GP Correction of Keratoconus

With Mr. Mike Ward and Dr. Ann Laurenzi

Links to Case Studies:

• Case 1

Case 1

By: Mr. Mike Ward

Historical Piggyback Lens Use

• Piggyback lens fitting is not new
• It has been used with varied success for decades
• Hypoxia was the most common complication limiting its use
• Often used as a last resort effort to delay corneal surgery

Indications for Tandem SCL/GP Lens Fitting

• First time GP lens wear
  • as a temporary crutch
• Previous GP or Hybrid lens failure
• Irregular surface
  • Apical nodule
  • KC-like post surgical ectasia
  • Epithelial basement membrane dystrophy

• Piggyback lens fitting has greatly increased in recent years.
• This is largely due to technological advances with high gas exchange silicone hydrogel and GP lens materials

Purpose

• A soft lens material is used
  • as a protective membrane over the cornea
  • Minimize FBS
  • Provide shape support to anterior ocular surface
  • Provide partial visual correction with SCL alone

Two Basic Methods of Piggyback Lens Fitting

1. Design GP to fit cornea, then dispense with SCL under GP
2. Place SCL on cornea, then fit GP to align with anterior SCL surface

Method 1 - Fit GP to Cornea

• Fit standard or custom KC designs per normal
• Choose SCL base lens to use at dispense

Method 2 - Fit GP to SCL

• Fit SCL on cornea
  • use Si-H materials when possible
• Measure keratometry over SCL
• Fit GP to SCL anterior surface
  • select initial BC on flat K
  • use fluorescein to check pattern

Rigid Lens Options

• Menicon Z (Dk=189)
  • Very High Dk
  • 30d CW approval
• Boston XO (Dk=100), Fluoroperm 92 (Dk=92), Optimum Extreme (Dk=125)
  • More machineable for custom designs

Tandem system

• Focus Night & Day base lens
• Rose K top lens

Tandem Acuvue Oasys as baseBoston BXO Soper Design as top

Keratoconus Fitting - Complications & Pitfalls

Apical Touch - Apical touch versus apical bearing

The most common error in keratoconus management is fitting lenses too tightly.

Corneal indentation noted following GP lens removal
  
Indentation - No contact lens on eye

Apical Nodule

Keratoconus apical nodule - topography

CRAR

The key to successful keratoconus management is choosing the appropriate form of visual correction for the individual patient.

Links to Case Studies:

• Go to Case 1
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