Marc L. Braithwaite, OD
Vision Care of Maine
Keratoconus

What have the years taught us?
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

Loss of Bowman’s Layer.

Stromal Thinning.

Apoptosis.

Increased Enzyme Activity.

Enlarged Prominent Corneal Nerves.
Causes of Keratoconus

Heredity vs. Mechanical

Cellular

Tissue

Genetic
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
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

Loss of Bowman’s layer.

Lamellar slippage.

Lack “anchoring” lamellar fibrils.

Apoptosis of the stroma causing anterior
thinning.
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
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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
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

UV exposure.

Allergies.

Vigorous eye rubbing.

Poorly fitting contact lenses.

Inflammation.
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
Central Steepening
 Steepest form

Keratoglobus
Wider – 75 to 90% of cornea.
 Not as steep.

Pellucid Marginal Degeneration

Peripheral Thinning
Orbscan Analysis
How to Treat Keratoconus

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Spectacles
Contacts
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Soft Standard
Soft Custom
RGP Standard
RGP Custom
Hybrid
Surgery
 Intacs
 Penetrating Keratoplasty

Riboflavin/UV treatment
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?

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
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
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 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

Too high – tighten edge lift
reduce OAD
steepen base curve

Too low – increase edge lift
increase OAD
flatten base curve
Fitting the Rose K2

Centrally fitting the
lens on a nipple
cone better insures
optimal acuity and
comfort.
Rose K2IC
IC stands for irregular cornea
 Larger diameter
 Larger optic zone
 Aspheric for aberration control
 Reverse geometry design

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PMD

Keratoglobus

LASIK induced ectasia

Corneal transplants

Corneal Dystrophies

Traumatic Corneas with Scars

Post RK

Irregular Astigmatism or Corneal
Warpage
What is That?
Asymmetric Corneal Technology

ACT.
ACT – Continued…
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 ACT
ACT - Improved comfort , lens stability and vision
NO ACT
WITH ACT
Toric Peripheral Curves
Fitting Pearls
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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?

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
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 Graft
PKP Topography
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
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.
Post Graft – Too Steep
Post Graft – Too Flat
Post Graft – Good Fit
Watch Vasculature
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.
What Do You Do?
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

Very Stable lens.

Fluid filled environment.

Improved comfort.

Good visual acuity.
Mini-Scleral Design
MSD – Fitting Pearls

Central Feather-touch.

Intra-limbal adjustment.

With or without
fenestration or
fenestrations.

Watch edge for
tightening.
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

Moderate – Large Diameter
 (10.5 mm Standard Diameter, 9.5 mm to
12.0 mm).

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Reverse Geometry Transition.
Post Surgical Central BC.
Curves
• Paracentral Fitting Curves.
• Asymmetric Corneal Technology
(ACT).
Thank You!