marc l braithwaite od vision care of maine
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Keratoconus And specialty contact lens fitting of irregular corneas

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Marc L. Braithwaite, OD Vision Care of Maine. Keratoconus And specialty contact lens fitting of irregular corneas. Keratoconus. What have the years taught us?. Keratoconus Characteristics. Non-inflammatory. Central or para -central corneal thinning. Corneal steepening or protrusion.

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keratoconus
Keratoconus
  • What have the years taught us?
keratoconus characteristics
Keratoconus Characteristics
  • Non-inflammatory.
  • Central or para-central corneal thinning.
  • Corneal steepening or protrusion.
  • Increased astigmatism and possibly myopia.
  • Loss of best spectacle corrected visual acuity.
  • Corneal striae and scarring.
  • Corneal hydrops (inflammatory).
pathology of keratoconus
Pathology of Keratoconus
  • Loss of Bowman’s Layer.
  • Stromal Thinning.
  • Apoptosis.
  • Increased Enzyme Activity.
  • Enlarged Prominent Corneal Nerves.
causes of keratoconus
Causes of Keratoconus
  • Heredity vs. Mechanical
  • Cellular
  • Tissue
  • Genetic
heredity vs mechanical
Heredity vs. Mechanical
  • Does eye rubbing cause Keratoconus?
  • 2 out of 250 doctors feel that rubbing is a cause.
  • KC patients do rub their eyes more often than those without KC.
  • What is it that makes KC patients rub their eyes?
cellular changes
Cellular Changes
  • Keratoconus cells are hypersensative.
  • Increased enzyme activity, lack of enzyme inhibitors.
  • Matrix substrate instability in response to environmental stress factors.
  • mtDNA damage and exaggerated oxidative response causing cellular damage.
tissue changes
Tissue Changes
  • Loss of Bowman’s layer.
  • Lamellar slippage.
  • Lack “anchoring” lamellar fibrils.
  • Apoptosis of the stroma causing anterior thinning.
genetics
Genetics
  • Autosomal dominant w/variable penetrance.
  • SOD1, an antioxidant enzyme, is abnormal in some KC corneas.
  • No single gene responsible.
  • 10 different chromosomes have been associated with KC.
  • Most likely multiple genes involved.
additional information
Additional Information
  • Male to Female Ratio = 3:1
  • Approximately 20% result in PKP.
  • 90% are diagnosed by optometrists.
  • Mean age of diagnosis is 22.88 years.
  • Visual outcome with RGP is better than PKP.
  • More prevalent in certain ethnic groups (4x higher in Asians from Indian sub-continent regions than White Europeans).
progression and prognosis
Progression and Prognosis
  • Age is a big factor.
  • The younger the diagnosis, the poorer the prognosis.
  • Less likely to progress to the point of a transplant if diagnosed in the 30’s.
  • 20% of Keratoconus patients result in corneal transplants.
  • 35 to 45% of all transplants are due to Keratoconus.
possible aggravating factors
Possible Aggravating Factors
  • UV exposure.
  • Allergies.
  • Vigorous eye rubbing.
  • Poorly fitting contact lenses.
  • Inflammation.
types of keratoconus
Types of Keratoconus
  • Nipple/Oval cone - central or mildly para-central localized thinning and steepening.
  • Keratoglobus - Large generalized thinning and steepening.
  • PMD (pellucid marginal degeneration) – peripheral thinning and steepening.
  • Keratoconus Fruste – Less progressive and less manipulative.
nipple oval cone
Nipple/Oval Cone
  • Central Steepening
  • Steepest form
keratoglobus
Keratoglobus
  • Wider – 75 to 90% of cornea.
  • Not as steep.
how to treat keratoconus
How to Treat Keratoconus
  • Spectacles
  • Contacts
    • Soft Standard
    • Soft Custom
    • RGP Standard
    • RGP Custom
    • Hybrid
  • Surgery
    • Intacs
    • Penetrating Keratoplasty
  • Riboflavin/UV treatment
when to intervene
When to Intervene?
  • Best Spectacle/Soft CL Acuity 20/30 or better?
    • Good tolerance of acuity.
    • Corneal health is not compromised.
    • “If it aint broke, don’t fix it.”
  • Best Spectacle/Soft CL Acuity worse than 20/30?
    • Specialized contact lenses.
    • My opinion, use RGP lenses.
which rgp design
Which RGP Design?
  • Early Keratoconus
    • Standard RGP
    • KC RGP
  • Mid-stage Keratoconus
    • KC RGP
    • Custom KC RGP
  • Advanced Keratoconus
    • Custom KC RGP
    • Intra-limbal or Scleral RGP
my go to lens rose k
My “GO TO” Lens – Rose K
  • Developed by Dr. Paul Rose.
  • Designed to fit the irregular cornea.
  • “Very forgiving lens”
  • Multiple designs to fit all shapes of corneas and corneal conditions.
  • Blanchard is very good to work with and has staff to assist with very difficult cases.
nipple oval cone fitting
Nipple/Oval Cone Fitting
  • Most common form of KC.
  • Early stages - simple RGP or KC RGP
  • Later stages – KC RGP usually small and steep.
  • The steeper the cone, the smaller the lens diameter.
rose k2
Rose K2
  • Rose K vs. Rose K2
  • 72% of patients notice an increase in acuity with aspheric, aberration control.
  • Lens to be centered on the cone.
  • Reduce excessive movement (1 to 2mm).
fitting the rose k2
Fitting the Rose K2
  • Too high – tighten edge lift

reduce OAD

steepen base curve

  • Too low – increase edge lift

increase OAD

flatten base curve

fitting the rose k21
Fitting the Rose K2
  • Centrally fitting the

lens on a nipple

cone better insures

optimal acuity and

comfort.

rose k2ic
Rose K2IC
  • IC stands for irregular cornea
  • Larger diameter
  • Larger optic zone
  • Aspheric for aberration control
  • Reverse geometry design
slide30

PMD

  • Keratoglobus
  • LASIK induced ectasia
  • Corneal transplants
slide31

Corneal Dystrophies

  • Traumatic Corneas with Scars
  • Post RK
  • Irregular Astigmatism or Corneal Warpage
fitting with act
Fitting with ACT

Using ACT ( Asymmetric Corneal Technology)

  • 3 standard grades available
  • Option also to specify degree of tuck in 0.1 steps from 0.4 to 1.5mm

Grade 3 (1.3mm steeper)

Grade 1 ( 0.7mm steeper)

Grade 2 (1.0mm steeper)

fitting with act1
Fitting with ACT

ACT - Improved comfort , lens stability and vision

NO ACT WITH ACT

fitting pearls
Fitting Pearls
  • Tendency to tighten after initial fitting.
  • Light central touch will increase acuity.
  • Avoid central staining.
  • Movement is necessary but slight movement is usually sufficient.
  • Pay attention to tear flow beneath lens.
  • The steeper the lens, the smaller OAD and less movement.
  • Don’t change too many parameters at once.
penetrating keratoplasty when to refer
Penetrating KeratoplastyWhen to refer?
  • Acuity is 20/50 or worse.
  • Patient intolerance to visual decrease.
  • Scars within the visual axis.
  • Multiple episodes of Hydrops.
  • Contact lens intolerance.
  • Unable to get adequate/healthy CL fit.
  • Consider OD to OD referral.
  • Give reasonable expectations.
post pkp management
Post PKP Management
  • How soon can you fit with lens?
  • Why are the curvatures so strange?
  • Do you have to wait for all sutures to be removed?
  • Corrective options.
    • Spectacles
    • RGP contact lenses.
    • LASIK
rose k2 post graft1
Rose K2 Post Graft
  • Much more difficult to fit than KC.
  • Patients are less tolerable to CL.
  • Eyes are more dry.
  • Ill-fitting contact lenses can lead to graft rejection.
  • Lens design is crucial to success.
k2pg fitting pearls
K2PG Fitting Pearls
  • Don’t be intimidated!
  • Watch tear flow!
  • Also good lens for ectasia patients.
  • Stay with your fitting basics
    • Fit base curves.
    • Adjust diameter.
    • Adjust peripheral curves.
    • Use ACT or Toric PC if needed.
the difficult ones
The Difficult Ones
  • Nothing is comfortable.
  • Acuity isn’t improving..
  • Eyes are too dry. (Sjogren’s Syndrome)
  • Cornea is too irregular for any lens to fit properly or in a healthy manner.
mini scleral design msd
Mini-Scleral Design - MSD
  • Large RGP
  • Vaults the cornea, rests on the sclera.
  • Creates a fluid filled environment.
  • Can be used to treat any corneal condition.
  • Can be used to treat other anterior segment conditions.
msd advantages
MSD - Advantages
  • Very Stable lens.
  • Fluid filled environment.
  • Improved comfort.
  • Good visual acuity.
msd fitting pearls
MSD – Fitting Pearls
  • Central Feather-touch.
  • Intra-limbal adjustment.
  • With or without fenestration or fenestrations.
  • Watch edge for tightening.
practice management issues
Practice Management Issues
  • Setting Fees.
  • Bill for services performed.
  • Insurances and fee collection.
  • Appropriate diagnostic and treatment equipment.
    • Topography/corneal mapping.
    • Pachymetry.
    • Fitting sets.
refractive surgery specific
Refractive Surgery Specific
  • Moderate – Large Diameter
    • (10.5 mm Standard Diameter, 9.5 mm to 12.0 mm).
  • Reverse Geometry Transition.
    • Post Surgical Central BC.
  • Curves
    • Paracentral Fitting Curves.
    • Asymmetric Corneal Technology (ACT).
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