Staying in “CONTACT” with Advanced AR Lenses

By Renato Cappuccitti
When discussing and handling advanced AR lenses it’s all about CONTACT. One specific improvement in AR lens technology responsible for the current surge in AR is the development of oleophobic (resists oils) surface treatments. Oleophobic AR coatings are slippery and make it difficult for skin oils, dirt and grime to adhere to the lenses while making cleaning a cinch. Great news for the wearer! Resistance to water (hydrophobic) and oil is measured by the CONTACT angle of a surface. Contact angle increases with the ability of a liquid drop to hold its spherical shape. Similar to how raindrops bead on a freshly waxed car. In common GOOD, BETTER, BEST positioning AR lenses can be grouped accordingly:

Position/AR surface/Description/Contact Angle

GOOD Standard AR • Poor water resistance <95 degrees • No oil resistance

BETTER Hydrophobic AR • Good water resistance 95 to 105 degrees • Some oil resistance

BEST Oleophobic AR • Excellent water resistance >105 degrees • Good oil resistance

Oleophobic AR lenses are well liked by consumers and practitioners, however this same affinity isn’t shared amongst many laboratory technicians. Standard leap pads used for edging do not hold the lens with enough force to prevent slipping during edging. These axis errors can be quite costly, especially when you consider progressives, bifocals and drill mount lenses that are much less forgiving to even minor axis shifts. An ECP that loses a patient on account of poorly edged lenses will eventually become a lost customer if this is a reoccurring problem. Most edger manufacturers have special settings to reduce RPM force during edging that in turn decreases the amount of torque created. Consult with the manufacturer for recommendations on what settings are best suited for oleophobic lenses. The change in settings alone is typically insufficient to eliminate the problem.

Increased surface CONTACT is imperative in reducing spoilage and axis errors on oleophobic AR lenses. Several new products are available to help with this and the incremental cost in using specifically designed products can far outweigh the cost of spoilage and potential lost business.

Many lens manufacturers recommend the use of non-slip membranes, or edging stickers, which have proven to be most efficient in reducing slippage. Non-slip membranes have a special adhesive that provides additional grip to the slippery lens surface while providing a non-slip surface for the leap pad to adhere to. For best results non-slip membranes are recommended for the convex and concave surfaces. Another development in reducing slippage is new leap pad technology. Leap pads specifically designed to reduce slippage consist of stronger adhesives that provide better grip of the oleophobic surface along with an anti-torque foam layer within the pad itself.

Quite often better results require extra steps in your process. The best results are achieved when a non-slip membrane is used on the front and back of the lens along with the anti-slip leap pads.

If you feel the anti-slip leap pads are sufficient for the front surface then it is still recommended that a non-slip membrane is applied to the back surface.

Don’t forget about the importance of a clean surface. If a surface has been touched before application of the leap pad or non-slip membrane then you’ve left behind an oily residue that can contribute to axis errors. This also includes touching the adhesive side of the membrane or leap pad prior to application. Oleophobic lenses are here to stay. Understanding proper handling is the key to success in using these high-tech products. Stay in CONTACT with your equipment and consumable providers to ensure you are up to date.

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May/June LabTalk 2017