Good Hope, Heartlands, and Solihull Eye Clinics

Keratoconus

David Kinshuck

Links

Some notes

http://www.kcnz.co.nz/what-is-keratoconus.html

www.kcnz.co.nzlthe curve of the keratoconic eye is like a rugby ball on its side; www.bluetrack.com

the front curve of the eye is like a rugby ball on its side

corneal topography in keratoconus: wikipedia

Keratoconus topography: in a healthy eye the red area is central, in keratoconus is is off-centre as shown here

papillae contribute to keratoconus: www.reviewofcontactlenses.com

Evert lids: papillae are seen.

  • S.B Kaye..some notes from his presentation
  • explanation ; early diagnosis BJO 14  see
  • The condition is linked to allergic eye disease and eye rubbing pathogenesis  oxidative stress    rubbing eye contributes to keratoconus   rubbing and allergic conjunctivitis.
  • It is always bilateral. There is irregular astigmatism, that is the front curve of the eye is like a rugby ball on its side. AJO 15
  • It starts early teens, but may be diagnosed later. 
  • First stage of keratoconus is thinning (normal central thickness 550); the corneal layers slip over each other. Cross linking sticks the layers together so they don't slip.
  • As the cornea thins it may scar; proud nebulee may develop.
  • Environmental and genetic factors Eye 14 . Gene: Znf 469.
  • Eye rubbing is a significant risk factor 50%
  • Allergic..atopy..risk factor.....makes it progress.
  • Much more evident in Asian population...2.5 x and patients present earlier.
  • 500 new cases a year in the UK
  • It is diagnosed by slit lamp and retinoscopy
  • Slit lamp ..look at posterior corneal profile view with a slit demonstrates the condition
  • Evert lids: papillae are seen.
  • Keratometry can be used to grade 48 normal, 55 severe grade 4 keratoconus: useful for referral.
  • Topography demonstrates the problem.
  • All young cases progress, until the age of 40y.
  • Kmax, kmax-kmin k 2
  • Refraction change is a clue the condition is progression.
  • Pachymetry, refractive astigmatism.
  • Similarly, symptomatic visual loss indicates progression.
  • Other signs:change in contact lens wear or comfort, corneal signs, epithelial change, striae.
  • Assessing contact lens fit: put hard contact lens look at fit with fluorescein 2% fluorescein.
  • Contact lens rubbing will cause progression.
  • Confocal epithelium shows changes with rubbing from contact lens, and nerves become visible.
  • With a contact lens, if get vascularisation, can cut feeder vessel with syringe.
  • Refer for cross linking if progressing.
  • May progress >age 30y BJO17

 

Irregular astigmatism

  • The astigmatism is irregular: many of us have irregular astigmatism 1d, but in Keratoconus it may be 8d
  • Kmax, kmax-kmin k 2

 

 

Acute hydrops

  • acute hydrops link   
  • treatment
    • hypertonic saline
    • lubricants
    • cycloplegics if sore, mydrilate 1% twice daily
    • antibiotic prophylaxis (if poor ocular surface, lids)
    • steroids helpful to reduce haze and neovascularisation
    • gas (not initially)

Cross linking

There are surgical treatments for keratoconus, but the new effective treatment is cross-linking. It is not yet approved by NICE for regular use. It should be used early in the condition: it is more effective in stabilising the condition. Explanation.

  • Crosslinking: Kmax treat...62>>>58
  • Refraction does improve
  • Keratometry reduces
  • vision sometimes improves, but condition does usually stabilise AJO 15
  • cost effective Eye 15
  • Contact lens gap interferes with mapping so can't judge progression..no lens 1 week before topography 
  • 1 diopter error in early,  4 d in stage 4 disease.
  • there are Hysteresis corrected IOP charts available

 

Case study: cross linking, CXL (SBK)

  • 16y boy
  • Reduced vision for 6 months:, 6/36, ...but left 6/9 with refraction, but the refraction has changed a lot over the last 6m. It was much better.
  • Patient has asthma, eye rubbing, hey fever, tarsal papillae, striae on inside of cornea, and keratoconic corneal profile
  • Start treating the allergic eye
    • mast cell stabilisers, lubricants, and Opatanol see
    • get atopy controlled with steroids or Cyclosporine first
    • ..treat underlying cause..see if the cause of the allergy can be identified, although this is seldom possible
    • Baseline orb scans: irregular 4d. Should be 1 d
  • this did not stabilise the condition, so he was referred for cross linking.
  • Risk: CXL Kills some corneal cells, later recover, if treated properly, must have corneal 380 microns or more. A bandage contact lens is may be used after the procedure, until the epithelium recovers: if  painful...have to remove contact lens.
  • But SBK now recommends post CXL chloramphenicol ointment with double padding instead a of a bandage contact lens.

Other corneal ectasias

These include... review..corneal ectasias BJO 16 

  • pellucid marginal degeneration
    • patients are older, changes are slower, and often manage the high cylinder with spectacles, even 8d
  • keratoglobus: thin peripherally 
  • and following surgery and refractive surgery (post-lasik ectasia)

Keratoconus management

corneal topography in keratoconus: wikipedia

Keratoconus topography: in a healthy eye the red area is central, in keratoconus is is off-centre as shown here

papillae contribute to keratoconus: www.reviewofcontactlenses.com

Evert lids: papillae are seen.

  • Identify keratoconus
  • identify and treat allergic eye disease
  • use topography of a placido disc
  • check if cylinder stable; if is changing over 6 months, or there is clear evidence it has changed recently, and the cornea is >400µ thick, cross linking is ideal
  • If the cycling/refraction is stable, try contact lenses, Kerasoft lenses
  • the cone may be nipple shaped or oval global
  • keratoconus may progress <40y
  • Usually progress till age 40
  • Kerasoft or Rose K contact lenses according to severity

 

 

 

 

 

 

Cross linking procedure

  • Remove epithelium ethanol 20%. 30s, wash off,
  • Debride
  • Ribflavin 10 m, then uv 30m and more riboflavin
  • Chloramphenicol 
  • Bandage cl 1 week
  • Nsaid, dex, paracetamol
  • Dex qid reducing
  • Moxifloxacin postop
  • Cornea hazy whilst healing

Contact lenses in keratoconus

  • Kerasoft or Rose K contact lenses according to severity
  • if patient can only wear lenses for a few hour, consider wear right am, left afternoon,
  • Piggy back soft under layers 

Corneal graft in keratoconus

  • Aim of graft is to enable contact lens use
  • Lamellar grafts last longer, lose one line vision
  • Penetrating are needed if cone is steep or if deep scarring is present
  • treat dry eye , allergies, blepharitis before graft
  • Post graft
  • Steroids 2 h 1 week, x 4 2m, then slow reduction 
  • Remove sutures 18 m:remove according to astigmatism ,but good vision leave longer