the anterior eye (keratoconus) Flashcards
what does corneal ectasia mean?
budging and thinning of the cornea due to stromal thinning causing the cornea to become more flexible
keratoconus is progressive non-inflammatory corneal ectasia
does keratoconus affect both eyes?
usually, yes but is asymmetric
is keratoconus more prevalent in males or females? Whats its inheritance like?
slightly more common in males, has no definite inheritance pattern
how does climate affect keratoconus?
more common in hot, dry, dusty, tropical and subtropical climates
give 4 possible things that can cause or trigger keratoconus
-atopy: check for the atopic triad which is asthma, eczema and allergic rhinitis as about 1/3 of keratoconus patients have atopy
-inheritance
-eye rubbing/ micro trauma
-connective tissue disorders like downs and marfans
give 3 risk factors of keratoconus
-family history
-atopy
-sleep apnea/ floppy eyelid syndrome: these patients already have abnormal collagen as do keratoconus patients.
how is keratoconus affected by ethnicity?
4x higher in asian (inida, pakistan bangladesh) compared to Caucasian patients
give 3 early (subtle signs) signs of keratoconus
-Patients with lots of changes in their prescription especially in their astigmatism and steepening Ks should make you suspicious of keratoconus
-Scissor and oil drop reflex on ret
-Prominent corneal curves (not just keratoconus patients)
give 3 moderate signs of keratoconus
-vogt’s striae = vertical stress lines in descemet’s membrane - by placing pressure on the globe, the lines will disappear
-Fleuscher’s ring = pigmented ring in the peripheral cornea due to iron deposits in the bowman’s layer, can be seen with cobalt blue filter. This is not always keratoconus
-Munson’s sign = v shaped indentation in the lower lid in downwards gaze
give 2 advanced signs of keratoconus
-Cornea is extremely thin which you can see in an optic section
-Stromal scarring due to corneal hydrops complication
How does corneal hydrops come about?
- cornea is very thin and stretched
- rupture in descemet’s membrane
- causing aqueous to leak into stroma and epithelium
- causing gross stromal oedema and epithelial oedema - leaves some corneal scarring
hence causes the patient alot of pain and discomfort
how does corneal hydrops get treated?
generally resolves by itself in 2-4 momths and can be good as usually causes the cornea to flatten which fixes the keratoconus
what is the numerical classification for mild keratoconus? (in terms of Ks)
> 7.50mm
what is the numerical classification for moderate keratoconus?
6.50-7.50mm
what is the numerical classification for advanced keratoconus? (in terms of Ks)
6.00-6.50mm
what is the numerical classification for severe keratoconus? (in terms of Ks)
<6.00mm
give three differential diagnoses of keratoconus
-pellucid marginal degeneration
-keratoglobus
-iatrogenic keratectasia
what is pellucid marginal degeneration? what are its symptoms?
stromal thinning of the inferior cornea instead of a central cone
what are the signs and symptoms of pellucid marginal degeneration?
-Usually asymptomatic until it gets really advanced as it does not affect central cornea so it’s mainly seen with a topographer
-central cornea remains clear
-bilateral
-has large amounts of against the rule astigmatism
what is keratoglobus?
diffuse thinning across the whole cornea, congenital and acquired type
what is iatrogenic (physical condition as a result of a medical intervention) keratectasia
keratectasia as a result of lasik with undiagnosed keratoconus/ insufficient stromal bed thickness/ irregular topography. Has a similar look to keratoconus
What are the surgical and non-surgical management strategies for early keratoconus?
non surgical
-specs
-soft cls
surgical
-collagen cross linking as it helps to halt progression of condition by increasing bonds within collagen in the stroma.
What are the surgical and non-surgical management strategies for moderate keratoconus?
non-surgical
-RGPs
-Hybrid lenses
surgical
-intacs implant
what are hybrid lenses
Cls with a rigid gas permeable centre surrounded by a soft lens skirt - gives good VA like an RGP but has comfort of a soft CL
What are the surgical and non-surgical management strategies for advanced keratoconus?
non-surgical:
-corneo-scleral lenses
-scleral lenses
surgical
-PK/ DALK (penetrating keratoplasty or deep anterior lamellar keratoplasty)
What is an intacs implant?
Small rings which try to flatten steepness which reduces distortion to allow a better visual outcome with glasses or CLs
what are PK and DALK?
a type of corneal graft - penetrating keratoplasty and deep anterior keratoplasty
look up the surgical interventions on youtube and see how theyre done
okay
what is the difference between PK and DALK?
PK is a full thickness graft whereas DALK is not a full thickness graft. This means in DALK , there is a much lower risk of graft rejection and heals quicker compared to PK
when should you fit Cls to keratoconus patients?
-generally, when VA us <6/9 or Px is symptomatic
-poor spectacle VA
what CL can you use for a keratoconus patient who needs RGPs for VA but does not tolerate them?
soft skirt (hybrid lenses)
what can you offer in terms of support to patients with keratoconus?
-local eye clinic liaison officer
-keratoconus support groups
