Layout 1
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.
John Patterson
Marietta
Vision, Marietta, GA
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Contact Lens Spectrum, Issue: February 2007