Questions and Answers
What is the radius of curvature of the anterior surface of the cornea?
7.8 mm
Which cells contribute to the formation of the corneal stroma and corneal endothelium?
Neural crest cells
What is the refractive power of the cornea?
45D
What is the central cornea thickness?
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Which blood source does NOT supply blood to the cornea?
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What type of cells make up the corneal epithelium?
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What type of cells join the basal layer of the epithelium to Bowman's membrane?
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Which layer of the cornea contains Na/K ATP pumps to regulate water and ion flow?
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Which corneal layers CANNOT regenerate?
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What is the average cell density of corneal endothelium in adults?
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Which nerve innervates the cornea?
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Where are corneal nerves located?
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What is the circular structure at the termination of the Descemet’s membrane in the limbus called?
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What types of cells make of the corneal endothelium?
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What forms a leaky barrier between the corneal stroma and the anterior chamber?
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What is the approximate thickness of the corneal epithelium?
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Which layer of the cornea is responsible for corneal epithelial renewal?
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What is the composition of Bowman’s layer?
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Which component of the corneal stroma contributes to its relatively high hydration?
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How are corneal endothelial cells linked together by?
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What passes through Bowman’s layer in the cornea?
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What is the approximate size of the cornea?
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What is the turnover time of corneal epithelial renewal?
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Which layer of the cornea is constantly produced and thickens throughout life?
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What is the composition of the corneal stroma?
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Of the total refractive power between 60-65, what amount is attributable to the cornea?
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Which layer of the corneal epithelium contains gap junctions?
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Which answer is correct regarding the corneal epithelium developement?
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As we age, the cell density of our corneal endothelium cells increases over time.
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There are corneal nerves found in the Descemet's layer and endothelium.
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When the corneal nerves pass through Bowman's clayer, they become un-myelinated.
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What is the primary contributor of glucose to all corneal layers?
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Which layers of the cornea is highly lipophilic?
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What is the principal provider of energy to epithelial cells?
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Corneal epithelial cells have the ability to alter corneal thickness by moving which ion into the tears?
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What does glucose convert to by glycolysis?
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What can lactic acid not pass through?
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What is the effect of corneal stress on lactic acid accumulation?
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What happens to oxygen levels during sleep?
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What drives the movement of K+ and Cl- into the corneal epithelium?
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What is the primary driving force for water movement out of the corneal endothelium?
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What happens to the partial pressure of O2 in the tears when the eye is closed?
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Where does the cornea primarily receives oxygen from where?
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What cells contribute to corneal regeneration and are derived from limbal stem cells?
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What is the primary driving force for water movement between the corneal endothelium and anterior chamber?
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What is the primary function of the K+ channel in response to corneal changes in pH?
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What is the primary factor contributing to the dehydration of the cornea?
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What is the first response of injury to epithelium?
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Which condition is characterized by small hyaline excrescences on the posterior surface of Descemet’s membrane at the periphery of the cornea?
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What corneal dystrophy is associated with the poor attachment between the epithelium and its basement membrane?
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What is the characteristic feature of keratoconus?
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What is the primary cause of corneal edema resulting in impaired visual acuity?
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What is the characteristic feature of corneal guttata?
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Which layer of the cornea can replace itself if damaged, leading to scar formation?
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Which condition is characterized by the projection of the affected area outward in a cone shape due to the force exerted on weakened areas by intraocular pressure?
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The limbal stem cells of the cornea are found in the Palisades of Vogt.
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You are only able to see Descemet's membrane when there is corneal swelling.
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Herpes simplex virus is always bilateral.
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What is the approximate thickness of the thinnest area of the sclera where EOM rectal muscles insertion occurs?
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Which type of collagen fibers makes up the majority of the composition of the scleral stroma?
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What is the primary function of the episclera in relation to the sclera?
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What is the primary contributor to the dehydration of the sclera?
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Which condition is characterized by a potentially destructive inflammatory process involving the scleral collagen or vasculitis?
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What is the primary cause of scleral ectasia?
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What is the primary blood supply for nourishment of the sclera?
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What part of the sclera attaches to the Tenon's capsule?
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What is the primary cause of scleral thinning in scleritis?
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What is the primary innervation of the posterior sclera?
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What is the characteristic feature of scleral foraminas?
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What is the posterior scleral spur an origin for?
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What is the primary component of the scleral stroma?
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What is the primary orientation pattern of the collagen bundles in the scleral stroma in relation to the extraocular muscle tendinous insertions?
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The stromal ground surface is similar to the cornea but has more fibroblasts and GAGs.
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Branches of the short ciliary nerves innervate the medial and anterior sclera.
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Medial and anterior sclera are innervated by long ciliary nerves.
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What disease is associated with the progression of myopia that thins the sclera?
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Which layer of the cornea can store O2?
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Study Notes
Corneal Histological Features
- The cornea is approximately 71mm in size and is the principal refracting component of the eye.
- It is transparent and avascular, providing optimal light transmittance.
- The corneal layers include the epithelium, Bowman’s layer, stroma, Descemet’s membrane, and endothelium.
- The corneal epithelium is a stratified squamous nonkeratinized epithelium, approximately 50 μm thick and consists of surface, wing, and basal layers.
- The basal layer contains stem cells responsible for corneal epithelial renewal, with a turnover time of approximately 7 days.
- Bowman’s layer is an acellular dense layer composed of random collagen fibrils, approximately 8-14 μm thick and is prenatally produced.
- The corneal stroma, also known as Substantia Propria, is approximately 500 μm thick and composed of collagen fibers, keratocytes, and extracellular ground substance.
- Collagen fibers in the stroma form parallel layers called lamellae, contributing to corneal transparency.
- Ground substance in the stroma contains proteoglycans and contributes to the relatively high stromal hydration.
- Descemet’s membrane is the true basement membrane of the endothelium, constantly produced, and thickens throughout life.
- It consists of two laminae, with the anterior lamina being 3μm thick and exhibiting a banded appearance.
- Corneal nerves pass through Bowman’s layer, losing their Schwann cell covering, and the endothelium's Descemet’s membrane thickens throughout life.
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