A cataract is a painless opacity of the lens that disrupts the light projecting onto the retina, resulting in a clouding of vision. It can cause partial or total blindness.
- Leading cause of blindness worldwide
- Affects all age groups
- Age-related cataract: most common type
- Prevalence in persons aged > 80 years: approximately 70%
- More common in women than men
- The lens is part of the eye’s refractive media.
- It is a transparent structure made of fibers.
- Lens fibers:
- Cortex: outer part; made of younger fibers
- Nucleus: deep part; made of older fibers
- Lens epithelium Epithelium The epithelium is a complex of specialized cellular organizations arranged into sheets and lining cavities and covering the surfaces of the body. The cells exhibit polarity, having an apical and a basal pole. Structures important for the epithelial integrity and function involve the basement membrane, the semipermeable sheet on which the cells rest, and interdigitations, as well as cellular junctions. Surface Epithelium: between fibers and the anterior capsule
- Lens capsule: outermost layer (anterior and posterior)
- Lens fibers:
Etiology and Pathophysiology
- The primary risk factor
- Aging increases the thickness of the lens.
- Cortical layers are added → cells become compressed in the center → loss of transparency + stiffening of lens
- Epithelial cell changes lead to altered lens fiber formation and homeostasis → affects transport of nutrients and antioxidants
- Oxidative damage contributes to cataract formation.
- Other risk factors:
- Excessive alcohol use
- UV light exposure
- Infrared radiation (especially common in glass workers)
- Electric shock Shock Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. Types of Shock (exposure to high-voltage current)
- Perforation of the eye
- Blunt injuries (direct blows to the eye)
- Miotics (cholinesterase inhibitors)
- Other medical conditions:
- Infections of the eye
- Chronic dialysis Dialysis Renal replacement therapy refers to dialysis and/or kidney transplantation. Dialysis is a procedure by which toxins and excess water are removed from the circulation. Hemodialysis and peritoneal dialysis (PD) are the two types of dialysis, and their primary difference is the location of the filtration process (external to the body in hemodialysis versus inside the body for PD). Overview and Types of Dialysis in patients with renal insufficiency
- Wilson’s disease
- Error in copper metabolism causing accumulation in cornea
- “Sunflower cataract”: greenish central disc with spoke-like radial opacities
- Glucose is processed by aldose reductase to sorbitol in the lens.
- ↑ glucose → ↑ sorbitol → ↑ osmolarity and fluid accumulation in the lens → cataracts
- HIV/ AIDS AIDS Chronic HIV infection and depletion of CD4 cells eventually results in acquired immunodeficiency syndrome (AIDS), which can be diagnosed by the presence of certain opportunistic diseases called AIDS-defining conditions. These conditions include a wide spectrum of bacterial, viral, fungal, and parasitic infections as well as several malignancies and generalized conditions. HIV Infection and AIDS: Patients undergo cataract surgery at a younger age than usual.
- Decreased or blurry vision:
- Can be unilateral or bilateral
- Often gradual and painless
- Diplopia or polyopia: Cataracts create multiple refractions (through clear areas and opacities).
- Glare sensitivity: to sunlight or headlights (at night)
- Color vision change: fading of objects
- Colored halos around the light: scattering of light by collection of water drops in lens
- Changes in refractive glasses
- Temporary myopic shift: increase in near vision
- Frequent changes in near and/or distant vision
- Visual acuity diminished unilaterally or bilaterally
- Nondilated funduscopic examination
- Darkening of red reflex
- Opacities within red reflex
- Fundus obscured
- Slit-lamp examination: examines the extent and type of lens opacity and other ocular structures
- Dilated funduscopic examination: examines the posterior pole, to rule out other pathology
Classification of diagnostic findings
- Types of cataracts based on maturity
- Variable Variable Variables represent information about something that can change. The design of the measurement scales, or of the methods for obtaining information, will determine the data gathered and the characteristics of that data. As a result, a variable can be qualitative or quantitative, and may be further classified into subgroups. Types of Variables amount of opacification
- Still allows for visualization of retina and has red reflex
- Mature: Cataract is opaque and there is no red reflex
- Dense opacity obscures the red reflex and the cortex has liquefied
- Morgagnian cataract: hypermature cataract with nucleus sinking inferiorly
- Types of cataracts based on the portion of the lens affected (often overlap)
- Posterior subcapsular
- Posterior portion of the lens
- Most common in metabolic disorders (diabetes and galactosemia Galactosemia Galactosemia is a disorder caused by defects in galactose metabolism. Galactosemia is an inherited, autosomal-recessive condition, which results in inadequate galactose processing and high blood levels of monosaccharide. The rare disorder often presents in infants with symptoms of lethargy, nausea, vomiting, diarrhea, and jaundice. Galactosemia)
- Nucleus or central portion of lens
- Cortex of the lens (lens fibers surrounding the nucleus)
- Most common type of acquired cataracts
- Posterior subcapsular
|Posterior subcapsular cataracts||Nuclear cataracts||Cortical cataracts|
|Diagnosis||Granular opacity in the posterior pole of cortex adjacent to the posterior capsule||
- Indicated when severe visual disturbances interfere with daily living
- Outpatient procedure, often under local anesthesia Anesthesia Anesthesiology is the field of medicine that focuses on interventions that bring a state of anesthesia upon an individual. General anesthesia is characterized by a reversible loss of consciousness along with analgesia, amnesia, and muscle relaxation. Anesthesiology: History and Basic Concepts
- Surgical techniques:
- Standard extracapsular cataract extraction:
- For removal of advanced cataracts
- Removal of lens nucleus in 1 piece, leaving capsule
- Intraocular lens (IOL) placed in the capsular bag
- Most common surgery in developed countries
- Small-incision surgery
- Phaco probe fragments hard central part of lens (with ultrasonic energy)
- IOL placed in lens capsule
- Intracapsular cataract extraction
- Rarely used, older technique
- Increased complications
- Standard extracapsular cataract extraction:
- Endophthalmitis Endophthalmitis Endophthalmitis is an inflammatory process of the inner layers of the eye, which may be either infectious or sterile. Infectious endophthalmitis can lead to irreversible vision loss if not treated quickly. Based on the entry mode of the infectious source, endophthalmitis is divided into endogenous and exogenous types. Endophthalmitis (infection within the eye)
- Intraocular malposition
- Retinal detachment Retinal detachment Retinal detachment is the separation of the neurosensory retina from the retinal pigmented epithelium and choroid. Rhegmatogenous retinal detachment, the most common type, stems from a break in the retina, allowing fluid to accumulate in the subretinal space. Retinal Detachment
- Macular degeneration Macular degeneration Age-related macular degeneration (AMD) is visual impairment due to changes in the macula, the area responsible for high-acuity vision. It is marked by central vision loss with peripheral vision relatively spared. Risk factors include advanced age, smoking, family history, and cardiovascular disease. Macular Degeneration
- Diabetes mellitus Diabetes mellitus Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus: a heterogeneous group of metabolic diseases characterized by hyperglycemia resulting from insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin resistance and deficiency. Diabetes mellitus Diabetes mellitus Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus can lead to a number of complications including transient error of refraction (from fluctuating glucose levels) and chronic retinopathy, which manifests as visual floaters and blurred vision.
- Glaucoma Glaucoma Glaucoma is an optic neuropathy characterized by typical visual field defects and optic nerve atrophy seen as optic disc cupping on examination. The acute form of glaucoma is a medical emergency. Glaucoma is often, but not always, caused by increased intraocular pressure (IOP). Glaucoma: an optic neuropathy with distinctive changes in the optic cup and visual field defect. Glaucoma Glaucoma Glaucoma is an optic neuropathy characterized by typical visual field defects and optic nerve atrophy seen as optic disc cupping on examination. The acute form of glaucoma is a medical emergency. Glaucoma is often, but not always, caused by increased intraocular pressure (IOP). Glaucoma is often associated with increased pressure within the eyeball (commonly within the anterior and posterior chambers), which results in gradual vision loss. This vision loss can occur acutely due to a blockage of the aqueous humor drainage (acute angle-closure glaucoma), which is a medical emergency. The majority of cases are due to open-angle glaucoma.
- Macular degeneration Macular degeneration Age-related macular degeneration (AMD) is visual impairment due to changes in the macula, the area responsible for high-acuity vision. It is marked by central vision loss with peripheral vision relatively spared. Risk factors include advanced age, smoking, family history, and cardiovascular disease. Macular Degeneration: degenerative disorder of the central portion of the retina. Primarily presents with loss of central vision. Patients rarely lose their peripheral vision. Diagnosis is by characteristic findings on slit-lamp examination (drusen, subretinal hemorrhage).
- Refractive errors Refractive errors By refraction, the light that enters the eye is focused onto a particular point of the retina. The main refractive components of the eye are the cornea and the lens. When the corneal curvature, the refractive power of the lens, does not match the size of the eye, ametropia or a refractive error occurs. Refractive Errors: These occur when the eye is unable to focus light on the retina. Factors affecting this include eye size and shape of the cornea. The main types of refractive errors are myopia (nearsightedness), hyperopia (farsightedness), and astigmatism.
- Uveitis Uveitis Uveitis is the inflammation of the uvea, the pigmented middle layer of the eye, which comprises the iris, ciliary body, and choroid. The condition is categorized based on the site of disease; anterior uveitis is the most common. Diseases of the Uvea: acute inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the uvea (middle layer of the eyeball) and the ciliary body. Uveitis Uveitis Uveitis is the inflammation of the uvea, the pigmented middle layer of the eye, which comprises the iris, ciliary body, and choroid. The condition is categorized based on the site of disease; anterior uveitis is the most common. Diseases of the Uvea can be caused by infections (herpes, syphilis Syphilis Syphilis is a bacterial infection caused by the spirochete Treponema pallidum pallidum (T. p. pallidum), which is usually spread through sexual contact. Syphilis has 4 clinical stages: primary, secondary, latent, and tertiary. Syphilis) or can be related to systemic inflammatory disease (inflammatory bowel disease, rheumatoid arthritis Rheumatoid arthritis Rheumatoid arthritis (RA) is a symmetric, inflammatory polyarthritis and chronic, progressive, autoimmune disorder. Presentation occurs most commonly in middle-aged women with joint swelling, pain, and morning stiffness (often in the hands). Rheumatoid Arthritis). Symptoms include blurry vision, red-eye with pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain (anterior uveitis) or without pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain (intermediate and posterior uveitis), and visual floaters (intermediate uveitis).
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