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Contact Lenses > keratoconus > Flashcards

keratoconus Flashcards

1
Q

what is keratoconus?

A

corneal thinning that leads to a protrusion in the form of a cone

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2
Q

onset?

A

usually in teenage years

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3
Q

is keratoconus sex linked?

A

no

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4
Q

is keratoconus genetic or sporadic?

A

can be - autosomal dominant inheritance
BUT most commonly sporadic

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5
Q

how do you know if someone has keratoconus?

A

spherical over refraction pr x-cyl doesn’t get the vision better

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6
Q

if pinhole improves the vision, what pathology does that exclude?

A

media opacities
retinal problems
neurological problems

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7
Q

name some corneal signs of KC?

A

Vogt’s striae
fleischer’s ring
apical scarring
munson’s sign

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8
Q

What is this?

A

vogt’s striae

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9
Q

What is this?

A

fleischer’s ring

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10
Q

What is this?

A

Apical scarring

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11
Q

What is this?

A

Munson’s sign

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12
Q

does slit lamp examination exclude KC? and explain?

A

no - early KC patients often dont show signs on slit lamp

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13
Q

what does keratometry show in a KC pateitn?

A

egg-shaped mires

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14
Q

does keratometry exclude KC?

A

no - only shows central 3mm of cornea therefore this area may or may not be distored

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15
Q

what does retinoscopy show in a KC px?

A

scissor reflex , not possible to fully neutralise

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16
Q

what does topography show you in a KC px?

A

usually inferior steepening
flattening in the opposite meridian

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17
Q

what are the different types of cones?

A
  • central
  • oval
  • inferior
  • superior (rare)
18
Q

how does the type of cone affect vision?

A

quality of vision will depend on how close the cone is to the visual axis

19
Q

which type of cone allows the px to see well?

A

inferior

20
Q

what happens with the px post-referral?

A

topography with ophthalmologist
may carry out OCT and pachymetry
may revommend cross linking if the px is progressing

21
Q

what is the aim of collagen cross linking?

A

stabilise KC

22
Q

when should you do cross linking?

A

early in the disease before cornea becomes too thin

23
Q

explain the procedure of cross linking?

A

topical anaesthetic
epithelium is abraded with a blunt spatula
riboflavin eyedrops are applied and cornea is exposed to UVA radiation

24
Q

will the px need correction after collagen corss-linking?

A

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

25
Q

when can the px resume CL wear after cross-linking?

A

6 weeks post treatment

26
Q

what are the CL options for KC?

A

soft KC lenses
corneal GP’s
sclerals
hybrids

27
Q

what are soft KC lenses made from?

A

thicker material (high modulus) therefore sihy

28
Q

what are the advantages of soft lenses for KC?

A

great initial comfort
familiar to alot of patients
usually straightforward to fit
good in dusty environment

29
Q

what are the disadvantages of soft lenses for KC?

A

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

30
Q

can you use standard RGP designs for KC?

A

no - they don’t flatten rapidly enough
centration may be poor depending on position of cone

31
Q

what is the most comely used fitting pattern for KC?

A

3 point touch

32
Q

what’s an example of RGP lens for KC?

A

Rose K

33
Q

when would you fit someone with a piggyback lens?

A
  • poor centration
  • poor comfort
  • recurrent corneal abrasions
  • chronic 3 and 9 o’clock staining
34
Q

what is a hybrid lens?

A

regular GP lens with a soft lens skirt

35
Q

benefit of hybrid lens?

A
  • improved comfort
  • no dust under lens
  • VA AMAZING
36
Q

why fit a scleral lens?

A
  • amazing VA
  • no need to fit irregular corneal shape
  • comfort is good
37
Q

do you need a topographer for scleral lens?

A

no

38
Q

how do you fit a scleral lens?

A
  • fitted by sag
  • lens should clear the cornea
  • lens should clear the limbus
  • lens should land on the sclera
39
Q

what are the 2 main options of corneal grafts?

A

DALK ( deep anterior lamellar keratoplasty)
Full thickness Penetrating Keratoplasty

40
Q

Penetrating keratoplasty

A
  • entire thickness of cornea is removed and replaced with donor corneal section
  • px has to be on anti-rejection steroids for years
41
Q

DALK

A
  • less invasive than a full PK
  • lower risk of rejection
  • can taper off steroids faster
  • better visual result
  • faster healing process
42
Q
A

Contact Lenses (16 decks)

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