7.3 Corneal ectasia
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What are corneal ectasias? (3)
- primary progressive
- protrusion/bulging of the cornea
Types of corneal ectasia (5)
- pellucid marginal degeneration
- posterior keratoconus
- post-LASIK ectasia (keratectasia)
What is PMD?
pellucid marginal degeneration
Which type of corneal ectasia is most common?
Keratectasia is also known as
Post-LASIK ectasia is also known as
Which 3 types of corneal ectasias are rare?
- post keratoconus
Is posterior keratoconus congenital or acquired?
Keratoglobus is __________ corneal thinning and steepening
PMD is ______________ thinning and steepening
KC is also known as
What type/shape does KC have?
nipple/oval cone type
KC is ______ or ________ __________ thinning and steepening
- mildly paracentral (nasal/inf)
Does KC have limited progression? Why?
What does form fruste mean?
incomplete/unusual form of a disease
Keratoglobus is __________ thinning and often thinner at the _____
In keratoglobus, the cone is ___% to ____% of the cornea and is not as steep as _____
Keratoglobus is associated with _________ disorders such as ____ and ______
- collagen synthesis
- Ehlers-Danos VI
What are the suggested 2 forms of keratoglobus?
What does a 'blue sclera' suggest?
- collagen synthesis problems
- thin sclera = can see choroidal vessels
What is the age range for PMD?
peripheral/central thinning if the cornea
Which part of the cornea is usually affected?
What symptoms are observed in PMD? (3)
- decr VA
- glare sens
- no irritation/scarring
What are the signs of PMD?
- ATR ast
- thinning 4-8o'clock
- epith intact
- NO vogt's striae or Fleisher's ring
What are the features of the ast seen in PMD? (3)
Where is thinning seen in PMD?
What are Vogt's striae?
vertical collagen tension lines on the post corneal stroma that disappears with external pressure on the globe
What is Fleischer's ring?
partial or complete deposition of iron in deep/basal epithelial cells at the peripheral cornea
DDX for PMD
- Mooren's ulcer
- Terrien's marginal degeneration
What is mooren's ulcer? (3)
- progressive inflammation
What is Terrien's marginal degeneration? (2)
- mostly superior cornea affected
- with lipid deposition
What is the prevalence for KC? (3) i.e. 1 in _________; which gender is more prevalent; what age range
- 1:2000 (range)
- late teens to mid 40s
Describe features of KC in 3 words
progressive or stable
inflammatory or non-inflammatory
Where do we see thinning/steepening in KC?
central or para-central
KC is caused by changes in
What are the main symptoms of KC? (5)
- refractive error changes
- irregular ast
- decreased contrast sensitivity
- corneal sensitivity
What are the associated risk factors of KC? (5)
- UV exposure
- Allergies/atopy --> vigorous eye rubbing
- poory fitting CL
- genetic background/ethnicity
What is the main indicator for penetrating keratoplasty and at what %?
What are the symptoms of KC? (6)
- progressive blurring, distortion (mostly bilateral, one eye earlier)
- photophobia, glare, ocular irritation
- monocular diplopia/polyopia
- BCVA may be normal early with decreased CS
- axis shift and irregular ast
- CLs more difficult to fit, uncomfy
Signs of KC (10)
- steep and irregular changes in the corneal curvature
- munson' sign
- Vogt's striae
- Fleischer's ring
- Apical ant stromal scarring
- scissors reflex with ret
- Charleux oil drop with ophthal
- Rizzuti's sign
- Prominent corneal nerves, decre sens
- breaks in descemet's and hydrops
a syndrome characterized by the tendency to be "hyperallergic"
What is Munson's sign?
profile of the cornea seen on the lower lid when px looks down with the upper lid held away
What are vogt's striae? (3)
- deep stromal striae
- vertical lines related to tension in collage layers due to apical stretching
- can involve deep stroma and descemet's membrane
What is Fleischer's ring? (5)
- iron ring at the base of cone in KC
- appears black with blue light
- can be partial or complete
- mainly collected along the basal epithelium
- severe if ions along the entire epith
Features of apical anterior stromal scarring
- may be related to CL wear e.g. rubbing of CL on apex
- KC fitting = light pressure on apex; excess --> scarring
What is the Charleux oil drop?
- oil drop reflex with ophthalmoscope
- internal reflection of light withing steeper region of the cone
- can be seen in SL
What is Rizzuti's sign?
steep cone focusses light shone from temporal edge of eye as a focal band on the nasal iris
Features of prominent corneal nerves
- decreased sensitivity
- thickened nerves
- diff distbn/density
- seen with confocal microscope
Compare normal corneal nerve organisation with KC
- normal: crop shape whorls, straight, dense
- KC: concentric pattern at base of steepening, tortuous, less dense
In the Amsler-Krumeich grading, mild, moderate and severe are classified by:
How are corneal ectasias detected clinically?
What are the newer imaging possibilities for corneal ectasias?
- ORBSCAN - SL and topography
- PENTACAM - ant segment tomography, 3D images of the cornea
- confocal microscopy
What are the corneal topography types?
- A. Nipple
- B. Oval
- C. Globus
What are the features of nipple-shaped topography?
- near central ectasia
- <5mm in cord dia
What are the features of oval-shaped topography?
- sup cornea normal
- steepening in the inf
What are the features of the globus-shaped topography?
- affects the largest are of the cornea
- area above the middle is affected
How do you assess the clinical sign of apical thinning?
- fine slit beam
- assess BE
- assess direct cross section
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