GP lens eye Rounds

HIGH ASTIGMATISM: Empirical Mandell-Moore

Will Skoog OD, FAAO

History

• 43 year-old Hispanic female.
• Interested in returning to GP contact lens wear. She stopped wearing contact lenses five years ago.

Clinical Data

• VA: 20/30 OD and OS
• MR: -10.25 -5.50 x 005 OD -10.25 -5.50 x 172 OS
• Ks: 41.6@180; 45.6 @ 090 OD: 42.25 @ 168; 45.50 @ 78 OS (Figures 1 and 2)
• Bitoric Lens Parameters:
  • OD: Powers: -9.00/-12.50D, BCR: 8.16/7.53mm, OAD: 9.60mm, Material: Optimum Extra (Contamac)
  • OS: Powers: -9.00/-12.50D, BCR: 8.04/7.54mm, OAD: 9.60mm, Material: Optimum Extra (Contamac)

Decision-Making Process

• Previous GP lens wearer
  • Do not switch to soft lenses.
• Hybrid lenses would have excessive residual astigmatism leading to poor VA
• Corneal cylinder ≥ 2.50D back or bitoric GP lens is recommended.
  • As refractive cylinder is not 1.5 times the corneal cylinder a bitoric design is needed.
• The Mandell-Moore Guide fitting method was used to empirically design the lenses.

Fitting and Evaluation

• Empirically fit using Mandell-Moore Guide method. (Appendix 1 and 2)

• When fit correctly, bitorics should have the same fluorescein pattern as a well fit spherical GP lens.
• The fluorescein pattern showed central alignment, mid-peripheral bearing, and adequate edge lift. It was a modified lid attached fit with 1mm of movement.

Clinical Pearls

1. A back toric or bitoric lens is needed if corneal cylinder is ≥ 2.50D
2. Mandell-Moore (MM) method is a straightforward, quick method to empirically design a bitoric GP.

Figure 1: Four maps refractive showing axial topography and elevation profile (front and back surface) for OD.

Figure 2: Four maps refractive showing axial topography and elevation profile (front and back surface) for O2.