Consultant's Corner
Fitting a new Keratoconus or Astigmatic patient
by Kelly Indovina, OD
Director of Professional Relations
Keratoconus or irregular astigmatism can be challenging to fit, especially if you have never seen the patient before. The best place to start is almost always with the patient’s current lens specifications. If you have the advantage of knowing what the patient is currently wearing, but the patient doesn’t have the lenses for whatever reason, it is recommended to evaluate the current lens specifications on the patient, especially if the lenses are just old or lost. In other words, order what you have and go from there. It is not as accurate or as efficient to start over and order empirically by taking new keratometry readings and a new prescription. In these situations, it’s best to follow the “If it isn’t broke, don’t fix it” philosophy. If the patient is wearing their old lenses and you are able to evaluate the fit and power and can verify the parameters, you can make changes accordingly.
If you don’t have the advantage of knowing the patient’s current lens specifications, but you are able to take keratometry readings, Art Optical can send you a fitting set in the correct dioptric range for your patient. We have three sets available; the flattest is an Envision set which is appropriate for base curve range of 8.30(40.62) to 7.00(48.25) with a 9.6 to 9.3 diameter. Our standard AKS keratoconus fitting set has a base curve range of 7.20(46.75) to 6.00(56.25) with an 8.50 diameter. Our extended range AKS fitting set has a base curve range of 6.20(54.37) to 5.00(67.50). If you are not able to take keratometry readings, you can put a +1.25 trial lens on the patient’s side of the keratometer and reference the conversion chart provided with the fitting set.
If you can provide corneal topography, please make sure the map is set to present the data as an axial map with a normalized scale and provide a separate scale for each eye. We have found this to be most helpful for contact lens fitting. You can either use the “yellow rule”, which is choosing the dioptric value of the yellow band as your starting base curve and choosing the diameter based on the size and location of the k-cone or irregularity; or you can send the map to our Consultation department and we will be happy to assist in designing a lens for you.
Email your topographies to us at topo@artoptical.com, or if you have a color fax machine, fax them to 800-421-5991.
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