GP lens eye Rounds

HIGH ASTIGMATISMCASE: Empirical Mandell-Moore

Will Skoog OD, FAAO

A 43-year-old Hispanic female presented with interest in returning to GP contact lens wear. She stopped wearing contact lenses five years ago.

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The patient’s entering visual acuities were 20/30 OD and OS.
Her manifest refraction was -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)

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.

The patient was a previous GP lens wearer so we did not switch her to soft lenses.
Hybrid lenses would have excessive residual astigmatism leading to poor VA
The patient’s corneal cylinder was ≥ 2.50D so a back or bitoric GP lens was recommended.
- As the refractive cylinder was not 1.5 times the corneal cylinder a bitoric GP design was needed.
The Mandell-Moore Guide fitting method was used to empirically design the lenses.

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The patient was empirically fit using the Mandell-Moore Guide fitting (Appendices 1 and 2)

Power(D)

Base Curve (mm)

Diameter(mm)

Material

-9.00/-12.50

8.16/7.53

9.60

Optimum extra

-9.00/-12.50

8.04/7.54

9.60

Optimum extra

When fit correctly, bitoric GP lenses should have the same fluorescein pattern as a well-fitted 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.

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