BE Free vs MoonLens

One of the primary questions that our team receives is about the difference between our two newest ortho k designs, the BE Free vs MoonLens. The second half of the question is often, “and which lens design is better?” Though neither lens is inherently better than the other, there are some key differences that suit different patients and/or practices better. Let’s take a look at some of the differences and similarities.

Similarities

The two lens designs are similar in many ways. In terms of diameter, both adjust to be bigger or smaller depending on a patient’s corneal diameter. This ensures that either lens design lands on the appropriate area of the peripheral cornea to optimize lens centration. Another key factor for lens centration is the ability of both lenses to be manufactured with a toric back surface. Better alignment to both the flat and steep meridians of the cornea means a better seal 360 degrees. The inability to adjust diameter and back surface toricity can make it difficult to achieve the desired treatment effect.

The optic zone of each lens design is similar as well. Both lens designs take advantage of OTZ® (Optimized Treatment Zone) technology. By using an OTZ® lens the optic zone size can be reduced from the standard 6.0 mm down to either a 5.5 mm or 5.0 mm. A smaller optical zone becomes important when evaluating a lens design for myopia management efficacy in children and young adults. Studies suggest smaller optical zone designs can slow eye growth more compared to conventional 6.0 mm optical zone. Either lens could be selected for myopia management.

One thing to note, not all smaller optical zone ortho k lenses are equivalent. The BE Free and MoonLens account for the overall lens depth changes that occur when optical zone size changes. This adjustment ensures a consistent lens fit and treatment effect. If compensating adjustments are not made to the lens when there is a reduction in optical zone size, the resulting treatment zone effect may be different from our expectations.

Differences

The area of the lens that differs the most between designs is in the alignment zone. In the BE Free design, the alignment zone employs an aspheric curve based on the patient’s corneal eccentricity. By creating the alignment zone this way, practitioners are able to match the alignment curve shape with that of the aspheric peripheral cornea. A consistent 360 degree alignment is critical for creating the seal necessary for the hydraulic forces of ortho to take effect. Quality information about the peripheral corneal shape is paramount with the Be Free design.

Designing a lens using accurate corneal shape data, like that captured with the Medmont meridia corneal topographer, ensures we can design a precise, highly customize alignment zone for each patient. Studies have shown BE Free lenses designed from quality Medmont topographies achieved a 95% first fit success rate.

In the MoonLens, the alignment zone is a tangent or straight line. The MoonLens uses a tangent landing to control centration by creating negative hydraulic force on either side of the point of alignment. Quality corneal data is still extremely valuable when fitting the MoonLens to ensure 360 alignment, just like the BE Free. In some eyes, tangent alignment zones result in better centration of the lens than an aspheric alignment would offer.

So which lens is right for me? BE Free or MoonLens?

Depending on the equipment you have, the clinic style, and personal preference, either lens may be a better fit. If you have a topographer that integrates with the KATT Cloud system like the Medmont meridia, then all you need to do is capture quality topographies and leave the rest up to us. If you prefer to see exactly what’s happening to each zone of lens when changes are made, the MoonLens system with its easy-to-use calculator would be a good fit. In many cases, eye care providers use both lens designs in their practice depending on the patient. For them, it is not BE Free vs MoonLens, it is BE Free AND MoonLens.

Offering both lens designs to your patients gives you more choice as well as communicates to your patients that you’re more than a one trick pony. If you’d like more information on the BE Free or MoonLens design, please contact consulation@ptsoptics.com