Contact Lens Business
Faster Fits for Astigmatic Patients
Try this system for speeding up your lens choices.

If your practice is like ours, most of your patients have some degree of astigmatism, and many of them want to wear contact lenses. Here, I'll outline a system that helps me quickly determine which type of lenses are likely to be best for each of my astigmatic patients.

DIVIDE AND CONQUER

The basis of the system is separating patients into four categories, depending on the amount of astigmatism:

• No astigmatism. About 18% of our patients with a refractive error have a spherical correction. Spherical soft contact lenses are fine for these patients.
• Between 0.25 and 0.50 diopters of astigmatism. About 41% of our prospective contact lens-wearing patients fall in this group. This is a relatively minor visual problem, and spherical lenses are less expensive than other options, so most of these patients should be fitted with a spherical soft lens.
  If a patient in this group is especially demanding about visual acuity, try a spherical aberration blocking lens. The aspheric front surface focuses more light rays at a common focal point than a regular spherical lens.
  This often results in improved vision for patients with low levels of astigmatism. (Two spherical aberration blocking lenses are commercially available: the Frequency 55 Aspheric from CooperVision and the Choice AB from Specialty Ultravision.)
• Between 0.75 and 2.50 diopters of astigmatism. These patients should be fitted with either a rigid gas permeable (RGP) lens or a toric soft lens. (I spend more time with these patients to make sure we find the best option.)
  In this category, it's important to consider the location of the astigmatism:
  • Most patients with 0.75 to 2.50 diopters of astigmatism have with-the-rule astigmatism. This makes them ideal candidates for either spherical RGPs or toric soft lenses. (Consider recreational activities and wearing schedule.)
  • If the patient has against-the-rule astigmatism, I generally prescribe toric soft lenses. The topography of the cornea (with the steep axis along the horizontal meridian) can be more challenging to manage with RGPs.
    I recommend soft toric planned replacement lenses. (Every major soft lens manufacturer in the United States now offers a 2-week toric lens.) We keep a fairly comprehensive inventory of these lenses in our clinic so that we can fit and dispense them during the patient's initial visit.
• More than 2.50 diopters of astigmatism. These patients usually need a bitoric rigid lens design or a custom soft toric lens design.
  Most custom soft lenses are fitted empirically. We provide the manufacturer with the patient's corneal measurements and refractive error. If the initial lens doesn't provide acceptable acuity, perform an over-refraction and order a second lens with the resulting power. (Most manufacturers allow exchanges for about 90 days after the initial order.)
  Although you might expect some of these prescriptions to be difficult to fit, we've found that empirical fitting actually makes them easy. Our results have been good. We did a 2-year retrospective study on 452 eyes we fitted with toric soft lenses using this method. Ninety-three percent of the patients continued to wear the lenses for at least 6 months.
  Some of the soft lens manufacturers provide a multipack of lenses after the initial fitting so that even patients with high degrees of astigmatism can replace their lenses quarterly. This gives all of our patients the opportunity to take advantage of a planned replacement program, which we believe is safer than conventional contact lens wear.

MORE OPTIONS, HAPPIER PATIENTS

Thanks to continuing advances in technology, contact lenses have become an excellent alternative for your astigmatic patients. And if you use a system like the one described above, fitting these patients can be efficient and effective. 

Mark Andre, F.A.A.O., is director of contact lens services at Casey Eye Institute in Portland, Ore.