Knowledge Flashcards
Spherical RGP lenses on against-the rule corneas tend to decenter…
laterally
by increasing the overall lens
diameter, increasing the size of the
optic zone or steepening the base
curve of the lens does this to an RGP lens
Steepens the lens to cornea relationship
A lens that has become adherent
to the cornea may leave an
impression that can be viewed
after the lens has been removed.
leaves slightly darker spot
Neovascularization of the cornea in a soft contact lens could indicate …
A lack of oxygen transmission through the lens, a tightly fitting soft lens or a situation in which the patient overwears
edge stand off or lift can occur
when soft contact is fit too flat to the cornea
Soft lens should be …mm larger than the patient’s HVID
2
Hvid= 11-12
diameter should be = 14ish
The difference between Neovascularization and Pannus is…
Neovascularization: develops in an already compromised cornea
Pannus: caused by ill fit, typically at superior limbus.
Is chalazion or stye (hordeolum) usually above the eye and a raised lump
Chalazion
Is chalazion or stye (hordeolum) a point/ pimple on lash line usually below eye
Stye
When Superficial Punctate Keratitis has an isolated pattern this is because…
there is a poor contact lens fit or infection
When Superficial Punctate Keratitis has a diffuse pattern this is because …
There may be solution toxicity or an interaction between certain lens/solution combinations or dry eye syndrome.
Steepest on 90 flattest on 180
With the rule astigmatism
a rigid lens will ride superior-inferior with the interaction of the eyelids during a blink
With the rule astigmatism
will tend to ride medial-lateral
Against the rule
inconsistent with the blinking action of the eyelids
Against the rule
Keratometer measures … after surgery
low
Average keratometer measurement is …
47-48
Above-average keratometer measurement means keratoconus
(52) (51)
Contact inverted and not inverted looks like
Inverted flares out at top and bottom more angular
correct way has rounded edges and bottom
Normal Tbut
greater than 10 seconds
Schrimer test 1
After 5 mins
Normal-greater than 15mm
Mild-10-14mm
Moderate- 5-9mm
Severe- less than 5mm
No drops
small strips of filter paper inside the lower eyelid
Schirmer test #2
Less than 6mm of wetting after 5 mins is abnormal
Anaesthetic drops used
A cotton swab inserted into the nose
Marginal Tbut
greater than 5 and less than 10
Low Tbut
Less than 5 seconds = dry eye symptoms
ptosis
Upper eyelid droops below normal position
trichiasis
eyelashes grow inwards toward the eye
Ectropion
Droop of the lower lid
lagophthalmos
incomplete closure of the eyelids
Entropion
turning inward of the eyelid making eyelashes touch globe
The deeper the layer of tears the … the fluorescein green will be.
brighter
The less tears in the tear layer the … the fluorescein green will be
darker
Before insertion scleral lenses are washed down with … and filled with …
saline solution
Involuntary, jerking movements of the eyes
nystagmus
Central Abrasion
This stain is caused by a large break or erosion in the corneal epithelium.
Can be caused by a flat lens or other mechanical irritation or extended corneal edema.
Pic:book
Peripheral abrasions
Caused by mechanical irritation or chipped/damaged lens. Could be poor insertion or removal techniques.
Pic:book
3-9 o’clock staining
Caused include poor blinking/incomplete blink, flat edge curves, and poor edge design(thick edge)
Dry tear film breakdown
Arcuate
Due to poor blends or peripheral curves
Dimple veil staining
Caused by air bubbles that have been trapped centrally under the lens due to a poor fit that is too steep, or in the limbal area by a lens that is too flat.
It is not a breakage but rather a denting of the surface of the epithelium
Stippling/punctate stains
Caused from dryness, lack of oxygen to cornea, associated with PMMA lenses, but can also be found in dirty gp lenses or low Dk gp lenses.
Chemical toxicity can also contribute
Solution induced corneal staining
Small dots around entire surface or in periphery caused by solution toxicity/insensitivity
