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OrthoK lens Architecture. What parameters does an Optometrist need to check? | OOLS |

Updated: Sep 30, 2020

Dr. Nitesh Barot, helps us understand the Ortho-K lens design parameters and how these parameters can be changed to achieve the ideal fit on the eye. He also introduces an innovative software ‘RGP Designer,’ which can potentially be used to fit ortho-K lenses virtually. The following Ortho-K lens parameters are explained with a focus on how each parameter will affect the fit:

1. Alignment/Fitting curve

2. Base curve

3. Reserve Curve

4. Peripheral curve

5. Jessen Factor and its considerations for myopia control

6. Horizontal Visible Iris Diameter (HVID)

7. E value

Dr. Barot describes the eccentricity value and the critical role it plays in the final lens parameters. He explains with schematics the ideal, steep, and flat fit along with their implications on the eye. He explains the different design philosophies, like using the diagnostic trial set, empirical fit, and a software lens design. He simplifies the RGP Designer, talks about its features, and demonstrates how this software can be used to create a custom design on your computer. He shows how the software generates a tear profile, fluorescein pattern, lens forces, and lens design. He concludes with a discussion on the changes needed for a myopia control Ortho-K lens, which is followed by an interactive Q and A session with students and expert practitioners.

Resources :

RGP Designer Software:

Textbooks for references Orthokeratology: Principles and Practice - By David Ruston, John

Mountford and Trusit Dave :

Contemporary Orthokeratology - By Michael J. Lipson (Free full pdf):

Orthokeratology Practice A Basic Guide for Practitioners:

Watch the complete session below:

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