letters to the editor
Fitting the BE Retainer
In the October article "A Successful Combination for Ortho-K," Deepa Chandrasekaran, OD, MS, may lead readers to believe that fitting the BE Retainer is straightforward and simple for practitioners new to ortho-k. I believe that inherent knowledge of topography as well as fluency in navigating the BE Software are necessary prerequisites to successful outcomes.
I would like to stress the importance of using Medmont topography for success with fitting the BE Retainer version of VST (Bausch & Lomb). The Medmont E300 Corneal topographer measures apical radius (Ro), sagittal height and HVID with great accuracy. You must enter this data into the BE Software to generate the recommended BE diagnostic lens base curve and, ultimately, to generate the final custom order. You can manipulate data within the software in several ways to achieve the desired trial and final custom lenses.
If using a topographer other than Medmont, you must use eccentricity values in place of sagittal height. This requires advanced navigation of the BE Software and diminishes the level of accuracy in calculating the custom order.
Certification in both the VST program and the BE Retainer lens design are required. A comprehensive online course is available at BERetainer.com, which offers detailed instruction on pre- and post-fitting topographic analysis. Interpretation of this data is critical to successful trial and custom lenses. Not all diagnostic lenses result in a bull's eye pattern, and you must be able to interpret the problem and to determine the next step. The BE system doesn't factor in lid tension or location of corneal apex, which can create difficulty with centration.
Expert consultation is available through Precision Technology Services, the North American distributor of Medmont and BE Retainer. Practitioners submitting topographic images other than Medmont may offer limited data for troubleshooting less-than-perfect outcomes.
Time saved by not having to evaluate fluorescein patterns of BE lenses on eye is spent evaluating topography images pre-and post-fitting and manipulating BE Software. This, I believe, is time well spent in developing inherent knowledge of topography and reverse geometry lens dynamics.
Dianne Anderson, OD, Aurora, IL
Dr. Chandrasekaran's Response
I wish to thank Dr. Anderson for her interest in this article. My intention was to let new practitioners know that fitting BE lenses with the help of the software is fairly straightforward. Just like any other software, familiarity and experience is essential to be successful. I don't mean to say that the BE Retainer lens works on every patient, but I did want to share my experiences with it.
I trialed the patients from my article based on accurate topography data. I entered this data into the fitting software, achieved a bull's eye pattern, responded with bull's eye pattern to the software with the measured Rx change and then calculated the custom lens, and this produced a good response. That's the way this system was designed to work. When I needed support, I contacted the consultant and got the assistance I needed.
The BE lens was designed to simplify orthokeratology. It relies heavily on fitting software rather than on practitioner experience with orthokeratology, reverse geometry or GP lenses. It also relies heavily on topography, which is objective, rather than on NaFl evaluation.
I believe the Humphrey topographer is fine to use with BE. It's accurate and provides the necessary data. Both are critical requirements for success. With the BE software, each screen asks the user to respond with the information that is readily available. It's a step-by-step process and very easy, especially if you have walked through the training course. As Dr. Anderson rightly pointed out, a comprehensive training course is available on the Web site as are consultants to support new orthokeratologists.
I disagree that using eccentricity diminishes the accuracy. Sag, E (eccentricity), P (shape factor) and asphericity values all describe the same thing: rate of corneal flattening. You can derive the same end point from any of these mathematical descriptors of the cornea. So using E does not diminish accuracy it's the same as entering the sag, and it will be converted to sag by the BE software.
Dr. Chandrasekaran acknowledges Mr. Randy Kojima of BE for his help with the patients mentioned in the article and for helping prepare this response to Dr. Anderson's letter.
Cosmetic Lenses Are Safe
My name is John Patterson and I own Marietta Vision. Among other things, Marietta Vision offers FDA-approved prosthetic and theatrical contact lenses to eyecare professionals not to the general public.
I hope that you don't lump all cosmetic and theatrical lenses into one group evil. There are safe and professional channels through which patients along with the involvement of an eyecare professional can obtain these lenses, such as through Jack Carter at FX Eyes and Stan Harper at Adventures in Color Technology as well as through Marietta Vision.
Marietta Vision, Marietta, GA
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