Cornea Anatomy and Clinical Management

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Questions and Answers

What is the approximate thickness of the epithelium in the cornea?

10-20um

50um (correct)

700um

500um

What is the primary component of the stroma, which accounts for over 90% of the corneal thickness?

Keratocytes and type 1 collagen

Basal and wing cells

Endothelium and Bowman's layer

Type 1 collagen and proteoglycans (correct)

What is the purpose of the Descemet's membrane?

To provide a barrier against foreign substances

To facilitate the transmission of light

To regulate the shape of the cornea

Not specified in the provided text (correct)

What is the approximate refractive index of the cornea?

1.3375 Signup and view all the answers

What is the wavelength of light at which the light transmission is maximal?

700nm Signup and view all the answers

What is the average radius of curvature of the cornea?

7.8mm Signup and view all the answers

What is the typical location of punctate epitheliopathy?

Epithelial layer Signup and view all the answers

What is the primary difference between a pterygium and a pinguecula?

Triangular shape and encroachment on the cornea Signup and view all the answers

Which of the following is NOT a characteristic of keratoconus?

Bilateral symmetry Signup and view all the answers

What is the typical age of onset for keratoconus?

Around puberty Signup and view all the answers

What is the name of the condition characterized by degeneration of collagen fibers in the conjunctival stroma?

Pinguecula Signup and view all the answers

Which of the following conditions is associated with keratoconus?

Both A and B Signup and view all the answers

What is the primary consideration when dealing with an embedded foreign body in the cornea?

Checking for signs of globe penetration Signup and view all the answers

What is the characteristic shape of the area of inferior corneal thinning in high increasing regular astigmatism?

Crescent shaped Signup and view all the answers

How would you typically remove a superficial foreign body from the eye?

Rinsing with topical saline and a cotton bud Signup and view all the answers

What percentage of Keratoconus cases require Epikeratoplasty or Penetrating keratoplasty?

10-20% Signup and view all the answers

What is a risk factor for developing corneal abrasions?

Contact lens wear Signup and view all the answers

What is the name of the condition characterized by greyish-white polygonal stromal opacities separate by clear spaces?

Crocodile Shagreen Signup and view all the answers

What wavelength of UV light is used in Corneal collagen crosslinking?

365nm Signup and view all the answers

What is the primary purpose of applying topical antibiotic ointment in cases of corneal abrasion?

To promote wound healing Signup and view all the answers

What is the age-related corneal opacity that frequently occurs bilaterally and is associated with hyperlipoproteinaemia?

Arcus Senilus Signup and view all the answers

What is the typical healing time after Corneal collagen crosslinking?

1 week Signup and view all the answers

What is the purpose of Seidel's test in the context of ocular foreign bodies?

To detect signs of globe penetration Signup and view all the answers

What is the term for the focal accumulations of collagen on the posterior surface of Descemet's membrane?

Corneal Guttata Signup and view all the answers

What is the treatment option for high increasing regular astigmatism?

Scleral lenses or corneal surgery Signup and view all the answers

Why is it important to assess and examine the extent of the defect in corneal abrasion?

To determine the risk of complications Signup and view all the answers

At what age does Keratoglobus typically onset?

At birth Signup and view all the answers

What is the age range for the onset of Pellucid Marginal Degeneration?

20-40 years Signup and view all the answers

What is the name of the condition characterized by bilateral narrow crescentic lines composed of chalklike flecks at the interpalpebral fissure on the nasal and temporal limbus?

Vogt White limbal girdle Signup and view all the answers

Study Notes

Corneal Epithelium Thickness

Approximately 50 micrometers thick

Corneal Stroma

Primary component, over 90% of corneal thickness
Composed of collagen fibers arranged in a highly organized, parallel fashion

Descemet's Membrane Purpose

Acts as a barrier against infection and inflammation
Plays a role in corneal wound healing

Corneal Refractive Index

Approximately 1.376

Corneal Light Transmission

Maximal transmission at 555 nm (green light)

Corneal Radius Of Curvature

Average radius of curvature: 7.8 mm

Punctate Epitheliopathy Location

Typically occurs on the corneal epithelium, often caused by dry eye, viral infections, or certain medications

Pterygium vs. Pinguecula

Pterygium: A triangular, fleshy growth of conjunctiva that extends onto the cornea
Pinguecula: A yellowish, raised nodule on the conjunctiva, usually on the nasal side of the cornea, does not extend onto the cornea

Keratoconus Characteristics

NOT a characteristic of Keratoconus: Myopia
Commonly seen in patients with keratoconus:
- Astigmatism
- Increased corneal curvature
- Thinning of the cornea
- Conical shaped protrusion of the cornea

Keratoconus Onset

Typically starts in adolescence (around 10-20 years old), but can develop later in life

Degeneration of Collagen Fibers in Conjunctival Stroma

Pinguecula

Keratoconus Associated Conditions

Down syndrome
Atopic keratoconjunctivitis
Ehlers-Danlos Syndrome

Embedded Foreign Body

Primary consideration: to ensure that the foreign body is not embedded in the cornea

Inferior Corneal Thinning Shape

The shape of the area of inferior corneal thinning is crescentic

Superficial Foreign Body Removal

Typically removed using a moistened cotton swab or a sterile saline solution
May use a needle or forceps in some cases

Keratoconus Treatment

Approximately 15-25% of Keratoconus cases require Epikeratoplasty or Penetrating keratoplasty

Corneal Abrasion Risk Factor

Dry eye

Greyish-White Polygonal Stromal Opacities

Matsen's dystrophy

Corneal Collagen Crosslinking UV Wavelength

308 nm

Topical Antibiotic Ointment Purpose

Prevents infection

Arcus senilis

Corneal Collagen Crosslinking Healing Time

Typically takes 3-6 months

Seidel's Test

Detects a leak in the cornea associated with foreign bodies

Focal Collagen Accumulations on Descemet's Membrane

Posterior polymorphous dystrophy

High Increasing Regular Astigmatism Treatment

Corneal refractive surgery, such as LASIK or PRK

Corneal Abrasion Defect Assessment

Assess the depth and extent of the corneal abrasion
Evaluate the risk of infection
Determine the need for treatment

Keratoglobus Onset

Typically onset in childhood

Pellucid Marginal Degeneration Age Range

Typically onset in the 2nd to 4th decade of life

Bilateral Narrow Crescentic Lines with Chalklike Flecks

Salzmann's nodular degeneration

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Description

Test your knowledge of cornea anatomy, signs and symptoms of corneal problems, and clinical management guidelines. Covers corneal ectasias, degenerations, dystrophies, and surgical procedures. Useful for optometry students and professionals.