Prescribing for Astigmatism

Internet Resources for You and Your Patients

prescribing for astigmatism
Internet Resources for You and Your Patients

The Internet can be a wonderful source of information for practitioners as well as for patients. We've found the following Web sites to be most useful and easy to maneuver.

Cross-Cylinder Sites

Several sites let you enter soft toric trial lens over-refraction data to obtain a suggested sphere, cylinder and axis correction using resultant cross-cylinder calculations. and are two that provide this useful tool. However CooperVision's program doesn't consider lens rotation in their calculations. (To access CooperVision's site without registering, go to

The Palm Pilot savvy can also download handheld versions of these calculators. offers a downloadable link to CooperVision's version. From you can purchase and download the Contact Lens Calculator+, which contains eight handy contact lens and refractive calculators.

Parameter Availability

Most contact lens practitioners keep a current copy of Tyler's Quarterly or the Contact Lenses & Solutions Summary (an annual supplement to Contact Lens Spectrum, also available online at nearby to determine if a needed lens power or axis is available. As proactive prescribers of silicone hydrogel lenses, we often need quick access to current parameter and design availability. If you don't subscribe to these guides, you can find this information quickly and easily online at One feature we especially enjoy is its listing of anticipated extended parameter options and approximately when they'll become available.

Bitoric Helpers

The Mandell-Moore guide can assist practitioners in designing bitoric GP lenses using kerato- metry readings (or simulated K readings) and the manifest refraction. This guide is available online at also offers a helpful online tutorial to accompany the Mandell-Moore guide.

Patient Education

Patients diagnosed with irregular astigmatism or other rare conditions such as keratoconus often desire additional sources of information about their conditions. Many sites sell procedures or products, but excellent sites exist that provide unbiased patient education and support. The National Keratoconus Foundation ( allows patients to download information on keratoconus and penetrating keratoplasty. It also lists patient resources and provides a forum for patients and their family members to ask questions. Other sites for keratoconus patients include, and

Practitioner Education

Several sites offer article and photograph archiving. archives (by subject, author and publication month) past and present articles and columns., and are excellent sources for downloading photographs of corneal conditions. Current research about silicone hydrogels is available at, and offers fluorescein patterns and GP lens fitting tips.

We know that this is just a small portion of sites relative to contact lenses available on the World Wide Web. If you have a favorite site that you'd like to share with our readers, please e-mail your suggestions and a brief description of the site's contents to Selected sites may be published in a future issue.

Dr. Edrington is a professor at the Southern California College of Optometry. E-mail him at Dr. Tran is a clinical instructor at the Southern California College of Optometry. E-mail him at