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Vertex Calculation Oddities

I received the following email from Eli today:

I have a question about your vertex calculator. If I try to vertex correct a refraction of -9.00-2.00x180, the diagram of the power cross that comes up on your website shows -8.00 in one meridian and -9.75 in the other meridian (a cylinder amount of -1.75), but the vertexed prescription is listed with -1.50 cylinder. It just seems like there is a discrepancy between your diagram and the vertexed prescription written just below it. Thanks for your help in understanding this.

vertexted refraction on optical crosses

This question pops up every once and a while, and it’s a good one.  This looks like a mistake, or at least a discrepancy, but it’s really simply a phenomena of rounding.

If you take the -11.00 D meridian and vertex it, the actual value you get is -9.72. However, I like the optical cross labels to look nice and tidy, so I wrote the program to round this up to the nearest quarter diopter, -9.75.

Similarly, the -9.00 D meridian ends up vertexing to -8.12. This gets rounded to -8.00 (but just barely - if it was more than -8.125 it would have been rounded to -8.25).

As a consequence, one meridian was rounded up to -9.75 and the other rounded down to -8.00, so the optical cross seems to show a -1.75 D cyl power.

However, the suggested cyl power uses the true calculated values, -9.72 and -8.12, and subtracts them to get the cyl power, which turns out to be -1.60 D in this case. Because I still wanted things to look pretty - and to be easier to compare to our real world contact lens options - this is rounded to 1.50 D.

In summary, when you see a discrepancy between the cylinder on the optical cross and the cylinder on the suggested Rx, the true, exact number rests somewhere between these values. However, rest assured that the cylinder in the suggested Rx will always be within an 1/8 D of the exact calculated power.

I hope that makes sense!

-Todd


 


Air Optix Colors now available in plus powers

Air optix colors

Just a quick note:

Air Optix Colors now go from +6.00 to -6.00 in 0.25 steps, and up to -8.00 in 0.50 steps.

Cooper Products Discontinued

CooperVision will be discontinuing Biomedics 38, Biomedics 55UV, and Proclear EP lenses on October 31 2015.

The trial lenses for these products will be discontinued on 12/31/2014.

“At CooperVision, we are committed to ensuring our product portfolio meets the needs of you and your patients - today, tomorrow, and beyond. To support this, we continually evaluate our portfolio’s relevance."

ProclearEP

Biomed38 Biomedics55

Johnson & Johnson introduces 1-DAY ACUVUE DEFINE cosmetic contacts

JOHNSON & JOHNSON VISION CARE, INC. INTRODUCES A NEW INNOVATION IN BEAUTY WITH INITIAL U.S. LAUNCH OF 1-DAY ACUVUE DEFINE BRAND CONTACT LENSES

Johnson & Johnson Vision Care, Inc. (JJVCI), today announced the initial launch of 1-DAY ACUVUE DEFINE Brand Contact Lenses with LACREON Technology, a new category of eye enhancement contact lenses that accentuate natural beauty while helping to support a healthy eye. The innovative brand, already the number-one beauty contact lens in Asia, is now available at a limited number of independent eye doctors' offices, with expanded product availability in the United States to follow in the first half of 2015.

Images

1-DAY ACUVUE DEFINE addresses a significant unmet need for natural-looking eye enhancement: the 2013 Gallup Study of the U.S. Consumer Contact Lens Market showed that one in three vision corrected teens/adults (32%) express a strong interest in purchasing a contact lens that enhances the natural beauty of their eyes.1 1-DAY ACUVUE DEFINE Brand has sophisticated iris-inspired designs that combine an outer darker limbal ring – to give eyes greater definition by creating contrast between the iris and sclera – and an inner translucent light-effects pattern – to add depth and definition without changing the eye's natural color. Independent research shows that people are more attracted to women and men with pronounced limbal rings, as limbal rings are associated with a healthy and youthful appearance.2Interviews with over 40,000 women informed the design of the lens.

1-DAY ACUVUE DEFINE Brand will be available in plano and vision correction ranges from +1.00 to -9.00 with a base curve of 8.5 and diameter 14.2mm and is being introduced in three styles to complement all eye colors:
• 1-DAY ACUVUE DEFINE Brand Contact Lenses NATURAL SPARKLE
• 1-DAY ACUVUE DEFINE Brand Contact Lenses NATURAL SHIMMER
• 1-DAY ACUVUE DEFINE Brand Contact Lenses NATURAL SHINE

"1-DAY ACUVUE DEFINE provides personalized eye enhancement that uniquely interacts with each iris pattern," explains Millicent Knight, OD, Head of Professional Affairs, JJVCI, U.S. "It is not a colored contact lens," she adds. "Colored contact lenses usually have opaque and pixelated, patterns that mask the natural beauty of the eye. 1-DAY ACUVUE DEFINE offers subtle, natural-looking enhancement that allows the beauty of the eye to shine through." 1-DAY ACUVUE DEFINE Brand also uses proprietary BEAUTY WRAPPED IN COMFORT Technology that fully encloses the pattern within the ultrathin lens material of 1-DAY ACUVUE MOIST Brand Contact Lenses, ensuring that the design pigments are not in contact with the surface of the eye or the eyelid.

Acuvue Oasys for Astigmatism available in -2.75 cyl

As of October 1st 2014 the Acuvue Oasys for Astigmatism lens will be available in -2.75 cyl power at all axes (10º steps).

Oasys astig