BASIC SCIENCES Flashcards
Dimensions of the cornea
The cornea is bigger horizontally (11.7 mm) than vertically (10.6 mm).
Clinical Criteria for Herpetic keratitis.
• Epithelial keratitis (dendritic ulcer)
• Stromal keratitis: vascularisation, scarring, lipid keratopathy, ulceration
• Endothelial keratitis: Stromal oedema and keratic precipitates
• Keratouveitis: Corneal epithelial and/or stromal edema, stromal keratitis, keratic precipitates, and anterior chamber cells
Diagnostic of HSK
Initially, herpes simplex keratitis is clinically diagnosed. Although polymerase chain reaction assay (PCR), enzyme-linked immunosorbent assay, and immunofluorescent antibody assay are additional studies that may be performed for diagnostic confirmation, a viral culture is the gold standard.
Fisiopathology of HSK and neurotrophic keratopathy?
A significant impact of HSV corneal infection is the degradation of corneal nerves, leading to a reduced sub-basal nerve plexus and, consequently, diminished corneal sensation. This sensory loss disrupts the normal blink reflex, potentially resulting in neurotrophic keratopathy. The mechanisms underlying HSV-induced damage to corneal nerves are subject to ongoing debate.
What is the most common cause of corneal blindness in the developed world?
Herpetic keratitis
How is the cornea curvature and thickness?
The cornea has the greatest curvature in the 3.0 center and flatters around the periphery. The center of the cornea is thinnest (540mm) and becomes thicker in the periphery.
Explain corneal layers from anterior to posterior.
Epithelium
Bowmans membrane
Stroma
Descemets membrane
Endothelium
What layers of the cornea do not regenerate?
Bowman’s layer and endothelium. BUT the endotelium cells loss is compensated by an increase in the size of cells, increasing in size and also becoming more irregular in shape. (Polymegethism)
What types of collagen do we find in cornea layers?
The stroma is TYPE I collagen, when the stroma is wounded, healing includes TYPE III collagen. The Descemet membrane is composed of TYPE IV collagen.
What are Vogts palisades?
They form the corneal epithelial stem cell niche andare located predominantly in the superior and inferior corneal limbus.
What’s the composition of the precorneal tear film?
Lipidic layer, the most external one, reduces evaporation and acts as a surfactant, originated in the meibomian glands.
Aqueous layer: Middle layer, supply oxygen, wash away debris, plus carry antibacterial elements (lactoferin) originated from the lacrimal glands: Principal & accessory ones (Krause and Wolfring)
Mucous layer: created by the Goblet cells (located in the conjunctiva) this sticky layer allows the aqueous layer to adhere to the epithelial cells.
What type of carcinoma can imitate blepharitis?
Sebaceous cell carcinoma.
What are the insertion diameters of the recti muscles from the cornea?
º medial rectus 5.6mm
º inferior rectus 6.6mm
º lateral rectus 7.0mm
º superior rectus 7.8mm
Whats the dioptric power of both athe nterior and posterior cornea?
The dioptric power of the anterior cornea is approximately 49 D and that of the posterior cornea is -6 D.
Measurements of megalocornea and microcornea.
In megalocornea the corneal diameter is more than 13 mm and in microcornea it is less than 10 mm.
Define dry eye disease according to the DEWS II.
“Dry eye is a multifactorial disease of the ocular surface characterized
by a loss of homeostasis of the tear film, and accompanied
by ocular symptoms, in which tear film instability and
hyperosmolarity, ocular surface inflammation and damage, and
neurosensory abnormalities play etiological roles.”
