Contact Lens Case Reports
Soft Custom Lens Succeeds Over Time for Keratoconus Patient
By Patrick J. Caroline, FAAO, & Mark P. André, FAAO
Today, a number of custom contact lens laboratories manufacture soft contact lenses for keratoconus. One of these lenses is Hydrokone by Visionary Optics. Our patient is a 33-year-old male whom we fitted with Hydrokone lenses in 2007. The lens incorporates a dual base curve design, with a steeper central radius to accommodate the ectasia and a flatter peripheral radius to align with the more normal peripheral cornea and sclera.
The original lens specifications were OD 7.85mm/8.60mm base curves, −6.50D power, 14.8mm diameter, 20/20 and OS 7.60mm/8.60mm base curves, −7.25D power, 14.8mm diameter, 20/30.
Figure 1. Difference display map of the patient’s right eye without (top left) and with (lower left) the custom soft contact lens.
Figure 2. Difference display map of the patient’s left eye without (top left) and with (lower left) the custom soft contact lens.
The difference display maps (Figures 1 and 2) demonstrate how much of the patient’s irregular corneal astigmatism is neutralized by the thickness of the soft contact lenses (Figure 3).
Determining Initial Parameters
In 2007, we selected the initial base curve radii using a three-step technique that we developed at Pacific University and continue to use today:
Step 1. Determine “mean K.” For our patient: 47.50 / 51.00, mean K is 49.25D.
Step 2. Convert dioptric power to millimeters. For our patient: 49.25D = 6.85mm.
Step 3. Add 1.0mm to mean K. For our patient: 6.85mm + 1.00mm = 7.85mm.
Step 1. Determine mean K. For our patient: 50.37 / 52.12, mean K is 51.25D.
Step 2. Convert dioptric power to millimeters. For our patient: 51.25D = 6.60mm.
Step 3. Add 1.0mm to mean K. For our patient: 6.60mm + 1.00mm = 7.60mm.
Five years later, the patient continues to be extremely successful with his custom soft contact lenses (Figure 4). His visual acuities and lens powers have remained unchanged, and his corneas are free of corneal edema and neovascularization. This case, again, illustrates how long-term success can be achieved in some patients wearing custom soft lenses for keratoconus. CLS
Figure 3. Central and peripheral OCT images of the patient’s right contact lens.
Figure 4. On-eye image of the patient’s custom soft contact lenses.
Patrick Caroline is an associate professor of optometry at Pacific University. He is also a consultant to Paragon Vision Sciences. Mark André is an associate professor of optometry at Pacific University. He is also a consultant for CooperVision.