Toric and Spherical Variations in RGP Contact Lenses - What's the Difference?




We recently had a very interesting case with a patient with a very high prescription who was wearing RGP (rigid gas permeable) lenses.

The lens on the right of the image (spherical back) was the patient's original lens from a prestigious eye hospital. They were comfortable in this lens, with the only complaint being that they had to wear reading glasses at age 38.


This patient has 5.0 Diopters of astigmatism on their cornea, which means that their cornea has two different shapes. The spherical lens they were wearing has one shape on the back which is why you can see a big band of green vertically.

Even though the patient was happy with the fit of their original lens, Dr. Morrison thought that a two-design back surface lens could give them an even BETTER fit and more comfort, so she designed a toric back surface GP (gas permeable) lens.


She also added in more PLUS prescription to get rid of their need for reading glasses (a common complaint for young farsighted patients).

Our patient is THRILLED with the updated toric back lenses (shown on the left in the image above). They report better comfort and improved vision - they went from 20/30 to 20/25 with the new lenses, and now they no longer need to use readers!

While there is no “right” way to design lenses, there are times when a lot of background knowledge of anatomy and lens design can help make good lenses even better, which we love for our patients.


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