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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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Marc l braithwaite od vision care of maine

Marc L. Braithwaite, OD

Vision Care of Maine

KeratoconusAndspecialty contact lens fitting of irregular corneas


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.


Pellucid marginal degeneration
Pellucid Marginal Degeneration

  • Peripheral Thinning



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


  • PMD

  • Keratoglobus

  • LASIK induced ectasia

  • Corneal transplants


  • 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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