Podcast
Questions and Answers
What is the primary function of the cornea regarding light?
What is the primary function of the cornea regarding light?
- Regenerate rapidly after damage
- Protect against infection
- Store nutrients for the eye
- Act as a primary refractive medium (correct)
Which layer of the cornea does not regenerate after damage?
Which layer of the cornea does not regenerate after damage?
- Stroma
- Epithelium
- Bowman's membrane (correct)
- Endothelium (correct)
What is the normal endothelial cell count at birth?
What is the normal endothelial cell count at birth?
- Around 4000 cells/mm2
- Less than 2000 cells/mm2
- About 2500 cells/mm2
- Greater than 3000 cells/mm2 (correct)
How does corneal thickness vary from the center to the periphery?
How does corneal thickness vary from the center to the periphery?
What device is used to measure the corneal power?
What device is used to measure the corneal power?
What is the typical power of the cornea, measured in diopters?
What is the typical power of the cornea, measured in diopters?
What happens to endothelial cell density with age?
What happens to endothelial cell density with age?
At which anatomical structure does Descemet’s membrane end?
At which anatomical structure does Descemet’s membrane end?
Which of the following maps can corneal tomography determine?
Which of the following maps can corneal tomography determine?
What supplies oxygen to the cornea?
What supplies oxygen to the cornea?
Which of the following is NOT a cause of corneal opacity?
Which of the following is NOT a cause of corneal opacity?
Which nerves are involved in the corneal sensitivity reflex?
Which nerves are involved in the corneal sensitivity reflex?
What structure primarily provides glucose and other nutrients to the cornea?
What structure primarily provides glucose and other nutrients to the cornea?
Which condition can cause decreased or lost corneal sensations?
Which condition can cause decreased or lost corneal sensations?
What is the primary factor that maintains corneal transparency?
What is the primary factor that maintains corneal transparency?
Which term describes a faint opacity from which the iris structure can still be seen?
Which term describes a faint opacity from which the iris structure can still be seen?
What characterizes leucoma?
What characterizes leucoma?
Which surgical procedure is associated with central corneal opacity?
Which surgical procedure is associated with central corneal opacity?
What is the main predisposing factor for typical corneal ulcers?
What is the main predisposing factor for typical corneal ulcers?
Which organism is most commonly associated with the use of contact lenses?
Which organism is most commonly associated with the use of contact lenses?
What best describes keratectasia?
What best describes keratectasia?
Which of the following is a type of bacterial corneal ulcer?
Which of the following is a type of bacterial corneal ulcer?
What distinguishes typical from atypical corneal ulcers?
What distinguishes typical from atypical corneal ulcers?
Which condition is NOT a risk factor for corneal ulcers?
Which condition is NOT a risk factor for corneal ulcers?
Which organism is most likely responsible for filamentous keratitis associated with trauma from a vegetable or contact lens?
Which organism is most likely responsible for filamentous keratitis associated with trauma from a vegetable or contact lens?
What is a common symptom of keratitis caused by yeast in immunocompromised patients?
What is a common symptom of keratitis caused by yeast in immunocompromised patients?
Which of the following is a suggested management approach for stromal keratitis?
Which of the following is a suggested management approach for stromal keratitis?
In the treatment of epithelial keratitis, which topical medication is commonly used?
In the treatment of epithelial keratitis, which topical medication is commonly used?
What is a typical sign of keratitis as seen under examination?
What is a typical sign of keratitis as seen under examination?
Which symptom is associated with spasm of the constrictor pupillae muscle?
Which symptom is associated with spasm of the constrictor pupillae muscle?
What complication occurs after corneal perforation that is larger in size than before?
What complication occurs after corneal perforation that is larger in size than before?
Which treatment is NOT recommended for immediate management of corneal issues?
Which treatment is NOT recommended for immediate management of corneal issues?
What symptom indicates the presence of nerve endings exposure?
What symptom indicates the presence of nerve endings exposure?
Which of the following is a sign of corneal perforation?
Which of the following is a sign of corneal perforation?
What must be observed in the eyes immediately after treating for infection?
What must be observed in the eyes immediately after treating for infection?
What type of corneal opacity occurs before perforation?
What type of corneal opacity occurs before perforation?
Which sign is used to measure the degree of anterior chamber inflammation?
Which sign is used to measure the degree of anterior chamber inflammation?
What is the primary source of oxygen for the cornea?
What is the primary source of oxygen for the cornea?
Which of the following does NOT contribute to corneal transparency?
Which of the following does NOT contribute to corneal transparency?
What is the effect of extended use of contact lenses on the cornea?
What is the effect of extended use of contact lenses on the cornea?
Which condition is least likely to cause corneal opacity?
Which condition is least likely to cause corneal opacity?
Which of the following factors most directly influences corneal sensitivity?
Which of the following factors most directly influences corneal sensitivity?
Which of the following statements regarding corneal healing is true?
Which of the following statements regarding corneal healing is true?
Which of the following is a common symptom of filamentous keratitis?
Which of the following is a common symptom of filamentous keratitis?
Corneal sensitivity testing may demonstrate decreased sensitivity due to which of the following factors?
Corneal sensitivity testing may demonstrate decreased sensitivity due to which of the following factors?
What is the management approach for stromal keratitis?
What is the management approach for stromal keratitis?
What type of corneal opacity is characterized by faint opacity from which the iris structure can still be seen?
What type of corneal opacity is characterized by faint opacity from which the iris structure can still be seen?
Which staining technique is used to observe the features of epithelial keratitis?
Which staining technique is used to observe the features of epithelial keratitis?
What is a distinctive sign of yeast-related keratitis in an immunocompromised individual?
What is a distinctive sign of yeast-related keratitis in an immunocompromised individual?
What is the typical duration for topical antifungal treatment in cases of keratitis?
What is the typical duration for topical antifungal treatment in cases of keratitis?
What distinguishes infective corneal ulcers from non-infective ones?
What distinguishes infective corneal ulcers from non-infective ones?
Which procedure is least likely to be performed for central corneal opacity?
Which procedure is least likely to be performed for central corneal opacity?
What is the most common organism responsible for typical corneal ulcers?
What is the most common organism responsible for typical corneal ulcers?
Which risk factor is NOT associated with the development of corneal ulcers?
Which risk factor is NOT associated with the development of corneal ulcers?
In which type of corneal opacity can the iris structure still be seen?
In which type of corneal opacity can the iris structure still be seen?
Which organism is most likely to invade intact corneal epithelium among the listed pathogens?
Which organism is most likely to invade intact corneal epithelium among the listed pathogens?
What treatment is typically NOT used for corneal ulcers with pus?
What treatment is typically NOT used for corneal ulcers with pus?
Which of the following conditions is classified as a non-infective corneal ulcer?
Which of the following conditions is classified as a non-infective corneal ulcer?
What characteristic distinguishes Bowman's membrane from the other layers of the cornea?
What characteristic distinguishes Bowman's membrane from the other layers of the cornea?
Which measurement indicates the health of the corneal endothelial cells?
Which measurement indicates the health of the corneal endothelial cells?
What role does the cornea play in the overall refractive power of the eye?
What role does the cornea play in the overall refractive power of the eye?
Which factor is primarily responsible for the variation in corneal thickness between the center and periphery?
Which factor is primarily responsible for the variation in corneal thickness between the center and periphery?
What is the significance of the corneal power measurement?
What is the significance of the corneal power measurement?
What changes occur at the limbus in relation to the corneal structure?
What changes occur at the limbus in relation to the corneal structure?
How does endothelial cell density change with aging, and what is its impact?
How does endothelial cell density change with aging, and what is its impact?
What is the primary composition of the stroma in the cornea?
What is the primary composition of the stroma in the cornea?
Which of the following symptoms is primarily caused by spasm of the orbicularis oculi muscle?
Which of the following symptoms is primarily caused by spasm of the orbicularis oculi muscle?
What complication is characterized by a total iris prolapse as a result of a corneal perforation?
What complication is characterized by a total iris prolapse as a result of a corneal perforation?
Which sign indicates a positive result on fluorescein staining related to corneal integrity?
Which sign indicates a positive result on fluorescein staining related to corneal integrity?
Which of the following is an expected sign immediately after corneal perforation?
Which of the following is an expected sign immediately after corneal perforation?
What treatment is specifically indicated to prevent synechia after ocular trauma?
What treatment is specifically indicated to prevent synechia after ocular trauma?
Which complication is associated with the development of peripheral synechia in response to anterior inflammation?
Which complication is associated with the development of peripheral synechia in response to anterior inflammation?
What immediate action is NOT recommended after a corneal perforation has occurred?
What immediate action is NOT recommended after a corneal perforation has occurred?
Which of the following represents a typical sign of corneal opacity observed before perforation occurs?
Which of the following represents a typical sign of corneal opacity observed before perforation occurs?
What are the distinguishing symptoms associated with filamentous keratitis?
What are the distinguishing symptoms associated with filamentous keratitis?
In the management of yeast keratitis in immunocompromised patients, what treatment is typically recommended?
In the management of yeast keratitis in immunocompromised patients, what treatment is typically recommended?
Which staining techniques are utilized to observe epithelial keratitis, and what do they reveal?
Which staining techniques are utilized to observe epithelial keratitis, and what do they reveal?
What is a common sign indicative of fungal keratitis as observed during examination?
What is a common sign indicative of fungal keratitis as observed during examination?
What are the primary differences between epithelial keratitis and stromal keratitis in terms of treatment?
What are the primary differences between epithelial keratitis and stromal keratitis in terms of treatment?
What nutrients are supplied to the cornea by the aqueous humor?
What nutrients are supplied to the cornea by the aqueous humor?
Which nerve is responsible for the afferent pathway in the corneal sensitivity reflex?
Which nerve is responsible for the afferent pathway in the corneal sensitivity reflex?
Name a cause of decreased corneal sensations related to trauma.
Name a cause of decreased corneal sensations related to trauma.
Identify a non-infectious cause of corneal opacity.
Identify a non-infectious cause of corneal opacity.
What is the response of the cornea's sensitivity reflex when stimulated?
What is the response of the cornea's sensitivity reflex when stimulated?
What condition can result from extended use of contact lenses?
What condition can result from extended use of contact lenses?
Describe a factor that contributes to corneal transparency.
Describe a factor that contributes to corneal transparency.
What term describes a more severe opacity from which iris details are not visible?
What term describes a more severe opacity from which iris details are not visible?
What is the main cause of pus in the hypopion corneal ulcer?
What is the main cause of pus in the hypopion corneal ulcer?
What type of corneal opacity cannot reveal the iris structure?
What type of corneal opacity cannot reveal the iris structure?
What surgical procedure is typically associated with superficial corneal opacity?
What surgical procedure is typically associated with superficial corneal opacity?
Which organism is most notably linked to contact lens-related corneal complications?
Which organism is most notably linked to contact lens-related corneal complications?
What condition is characterized by corneal thinning and dense scarring?
What condition is characterized by corneal thinning and dense scarring?
What type of corneal ulcer is primarily caused by pneumococci?
What type of corneal ulcer is primarily caused by pneumococci?
What is the most significant risk factor contributing to corneal ulcers?
What is the most significant risk factor contributing to corneal ulcers?
Name a condition that can lead to exposure keratitis.
Name a condition that can lead to exposure keratitis.
What are the main components of the stroma layer of the cornea?
What are the main components of the stroma layer of the cornea?
Explain the function of Descemet's membrane in the cornea.
Explain the function of Descemet's membrane in the cornea.
How does the cornea's refractive power depend on its curvature?
How does the cornea's refractive power depend on its curvature?
What role does Bowman's membrane play in the cornea's structure?
What role does Bowman's membrane play in the cornea's structure?
What is the typical corneal endothelial cell density at birth, and how does it change with age?
What is the typical corneal endothelial cell density at birth, and how does it change with age?
Describe the transition of the corneal layers at the limbus.
Describe the transition of the corneal layers at the limbus.
What are the implications of a decrease in endothelial cell density below 500 cells/cm2?
What are the implications of a decrease in endothelial cell density below 500 cells/cm2?
How is corneal thickness measured and how does it vary from the center to the periphery?
How is corneal thickness measured and how does it vary from the center to the periphery?
What are the symptoms that indicate nerve endings exposure in the eye?
What are the symptoms that indicate nerve endings exposure in the eye?
Which sign indicates a significant decrease in intraocular pressure (IOP) after corneal perforation?
Which sign indicates a significant decrease in intraocular pressure (IOP) after corneal perforation?
Identify at least two complications that may arise from a central large corneal perforation.
Identify at least two complications that may arise from a central large corneal perforation.
What is the condition characterized by the formation of peripheral anterior synechia in peripheral small corneal perforations?
What is the condition characterized by the formation of peripheral anterior synechia in peripheral small corneal perforations?
What immediate management steps should be taken to prevent complications after corneal scrap culture?
What immediate management steps should be taken to prevent complications after corneal scrap culture?
Explain the significance of fluorescein staining in the context of corneal ulcers.
Explain the significance of fluorescein staining in the context of corneal ulcers.
What role do vitamins A and C play in managing corneal issues?
What role do vitamins A and C play in managing corneal issues?
Describe the effect of contact lens use on corneal sensitivity.
Describe the effect of contact lens use on corneal sensitivity.
What are two common symptoms associated with epithelial keratitis?
What are two common symptoms associated with epithelial keratitis?
Describe the typical management approach for filamentous keratitis caused by Aspergillus or Fusarium.
Describe the typical management approach for filamentous keratitis caused by Aspergillus or Fusarium.
What is the importance of double staining with rose Bengal and fluorescein in diagnosing keratitis?
What is the importance of double staining with rose Bengal and fluorescein in diagnosing keratitis?
Which systemic treatment is recommended for managing stromal keratitis caused by herpes simplex virus?
Which systemic treatment is recommended for managing stromal keratitis caused by herpes simplex virus?
What are the typical signs of keratitis observed during an eye examination?
What are the typical signs of keratitis observed during an eye examination?
What are the main components of the cornea and their functions?
What are the main components of the cornea and their functions?
How does the curvature of the cornea influence its refractive power?
How does the curvature of the cornea influence its refractive power?
What is the significance of the endothelial cell density in the cornea?
What is the significance of the endothelial cell density in the cornea?
Explain the role of Bowman's membrane in the cornea.
Explain the role of Bowman's membrane in the cornea.
What occurs at the limbus regarding the transition of corneal tissues?
What occurs at the limbus regarding the transition of corneal tissues?
What are the primary nutritional sources for the cornea?
What are the primary nutritional sources for the cornea?
How can corneal thickness vary, and what are its average measurements?
How can corneal thickness vary, and what are its average measurements?
Which conditions can lead to decreased or lost corneal sensations?
Which conditions can lead to decreased or lost corneal sensations?
Describe the role of Descemet's membrane in the cornea.
Describe the role of Descemet's membrane in the cornea.
Explain the term 'corneal pannus' and its relevance to corneal vascularization.
Explain the term 'corneal pannus' and its relevance to corneal vascularization.
What is measured by corneal tomography (Pentacam)?
What is measured by corneal tomography (Pentacam)?
What are the implications of corneal topography in clinical practice?
What are the implications of corneal topography in clinical practice?
Identify the significance of corneal transparency for the functioning of the eye.
Identify the significance of corneal transparency for the functioning of the eye.
What role does the Cochet Bonnet aesthesiometer play in ophthalmology?
What role does the Cochet Bonnet aesthesiometer play in ophthalmology?
List the factors that contribute to maintaining corneal transparency.
List the factors that contribute to maintaining corneal transparency.
Describe what a 'nebulous' opacity is in relation to the cornea.
Describe what a 'nebulous' opacity is in relation to the cornea.
What symptom indicates irritation due to spasm of the constrictor pupillae muscle?
What symptom indicates irritation due to spasm of the constrictor pupillae muscle?
What pathological change occurs to the anterior chamber after corneal perforation?
What pathological change occurs to the anterior chamber after corneal perforation?
Identify one common sign of corneal perforation.
Identify one common sign of corneal perforation.
What is a common treatment used to prevent synechia in acute corneal conditions?
What is a common treatment used to prevent synechia in acute corneal conditions?
How does the cornea appear before perforation compared to after perforation?
How does the cornea appear before perforation compared to after perforation?
What is one possible consequence of severe ciliary muscle spasm due to irritation?
What is one possible consequence of severe ciliary muscle spasm due to irritation?
Mention one complication that can arise after corneal perforation.
Mention one complication that can arise after corneal perforation.
What is the role of vitamins A and C in the management of corneal issues?
What is the role of vitamins A and C in the management of corneal issues?
What are the two main types of corneal opacity mentioned?
What are the two main types of corneal opacity mentioned?
Identify one cosmetic and one surgical approach to managing peripheral corneal opacity.
Identify one cosmetic and one surgical approach to managing peripheral corneal opacity.
Which infections are most commonly associated with bacterial corneal ulcers?
Which infections are most commonly associated with bacterial corneal ulcers?
What type of corneal ulcer is characterized by the presence of pus in the anterior chamber?
What type of corneal ulcer is characterized by the presence of pus in the anterior chamber?
What is the most common organism linked to infections caused by contact lens usage?
What is the most common organism linked to infections caused by contact lens usage?
Name one non-infective cause of corneal opacity.
Name one non-infective cause of corneal opacity.
List two risk factors that can contribute to the development of corneal ulcers.
List two risk factors that can contribute to the development of corneal ulcers.
What surgical procedure is performed on superficial central corneal opacity?
What surgical procedure is performed on superficial central corneal opacity?
Flashcards
Cornea function
Cornea function
The cornea is the main refractive medium of the eye, with a power of approximately 42 Diopters. Its shape and refractive index contribute to the eye's focusing ability.
Corneal thickness
Corneal thickness
The corneal thickness varies across the eye's surface with the center being thinner than the periphery.
Endothelial Cells
Endothelial Cells
A single layer of cells that don't regenerate on damage. Critical for maintaining corneal hydration and preventing swelling. A critical normal density is > 500 cells/mm2
Bowman's Membrane
Bowman's Membrane
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Descemet's Membrane
Descemet's Membrane
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Limbus
Limbus
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Corneal Epithelium
Corneal Epithelium
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Corneal Stroma
Corneal Stroma
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Corneal Tomography
Corneal Tomography
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Corneal Nutrition
Corneal Nutrition
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Corneal Infection Causes
Corneal Infection Causes
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Corneal Sensation Pathway
Corneal Sensation Pathway
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Decreased Corneal Sensation Causes
Decreased Corneal Sensation Causes
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Corneal Transparency Factors
Corneal Transparency Factors
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Corneal Opacity Causes
Corneal Opacity Causes
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Corneal Facet/Nebula/Macula
Corneal Facet/Nebula/Macula
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Filamentous Keratitis
Filamentous Keratitis
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Yeast Keratitis
Yeast Keratitis
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Epithelial Keratitis
Epithelial Keratitis
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HSV Stromal Keratitis
HSV Stromal Keratitis
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Treatment for Keratitis
Treatment for Keratitis
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Corneal Perforation
Corneal Perforation
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Hypotony
Hypotony
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IOP
IOP
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Anterior Synechia
Anterior Synechia
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Central Large Corneal Perforation
Central Large Corneal Perforation
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Peripheral Small Corneal Perforation
Peripheral Small Corneal Perforation
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Photophobia
Photophobia
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Blepharospasm
Blepharospasm
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Leucoma
Leucoma
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Keratectasia
Keratectasia
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Hypopion
Hypopion
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Bacterial corneal ulcer
Bacterial corneal ulcer
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Corneal Abrasion
Corneal Abrasion
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Risk Factors (Corneal Ulcers)
Risk Factors (Corneal Ulcers)
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Contact Lens-Associated Infection
Contact Lens-Associated Infection
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Chronic Dacryocystitis
Chronic Dacryocystitis
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Cornea Definition
Cornea Definition
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Limbus Location
Limbus Location
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Corneal Epithelium Regeneration
Corneal Epithelium Regeneration
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Descemet's Membrane Function
Descemet's Membrane Function
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Endothelial Cell Density
Endothelial Cell Density
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Corneal Refraction Power
Corneal Refraction Power
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Corneal Thickness Measurement
Corneal Thickness Measurement
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Corneal Stroma Composition
Corneal Stroma Composition
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Corneal Tomography
Corneal Tomography
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Corneal Nutrition
Corneal Nutrition
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Corneal Infection Causes
Corneal Infection Causes
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Corneal Sensation Pathway
Corneal Sensation Pathway
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Decreased Corneal Sensation Causes
Decreased Corneal Sensation Causes
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Corneal Transparency Factors
Corneal Transparency Factors
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Corneal Opacity Causes
Corneal Opacity Causes
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Corneal Facet/Nebula/Macula
Corneal Facet/Nebula/Macula
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Leucoma
Leucoma
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Keratectasia
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Hypopion
Hypopion
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Bacterial Corneal Ulcer
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Chronic Dacryocystitis
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Corneal Abrasion
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Risk Factors (Corneal Ulcers)
Risk Factors (Corneal Ulcers)
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Contact Lens-Associated Infection
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Filamentous Keratitis
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Yeast Keratitis
Yeast Keratitis
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Epithelial Keratitis
Epithelial Keratitis
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HSV Stromal Keratitis
HSV Stromal Keratitis
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Treatment for Keratitis
Treatment for Keratitis
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Corneal Perforation
Corneal Perforation
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Central Large Corneal Perforation
Central Large Corneal Perforation
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Peripheral Small Corneal Perforation
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Anterior Synechia
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Photophobia
Photophobia
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Blepharospasm
Blepharospasm
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Hypotony
Hypotony
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Corneal Ulcer
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Cornea Definition
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Limbus Location
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Corneal Epithelium Regeneration
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Descemet's Membrane Function
Descemet's Membrane Function
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Endothelial Cell Density
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Corneal Refraction Power
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Corneal Thickness Measurement
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Corneal Stroma Composition
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Corneal Tomography (Pentacam)
Corneal Tomography (Pentacam)
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Corneal Nutrition Sources
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Corneal Infection Causes
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Corneal Sensation Pathway
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Decreased Corneal Sensation Causes
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Corneal Transparency Factors
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Corneal Opacity Causes
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Corneal Facet/Nebula/Macula
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Leucoma Definition
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Keratectasia Definition
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Hypopion Definition
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Bacterial Corneal Ulcer
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Chronic Dacryocystitis Definition
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Corneal Abrasion Definition
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Risk Factors (Corneal Ulcers)
Risk Factors (Corneal Ulcers)
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Contact Lens-Associated Infection
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Filamentous Keratitis
Filamentous Keratitis
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Yeast Keratitis
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Epithelial Keratitis
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HSV Stromal Keratitis
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Treatment for Keratitis
Treatment for Keratitis
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Loss of sensations (anesthesia/hypesthesia)
Loss of sensations (anesthesia/hypesthesia)
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Corneal Perforation (Before)
Corneal Perforation (Before)
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Corneal Perforation (After)
Corneal Perforation (After)
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Central Large Corneal Perforation
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Peripheral Small Corneal Perforation
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Photophobia
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Blepharospasm
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Anterior Synechia
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Cornea Definition
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Limbus Location
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Corneal Epithelium Regeneration
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Descemet's Membrane Function
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Endothelial Cell Density
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Corneal Refraction Power
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Corneal Thickness Measurement
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Corneal Stroma Composition
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Corneal Tomography
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Corneal Nutrition
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Corneal Infection Causes
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Corneal Sensation Pathway
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Decreased Corneal Sensation Causes
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Corneal Transparency Factors
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Corneal Opacity Causes
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Corneal Facet/Nebula/Macula
Corneal Facet/Nebula/Macula
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Leucoma
Leucoma
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Keratectasia
Keratectasia
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Hypopion
Hypopion
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Bacterial Corneal Ulcer
Bacterial Corneal Ulcer
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Chronic Dacryocystitis
Chronic Dacryocystitis
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Corneal Abrasion
Corneal Abrasion
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Risk Factors (Corneal Ulcers)
Risk Factors (Corneal Ulcers)
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Contact Lens-Associated Infection
Contact Lens-Associated Infection
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Loss of Sensations (Hypesthesia/Anesthesia)
Loss of Sensations (Hypesthesia/Anesthesia)
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Corneal Perforation (Before)
Corneal Perforation (Before)
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Central Large Corneal Perforation
Central Large Corneal Perforation
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Peripheral Small Corneal Perforation
Peripheral Small Corneal Perforation
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Anterior Synechia
Anterior Synechia
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Photophobia
Photophobia
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Blepharospasm
Blepharospasm
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Corneal Perforation (After)
Corneal Perforation (After)
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Filamentous Keratitis
Filamentous Keratitis
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Yeast Keratitis
Yeast Keratitis
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Epithelial Keratitis
Epithelial Keratitis
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HSV Stromal Keratitis
HSV Stromal Keratitis
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Treatment for Keratitis
Treatment for Keratitis
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Study Notes
Cornea Anatomy and Histology
- Definition: The cornea is the transparent anterior 1/6 of the outer coat of the eye. The limbus is the junction between the cornea and sclera.
- Epithelium: Non-keratinized stratified squamous epithelium, covered by a tear film. It regenerates rapidly.
- Bowman's Membrane: A condensed superficial layer of the stroma. It does not regenerate.
- Stroma: Comprising 90% of corneal thickness, it has uniformly spaced collagen fibers. Scarring rather than regeneration occurs. Recent surgical tissue is different from that found anatomically.
- Dua (Pre-Descemet's membrane): Recent term for a surgical tissue rather than an anatomical structure.
- Descemet's Membrane: The basement membrane of the endothelium.
- Endothelium: A single layer of polygonal cells that do not regenerate upon damage.
Corneal Function and Refraction
- Refraction and Power: The cornea is the main refractive media in the eye (power 42 diopters). Its power depends on corneal curvature (anterior surface ~7.8mm & posterior ~6.5mm) and refractive index (1.33).
- Measurement: Corneal power can be measured using a keratometer (power and axis of the steepest and flattest meridians) or corneal topography (power at each point).
- Corneal Thickness: Measured using ultrasound pachymetry or corneal tomography (e.g., Pentacam). Varies between 0.5-0.9mm at center and periphery.
- Nutrition: Corneal is avascular. Nutrition is provided by perilimbal vessels, aqueous humor, and tear film..
Corneal Sensitivity and Sensations
- Corneal Sensitivity Test: Tested using Cochet Bonnet aesthesiometer
- Corneal Vascularization and Causes: Cornea has no blood vessels. Causes are infection, chemical injury, autoimmune diseases, corneal hypersensitivity, corneal pannus, post-corneal transplantation, post-traumatic, and extended use of contact lenses.
- Decreased/Lost Corneal Sensations: Factors are infections (herpes, syphilis, leprosy), trauma, post-operative, post-irradiation, and compression of orbital structures (e.g tumors like orbital apex syndrome, superior orbital fissure syndrome).
Corneal Opacity and Treatment
- Corneal Transparency Factors: Factors important for transparency include avascularity, non-myelinated nerves, uniformity of collagen bundles, non-keratinized epithelium, and integrity of the endothelium.
- Types & Causes of Opacity: Corneal opacities can result from inflammation (keratitis), degeneration, dystrophies (corneal ectasia), edema, pigmentation, or pannus formation. Other causes described are: nebula, macula, leucoma, and keratectasia
- Treatment for opacity: Cosmetic treatments (colored contact lenses, tattoos, glasses) and surgical treatments are described. Peripheral treatment: colored contact lens, tattooing, astigmatism correction, glasses, or contact lenses. Central treatment: Phototherapeutic keratectomy (PTK), deep anterior lamellar keratoplasty (DALK), and penetrating keratoplasty (PKP)
Keratitis (Corneal Ulcers)
- Infective & Non-Infective Causes: Infective causes include bacterial (hypopion), fungal (mycotic), viral (herpetic), and protozoal (acanthamoeba). Non-infective causes include: marginal catarrhal ulcers, exposure keratitis, traumatic, neuropathic keratopathy, keratomalacia, and atheromatous ulcers.
- Hypopion Corneal Ulcer: Pus in anterior chamber (usually bacterial in origin but may be sterile). Typical cases (70–80%) are caused by pneumococci, atypical by staphylococci, or other pathogens. Chronic dacryocystitis is a key predisposing factor.
- Key Risk Factors: Corneal abrasion/trauma (most important) , dryness (xerosis), exposure, loss of sensation, long-term steroid use, contact lens use, poor hygiene.
- Complications of Corneal Ulcer: Sudden decreased intraocular pressure (IOP), pain, and improved corneal nutrition can be caused by perforation. Other complications described are corneal opacity and vascularization, toxic iridocyclitis, secondary glaucoma, descemetocele/keratocele.
Viral Corneal Conditions
- Herpetic Keratitis: Self-limiting condition where the virus is latent in the trigeminal ganglion. Can lead to primary, recurrent (dendritic, stromal, endothelial, geographic type) and disciform types
- VZV Keratitis: Associated with Chickenpox and shingles. Symptoms can include: dermatitis, epithelial/stromal keratitis, scleritis, episcleritis, iridocyclitis, chorioretinitis, or optic neuritis.
- Acanthamoeba Keratitis: Related to contact lens use/swimming pools. Characterized by severe pain, dendritic-like peripheral perineural infiltrates ("ring ulcers").
Treatments for Corneal Ulcers
- General Treatment Approach: Corneal scrap with sensitivity, immediate broad spectrum antibiotic, mydriatic (prevents synechia, cycloplegic), eye protection, with vitamins (A&C) & lubricants.
- Steroids & Topical Anaesthetics: These are discouraged
- Specific Treatments: Anti-herpetic (acyclovir or gancyclovir), anti-fungal (e.g., natamycin, voriconazole), systemic antiherpetics, topical antibiotics, cycloplegics, lubricants, and (in severe cases) keratoplasty are used.
Other information
- Symptoms: Pain, lacrimation, photophobia, blepharospasm, haloes around light, and blurring of vision are all described. Lid edema, ciliary injection (circumcorneal ciliary flush), corneal ulceration, and anterior chamber reaction are also described. Pupillary constriction (miosis) and fluorescein staining are diagnostic signs (inferred).
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