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Contact Lens Spectrum

Article

CONTACT LENS CASE REPORTS

MODERN HYPEROPIC ORTHOKERATOLOGY

Contact Lens Spectrum August 1, 2018 Vol 33, Issue August 2018 Page(s): 52
PATRICK J. CAROLINE & MARK P. ANDRÉ

Our patient was a 49-year-old female who had a history of intolerance to soft contact lenses due to ocular dryness. She is an emmetrope with a distance correction of plano sphere in both eyes and was wearing a +2.00D soft lens on her left eye for monovision correction of her presbyopia. She had adjusted well to the optics of a +2.00D monovision correction; however, her wearing time was limited to four hours a day. After trying numerous soft contact lenses, we began the discussion of hyperopic orthokeratology (ortho-k) for the near correction of her left eye.

Hyperopic ortho-k has been available for many years, yet its usage in clinical practice has been limited. The primary goal of the technique is to create apical clearance and a ring of epithelial compression at a chord of 5.0mm. The midperipheral compression creates a steeper radius of curvature at the apex of the cornea, resulting in increased minus power. The blue compression ring can be easily seen with the tangential display of the corneal topographer (Figure 1).

Figure 1. The tangential map of a corneal topographer best shows the ring of epithelial compression at a chord of 5.0mm for hyperopic ortho-k.
Figure 1. The tangential map of a corneal topographer best shows the ring of epithelial compression at a chord of 5.0mm for hyperopic ortho-k.

Steps to Successful Fits

At Pacific University, we have developed a step-by-step fitting technique for hyperopic ortho-k using ortho-k design software:

Figure 2. The base curve eccentricity required to create the epithelial compression at 5.0mm.
Figure 2. The base curve eccentricity required to create the epithelial compression at 5.0mm.
Figure 3. The base curve apical clearances required to create +1.00D, +2.00D, and +3.00D corrections.
Figure 3. The base curve apical clearances required to create +1.00D, +2.00D, and +3.00D corrections.
  1. Measure the horizontal visible iris diameter (HVID) and design the lens with a diameter 0.8mm smaller than the HVID. For example, if the HVID is 11.8mm, the overall lens diameter should be 11.0mm.
  2. Select an aspheric base curve radius (Figure 2).
  3. Select a base curve radius that will provide the desired apical clearance (Figure 3).
  4. Select an alignment curve radius 1.00D (0.20mm) flatter than the flat K.
  5. Finally, connect the aspheric base curve to the alignment curve with a reverse curve.

Figure 4 shows the parameters of the final lens design to create a +2.00D apical power.

Figure 4. The final lens parameters to create a hyperopic orthokeratology lens.
Figure 4. The final lens parameters to create a hyperopic orthokeratology lens.

Our patient was dispensed the hyperopic ortho-k lens design (left eye only) for overnight lens wear with daily disinfection using a hydrogen peroxide system. Today, the patient enjoys comfortable overnight lens wear and, following lens removal in the morning, excellent aspheric monovision throughout the entire day. CLS

Patrick Caroline is an associate professor of optometry at Pacific University.

Mark André is an associate professor of optometry at Pacific University. He is also a consultant to CooperVision

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