keratoconus Flashcards
what is keratoconus?
corneal thinning that leads to a protrusion in the form of a cone
onset?
usually in teenage years
is keratoconus sex linked?
no
is keratoconus genetic or sporadic?
can be - autosomal dominant inheritance
BUT most commonly sporadic
how do you know if someone has keratoconus?
spherical over refraction pr x-cyl doesn’t get the vision better
if pinhole improves the vision, what pathology does that exclude?
media opacities
retinal problems
neurological problems
name some corneal signs of KC?
Vogt’s striae
fleischer’s ring
apical scarring
munson’s sign
What is this?
vogt’s striae
What is this?
fleischer’s ring
What is this?
Apical scarring
What is this?
Munson’s sign
does slit lamp examination exclude KC? and explain?
no - early KC patients often dont show signs on slit lamp
what does keratometry show in a KC pateitn?
egg-shaped mires
does keratometry exclude KC?
no - only shows central 3mm of cornea therefore this area may or may not be distored
what does retinoscopy show in a KC px?
scissor reflex , not possible to fully neutralise
what does topography show you in a KC px?
usually inferior steepening
flattening in the opposite meridian
what are the different types of cones?
- central
- oval
- inferior
- superior (rare)
how does the type of cone affect vision?
quality of vision will depend on how close the cone is to the visual axis
which type of cone allows the px to see well?
inferior
what happens with the px post-referral?
topography with ophthalmologist
may carry out OCT and pachymetry
may revommend cross linking if the px is progressing
what is the aim of collagen cross linking?
stabilise KC
when should you do cross linking?
early in the disease before cornea becomes too thin
explain the procedure of cross linking?
topical anaesthetic
epithelium is abraded with a blunt spatula
riboflavin eyedrops are applied and cornea is exposed to UVA radiation
will the px need correction after collagen corss-linking?
if they needed it before they will need it after but will often need re fitting as the cross linking can flatten the corneal curvature
when can the px resume CL wear after cross-linking?
6 weeks post treatment
what are the CL options for KC?
soft KC lenses
corneal GP’s
sclerals
hybrids
what are soft KC lenses made from?
thicker material (high modulus) therefore sihy
what are the advantages of soft lenses for KC?
great initial comfort
familiar to alot of patients
usually straightforward to fit
good in dusty environment
what are the disadvantages of soft lenses for KC?
thick lenses so even in high o2 materials dk/t isnt great
best for early to mod KC as may not improve VA enough in advanced disease
can you use standard RGP designs for KC?
no - they don’t flatten rapidly enough
centration may be poor depending on position of cone
what is the most comely used fitting pattern for KC?
3 point touch
what’s an example of RGP lens for KC?
Rose K
when would you fit someone with a piggyback lens?
- poor centration
- poor comfort
- recurrent corneal abrasions
- chronic 3 and 9 o’clock staining
what is a hybrid lens?
regular GP lens with a soft lens skirt
benefit of hybrid lens?
- improved comfort
- no dust under lens
- VA AMAZING
why fit a scleral lens?
- amazing VA
- no need to fit irregular corneal shape
- comfort is good
do you need a topographer for scleral lens?
no
how do you fit a scleral lens?
- fitted by sag
- lens should clear the cornea
- lens should clear the limbus
- lens should land on the sclera
what are the 2 main options of corneal grafts?
DALK ( deep anterior lamellar keratoplasty)
Full thickness Penetrating Keratoplasty
Penetrating keratoplasty
- entire thickness of cornea is removed and replaced with donor corneal section
- px has to be on anti-rejection steroids for years
DALK
- less invasive than a full PK
- lower risk of rejection
- can taper off steroids faster
- better visual result
- faster healing process
