems.
This document summarizes different types of anti-glaucoma drugs. It discusses the classification of these drugs based on their mechanism of action, which includes reducing aqueous production, increasing aqueous outflow, or both. The main classes covered are beta blockers, prostaglandin analogues, parasympathomimetics, sympathomimetics, carbonic anhydrase inhibitors, and hyperosmotics. Specific drugs are provided within each class along with their indications, mechanisms, dosages, and potential side effects. Combination drug therapies are also mentioned. Treatment protocols are outlined for primary open angle glaucoma and acute primary angle-closure glaucoma.
Toxicokinetics describes how chemicals enter and pass through the body, including absorption, distribution to tissues, biotransformation by the body, and excretion from the body. Key factors that influence toxicity include how well a substance is absorbed, whether it is transformed into more or less toxic metabolites, and how quickly it is removed from the body. Toxicokinetics examines these processes for chemicals at high, toxic doses and is thus important for understanding health risks from chemical exposures.
The document discusses optical aberrations in the eye, including monochromatic and chromatic aberrations. It describes how aberrations can be measured using wavefront analysis techniques like the Shack-Hartman test. Common aberrations discussed include defocus, astigmatism, coma, and spherical aberration. The document explains how these aberrations affect image quality and discusses techniques to measure and correct for aberrations.
This document defines exposure to toxicants and the factors that influence toxicity. It discusses the major routes of exposure including ingestion, inhalation, and dermal absorption. The effectiveness of different routes depends on how directly the chemical enters the bloodstream, with intravenous being most effective. Occupational exposures typically involve inhalation or dermal contact, while accidental poisonings often involve ingestion. Duration and frequency of exposure are also important, and are classified as acute, subacute, chronic, or sub-chronic depending on the length of exposure.
The document discusses various concepts related to pharmacology including dose-response relationships, drug potency and efficacy, therapeutic index, and factors that can influence drug response. It describes the graded and quantal types of dose-response curves and defines potency as the amount of drug required to produce a desired response. Therapeutic index is defined as the ratio of lethal to effective doses. The document also discusses how drug responses can be increased or decreased through summation, synergism, potentiation, and antagonism. Multiple factors are described that can affect drug response including route of administration, presence of other drugs, accumulation, and patient-related factors.
This document discusses various antifibrotic agents used in ophthalmology, including 5-fluorouracil, mitomycin C, and amniotic membrane. 5-fluorouracil inhibits DNA synthesis to reduce fibroblast proliferation and is used after glaucoma surgery and for ocular surface tumors. Mitomycin C inhibits cell proliferation and is applied during pterygium removal and glaucoma surgery to prevent scarring. Amniotic membrane promotes wound healing and inhibits scarring. It is used for ocular surface reconstruction after injuries or surgery.
The document discusses the principles of analytic toxicology. It describes how analytic toxicology involves the detection, identification, and measurement of foreign compounds in biological specimens using tools from analytical chemistry. It has several applications, including in general toxicology, clinical toxicology, therapeutic drug monitoring, and forensic toxicology. In forensic toxicology, analytic toxicology is used to identify toxins in autopsy specimens to determine cause of death or injury and provide evidence for the courts.
This is a slideshow presentation about common antimetabolites usage in ophthalmology. It included the summary of mode of actions, indication, contraindication, preparation, pharmacokinetic and pharmacodynamic of each drugs.
This document provides an overview of auditory and visual evoked potentials. It discusses brainstem auditory evoked potentials (BAEPs) and visual evoked potentials (VEPs). For VEPs, it describes the visual pathway and how VEPs are recorded and analyzed. Common VEP waveforms like P100 are discussed along with factors that influence VEPs. For BAEPs, it outlines the auditory pathway and describes the waves recorded, including waves I-V. It discusses how BAEPs are measured and clinical applications for both VEPs and BAEPs in evaluating diseases that impact the visual and auditory pathways.
Ophthalmology literally means "the science of eyes”. The branch of Ophthalmology and Visual Sciences is related with helping patients improve and maintain their vision. Ophthalmology is the study of medicine that deals with the diseases and surgeries of the eye. An ophthalmologist is a specialist in visual medical and surgical eye problems.These kind of treatments can be treated in Multispeciality hospitals
This document summarizes a study that used a fluorescence biomicroscope to simultaneously measure lens autofluorescence and Rayleigh scattering in 127 healthy subjects aged 21-70. Key findings include:
1. Lens autofluorescence intensity increased linearly with age, consistent with previous studies.
2. A nonlinear model best fit the relationship between fluorescence ratio (autofluorescence divided by scatter) and age, with the ratio leveling off at older ages.
3. The study establishes baseline measurements of lens autofluorescence and ratio values in healthy eyes that can help clinicians identify potentially abnormal levels in patients.
Evaluation of visual function with opaque media Kunal Shinde
This document discusses methods for evaluating visual function when the ocular media is opaque, preventing direct visualization of the fundus. Both subjective and objective tests are described. Subjective tests include visual acuity, perception of light, entoptic phenomena using the Maddox rod or retinal blood vessels, and potential acuity meter. Objective tests include examination of the pupil, ultrasonography, electroretinography, electrooculography, and visual evoked potentials to assess retinal and macular integrity when the media is opaque. The results of these tests can help determine visual potential and guide surgical management.
This document summarizes recent advancements in optometry. It discusses developments such as antimicrobial coatings for contact lenses, advancements in treating diabetic eye diseases using scatter laser treatment, stem cell therapy for retinal and optic nerve problems, Optiwave refractive analysis technology that allows surgeons to analyze eyes during cataract surgery, and Optos retinal scanning that eliminates the need for dilating drops and allows viewing of the entire retina. It also mentions visual prosthetics, advances in ocular drug delivery systems, and orthokeratology. Overall, the document outlines several important technological innovations that have improved eye care and vision correction.
This document provides an introduction to ocular drug delivery systems (ODDS). It discusses the anatomy and physiology of the eye, challenges with conventional ophthalmic dosage forms, and advantages of new drug delivery systems. Various types of ocular drug delivery systems are described, including inserts, contact lenses, and vesicular systems like liposomes, niosomes, and pharmacosomes. Routes of ocular drug administration and mechanisms of drug absorption through the eye are also summarized. Common eye infections that can be treated with these drug delivery systems are listed.
The document provides an overview of optometry and eye exams. It discusses the history of optometry, what a standard eye exam involves, including case history, refractive tests, binocular and accommodation tests, and ocular health evaluation. It then describes how some optometrists are modernizing exams with new technologies like optical coherence tomography, fundus photography, and automated testing to provide more detailed analysis of the eye.
AN OVERVIEW OF OCULAR DRUG DELIVERY SYSTEM INCLUDING ROLE OF OCULAR INSERTS I...SriramNagarajan19
Eye is the organ of human body having main function of vision. Ocular drug delivery is the alternative route for the systemic treatment of disease and also a route for the treatment of eye diseases such as conjunctivitis, keratitis etc. Ocular inserts are the one of the most useful and innovative technique for the treatment of eye diseases by increase contact time and providing control release of drug. This review is generated to provide an overview of ocular drug delivery including role of ocular inserts in treatment of eye disorders.
This document provides information on pupillary anatomy, physiology, and examination. It discusses the normal anatomy and functions of the pupil. It describes how to perform a systematic pupillary examination, including testing the light reflex and near reflex. It covers common and uncommon disorders that can be diagnosed based on pupillary examination findings, such as Horner's syndrome and Adie's tonic pupil. The document emphasizes that the pupillary examination can provide useful clues about underlying ocular and neurological conditions.
This document discusses pupillary examination and various aspects of pupillary reflexes. It begins by describing the pathway of the pupillary light reflex from the retina through the brain. It then discusses the efferent pathway from the Edinger-Westphal nucleus to the iris sphincter muscle. The document also covers the near reflex pathway and differences between the light and near reflexes. It provides tips for examining pupillary reflexes, potential causes of anisocoria, and tests such as color vision testing and confrontation visual field testing.
Syllabus of PCL in ophthalmic Assistant by NHPCKapil Gautam
This document outlines the syllabus for the Licensing Examination of PCL in Ophthalmic Science/Diploma in Ophthalmic Technique in Nepal in 2021. It includes 13 topics that will be covered in the exam, along with the percentage of marks allocated to each topic. The topics cover basic sciences, anatomy and physiology, ophthalmic specialties like pharmacology, pathology, optics and refraction. It also includes operational areas like ophthalmic nursing care, assisting in ocular surgery and community ophthalmology. The document provides a brief overview of the content that will be assessed under each topic in the licensing examination.
Light and laser sources can cause retinal injury through photochemical and thermal mechanisms. The retina is susceptible to damage from sunlight, welding arcs, medical instruments like operating microscopes, and lasers. Protective mechanisms like the cornea, lens, and retinal pigment help absorb harmful wavelengths. Retinal injuries present as yellow lesions and can cause vision loss, though recovery is possible. Precautions like filters, goggles, and minimizing exposure times are important to prevent light and laser injuries.
This document summarizes research on the effectiveness of vision therapy in improving visual function. It discusses what vision therapy is and how it can be used to treat various visual disorders like binocular vision problems, eye movement issues, focusing difficulties, strabismus, amblyopia, and nystagmus. The document reviews numerous studies demonstrating that vision therapy can successfully modify and improve visual skills like eye coordination, eye movements, and focusing abilities. It concludes that vision therapy is an effective clinical approach supported by a significant amount of research.
Cataract surgery is the most common surgery that we perform on a outpatient basis. Evaluation of the patient is critical and essential for a desirable visual outcome.
PRE-OPERATIVE EVALUATION IN CATARACT SURGERYAlexLino17
This document summarizes the key points in assessing a patient for cataract surgery. It discusses obtaining a thorough history including vision symptoms, medical history, medications and allergies. A comprehensive eye exam evaluates visual acuity, refraction, external exam, slit lamp exam of the anterior segment and dilated fundus exam. Additional tests may include biometry to calculate IOL power, corneal topography and lab tests. Special considerations are discussed for conditions like uveitis, glaucoma, retinal disease and prior refractive surgery. A complete pre-op evaluation is important to identify risks and ensure the best surgical outcome and post-op visual rehabilitation.
Lupus can affect any part of the body, including the eyes. Complications affecting the eye may be a result of the disease itself, an overlap disease, and/or a result of medication side effects. Individuals with lupus should be aware of how lupus can impact the eyes and what individuals with lupus can do to improve eye health. Dr. Solomon offers insight into how lupus can affect eye health. In addition, he provides information on what steps can be taken to prevent eye complications and promote eye health.
This document reviews various methods for detecting glaucoma from medical images and proposes a new method. It discusses both manual and automatic detection techniques, including scanning laser polarimetry, optical coherence tomography, wavelet Fourier analysis, and analyzing features from fundus images. The proposed method uses discrete wavelet transforms to extract energy features from retinal images, feeds these features into an artificial neural network for classification of images as normal or glaucomatous, and applies clustering for segmentation to detect affected parts in glaucomatous images. The goal is an automatic system for classifying and segmenting glaucoma from retinal images based on wavelet analysis and neural networks.
introduction to phototoxicity
causes
etiology
types of phototoxicity testing methods
detection of phototoxicity
methods to reduce toxicity
regulatory toxicology
bioassays
in vitro metods
in vivo methods
Describe the visual receptors
List the types of lenses and recognize how they work
Determine the power of lenses
Describe accommodation for near vision and far vision
Recognize nearsightedness and farsightedness and determine its correction
Schematic eye.
Determine intraocular pressure and glaucoma
Introduction
Anatomy and physiology of human eye
Ocular delivery system
Optimum characters of ophthalmic drugs
Routes of ophthalmic drugs
Mechanism of ocular drug absorption
Barriers and fate of ocular drug delivery
Formulation consideration of ocular dosage forms
Evaluation tests
References
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Toxic responses of the ocular and visual system
1. Toxic Responses of the Ocular and
Visual System
Khaled A. Alrasheedi
PharmD, Clinical Toxicologist
2. Outline
INTRODUCTION TO OCULAR AND
VISUAL SYSTEM TOXICOLOGY
EXPOSURE TO THE EYE AND VISUAL
SYSTEM
EVALUATING OCULAR TOXICITY AND
VISUAL FUNCTION
TARGET SITES AND MECHANISMS OF
ACTION: CORNEA
• Acids
• Bases or Alkalies
• Organic Solvents
• Sur actants
TARGET SITES AND MECHANISMS OF
ACTION: LENS
TARGET SITES AND MECHANISMS OF
ACTION: RETINA
• Retinotoxicity of Systemically Administered
• Retinotoxicity of Known Neurotoxicants
TARGET SITES AND MECHANISMS OF
ACTION: OPTIC NERVE AND TRACT
• Acrylamide
• Carbon Disulf de
• Ethambutol
TARGET SITES AND MECHANISMS OF
ACTION: THE CENTRAL VISUAL
SYSTEM
3. INTRODUCTION TO OCULAR AND VISUAL
SYSTEM TOXICOLOGY
Environmental and occupational exposure to toxic chemicals,
gases, and vapors as well as side effects resulting from
therapeutic drugs frequently result in structural and functional
alterations in the eye and central visual system.
The retina and central visual system are especially vulnerable
to toxic insult.
4.
5. EXPOSURE TO THE EYE AND
VISUAL SYSTEM
Ocular Pharmacodynamics and Pharmacokinetics
Toxic chemicals and systemic drugs can affect all parts of the eye.
Factors determining whether a chemical can reach a particular ocular site
of action include :
1- physiochemical properties of the chemical
2- concentration
3- duration of exposure
4- movement across ocular compartments
5- barriers.
The cornea, conjunctiva, and eyelids are ofen exposed directly to
chemicals, gases, drugs, and particles. The first site of action is the tear
film, a three-layered structure with both hydrophobic and hydrophilic
properties.
6. Nanoparticles and Ocular Drug Delivery
The main ocular target sites of importance or disease treatment
and neuroprotection are the anterior segment and posterior
retina.
There are numerous barriers that restrict bioavailability,
decrease therapeutic efficacy, and increase side effects.
Development of nanoscale preparations or drug delivery is
a new approach to drug delivery which can substantially enhance
penetration from the cornea, deliver a wide variety of drugs and
molecules, and increase the concentration and contact time of
drugs with these tissues
7. A wide variety of nanoformulations have been considered
including solid lipid nanoparticles containing :
• lipids, phospholipids, and/or metals; liposomes;
nanosuspensions; and emulsions; and the use of biocompatible
coatings such as chitosan.
Metallic particles that enable remote magnetic targeting of
drug delivery also are under development.
8. Ocular Drug Metabolism
Metabolism of xenobiotics occurs in all compartments of
the eye by well-known phase I and II xenobiotic biotrans
forming enzymes.
Drug-metabolizing enzymes that are present in the tears,
iris ciliary body, choroid, and retina of many different
Species.
9. Central Visual System Pharmacokinetics
The penetration of potentially toxic compounds into visual
areas of the central nervous system (CNS) is governed by the
Blood brain barrier.
which is differentially permeable to compounds depending on
their size, charge, and lipophilicity.
Compounds that are large, highly charged, or otherwise not
very lipid soluble tend to be excluded from the brain, where as
smaller, uncharged, and lipid-soluble compounds more readily
penetrate into the brain tissue.
10. Light and Phototoxicity
The most important oxidizing agents are visible light and
UV radiation, particularly UV-A (320 to 400 nm) and
UV-B (290 to 320 nm), and other forms of electromagnetic
radiation.
Light- and UV-induced photooxidation leads to generation of
reactive oxygen species (ROS), and oxidative damage that can
accumulate over time.
Higher energy UV-C (100 to 290 nm) is even more damaging.
11. The cornea absorbs about 45% of light with wavelengths below
280 nm, but only about 12% between 320 and 400 nm.
The lens absorbs much of the light between 300 and 400 nm and
transmits 400 nm and above to the retina.
Absorption of light energy in the lens triggers a variety of
photoreactions, including the generation of fluorophores and
pigments that lead to the yellow-brown coloration of the lens.
12. Drugs and other chemicals can mediate photo-induced
toxicity in the cornea, lens, or retina.
This occurs when the chemical structure allows absorption of
light energy and the subsequent generation of activated
intermediates, free radicals, and ROS.
The propensity of chemicals to cause phototoxic reactions can
be predicted using photophysical and in vitro procedures.
13. EVALUATING OCULAR TOXICITY
AND VISUAL FUNCTION
Evaluation of Ocular Irritancy and Toxicity
The so-called Draize test, with some additions and revisions,
has formed the basis of standard procedures employed or evaluating
ocular irritation and safety evaluations.
The procedure involves:
instillation of 0.1 mL of a liquid or 100 mg of a solid into the
conjunctival sac of one eye and then gently holding the eye closed or 1 s.
The untreated eye serves as a control.
Both eyes are evaluated at 1, 24, 48, and 72 h after treatment.
if there is evidence of damage in the treated eye at 72 h,
the examination time may be extended.
14. The cornea, iris, and conjunctiva are evaluated and scored according to a weighted
scale.
The cornea is scored or both the degree of opacity and area of involvement, with
each measure having a potential range from 0 (none) to 4 (most severe).
The iris receives a single score (0 to 2) or irritation, including degree of swelling,
congestion, and degree o reaction to light.
The conjunctiva is scored or the redness (0 to 3), chemosis (swelling 0 to 4), and
discharge (0 to 3).
The individual scores are then multiplied by a weighting actor: 5 or the cornea, 2 or
the iris, and 5 or the conjunctiva.
The results are summed or a maximum total score of 110.
In this scale, the cornea accounts or 73% of the total possible points, in accordance
with the severity associated with corneal injury.
15. Ophthalmologic Evaluations
There are many ophthalmologic procedures or evaluating
the
health of the eye.
Examination of the adnexa includes evaluating the eyelids,
lacrimal apparatus, and palpebral (covering the eyelid) and
bulbar (covering the eye) conjunctiva.
The adnexa and surface of the cornea can be examined
initially with the naked eye, a hand-held light, or a slit-
lamp biomicroscope, using a mydriatic drug (which causes
pupil dilation) i the lens is to be observed.
16. The width of the reflection of a thin beam of light projected
rom the slit lamp is an indication of the thickness of the
cornea and may be used to evaluate corneal edema.
Lesions o the cornea can be better visualized with the use of
fluorescein dye, which is retained where there is an
ulceration of the corneal epithelium.
Examination of the fundus requires use of a mydriatic drug
and a direct or an indirect ophthalmoscope.
17. An examination of the direct pupillary reflex involves
shining
a bright light into the eye and observing the reflexive pupil
constriction in the same eye.
The absence of a pupillary reflex is indicative of damage
somewhere in the reflex pathway, and differential
impairment of the direct or consensual reflexes can indicate
the location of the lesion.
18. Electrophysiologic Techniques
Most electrophysiologic or neurophysiologic procedures
or testing visual function in a toxicologic context involve
stimulating the eyes with visual stimuli and electrically
recording potentials generated by visually responsive
neurons.
The most commonly used procedures are:
1- The flash-evoked electroretinogram (ERG)
2- Visual-evoked potentials (VEPs)
3- less often , the electrooculogram (EOG).
19. The flash-evoked electroretinogram (ERG)
ERGs are typically elicited with a brie flash of light and recorded
from an electrode placed in contact with the cornea.
A typical ERG wave form includes an a-wave that reflects
the activation of photoreceptors and a b-wave that reflects the
activity of retinal bipolar cells (BC) and associated membrane
potential changes in Müller cells (MC).
A standard set of ERG procedures includes the recording of
(1) a response reflective of only rod photoreceptor function
in the dark-adapted eye
(2) The maximal response in the dark-adapted eye
(3) a response developed by cone photoreceptors
(4) oscillatory potentials
(5) the response to rapidly flickered light.
20. Visual-evoked potentials (VEPs)
Flash-elicited VEPs are recorded from electrodes overlying
visual (striate) cortex, and they reflect the activity of the
retinogeniculostriate pathway and the activity of cells in the
visual cortex.
Pattern-elicited VEPs (PEPs), which are widely used in
human clinical evaluations, have diagnostic value.
21. The electrooculogram (EOG).
The EOG is generated by a potential difference between the front and
back of the eye, which originates primarily within the RPE.
The magnitude of the EOG is a function of the level of illumination and
health status of the retinal pigment epithelium (RPE) .
Electrodes placed on the skin on a line lateral or vertical to the eye
measure potential changes correlated with eye movements as the
relative position of the ocular dipole changes. Thus, the EOG
finds applications in assessing both RPE status and measuring
eye movements. The EOG is also used in monitoring eye movements
during the recording of other brain potentials, so that eye movement
artifacts are not misinterpreted as brain generated electrical activity.
22. Color Vision Testing
Color vision deficits are either inherited or acquired.
Hereditary red–green color deficits occur in about 8% of males (X-
linked) whereas only about 0.5% of females show similar congenital
deficits.
Inherited color deficiencies take two common forms:
1- protan, a red–green confusion caused by abnormality or absence
of the long-wavelength (red) sensitive cones (L-type cones).
2- Deutan caused by abnormality or absence of the middle
wavelength sensitive (green) cones (M-typecones).
23. Most acquired color vision deficits, such as those caused
by drug and chemical exposure, begin with a reduced ability to
perform blue–yellow discriminations.
With increased or prolonged low-level exposure, the color
confusion can progress to the red–green axis as well.
Generally, disorders of the outer retina produce blue–yellow
deficits, whereas disorders of the inner retina and ON produce
red–green perceptual deficits.
Bilateral lesions in the visual cortex can also lead to color
blindness.
24. TARGET SITES AND MECHANISMS OF
ACTION: CORNEA
The cornea provides three essential functions.
First, it provides a clear refractive surface and the curvature of
the cornea must be correct or the visual image to be focused at
the retina.
Second, the cornea provides tensile strength to maintain
the appropriate shape of the globe.
Third, the cornea protects the eye from external actors, including
potentially toxic chemicals.
25. T e cornea is transparent to wavelengths of light ranging
between 310 nm (UV) and 2 500 nm (IR). Exposure to UV light
below this range can damage the cornea. It is most sensitive to
wavelengths of approximately 270 nm. Excessive UV exposure
leads to photokeratitis and corneal pathology, the classic example
being welder’s-arc burns.
Products at pH extremes ≤ 2.5 or ≥ 11.5 can cause severe ocular
damage and permanent loss o vision.
The most important therapy is immediate and adequate irrigation
with large amounts of water or saline.
26. Acids
The most significant acidic chemicals in terms of the
tendency to cause clinical ocular damage are:
Hydrofluoric acid, Sulfurous acid, Sulfuric acid, and
Chromic acid, followed by Hydrochloric and Nitric acid and
finally Acetic acid.
pH between 2.5 and 7 produce pain or stinging, but with only a brie contact
Mild burns The corneal epithelium may become turbid as the corneal
stroma swells (chemosis).
Rapid regeneration of the corneal epithelium and full
recovery.
Severe burns, The epithelium of the cornea and conjunctiva become
opaque and necrotic and may disintegrate over the course
of a few days
There may be no sensation
o pain because the corneal nerve endings are destroyed
27. Bases or Alkalies
Compounds with a basic pH are potentially more damaging to
the eye than are strong acids.
The compounds of clinical significance in terms of frequency and
severity of injuries are :
1- Ammonia or ammonium hydroxide
2- Sodium hydroxide (lye)
3- Potassium hydroxide (caustic potash)
4- Calcium hydroxide (lime)
5- Magnesium hydroxid
One reason that caustic agents are so dangerous is their ability to
rapidly penetrate the ocular tissues.
28. Organic Solvents
When organic solvents are splashed into the eye, the result is
typically a painful immediate reaction.
Exposure o the eye to solvents should be treated rapidly
with abundant water irrigation.
Most organic solvents cause minimal chemical burns to the
cornea. In most cases, the corneal epithelium will be
repaired over the course of a few days and there will be no
residual damage.
29. Surfactants
These compounds have water-soluble (hydrophilic)
properties
at one end of the molecule and lipophilic properties at the
other end that help to dissolve fatty substances in water and
also serve to reduce water surface tension.
The widespread use of these agents in soaps, shampoos,
detergents, cosmetics. Many of these agents may be
irritating or injurious to the eye.
30. TARGET SITES AND MECHANISMS OF
ACTION: LENS
The lens of the eye plays a critical role in focusing the visual
image on the retina.
The high transparency of the lens to visible wavelengths of
light is a function of its chemical composition.
The lens is a metabolically active tissue that maintains
careful electrolyte and ionic balance.
Cataracts are decreases in the optic transparency of the lens
that ultimately can lead to functional visual disturbances.
31. Risk actors or the development of cataracts include:
Aging, Diabetes, Low antioxidant levels, and Exposure to
a variety of environmental factors.
Several different mechanisms have been hypothesized to
account or the development of cataracts. These include the
disruption of lens energy metabolism, hydration and/or
electrolyte balance, oxidative stress due to the generation of
free radicals and ROS, and the occurrence of oxidative
stress.
32. Corticosteroids
There are two proposed mechanisms by which systemic
treatment with corticosteroids may cause cataracts.
Corticosteroids alter lens epithelium electrolyte balance,
which disrupts the normal lens epithelial cell structure
causing gaps to appear between the lateral epithelial cell
borders.
Another theory is that corticosteroid molecules react with
lens crystallin proteins, producing corticosteroid–crystallin
adducts that would be light-scattering complexes.
33. Naphthalene
Accidental exposure to naphthalene results in cortical
cataracts and retinal degeneration.
The metabolite naphthalene dihydrodiol is the cataract-
inducing agent instead of naphthalene itself .
Subsequent studies showed that aldose reductase in the rat
lens is the enzyme responsible or the ormation of
naphthalene dihydrodiol, and that treatment with aldose
reductase inhibitors prevents naphthalene-induced cataracts.
34. Phenothiazines
Schizophrenics receiving phenothiazine drugs develop pigmented
deposits in their eyes and skin.
The phenothiazines combine with melanin to form a photosensitive
product that reacts with sunlight, causing formation of the deposits
in lens and cornea.
The amount of pigmentation is related to the dose of the drug, with
the annual yearly dose being the most predictive dose metric. More
recent epidemiologic evidence demonstrates a dose-related increase
in the risk of cataracts from use of nonantipsychotic
phenothiazines.
35. TARGET SITES AND MECHANISMS OF
ACTION: RETINA
The mammalian retina is highly vulnerable to toxicantinduced
structural and/or functional damage due to:
(1) The highly enestrated choriocapillaris.
(2) the very high rate of oxidative mitochondrial metabolism.
(3) high daily turnover of rod and cone outer segments.
(4) high susceptibility of the rod and cones to degenerate.
(5) presence of specialized ribbon synapses and synaptic contact
sites.
(6) Presence of numerous neurotransmitter and neuromodulatory systems
(7) presence of numerous and highly specialized gap junctions.
(8) Presence of melanin in the choroid and RPE and also in the iris and pupil.
(9) a very high choroidal blood flow rate.
(10) the additive or synergistic toxic action of certain chemicals with ultraviolet
and visible light
36. Retinotoxicity of Systemically
Administered Therapeutic Drugs
Cancer Chemotherapeutics.
Ocular toxicity is a common side effect of cancer
chemotherapy
The retina, due to its high metabolic activity and choroidal
circulation, appears to be particularly vulnerable to
numerous cytotoxic drugs such as the alkylating agents
cisplatin, carboplatin, and carmustine
37. Chloroquine and Hydroxychloroquine
Chloroquine (Aralen) and hydroxychloroquine (Plaquenil)
are 4- aminoquinoline derivatives used as antimalarial and
antiinflammatory drugs that can cause irreversible loss of
retinal function.
Prolonged exposure of the retina to these drugs, especially
chloroquine, may lead to an irreversible retinopathy.
38. Digoxin and Digitoxin
Digitalis-induced visual system abnormalities include
decreased vision, flickering scotomas, and altered color
vision.
The retina has the highest number of Na+ ,K+ -A Pase sites
of any ocular tissue, which are potently inhibited by digoxin
and digitoxin.
39. Retinotoxicity of Known Neurotoxicants
Inorganic Lead
Lead poisoning in humans produces amblyopia, blindness, optic
neuritis or atrophy, peripheral and central scotomas, paralysis
of eye muscles, and decreased visual function.
Moderateto to high-level lead exposure produces scotopic and
temporal visual system deficits in occupationally exposed factory
workers, and developmentally lead-exposed monkeys and rats.
This lead exposure dosage produces irreversible retinal deficits in
the experimental animals.
40. TARGET SITES AND MECHANISMS OF
ACTION: OPTIC NERVE AND TRACT
The ON consists primarily of RGC axons carrying visual in
formation from the retina to several distinct anatomical
destinations in the CNS. Disorders of the ON may be termed
optic neuritis, optic neuropathy, or ON atrophy, referring to
inflammation, damage, or degeneration, respectively, of the
ON.
Retrobulbar neuritis refers to inflammation or involvement
of the orbital portion of the ON posterior to the globe.
41. Acrylamide
Acrylamide monomer is used in a variety of industrial and
laboratory applications, where it serves as the basis or the
production of polyacrylamide gels and other polyacrylamide
products.
Exposure to acrylamide produces a distal axonopathy in
large-diameter axons of the peripheral nerves and spinal cord
that is well documented in humans and laboratory animals.
In contrast, middle diameter axons of optic tract are affected,
specifically, RGCs that project to the parvocellular layers of the
LGN.
42. Carbon Disulfide
Carbon disulfide (CS2) is used in industry to manufacture viscose
rayon, carbon tetrachloride, and cellophane.
CS2 damages both the PNS and CNS, and has profound effects on vision.
In the visual system, workers exposed to CS2 experience loss of visual
function accompanied by observable lesions in the retinal vasculature.
Central scotoma, depressed visual sensitivity in the peripheral visual field,
optic atrophy, pupillary disturbances, blurred vision, and disorders of
color perception have all been reported.
The retinal and ON pathologies produced by CS2 are likely a direct
neuropathologic action and not the indirect result of vasculopathy.
43. Ethambutol
The dextro isomer of ethambutol is widely used as an
antimycobacterial drug or the treatment of tuberculosis.
Ethambutol produces dose-related alterations in the visual
system, such as blue–yellow and red–green dyschromatopsias,
decreased contrast sensitivity, reduced visual acuity, and visual
field loss.
44. TARGET SITES AND MECHANISMS OF
ACTION: THE CENTRAL VISUAL SYSTEM
Lead
In addition to the retinal effects of lead.
Lead exposure during adulthood or perinatal development
produces structural, biochemical, and functional deficits
in the visual cortex of humans, nonhuman primates, and
rats.
45. Methyl Mercury
Methyl mercury–poisoned individuals experience a striking
and progressive constriction of the visual field (peripheral scotoma).
The narrowing of the visual world gives impression of looking
through a long tunnel, hence the term tunnel vision.
The damage is most severe in the regions of primary visual
cortex subserving the peripheral visual field, with relative sparing
of the cortical areas representing the central vision.
Methylmercury–poisoned individuals also experience poor night
vision that is also attributable to peripheral visual field losses.