prescribing for astigmatism

My Top Five List for Toric Hydrogel Lenses
BY JOHN MARK JACKSON, OD, MS, FAAO

The other day yet another patient told me that she wished she could see better with her contact lenses. Alas, she had astigmatism, and several eyecare practitioners had told her that the vision through with her spherical hydrogel lenses was the best she was going to get. No one had offered her toric hydrogels (or GPs for that matter) to correct her astigmatism.

Her spectacle Rx was –3.00 –1.25 x180 OD and –2.75 –1.00 x175 OS. Acuity with her soft spheres was 20/30 OD and 20/25 OS. It's difficult to imagine a patient whom you could more easily satisfy with toric hydrogels, yet this scenario happens all the time with patients who are new to me. Why do some practitioners resist fitting toric hydrogels and worse, tell patients they have no other option besides spherical lenses?

Why Toric Hydrogels?

At the risk of preaching to the choir, let me offer my top five list of what I think are great about modern toric hydrogels that may persuade you to take the plunge.

Number 5: Acronyms. Our profession uses many acronyms, but my favorite is LARS (left-add, right-subtract). Of course, we use LARS to adjust the cylinder axis to compensate for any lens rotation on the eye.

And if LARS doesn't work for you, then you can use SCOR (spherocylinder over-refraction) and a cross-cylinder calculator to determine your final prescription.

Number 4: Minimal Rotation. Inconsistent lens rotation has always been the trouble with torics (hence Number 5), but the newest lens designs are very stable. I find most lenses consistently rotate very little so that I have to compensate for lens rotation less and less.

Number 3: Plenty of Oxygen. Prism ballasting of torics makes the bottom of the lens thicker than the top. This results in less oxygen reaching the bottom of the cornea than elsewhere, increasing the risk of neovascularization inferiorly.

The introduction of silicone hydrogels in toric designs has minimized the risk of inferior corneal neovascularization, resulting in eyes that are whiter and more comfortable.

Number 2: Frequent Replacement. Long gone are the days of conventional replacement for most torics. Even in high-power prescriptions, quarterly replacement is affordable; for common prescriptions, the norm is now two-week replacement. Daily disposables are also available. In short, we can offer our astigmatic patients healthy lens wear with clean, fresh lenses just as we can for our spherical patients.

Number 1: Great Vision. Patients come to us because they want to see well. If you aren't correcting their astigmatism, they aren't seeing as well as they could and you aren't providing optimal care. We fit our new patient described earlier in a two-week replacement silicone hydrogel toric lens design. Her acuity improved to 20/15 in each eye. She was quite pleased with the increased sharpness in her vision. She was also quite indignant that no one had offered them to her before.

Try it!

Lens fitting has never been easier with modern toric hydrogels, and lens choices are almost limitless. If you aren't prescribing them as often as you should, make the effort to start using them on a more consistent basis. Better vision is within your patients' reach.

Dr. Jackson is an assistant professor at Southern College of Optometry where he works in the Advanced Contact Lens Service, teaches courses in contact lenses and performs clinical research.