Lens Dynamics, Inc.

These patients present with corneas that are flattened centrally in a 6-8mm zone. It is best to think of this fitting challenge as fitting two distinct areas - the flatter ablated zone and the original host cornea.

Starting Trial Lens

Topography Fitting: Take the central K's and a reading at the 4mm temporal area.

Manual Keratometer Fitting: Take central K's and then get temporal measurements or use pre-surgery K readings.

The base curve of the Special Reverse Geometry lens will be 1 diopter steeper than the flat central K. To determine the amount of reverse curve needed, calculate the difference between the base curve and the 4mm temporal measure i.e. central K's of 40.00/42.00 and 4mm temporal K of 44.00. Select a trial lens of 41.00 with 3 diopters or the Series B lens.

Flat K = 40.00

One D steeper than flat central K of 40.00D + 1 = 41.00D

Base curve is 41.00D

Difference between base curve of 41.00D and temporal K of 44.00 = 3D

Try a series B Special Reverse Geometry lens that has a 3D reverse curve.

Desired Fluoroscein Pattern

An alignment pattern is the ultimate goal, but that is difficult to achieve. Get as close to alignment pattern as possible. You want to see minimal vaulting in the central region. The lens is made from Menicon Z® material for good oxygen transmission and good wetting so metabolic wastes are washed away.

In our example, if the mid-peripheral area is pinched off, you need less reverse curve so go to a Series A. This increases the lift. If the mid-peripheral area is showing pooling, you need more reverse curves so go to a Series C. This decreases the lift.

Last Updated 5/7/2008