Keratoconus

Links

• crosslinking BJO11     BJO16  Moorfields
• PubMed 2012
• Explanation
• UK   http://www.keratoconus-group.org.uk/
• inaccurate pressures BJO12
• http://www.nkcf.org/
  National Keratoconus Foundation 8733 Beverly Blvd., Suite 201, Los Angeles, CA 90048 United States E-mail your questions or requests for information to: nkcf@csmc.edu. Be sure to include: YOUR NAME AND MAILING ADDRESS.
• Word leaflet Keratoconus
• sterile keratitis after crosslinking Eye14
• review..corneal ectasias BJO16 
• Other corneal ectasias
• IOP Eye 16

Some notes

• 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     Eye 18  acclerated equally effective.
• 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

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

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