Podcast
Questions and Answers
A patient with myopia experiences blurred vision because the focal point of light entering their eye falls where?
A patient with myopia experiences blurred vision because the focal point of light entering their eye falls where?
- On the lens
- In front of the retina (correct)
- Behind the retina
- Directly on the retina
Which layer of the cornea is responsible for preventing the invasion of epithelial malignancy?
Which layer of the cornea is responsible for preventing the invasion of epithelial malignancy?
- Descemet membrane
- Stroma
- Epithelium
- Bowman layer (correct)
Transparency of the corneal stroma depends primarily on maintaining what two conditions?
Transparency of the corneal stroma depends primarily on maintaining what two conditions?
- High cellularity and vascularity
- Collagen alignment and dehydration (correct)
- High vascularity and hydration
- Collagen disarray and hydration
Which of the following best describes the role of the corneal endothelium in dehydration?
Which of the following best describes the role of the corneal endothelium in dehydration?
Kayser-Fleischer rings, indicative of Wilson disease, are found in which layer of the cornea?
Kayser-Fleischer rings, indicative of Wilson disease, are found in which layer of the cornea?
Stromal edema and bullous keratopathy are most likely the result of a malfunction in which corneal structure?
Stromal edema and bullous keratopathy are most likely the result of a malfunction in which corneal structure?
Corneal vascularization is often a consequence of chronic activation of which factor?
Corneal vascularization is often a consequence of chronic activation of which factor?
What process directly leads to corneal opacification following trauma or chronic inflammation?
What process directly leads to corneal opacification following trauma or chronic inflammation?
In corneal ulcers, stromal degradation is due to the activation of what enzyme?
In corneal ulcers, stromal degradation is due to the activation of what enzyme?
The presence of inflammatory exudate in the anterior chamber visible with a penlight is known as:
The presence of inflammatory exudate in the anterior chamber visible with a penlight is known as:
Which histological finding is characteristic of chronic herpes simplex keratitis?
Which histological finding is characteristic of chronic herpes simplex keratitis?
What differentiates corneal dystrophies from corneal degenerations?
What differentiates corneal dystrophies from corneal degenerations?
Calcium deposition in the Bowman layer, known as calcific band keratopathy, is often associated with which condition?
Calcium deposition in the Bowman layer, known as calcific band keratopathy, is often associated with which condition?
Actinic band keratopathy results from exposure to what?
Actinic band keratopathy results from exposure to what?
Hydrops in keratoconus involves rupture of which corneal layer?
Hydrops in keratoconus involves rupture of which corneal layer?
Which of the following systemic conditions is associated with keratoconus?
Which of the following systemic conditions is associated with keratoconus?
Guttata, an early sign of Fuchs' endothelial dystrophy, are abnormal formations found in what location?
Guttata, an early sign of Fuchs' endothelial dystrophy, are abnormal formations found in what location?
What is the primary cause of corneal edema and bullous keratopathy in Fuchs' endothelial dystrophy?
What is the primary cause of corneal edema and bullous keratopathy in Fuchs' endothelial dystrophy?
What is pseudophakic bullous keratopathy?
What is pseudophakic bullous keratopathy?
A patient presents with a ground-glass cornea and poor visual acuity. This is a late-stage symptom of which corneal dystrophy?
A patient presents with a ground-glass cornea and poor visual acuity. This is a late-stage symptom of which corneal dystrophy?
Flashcards
Cornea
Cornea
The main refractive surface of the eye, along with the tear film.
Myopia
Myopia
Eye too long causing the focal point to be before the retina.
Hyperopia
Hyperopia
Eye too short causing the focal point to be behind the retina.
Corneal Epithelium
Corneal Epithelium
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Bowman Layer
Bowman Layer
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Corneal Stroma
Corneal Stroma
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Descemet Membrane
Descemet Membrane
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Kayser-Fleischer Rings
Kayser-Fleischer Rings
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Hypopyon
Hypopyon
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Corneal Degeneration
Corneal Degeneration
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Corneal Dystrophy
Corneal Dystrophy
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Calcific Band Keratopathy
Calcific Band Keratopathy
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Actinic Keratopathy
Actinic Keratopathy
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Keratoconus
Keratoconus
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Corneal Hydrops
Corneal Hydrops
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Fuchs Endothelial Dystrophy
Fuchs Endothelial Dystrophy
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Guttata
Guttata
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Study Notes
Cornea Functional Anatomy
- The cornea and tear film, not the lens, serve as the eye's main refractive surface.
- Myopia occurs when the eye is too long, causing the focal point to fall in front of the retina.
- Hyperopia occurs when the eye is too short, causing the focal point to fall behind the retina.
- Procedures like LASIK modify the corneal shape to correct refractive errors.
Histological Layers of the Cornea
- Epithelium: A layer resting on a basement membrane.
- Bowman Layer: An acellular barrier that prevents epithelial malignancy invasion.
- Stroma: Avascular and transparent. Its transparency depends on collagen alignment and deturgescence (a dehydrated state).
- Corneal Endothelium: Maintains stromal transparency by pumping fluid into the anterior chamber.
- Descemet Membrane: The basement membrane for the corneal endothelium, thickens with age, and is the site of Kayser-Fleischer rings in Wilson disease.
Corneal Edema and Vascularization
- Stromal edema and bullous keratopathy result from disruption of endothelial function.
- Vascularization is caused by chronic inflammation, trauma, or VEGF activation.
- Scarring and edema distort collagen arrangement, leading to opacification.
Keratitis and Ulcers
- Keratitis and ulcers can be caused by bacteria, fungi, viruses such as HSV and HZV, and protozoa like Acanthamoeba.
- Corneal ulcers lead to stromal degradation through collagenase activation.
- Hypopyon is an inflammatory exudate in the anterior chamber, and is visible even with a penlight.
- Herpes simplex keratitis may show a granulomatous reaction in Descemet's membrane which is a histological hallmark of chronic herpes simplex keratitis.
Corneal Degenerations vs. Dystrophies
- Degenerations are usually unilateral and non-hereditary.
- Dystrophies are typically bilateral, hereditary, and affect specific or multiple corneal layers.
Band Keratopathies
- Calcific: Calcium deposition in Bowman's layer, associated with chronic uveitis like JRA.
- Actinic: Caused by UV light exposure, leading to solar elastosis in corneal collagen. Appears yellow("oil-droplet keratopathy").
Keratoconus
- Common, affecting 1 in 2000 individuals, and causes conical cornea and irregular astigmatism.
- Histology: thinning of the cornea, breaks in Bowman's layer.
- Hydrops: Rupture of Descemet's membrane, leading to acute stromal fluid entry, scarring, and sudden vision loss.
- Associated with Down syndrome, Marfan syndrome, and atopic conditions.
- Rigid contact lenses help early on; corneal transplant may be needed.
Fuchs Endothelial Dystrophy
- This is one of the most common indications for corneal transplant in the US.
- Primary defect: loss of endothelial cells → stromal edema, bullous keratopathy.
- Early sign: guttata (abnormal basement membrane drops).
- Late stage: ground-glass cornea, poor visual acuity, eventual vascularization.
- Can occur post-cataract surgery without preexisting Fuchs, leading to pseudophakic bullous keratopathy.
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