Changes In Myopia And Aging Flashcards
T/F: at birth the cornea has full adult thickness
True
At birth, what is the horizontal diameter of the cornea?
10mm, 90% of the adult value
At birth, the axial length is just over?
2/3 of adult
At birth, the cornea occupies ___ of the eye surface
25%
When does the cornea acquire adult size?
3 years
When does the sclera stop growing?
10-12 years
Do children start out hyperopic or myopic?
Hyperopic
When do we begin to become emmetropic?
6-8 years old
T/F: changes to the cornea are detrimental.
False. It isnt detrimental unless there is changes to the central cornea or the transparency
What are the 5 changes of the cornea due to aging?
- decrease in corneal sensitivity
- increase in light scatter
- flattening of the cornea (especially vertically)
- –against the rule
- stippling of bowmans membrane
- thickening of descemets membrane
The most common aging change in the cornea
Corneal arcus
Describe corneal arcus
Yellow-white deposit located in the peripheral stroma
- the deposits are cholesterol and cholesterol esters
- Ring separated from the limbus by a zone of clear cornea
Asymptomatic
Bilateral
Involves Bowmans layer
Can extend anteriorly over time to bowmans or into the central cornea
Normal in people 60-80 years old
If someone has arcus under 40 what can we suspect
That they have high cholesterol, so we need them to get that checked
How does age affect the corneal epithelium?
Alternations to the cellular transmembrane receptors (integrins) can occur
- this causes a reduction in the adhesion molecules necessary for intercellular junction construction
Decreased keratocyte density can affect?
- wound healing
- collagen fibril degradation produces spaces that can disrupt transparency and create opacities
Iron deposits in the epithelial cell cytoplasm that produces a horizontal pigmented line
Hudson-Stahli line
Where is the iron deposits (Hudson stahli) more concentrated?
Basal cells
Where is the Hudson Stahli line evident?
At the level of the lower lid margin
Describe limbal girdle of Vogt
Degeneration of bowmans layer
Yellowish opacity located at the 3 and 9 o’clock positions
A clear interval separating the opacity from the limbus may be seen
What type of limbal girdle of Vogt will you see a clear interval separating the opacity from the limbus?
What type will not be seen?
Seen: Type 1
Not seen: type 2
What other factors may you be able to see with limbal girdle of Vogt?
- degeneration of the anterior stroma
- calcium deposits
- hypertrophy of the overlying epithelium
What happens to the descemets membrane with age?
- increases in thickness
- Hassan-henle increase in the periphery
Describe Hassall-Henle bodies (descemets warts)
- asymptomatic
- Small round peripheral endothelial indentations
- Produced by thickening of Descemet’s membrane
- Appear as corneal guttata (peripheral)
- Peripheral Edema
- May cause atypical arcus
T/F: endothelial cell density decreases with cell loss
True
How does aging change the corneal endothelium?
-decreases cell density
Greater than normal variation in size of the corneal endothelial cells
Polymegathism
Increased variability in size and shape
Pleomorphism
Pigment deposits on the posterior cornea with a vertical orientation
Krukenbergs spindle
T/F: Krukenbergs spindle decreases with age
False: it increases with age
T/F: A decrease in corneal sensitivity corresponds to a loss of corneal nerves with age.
True
T/F: myopic eyes are longer than emmetropic or hyperopic eyes
True
When do people begin to develop myopia?
8-14
What is the most often cause of myopia?
Lengthening of the posterior pole, containing the vitreous
Scleral remodeling causes ____in myopia
Axial lengthening
When the axial length of the eye increases, how does the affect the sclera?
It causes it to stretch the scleral tissue. This weakens and thins the tissue
What happens in progressive myopia?
- existing collagen is degraded
- production of new collagen is decreased
- matrix proteoglycans are lost
- scleral thinning in the posterior pole
- collagen fibril diameter and bundle size are reduced
What is scleral ectasia?
Scleral tissue bulging due to scleral thinning
How does age affect the sclera?
- build up of fatty deposits can cause it be appear yellow
- scleral collagen and elastic fibers degenerate
- concentration of some proteoglycans decrease
- fibers of the lamina cribrosa become stiffer and less resilient
How would the change in lamina cribrosa pores affect us?
It may make nerve fibers passing through the openings more susceptible to injury, contributing to an increased susceptibility to glaucomatous damage
